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Author Topic: Bass setting not saving  (Read 7307 times)

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revhed666

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Bass setting not saving
« on: Time Format »

gday from Australia guys. i recently scored an MP-1 and all seemed fine but i have noticed the bass setting is not saved correctly when saving patches. i can dial a patch and the bass parameter edits just like it should but with any setting that boosts bass as soon as i change to another patch and back again the bass audibly defaults to zero even though the saved parameter value reads correctly. strangely this only affects boosted bass values (ie +2 +4 + +9 +12 +16) i can save at anywhere from 0 to -16 and it saves and plays back correctly after changing patches but saving a boosted bass setting reverts to around 0db after changing patches even though the value reads correctly. mid/treble/pres all edit and save fine. firmware ver 1.38
any insight is appreciated thanks
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MarshallJMP

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Re: Bass setting not saving
« Reply #1 on: Time Format »

So the reading is correctly saved but you hear a difference in sound?
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revhed666

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Re: Bass setting not saving
« Reply #2 on: Time Format »

correct. if for instance i save a patch with bass at +16, on reloading the patch the bass level sounds like it is set to zero even though the parameter reads +16. if i then enter edit mode and drop bass from +16 to +12 a huge jump in bass level then occurs and it sounds as it should for +12 setting. it works fine while editing it is only when returning to a saved patch that the bass setting works incorrectly and sounds like it reverts to zero
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revhed666

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Re: Bass setting not saving
« Reply #3 on: Time Format »

some more detail to add. when in edit mode if the bass level is at a boosted level, editing chorus or mid, treble or presence value up or down will also cause audible bass level to immediately revert to around 0db even though the bass parameter still reads +2 to +16. still same behaviour when changing patches whether using up/down arrows to change patch or direct selecting the patch
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rnolan

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Re: Bass setting not saving
« Reply #4 on: Time Format »

Hey revhead, greetings from Canberra  :thumb-up: Very perplexing, one thing worth doing is the later firmware (v 2.01 EPROM) update (http://www.marshalljmpmodshop.net/miscellaneous_parts_and_replacement_tubes.htm), not that it will/or wont influence this issue.  MJMP will hopefully have some ideas, it seems to me like a problem with the VCA (or whatever bit or circuit controls the bass filter boost/cut).  So the parameter "value" is storing correctly and being recalled correctly just not being applied ( +ve boost only) correctly.  (editing chorus or mid, treble or presence value up or down will also cause audible bass level to immediately revert to around 0db) this is probably because the other parameter settings are being reapplied after each edit so it has the same affect (issue) as changing patch (my guess).

So here's my take on it, the parameter values are just an entry in a file/memory location (kept alive by the battery).  When you initiate/cause (by editing) a patch change various parts of the MP1 circuit are sent updated values to change to.  The MP1 is analogue so the various bits of the circuit are controlled by analogue devices (e.g. Voltage Controlled Amplifiers (VCA)).  These devices accept a signal from the parameter file/memory (or front panel in edit mode) and adjust accordingly.  In this case, the device that controls the bass boost/cut is not reacting to  +ve values properly and is defaulting to 0.  Also it only happens when it's sent a change from memory as you can edit the value directly and it responds appropriately to that (as long as that's the last thing you change).

So I'm thinking there is either an issue in the data/signal path from memory to the bass boost/cut controller (i.e. the  +ve bit/signal is not getting through/being recognised) or the controller device has an issue of some kind (less likely I recon as you can turn it up/down directly in edit mode (the edit signal would be a slightly different (direct) data/signal path than from the memory ??)).  The device that controls bass boost/cut will receive a signal that represents a number (0 to 16) and a +ve/-ve indicator (1 bit in computer stuff, 0 or 1 though not sure how the MP1 circuit does it).  It would seem the +ve value  indicator of the signal is not getting through to the controller device from memory or is being corrupted in some way causing a default to 0 (controller throws the towel in).

Cheers Richard
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MarshallJMP

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Re: Bass setting not saving
« Reply #5 on: Time Format »

So you have no problem with the presence?Just asking since bass and presence control use the same ic.

What you can try is to swap the the TC9170AP ic's and see if the problem shifts to mid/treble control.These are in a socket so easy to swap.See attachment for location of U19,U20 (TC9170AP,green circle).
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revhed666

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Re: Bass setting not saving
« Reply #6 on: Time Format »

thanks guys i appreciate the help.
presence was not affected
i swapped the IC's and the problem indeed shifted to the treble control.
mid was not affected
if it helps i tooled around a bit more and the gain controls also cause the bass (in original position)/treble (in swapped position) setting to be corrupted in same manner as the other tone controls. this is with the IC's in original and swapped position.
rnolan might you know of anyone that repairs MP-1's in australia? googling revealed zilch. im in sydney but would post it wherever i need to. i planned to purchase a mod board from MarshallJMP and either fit it myself or have a tech do it so that plan is dead and buried at this point. ive looked high and low and this MP-1 is the only one ive seen for sale in OZ so i'd like to get it going if possible
« Last Edit: Time Format by revhed666 »
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revhed666

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Re: Bass setting not saving
« Reply #7 on: Time Format »

ok so i assume that the chip is at fault? so hopefully dropping in a new chip would solve my dilemma? is this the same part? that would be soooo cool
http://www.ebay.com/itm/TC9170AP-Manu-TOSHIBA-Encapsulation-DIP-16-/120922032893
on closer inspection the secondary numbers do not match, the original TC9170AP has 8848H. the part on ebay has 9027H . i dont know what this means. are they still compatible?
Marshall JMP do you have the part? it isn't listed on your parts list. if so i would purchase from you
« Last Edit: Time Format by revhed666 »
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MarshallJMP

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Re: Bass setting not saving
« Reply #8 on: Time Format »

If you want i have the TC9170AP in stock.It's listed but as TC9170P,need to change that.Should be TC9170AP and TC9176P.
« Last Edit: Time Format by MarshallJMP »
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revhed666

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Re: Bass setting not saving
« Reply #9 on: Time Format »

are you confident it would solve the problem? if so i would order two chips, the eprom v2.01 and a tube board simultaneously. deciding between 3.666 and 3TM. thinking i might prefer the tone of the 3.666 but if it adds no gain then i would go the 3TM as i would really like a bit more gain and its easy to shape the tone with eq etc. thank you for all your help!
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rnolan

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Re: Bass setting not saving
« Reply #10 on: Time Format »

Cool, go MJMP, glad you got it sussed.  Pro Audio in Canberra were the Australian distributor and used to fix them.  I don't know if their current tech (John) is across ADA gear, he didn't fix my B200 after 2 goes at it  :( .  They used to have some parts but I think sold them all to someone years ago, just after I joined the original depot, I wanted to get hold of them for other members and just missed out.  Give them a call (0262497766) ask to talk to Packo, he was working there back then and may know a tech.
If you're buying bits from MJMP it makes sense to buy/do the MDRT transformer upgrade (which is I suspect where the pic he posted comes from  ;) , nice 3TM MJMP).
Alternately, send it to MJMