ADA Depot Too - A Forum To Support Users of ADA Amplification Gear

Non ADA Gear => Rack Gear => Topic started by: AxeHarmony on January 06, 2014, 08:41:08 PM

Title: Twin Tube GFX-1
Post by: AxeHarmony on January 06, 2014, 08:41:08 PM
Twin Tube GFX-1  always wanted one as I had a GSP-21 back in the 80's.
my old gsp-21 foot controller works perfect with this unit...

i really think Digitech checked out the MP-1 before making this pre... ??? lots of similar parts and I basically did the same noise mod to it and some other obvious stuff ...  and quite an impressive pre, really - real fun to play with as it has a full array of effects, the flanger is awesome while the delay and reverbs need to be subtle ...

matbe some mods to this one ?  ... ...
Title: Re: Twin Tube GFX-1
Post by: Dante on January 08, 2014, 03:44:58 PM
I bought one of those for a backup when my MP-2 was at a local shop, and used it with my ol' B200s. It was a very good preamp, but I remember it being a pain to program (something about scrolling through all the settings to get to save? - I can't remember specifically)

That said, if I see another one pop up on Criagslist, I'll probably grab it ;)

BTW: I sold mine to pay for my MP-1 Classic  :metal:
Title: Re: Twin Tube GFX-1
Post by: AxeHarmony on January 10, 2014, 07:00:49 PM
neat how things come together, Dante did you notice how much cleaner this unit is than the ADA's ?? sure a little less organic sound than the ADA's but damn it's a clean low noise/hum compared to the ADA's  !!!
Title: Re: Twin Tube GFX-1
Post by: Dante on January 13, 2014, 05:36:10 PM
Yes, I did. It's a very quiet unit on the dirty stuff fo sho.

However, as you state, the 'organic' feel of it left a bit to be desired in a live situation. Many of the gear I try sounds fantastic by itself, but the true test is the BAND. How does it fit in the mix? How does it cut through the mix (or not)? Those are the questions that determine actual functionality of gear.

That said, I love Love LOVE my MP-2. I have for years. The MP-1 Classic still cuts through better to my ears, but the MP-2 has a LOT more bells & whistles.

I like ringing bells and blowing whistles
Title: Re: Twin Tube GFX-1
Post by: sebastien on May 07, 2014, 11:49:29 AM
i had one some months ago, i found it was "old date" sound, with nuch such gain as ADA mp1 or 2
but quite good preamp.
Title: Re: Twin Tube GFX-1
Post by: Sparker on May 25, 2014, 08:13:53 AM
Just got one of these, super-cheap from EB, ... but super high gain squealing as well (probably why super-cheap!!! Gotta love EB). Anyway, changed the 'hooting' tubes out and I'm really pleased with it, to my ears sounds like rich organic overdrive plus super high gain as well. Totally agree Digitech must have been checking out the ADA MP's when pushing this one out (weird with 2 transformers eh?). Strange none of their subsequent rack tube preamps sounded as good. Axe - I would like to hear more about your mods to this pre (I see the twisted wires to the tube board and the changed out caps), have you got any more mods in there? Got any schematics as well? I've emailed Digitech for some, but won't hold my breath.

Cheers

Mike
Title: Re: Twin Tube GFX-1
Post by: Sparker on June 14, 2014, 02:20:50 PM
Digitech came good!! Got schematics if anyone needs them. Still loving this thing btw.
Title: Re: Twin Tube GFX-1
Post by: rnolan on June 14, 2014, 09:23:32 PM
Go Sparker, good to hear, I've always had a soft spot for Digitech and my IPS33 has always been solid and still going strong 20+ years later...
Title: Re: Twin Tube GFX-1
Post by: Dante on June 26, 2018, 10:27:00 PM
Whelp, here's an OLD bump...

I just picked up one of these GFX-1 units for less than $100. I figured, why not? It does not disappoint. I don't remember it sounding this good when I had one before.

When I brought it home, I could hear something inside rattling around....hmm... I opened up the case (each screw a new experience - lol) Man, it was dusty inside...and many loose screws. The tube board had three screws, one of which actually had a nut. DOH! I tightened that up as much as I could and it's much more solid now. The tubes were covered in dust and gunk - I wiped them off with a clean rag and found out they are Groove Tube GT 7025 tubes. Not particularly great in my Microtube power amp, but (from what I hear from Harley), they are good preamp toobs. Circa 1993-5 (I think - correct me if I'm wrong), they sound great.

I'm loving this thing and I'm gonna keep it as an emergency backup rig or a fly rig. Does it have what I NEED for a gig? Yes. Does it have everything I WANT for a gig? no...almost...
Title: Re: Twin Tube GFX-1
Post by: rnolan on June 27, 2018, 04:26:27 AM
 :thumb-up: :whoohoo!:
Title: Re: Twin Tube GFX-1
Post by: Iperfungus on May 15, 2019, 03:23:38 AM
Hi guys!

Could any owner of this unit, please, let me know where battery is located and what's battery type?
Does the Twin Tube have some reverb effects inside or just flanger/chorus/delay?

Thanks a lot!  :banana-dance:
Title: Re: Twin Tube GFX-1
Post by: Dante on May 15, 2019, 07:23:34 AM
I'll have to find it (in the garage) and open it up for you. I just moved, so everything is in disarray right now.

I'm not sure if there's a reverb, I only used it for distortion/gains and had another FX unit for that. I didn't want to be limited by only ONE effect at a time in the GFX-1
Title: Re: Twin Tube GFX-1
Post by: vansinn on May 15, 2019, 11:37:49 AM
It has at least reverb, delay, chorus, flange..

EDIT: oh well, clips I heard sounded like reverb..
Title: Re: Twin Tube GFX-1
Post by: Dante on May 16, 2019, 09:18:52 AM
I found the manual - no Reverb :( Just a Digital Delay (quite the rage back then)

Like I said, I would really only use it as a programmable dirt box, then use something else for FX. It is limiting in the effects arena, I believe it was Digitech's first attempt at a rack mount tube preamp.  :dunno:
Title: Re: Twin Tube GFX-1
Post by: Iperfungus on May 19, 2019, 02:59:18 PM
Hi gents!

Thanks for hints and information.
I found a Twin Tube for 60 euros and this could be a very good deal.
Looks in good shape and fully functional.

It's not close to home and the owner doesn't ship it...but, lucky me, the unit is for sale in the same town where my brother in law works...so I will ask him to get it for me.

It has a GT and a Marshall tubes inside...curious combination.
The battery looks like a normal 1.5V battery, even if it should be a 4.5V one, and it should be possible to remove it and replace it in a very easy way.

I think I'll give the thing a try: I can use the Intellifex as FX and reverb unit.  :thumb-up:
Title: Re: Twin Tube GFX-1
Post by: Iperfungus on May 30, 2019, 04:42:19 PM
So...I'm about to buy a Digitech Twin Tube for 60 euros and that's a good deal, since it's in good shape and 100% working.

I'm planning to pair it with the Zoom 9150 for missing effects and go through the Marshall 8004 power amp...
Title: Re: Twin Tube GFX-1
Post by: rnolan on May 30, 2019, 10:05:42 PM
Cool, should sound good  :thumb-up:
Title: Re: Twin Tube GFX-1
Post by: Dante on May 31, 2019, 02:05:28 PM
I don't think you can go wrong with that, good luck!
Title: Re: Twin Tube GFX-1
Post by: Iperfungus on June 03, 2019, 07:20:21 AM
I don't think you can go wrong with that, good luck!

I think I'll be happy with a third rack...  :headbanger:
Title: Re: Twin Tube GFX-1
Post by: Iperfungus on June 13, 2019, 06:41:22 AM
Got it!  :banana:

My brother-in-law has it at home...

I hope to have it home ASAP!  :headbanger:
Title: Re: Twin Tube GFX-1
Post by: Riccardo on February 26, 2020, 02:55:56 AM
Hi All......I'm new in the forum....I write from Italy. Sorry for my english.
I have a digitech GFX1 too that not working. I have read that someone have the schematic.
I'm interesting in it to fix the problem by myself. Can someone share it???
Thank you from italy.....
Riccardo.
Title: Re: Twin Tube GFX-1
Post by: rnolan on February 26, 2020, 11:30:53 PM
Digitech came good!! Got schematics if anyone needs them. Still loving this thing btw.
Looks like Sparker has the schematics, send him a PM or maybe he can post them here as I'm sure other GFX1 owners would like them  :thumb-up:
Title: Re: Twin Tube GFX-1
Post by: Riccardo on February 27, 2020, 03:50:59 AM
Yes, I think so......the schematics are always welcome......I have tried to send him a private message, but i'm not sure to know the right way to do it.
Infact he haven't answere.......sorry for my english....
I will wait few days, than I will try again to contact him.
Digitech have sell a lot of GFX1 and on google is impossible to found it.
 :(
Title: Re: Twin Tube GFX-1
Post by: Rusty on February 27, 2020, 05:58:12 AM
Hi All......I'm new in the forum....I write from Italy. Sorry for my english.
I have a digitech GFX1 too that not working. I have read that someone have the schematic.
I'm interesting in it to fix the problem by myself. Can someone share it???
Thank you from italy.....
Riccardo.

Hello Riccardo, your english is good,

Try getting the schematics, we can help you !

Welcome to club ADA.   :thumb-up:
Title: Re: Twin Tube GFX-1
Post by: rnolan on February 27, 2020, 09:34:02 PM
You could try what Sparker did and contact Digitech.To send a PM select the My Messages tab, select New Messages in the left hand side menu, type Sparker in the To: field (it's case sensitive), enter a subject (not mandatory) say GFX-1 schematics, enter a short message and click Send Message button.Although I suspect you already worked this all out.  Give him a while to respond, he may not be around or looking.  Usually you get an email notification when someone sends you a PM but they don't always work (as I posted about in discussions).
Title: Re: Twin Tube GFX-1
Post by: vansinn on February 28, 2020, 05:33:18 AM
Regarding schematics or service manual:
Contact Digitech for these - they will charge for it.

I usually can find schematics and/or service manuals, but some products have always eluded me, like the Digitech TSR24S - for obvious reasons, as this one was close to an Eventide 7000, and, as Digitech was bought up by Harman Kardon, who also owns Eventide, they want anything about the TSR24S gone from the net ;)

I haven't been able to locate schematics or service manual for the GFX-1, so...

However, I did find it for the 2120 on elektrotanya, using this query:
 site:elektrotanya.com product schematics
or
 site:elektrotanya.com product service manual

Best of lück
Title: Re: Twin Tube GFX-1
Post by: Riccardo on February 29, 2020, 10:10:03 AM
Hello to everyone, my dear friends.
I have write to digitech, but they told me that they can't give their electronic schemes due to their commercial politics. I understand that the know how is important but the Twin tube GFX1 is a 1992 product......I can't understand this. Then, they send my the list of USA digitech technical labs....but i'm in ITALY!!!!!!!! ;D ;D ;D ;D ;D ;D......They are crazy....Then, I have write to every single Digitech USA reair lab, but no one can give me the scematic by contract with digitech.
I have found the ELECTROTANYA like suggest....there isn't the gfx1 schematic, but I have found one similar. It can be important to have something to have a look.
I will try to contact "Sparker" next week......
thank you my friends. Rock'n'roll
Riccardo.
Title: Re: Twin Tube GFX-1
Post by: vansinn on February 29, 2020, 11:41:49 AM
Nonono, they did not send you a list of Digitech repair centers for you to write to about schematics, but rather so you could send your Digitech product to one of these for repair.
It's just their way of telling users that they won't give way 'secrets'..
So, writing to these repair centers will likely be wasting your time.
Title: Re: Twin Tube GFX-1
Post by: Sparker on April 21, 2020, 08:53:09 AM
All - apologies, should have done this ages ago, been away too long!! See attached.

Thanks
Mike
Title: Re: Twin Tube GFX-1
Post by: Sparker on April 21, 2020, 08:58:08 AM
And the user manual.
Title: Re: Twin Tube GFX-1
Post by: MarshallJMP on April 21, 2020, 09:45:22 AM
Thanks Sparker!
Title: Re: Twin Tube GFX-1
Post by: Iperfungus on May 26, 2020, 05:39:17 PM
Ciao Riccardo!

Max from Italy (we can exchange private messages in italian  :lol:).

The first GFX1 unit I put my hands on revealed an obvious issue: internal battery was dead.
Now the problem is that it's not so easy to find those damned 4.5V batteries around...but, after a very long quest, I ended to find them for a reasonable price from Amazon US:

https://www.amazon.com/gp/product/B00FED2M9K/ref=ppx_yo_dt_b_asin_title_o00_s00?ie=UTF8&psc=1

So, if you have a dead battery inside your Twin Tube (and I bet it is...), have a look there: that's the only place where you'll find the battery and get a shipment to Italy for a price that's not robbery.
Just to be sure...I bought 2!  :banana-dance:

The second issue was a little more annoying: battery holder destroyed by acid leaking from the battery (shit).
After tons of blasphemies, I found another unit with issues (there's some broken component (a resistor, I bet) in the board that makes the unit smoke as a cigarette 10 seconds after being turned on...) sold for 30 euros with original pedalboard...and with a perfect battery holder!
So I bought it and now I'm going to put a full working unit together from the two.
Another reason why I bought the second unit was the display, since I noticed that first unit's display is a little hard to read...but...surprise! Also the second unit's display shows the same behavior....maybe all GFX1 units had bad displays?
It doesn't matter.

Anyway, I think I will sell the working unit after I'll complete the job (I collected too much stuff...).
If you're interested on what will remain of the second unit for spare parts...just let me know.
Let's keep in contact to see how it will end for both of us, mate.

Thanks for the schema, Sparker!
Title: Re: Twin Tube GFX-1
Post by: Iperfungus on August 20, 2020, 07:47:10 AM
Hi folks!

How are you doing, wherever you are?

Just a short update about the Digitech GFX1 Twin Tubes.
At the end, I succeeded in putting a 100% fully working unit together.
I picked up the battery holder from the other "broken" unit, removed the damaged holder, soldered the new one and installed the 4.5V battery: now everything works fine again.
I removed the 7025 Groove Tubes and replaced with common ECC83s JJs, since GT are too good for this thing and there's no difference in tone, whatever tubes one uses.
I've to say, to be honest, that I had better memories of these units, but I was wrong.

The overall tone is too compressed (even with compressor turned to off) and a bit too fizzy and fuzzy...
As a preamp, my MP1, JMP1 and PSA rip the Twin Tube in two very easily.
I placed in the MP1 a couple of Ei tubes that performs very well with no noise or microphonic and it plays awesome as I never heard it.

Digital effects? Well...no comparison with a Quadraverb or an Intellifex.

The only positive note is that the GFX1 is very quiet even with gain turned to max and the noise gate works really well (like the one on Quadraverb GT).

Now, the interesting note is that the unit that was intended to be "broken", looks not broken at all.
The previous owner changed one of the two transformers but he mounted the connector on the main board upside down.
Results: holy smoke!!! And smell, of course.
I reversed the connector and there's no smoke anymore, of course.
I anyway assume that some damage somewhere took place, because I start feeling a bad smell a few seconds after turning it on and the connector becomes hot very quickly.
Nothing strange seems to happen and the unit stays on...but I don't like that...the other one shows not these behaviors and it does not smell at all.
I will check and see if the unit can be repaired, but I think it can be.
I will then buy a new holder for the battery (I bought two) and most probably I will sell both the units and the original pedalboard.

It's funny to keep them alive, but I don't like them that much.  :lol:
Title: Re: Twin Tube GFX-1
Post by: Iperfungus on August 21, 2020, 01:36:49 AM
I just discovered another plus of the Twin Tube: it loves overdrive pedals a lot.
And it remains absolutely QUIET even with tons of insane added gain: truly remarkable.
This thing is dead silent: the quitest tube preamp I ever heard.

And it has some interesting hard rock and metal tones as well.
It is not so versatile, you cannot play jazz or blues with this unit, although clean and crunch tones aren't that bad (but there's a noticeable lack of dynamics...).
But if one wants some H/M from the 80s...

A BBE Sonic Maximizer will help, anyway.

I've to spend some more time with GFX1 programming (and, to be honest, it is not a pain in the ass to program...very user friendly).
Title: Re: Twin Tube GFX-1
Post by: Dante on August 21, 2020, 11:22:21 AM
I hooked mine up the other day, with my BOSS GX-700 & it reminds me of my MP-2...alot.

The tones are dark and wooly, not high and shrill, when you get them overly saturated. The picking dynamics, as stated, are not easy. I'll try some pedals in front of it, thanks for the tip!
Title: Re: Twin Tube GFX-1
Post by: Iperfungus on August 21, 2020, 03:15:05 PM
I never owned a MP2, but the Twin Tube is as you just described it.

I've to admit it's not that bad, but comparing it to an MP1 is far away from reality a lot.

In any case, if you put a simple booster or overdrive in front of it, you will be pleased by tone and silence: it opens a bit and stays quiet.

Nothing esoteric: something like a good, old Boss DS-1 with low gain will work fine there.

I will pass it through the Quadraverb, before BBE and Intellifex. It will improve everything, as usual.
Title: Re: Twin Tube GFX-1
Post by: Iperfungus on September 03, 2020, 03:55:29 PM
Ok guys.

Having played with this toy for quite a while now, I've to say that's not bad at all.
You've to adjust the eq in the right way and the Twin Tube can provide interesting overdrive and distortion sounds.
The clean sound that can be obtained by turning off tubes is absolutely nice!

On board effects are not bad, even if not so usable like the ones in other units like the Quadraverb or the Intellifex.

Now that I found good tones from the preamp, I'm gonna modify some patches on the Intellifex to add a little bit of chorus and delay.

What about yours, Dante?
Did you manage to make it ROAR???

The best feature of this unit it's the SILENCE.
I repeat: the quietest tube preamp I ever heard.
Title: Re: Twin Tube GFX-1
Post by: Iperfungus on September 03, 2020, 05:55:03 PM
I had some time to do tubes rolling and I had to change my mind once again, about this unit.
I was wrong when I stated that it doesn't matter which tubes you use, because the Twin Tube will always sound the same way.
No, it doesn't.

I tested some different tubes there and the winners are....the original long plates 7025 Groove Tubes.
They remind me of the Ei I've put in the MP1, in many ways: they have the best balance between gain and tone.
I start to assume that Twin Tubes voicings are designed around THESE tubes, to get the best results.

The worst result? Standard ECC83s JJs: they have gain, yes...but the Twin Tubes sounds too much compressed, dark and fizzy.
And, in any case, they have the same gain amount of the GTs or just a little more.

Other tested tubes:

1) TAD 7025s Highgrade (V1) and 7025 Highgrade (V2): very nice tone, but less gain. Good results pushing tubes with an external overdrive (a Boss DS-1 is always good).
2) Ruby JJ ECC83s HG+ (V1) and Ruby JJ ECC83s HG (V2): very different from standard JJs! Good gain (but a little less than GTs) and very nice tone (a little better than with the TADS...more round and punchy). Not compressed nor fizzy sound.

I didn't test with mixed tubes, but I'm curious to try the HG+ JJ in V1 and a GT in V2.

Since I decided to keep this unit (I like it more than the Rocktron Chameleon, now that I learned how to use it), I will repair and sell the other one.
And I will keep the GTs!
Title: Re: Twin Tube GFX-1
Post by: Dante on September 04, 2020, 07:48:34 AM
Thanks for the tube rolling!! That helps immensely

I can get good tones out of my unit..if I shut off the FX. I don't need that thing muddling up my signal chain, I have the Boss GX700 for that. As long as I use it for a preamp only...it works. Great little backup...I'm not fond of the direct sound, but I'm toying with it...possibly get a GCS to tame the fizz.
Title: Re: Twin Tube GFX-1
Post by: Iperfungus on September 04, 2020, 08:52:17 AM
Hey Dante!  :wave:

Next tubes test: original chinese ADA MP1 tubes! The ones with the 12AX7A red logo only.
Now the Ei tubes are in the MP1 and I forgot its original tubes: they worth a try in the Twin Tube, just to hear...

At the moment, GTs 7025 are the winners.
Otherwise, I would go for Ruby JJs ECC83s HG+ and HG.

I will let you know soon.

About effects, to be honest, I found chorus and flanger quite useless.
But I like that kind of 3D delay, even if it's not so present in the mix and it's short: most of the times, I hear the repeats all around the room, coming from different directions!
Something I never experienced with other delay units.

For other stuff, I prefer the Intellifex a lot.
I didn't test the Digitech with the Quadraverb yet.

Anyway, I share your point of view: very good backup unit.
Title: Re: Twin Tube GFX-1
Post by: Iperfungus on September 04, 2020, 10:06:48 AM
Jesus Christ!!!

The original MP1 tubes are MONSTERS!
They deliver TONS of gain...

If I want to use the external overdrive with these, I've to lower the gain and/or set the noise gate threshold at higher level.
But, to be honest, you don't need an overdrive with these tubes: just crank the Input Level and that's it!
Wow....f**king, brutal, shreddy tones!

The GTs have a slightly better overall tone, but the anonymous chinese tubes have the highest gain level I ever experienced: with these tubes, I've to set tubes gain and saturation at 9.6 or 10 to get the same gain I've with the GTs at 11 for both saturation and gain, with the same Input Level.
And the tone is very good, anyway.

After some A/B testing, I ended up leaving the original GT tubes inside the preamp, because they have the best definition and clarity, even with insane amounts of gain.
And I like to use an external overdrive.

The little chinese tubes have a lot of gain, but I don't need ALL that gain...  :lol:
And, when pushed to the limit, they tend to loose definition.

I really think that those 7025s are the best tubes for the GFX-1, for both gain and tone.

Definitely, tubes rolling makes sense with the Twin Tube.
I was totally wrong!

Dante, for your reference, I'm using "MAIN METAL SOLO" patch (#1 or #61) with modified EQ (more mids and mid-highs).
Title: Re: Twin Tube GFX-1
Post by: Dante on September 04, 2020, 11:30:21 AM
I used that #1 patch for my 'modern gain' setting (no FX)
Title: Re: Twin Tube GFX-1
Post by: Chip Roberts on September 04, 2020, 01:32:23 PM
This is a very enlightening thread.  I've seen these units pop up on the used market every now and again and always wondered if they could work as a backup.  It sounds like Iperfungus was able to get some pretty usable sounds out of them (after some fiddling and experimentation  ;) ) I'll definitely check one of these out next time they pop up in my searches.
Title: Re: Twin Tube GFX-1
Post by: Iperfungus on September 04, 2020, 03:48:49 PM
Hey Chip!

Yes, I found interesting tones playing with the Twin Tube.
You've to spend some time adjusting the eq and delay settings and this thing will start making you smile.
Many of the presets are ridiculously ugly, but you have to never trust presets!  :lol:

If you'll find one at reasonable price, give it a chance: it worth a try!
Just remember that most probably battery will be dead and you'll have to replace it.
Have a look here to buy a 100% compatible battery, but in the US it's very easy to find a replacement:

https://www.amazon.com/gp/product/B00FED2M9K/ref=ppx_yo_dt_b_asin_title_o00_s00?ie=UTF8&psc=1

If you'll find that the battery holder is damaged by acid from battery, just buy a Keystone NO 139 from Mouser or DigiKey, but be careful and buy one with lugs good to be soldered to the board.

This one:

https://www.amazon.com/Battery-Holder-Keystone-modified-terminals/dp/B00SXBGN7M

Just prepare yourself for a long and funny work: to remove the old holder and install the new one, I had to completely disassemble the unit to have access to bottom of main board (there's no a removable bottom lid here, as in the MP1, unfortunately) and do a clean work.
The easy part is that daughter board can be easily removed: it's connected to the main board by 5 connectors and some screws.
Just be careful with the tubes board: it's connected to daughter board with some cables and you've to remove them together, before removing the main board.
Anyway, that's a lot more easy to do the job than describe it: I've done it so many times, that now I can disassemble the Twin Tube and assemble it back in 5 minutes. Blindfolded.  :lol:

Where are you from, mate?
There's one for sale here in Italy for 50 euros:

https://www.mercatinomusicale.com/mm/a_digitech-twin-tube-gfx1-guitar-preamp_id6434339.html

You could contact the seller to see if an international shipment could be arranged, but it could cost more than the preamp.
Title: Re: Twin Tube GFX-1
Post by: bunkyloo on September 04, 2020, 04:58:36 PM
Thanks Iperfungus I just grabbed one with the controller (no cords or cables ) fairly cheap but rattling nuts a loose tube board crappy tubes and a destroyed battery holder and custom graphics  :facepalm:. I fixed with hot glue but  I wouldn't trust it. I just found another one I purchased and I will build the best of two like you did.
Thanks for the info.
Steve
I do agree with everyone though the tone is ok the effects are almost not there.
Title: Re: Twin Tube GFX-1
Post by: Iperfungus on September 04, 2020, 05:49:44 PM
We're making the Twin Tube's Family grow!  :lol:

I assume we'll soon be banned from the Depot...  :facepalm:

I also have an original controller and cable, but I never use it: I just tested if it works.
It's a shame that's not a MIDI controller: remote control only.
That's ok for the unit, of course: it's dedicated, no need for external power supply...

By the way, I tested the "broken" unit: it f**king works and tones are exactly the same as the other unit.
Of course, there's no holder and there's no battery there...

The bad smell and the fact that connector from transformer became hot in less than one minute from powering the unit on, worry me a lot: something is not ok somewhere.
But I'll try to fix this one as well: it's a shame to use it for spare parts and throw it in the garbage.
If only the original owner had not inverted that connector from tansformer on the main board...or if I had a better look before powering the unit on...I would have bought a working one for 30 euros ... :facepalm:

Oh, if you have the chance...try it with a Mooer Radar with Marshall-like IRs and good headphones...it will surprise you again!
And internal effects will start to make sense.
Title: Re: Twin Tube GFX-1
Post by: bunkyloo on September 06, 2020, 12:01:42 PM
Actually it looks like my transformer was plugged in backwards as well and still is and works fine.
Not sure why. Here is a picture showing the harness and after i swapped tubes and fixed all the problems.
Title: Re: Twin Tube GFX-1
Post by: Iperfungus on September 06, 2020, 02:15:08 PM
Uhm...to be honest, it looks cables from transformers to main board are not backwards but in the right position.
Exactly in the same way they are positioned on my functioning one, as far as I can see.
Anyway, I wouldn't try to reverse them...  :lol: :lol: :lol: :lol: :lol:

What about battery? Is still the original or you changed it?
Did you repair the battery holder as well?

Very good job, by the way!
Title: Re: Twin Tube GFX-1
Post by: bunkyloo on September 06, 2020, 02:39:51 PM
The only reason i say it looks backwards is the outline of the connector on the board and the actual connector are opposite the picture doesn't show the other side and the battery still worked so it is the same but I hot glued the battery holder. It works but I don't think I would trust it for the long haul.
Title: Re: Twin Tube GFX-1
Post by: Iperfungus on September 06, 2020, 02:53:21 PM
You're right!

The top connector is put upside down: opposite to the mark on the board.
I had a better look to your pictures.

On mine, the reversed connector was the other one, the bottom one coming from the MADE IN CHINA transformer.

I'm not sure, but maybe...in this case....I would reverse that connector.

About the battery holder, it looks that Keystone does not produce anymore that model.
This will make my second repairing a pain in the ass for sure.  :facepalm:

The original battery still charged is a stroke of luck.
Title: Re: Twin Tube GFX-1
Post by: bunkyloo on September 06, 2020, 03:33:55 PM
If you get the black heavy duty glue sticks it works out pretty solid I guess if thats all we can do. That is really a bummer about no replacement. Perhaps the Mighty MJMP has a suggestion ?
Title: Re: Twin Tube GFX-1
Post by: Iperfungus on September 07, 2020, 02:08:03 AM
Mouser has this one:

https://www.mouser.it/ProductDetail/Keystone-Electronics/2224?qs=%2Fha2pyFadugenAX7QbWVFAtBL7ngADIAmZuo9%252BFPgqPfH15sDT0VIA%3D%3D

It looks closer to the old one, but I'm not sure if battery will fit there.

I could try to repair the old battery holder by soldering, maybe.

The battery in yours is a Duracell??
Title: Re: Twin Tube GFX-1
Post by: rnolan on September 07, 2020, 02:19:19 AM
We're making the Twin Tube's Family grow!  :lol:

I assume we'll soon be banned from the Depot...  :facepalm:
Hey Max, that would be a bit harsh LoL, I'm watching on with interest  :thumb-up: and hey, Dante has one...  Interesting result with the original Chinese bottles BTW.
Title: Re: Twin Tube GFX-1
Post by: Iperfungus on September 07, 2020, 03:58:09 AM
Hey Max, that would be a bit harsh LoL,

 :lol: :lol: :lol: :lol: :lol: :lol: :lol: :lol: :lol: :lol: :lol:

I'm watching on with interest  :thumb-up: and hey, Dante has one...  Interesting result with the original Chinese bottles BTW.

Oh yes....the original MP1's bottles are KILLERS.
Too much, maybe...  :lol:

AS I wrote, at the moment 7025 GT tubes are the best inside the GFX1.
Title: Re: Twin Tube GFX-1
Post by: Iperfungus on September 07, 2020, 06:23:01 AM
Mmmmmmmmh.....maybe I can repair the original holder, damaged by battery's acid.

Luckily I'm a kind of maniac and I saved the original holder ('cause you never know...), including the lug and the internal pin that have come off.
Plus, I'm italian and we're rich in fantasy!  :lol:
With a small screw, a nut and a couple of washers, it could work again!

f*ck Keystone!  :lol:
Title: Re: Twin Tube GFX-1
Post by: MarshallJMP on September 07, 2020, 08:14:50 AM
Ok seems I'm missing out on something here  ;D So maybe I can have a look at some battery holders but I need some more info. As far as I can see it looks like an AA battery? Pins into the pcb?

BTW a battery doesn't loose acid but an alkaline. Alkaline is as bad as an acid so if it's on the pcb it will "eat" the traces so you will need to neutralise it with you guessed it with an acid. There are a lot of vids on youtube on how to do this.
Title: Re: Twin Tube GFX-1
Post by: Iperfungus on September 07, 2020, 08:37:53 AM
Ciao Phil!

The battery is a sort of AA, yes.
Alkaline, 4.5V, neverseenbefore format.  :lol:
Original battery no longer in production, but here's a compatible one:

https://www.amazon.com/gp/product/B00FED2M9K/ref=ppx_yo_dt_b_asin_title_o00_s00?ie=UTF8&psc=1

The holder is a Keystone, No 139 with PC mount lugs.
Original one is in the attached picture, but it seems Keystone does not produce it anymore.

A similar one:

https://www.mouser.com/ProductDetail/Keystone-Electronics/2224?qs=%2Fha2pyFadugenAX7QbWVFAtBL7ngADIAmZuo9%252BFPgqPfH15sDT0VIA%3D%3D

In my case, acid from battery only damaged holder...luckily: traces are ok and safe.
The rings that kept lug and pin together and in place in the holder have been destroyed by acid.
But I kept holder, lug and pin and I think a small screw, a nut and a couple of washers could help to fix it and put it back in place.
Title: Re: Twin Tube GFX-1
Post by: MarshallJMP on September 07, 2020, 09:50:21 AM
Farnell and RS still carry the 139 but with solder lugs, not  pcb pins.

The battery is for the RAM backup?
Title: Re: Twin Tube GFX-1
Post by: Iperfungus on September 07, 2020, 04:19:33 PM
Farnell and RS still carry the 139 but with solder lugs, not  pcb pins.

The battery is for the RAM backup?

Mouser and DigiKey have the same holder (139) as well, but no pcb pins.  :facepalm:

Yes, it's the internal backup battery for RAM...to keep settings and patches while the unit is powered off.

By the way....maybe I fixed the old holder...   :lol:
It seems to work.
Title: Re: Twin Tube GFX-1
Post by: MarshallJMP on September 08, 2020, 02:09:38 PM
Is it held on the pcb by the pcb pins?

I think you can also use 3.6V AA battery's normally, these are  a lot easier to find.
Title: Re: Twin Tube GFX-1
Post by: bunkyloo on September 08, 2020, 02:39:11 PM
I was actually able to buy two holders and two batteries on amazon. that link you had was good and said in stock so i bought them. The batteries came already they are fine and the holders already shipped we'll see. I get my other unit on friday so well see the condition of that.
Title: Re: Twin Tube GFX-1
Post by: Iperfungus on September 09, 2020, 03:27:02 AM
Is it held on the pcb by the pcb pins?

I think you can also use 3.6V AA battery's normally, these are  a lot easier to find.

The battery, at the moment, it's not an issue: the Exell A21 is a fully compatible 4.5V battery, that fits the holder and works fine.
Mine measure 4.68V!

The Keystone 139 with PC pins is an issue...  :facepalm:
To answer your question, yes..the holder is soldered to PCB by PC pins.

Title: Re: Twin Tube GFX-1
Post by: Iperfungus on September 09, 2020, 03:31:43 AM
I was actually able to buy two holders and two batteries on amazon. that link you had was good and said in stock so i bought them. The batteries came already they are fine and the holders already shipped we'll see. I get my other unit on friday so well see the condition of that.

Very good!
So you've got both batteries and correct holder from Amazon?

I bought another 2 batteries: one for spare (you never know) and the other for the 2nd Twin Tube I will try to fix.
The problem for me is that NONE would ship those holders to Italy....Jesus Christ....to buy drug or cobalt from US is easier.

At the moment, I fixed the original holder with a screw and a nut.  :lol:
The battery stays in place and there are 4.68V between lugs...so it should work, once soldered to PCB.
I'm not sure if the 2222 Keystone Holder, that should be for AA batteries and has PC pins, would fit 139 measures nor if the battery would fit this new holder.
Title: Re: Twin Tube GFX-1
Post by: bunkyloo on September 11, 2020, 04:23:12 PM
Well I received and installed the new holder works great and the other unit that arrived today was in really good condition and didn't need half the things I was figuring. So I am going to sell the one with the new holder ( I felt to bad to sell it with hot glue repair) because the face is a little rough and the new one is near perfect and it came with ruby tubes hah remember those? I haven't heard about them in years but anyway it's a newer unit too so there is that. I will update after I give it a play and make the final decision.
Title: Re: Twin Tube GFX-1
Post by: rnolan on September 14, 2020, 02:05:05 AM
 :whoohoo!: good news for modern man  :thumb-up:
Title: Re: Twin Tube GFX-1
Post by: Iperfungus on September 16, 2020, 03:23:24 AM
Well I received and installed the new holder works great and the other unit that arrived today was in really good condition and didn't need half the things I was figuring. So I am going to sell the one with the new holder ( I felt to bad to sell it with hot glue repair) because the face is a little rough and the new one is near perfect and it came with ruby tubes hah remember those? I haven't heard about them in years but anyway it's a newer unit too so there is that. I will update after I give it a play and make the final decision.


So, you've got new holder from Amazon. Is that the correct one, equal to the original?
Can you post a picture? I cannot find a way to buy one, damn' it!

Are you based in the US? Yes, I suppose...
Is there an easy way for you to buy a couple of those holders for me and ship them to Italy?
If that can be arranged and it doesn't cost too much, I could send you the money by PayPal.

Did you test the unit already? What about?
I know Ruby tubes very well.  :lol:
Title: Re: Twin Tube GFX-1
Post by: bunkyloo on September 16, 2020, 02:10:07 PM
Heres a picture of the one I am saving for the future. It is a exact replacement and yes I am in the US and they were only i think 4 dollars each if you want to send me an address i can get a shipping quote for you not a problem. The newer unit seems to sound much heavier but truly just as clean. I haven't dug too deep yet but I will soon. Steve
Title: Re: Twin Tube GFX-1
Post by: Iperfungus on October 09, 2020, 07:47:39 AM
Heres a picture of the one I am saving for the future. It is a exact replacement and yes I am in the US and they were only i think 4 dollars each if you want to send me an address i can get a shipping quote for you not a problem. The newer unit seems to sound much heavier but truly just as clean. I haven't dug too deep yet but I will soon. Steve

Hi Steve!
Apologies for the late reply.
Well, the price for those items is around 4 dollars, right.
The main problem, of course, are shipping costs....basically, being in Italy and buying from the US, I risk to buy a 4 dollars item and have it shipped for 30/40 dollars...which makes no sense, obviously.

Anyway, I live in Genova, Italy.
ZIP code is 16149.
If you've time to let me have a shipping quote from there, it would be widely appreciated!

Thanks a lot!  :thumb-up:
Title: Re: Twin Tube GFX-1
Post by: bunkyloo on February 25, 2021, 10:59:26 AM
Bumping a old thread here but I purchased another GFX1 and of course dead battery and broken holder and since I had a extra one of each from the last one I repaired I just swapped it out.
Well after replacing it the unit will not boot up. If you bull the battery out it works fine. I rechecked my work 2 times disassemble and check again everything is solid.
It must have been this way because it always booted before with a dead battery. Any ideas or thoughts would be great.
Thanks in advance steve.
Title: Re: Twin Tube GFX-1
Post by: MarshallJMP on February 25, 2021, 02:14:11 PM
Just had a look at the schematics ,there is backup management system ic (U19) in this thing (ICL7673) maybe there is something wrong there. I see it's also connected to the RAM CE2 (Chip Enable) input .So... just guessing here.

What happends if you start it up without battery and then put the battery in when it's running?
Title: Re: Twin Tube GFX-1
Post by: bunkyloo on February 25, 2021, 02:18:21 PM
It will crash instantly when I install the battery.
Title: Re: Twin Tube GFX-1
Post by: bunkyloo on February 25, 2021, 04:08:38 PM
I removed U19 and it boots up normally  makes sense so fingers crossed I ordered a new one from mouser we shall see.
Thanks MJMP great help as always.
Title: Re: Twin Tube GFX-1
Post by: Dante on February 25, 2021, 05:49:59 PM
daayyumm, MJMP is like McGyver on a PCB
Title: Re: Twin Tube GFX-1
Post by: MarshallJMP on February 26, 2021, 07:37:40 AM
daayyumm, MJMP is like McGyver on a PCB

 ;D

@bunkyloo, don't fire it up again until you get the replacement, since the CE2 of the RAM is floating now, you could get some weird stuff this way. I do hope this was the problem.

Edit: just saw that CE2 is not floating without U19, my bad.

Title: Re: Twin Tube GFX-1
Post by: bunkyloo on February 26, 2021, 04:45:12 PM
@MJMP 10-4 thanks!
Title: Re: Twin Tube GFX-1
Post by: bunkyloo on March 05, 2021, 03:50:51 PM
Well I replaced r19 and its back to the same stuff. Would my next course of action be replacing the ram chip as it is affected next in line? Any ideas where to look next would be cool.
Thanks Steve.
Title: Re: Twin Tube GFX-1
Post by: MarshallJMP on March 06, 2021, 11:43:34 AM
Can you measure the voltage on pin 8 en pin 2 (4 is ground) and let me know. You must insert the battery for this and turn the unit on, even if it doesn't boot up.
Title: Re: Twin Tube GFX-1
Post by: bunkyloo on March 06, 2021, 12:01:23 PM
On U19 pin 2 reads 4.71 volts and pin 8 reads 4.73 volts.
Title: Re: Twin Tube GFX-1
Post by: MarshallJMP on March 06, 2021, 12:41:20 PM
Ok here's your problem, the difference between these 2 inputs must be between +- 10mv and 50mV. Since you only have 20mv it switches on the battery input, which means it shorts the capacitor C3 of the reset circuit to ground, which causes the µP to go into reset mode and it makes CE2 of the RAM low which is active high. That's why if you insert the battery it shuts off.

It seems your 5V supply is a bit on the low side. Most 7805 5V regulators have 4% tolerance, so it's below that (should be at least 4.8V), what I would do is replace the 7805 with a 7805ACT which is 2% and replace cap C85 (470µF/25V) and C86 (10µF) while you at it. Or use a battery of 3.6V.

Title: Re: Twin Tube GFX-1
Post by: bunkyloo on March 06, 2021, 01:31:51 PM
Great I appreciate the help I will order those up and will let you know the results thanks again Steve.
Title: Re: Twin Tube GFX-1
Post by: MarshallJMP on March 07, 2021, 03:27:31 AM
ok keep me updated.

BTW this the mouser part number  863-MC7805ACTG
Title: Re: Twin Tube GFX-1
Post by: bunkyloo on March 18, 2021, 02:30:55 PM
Well just got my last capacitor today, got it put back together and bam, same thing any ideas where to go next?
Thanks Steve.
Title: Re: Twin Tube GFX-1
Post by: MarshallJMP on March 20, 2021, 08:16:05 AM
What about those voltage son pin 2 and 8? Can you measure these again?
Title: Re: Twin Tube GFX-1
Post by: bunkyloo on March 20, 2021, 10:27:08 AM
Pin 2 reads 3.51 and pin 8 reads 4.10 .
Title: Re: Twin Tube GFX-1
Post by: Iperfungus on March 20, 2021, 03:01:30 PM
Hey guys!

I ended up selling my second unit with its pedalboard to a guy who will do the repair job.
I hope Fabrizio will join the Depot Family soon!

Phil, prepare yourself for other questions.  :lol:
Title: Re: Twin Tube GFX-1
Post by: bunkyloo on March 21, 2021, 03:41:10 PM
@ Iperfungus
Looks like these units have quirks of there own. :facepalm:
Title: Re: Twin Tube GFX-1
Post by: Iperfungus on March 22, 2021, 05:22:59 AM
@ Iperfungus
Looks like these units have quirks of there own. :facepalm:

That's the funny side, Steve!  :lol:

I like mine a lot, now.
Happy to have a 100% working unit, I don't need a second one.

But I'm also happy that my second one went on the hands of someone who will give it new life!

@rnolan: Rich, Fabrizio is attempting to register to the Depot...but new users registration is suspended. I suggested to use the NEED HELP button and to shot you an email.
Title: Re: Twin Tube GFX-1
Post by: Iperfungus on March 22, 2021, 02:11:44 PM
Update.
Fabrizio found the problem and the damage, due to a wrong connection of the transformer to the motherboard pins: not upside down but moved to one side, leaving one pin free, so that the whole pin connection was wrong.
Some diodes are shorted and need to be replaced.
But he'll explain it himself, once he joins the Depot family.
Title: Re: Twin Tube GFX-1
Post by: MarshallJMP on March 22, 2021, 02:20:22 PM
Pin 2 reads 3.51 and pin 8 reads 4.10 .

Wow why are the voltages so different now? pin 8 should read 5V? and why did the battery voltage drop by almost 1V?
Title: Re: Twin Tube GFX-1
Post by: bunkyloo on March 22, 2021, 03:33:08 PM
I have no clue but I did swap all 3 components. Also that was without the battery installed.
Installed the battery and  pin 2 is 4.67 and pin 8 is 4.85. Sorry for the misunderstanding. Steve
Title: Re: Twin Tube GFX-1
Post by: rnolan on March 23, 2021, 12:36:49 AM
@rnolan: Rich, Fabrizio is attempting to register to the Depot...but new users registration is suspended. I suggested to use the NEED HELP button and to shot you an email.
Hey Max, I got your email, done  :thumb-up:
Title: Re: Twin Tube GFX-1
Post by: MarshallJMP on March 23, 2021, 01:13:38 PM
I have no clue but I did swap all 3 components. Also that was without the battery installed.
Installed the battery and  pin 2 is 4.67 and pin 8 is 4.85. Sorry for the misunderstanding. Steve

Do you have a battery with a lower voltage? like a 3V or 3.6V.
Title: Re: Twin Tube GFX-1
Post by: bunkyloo on March 23, 2021, 02:30:03 PM
I found a 3.6 volt AA size on amazon. Do you think that will work?
Title: Re: Twin Tube GFX-1
Post by: MarshallJMP on March 23, 2021, 02:50:58 PM
It should work, the RAM is the same type used in the MP-1 and that works on 3V. For some reason the IC won't switch between battery power and main 5V. Although the difference is now more than 50mV it still doesn't seem to work. Strange.
Title: Re: Twin Tube GFX-1
Post by: Iperfungus on March 24, 2021, 07:52:27 AM
Hey Max, I got your email, done  :thumb-up:

Ciao Rich!
Yes, I saw!
Thank you very much!  :thumb-up:

Fabrizio knows a lot about Digitech stuff and he did a lot of work and modifications on those units in the past years.
Maybe he could be of help here!
Title: Re: Twin Tube GFX-1
Post by: bunkyloo on March 24, 2021, 06:18:41 PM
Just installed the new battery the 3.6 volt and it powers up no problem , so now just seeing if it will save a patch unplugged. Just so annoying I can't use the OEM battery UGGGH.
Thanks for the help all especially MJMP. If Fabrizio has an idea I am all ears Thanks guys. Steve
Title: Re: Twin Tube GFX-1
Post by: MarshallJMP on March 25, 2021, 11:05:50 AM
Ok keep me updated. Also strange that the 5V is not in spec, should be at least 4.9V, can you measure the volatge at the 7805 between pin 2 (ground) and pin 3 (out), also between pin 2 and 1 ?
Title: Re: Twin Tube GFX-1
Post by: bunkyloo on March 25, 2021, 04:30:45 PM
Well got too excited, as soon as I tested the unit powered up battery installed it read pin 1- 7.18 and 3-4.99 and then it crashed while testing so I tested battery in and 1 was5.15 and 3 was 3.642.
I then tested no battery and 1 was 5.54 and 3 was 4.04 and now won't boot with the 3.6 volt battery. :facepalm: .
Title: Re: Twin Tube GFX-1
Post by: Iperfungus on March 26, 2021, 01:59:40 AM
Well got too excited, as soon as I tested the unit powered up battery installed it read pin 1- 7.18 and 3-4.99 and then it crashed while testing so I tested battery in and 1 was5.15 and 3 was 3.642.
I then tested no battery and 1 was 5.54 and 3 was 4.04 and now won't boot with the 3.6 volt battery. :facepalm: .

It looks that unit is playing jokes for (its) fun.  :facepalm:
Title: Re: Twin Tube GFX-1
Post by: Harley Hexxe on March 26, 2021, 01:40:04 PM
It looks that unit is playing jokes for (its) fun.  :facepalm:


    I think the Flux Capacitor gave out :dunno:
Title: Re: Twin Tube GFX-1
Post by: bunkyloo on March 26, 2021, 06:23:51 PM
Well it may just end up for parts backup if we can't get it sorted. I hope its not the flux capacitor that's only available in 1985 I believe  :lol:
Title: Re: Twin Tube GFX-1
Post by: MarshallJMP on March 27, 2021, 12:06:14 PM
Try this, get the battery out and measure over the battery connections.
Title: Re: Twin Tube GFX-1
Post by: bunkyloo on March 27, 2021, 12:31:52 PM
It starts at 0.7 and continues to drop
Title: Re: Twin Tube GFX-1
Post by: MarshallJMP on March 27, 2021, 12:34:51 PM
Did you start the unit?
Title: Re: Twin Tube GFX-1
Post by: bunkyloo on March 27, 2021, 04:35:17 PM
Yes I did start it and it responds the same either way.
Title: Re: Twin Tube GFX-1
Post by: bunkyloo on April 02, 2021, 06:18:28 AM
Is there anything else worth trying on this thing? Any thoughts would be great.
Steve.
Title: Re: Twin Tube GFX-1
Post by: MarshallJMP on April 02, 2021, 11:24:01 PM
Well got too excited, as soon as I tested the unit powered up battery installed it read pin 1- 7.18 and 3-4.99 and then it crashed while testing so I tested battery in and 1 was5.15 and 3 was 3.642.
I then tested no battery and 1 was 5.54 and 3 was 4.04 and now won't boot with the 3.6 volt battery. :facepalm: .

The input voltage is too low, it needs to be at least 7.5V, with an absolute minimum of 7V. So 7.18 is already quite low, 5.15 won't work as you can see the output is only 3.64V, not nearly enough for all the 5V logic to work. Could be a few things, transformer, bridge rectifier BR2 or somethings is drawing too much current on the 5V line. Can you measure the AC voltage coming from the transformer? From what I can see it should be the 2 yellow wires on the connector next to BR1 and BR2. you should also be able to measure it on BR2 pin 3 and 4. BTW don't forget to put the meter on AC voltage!!
Title: Re: Twin Tube GFX-1
Post by: bunkyloo on April 03, 2021, 02:57:42 PM
Ok across the the yellow wires unplugged I get 10.71 volts and plugged in I get 8.16 volts.
Title: Re: Twin Tube GFX-1
Post by: MarshallJMP on April 03, 2021, 09:46:26 PM
Ok that looks good to me, and you still have only 5.15V on the input of the 7805?
Title: Re: Twin Tube GFX-1
Post by: bunkyloo on April 04, 2021, 09:44:29 AM
Ok the 1 and 2 pins read 5.98 with battery out and 7.62 with battery in.
Title: Re: Twin Tube GFX-1
Post by: MarshallJMP on April 05, 2021, 06:46:16 AM
Strange that the voltage changes with the battery in or out?

Do you have have the old ic that you changed out?
Title: Re: Twin Tube GFX-1
Post by: bunkyloo on April 05, 2021, 06:55:28 AM
No I don't but i did buy an extra one I believe.
Title: Re: Twin Tube GFX-1
Post by: MarshallJMP on April 05, 2021, 11:46:24 AM
I checked the whole schematic and that ic is the only one where the 5V and the battery come togheter. So if you have a spare try to replace it.
Also before you put the new one in (and the old one is out) measure the voltages again. There is something very weird going on here.
Title: Re: Twin Tube GFX-1
Post by: bunkyloo on April 11, 2021, 12:44:07 PM
I swapped it out again and its the same old thing. This is really frustrating that we are running out of things to try.
Title: Re: Twin Tube GFX-1
Post by: MarshallJMP on April 13, 2021, 10:41:28 AM
Did you measure the voltages before you put the new one in?
Title: Re: Twin Tube GFX-1
Post by: bunkyloo on April 13, 2021, 01:39:47 PM
Well no I forgot to do that. :facepalm: I had been busy with work and when I had a moment I just did it.
Title: Re: Twin Tube GFX-1
Post by: MarshallJMP on April 14, 2021, 09:15:58 AM
Do you see any signs of modifications done to the unit?
Title: Re: Twin Tube GFX-1
Post by: bunkyloo on April 14, 2021, 09:33:54 AM
The only thing i see is the input and output pots have been replaced and wired to th board instead of pcb mount and they work fine but besides that no.
Title: Re: Twin Tube GFX-1
Post by: MarshallJMP on April 14, 2021, 02:04:54 PM
Ok the 1 and 2 pins read 5.98 with battery out and 7.62 with battery in.

I just can't figure out why the voltage rises when you put a battery in it.

Can you send (by email) a few high res pics of the inside of the unit? Maybe I can see something.
Title: Re: Twin Tube GFX-1
Post by: bunkyloo on April 14, 2021, 05:01:15 PM
Will do  this weekend . :bow:  :thumb-up:
Title: Re: Twin Tube GFX-1
Post by: MarshallJMP on April 15, 2021, 07:22:20 AM
Ok thanks, it has been bugging me for days now, I really hope we can get it fixed  :thumb-up:
Title: Re: Twin Tube GFX-1
Post by: bunkyloo on June 01, 2021, 06:45:45 PM
Well I sold it on Ebay as is and fully disclosed. I did get it cheap and we know why now . Well we tried and thanks MJMP as always sometimes its not worth it.
Steve.
Title: Re: Twin Tube GFX-1
Post by: MarshallJMP on June 02, 2021, 01:11:06 PM
Too bad we couldn't figure out the problem.
Title: Re: Twin Tube GFX-1
Post by: bunkyloo on June 11, 2021, 05:54:49 PM
Agreed but I feel more problems on the rise HAHA.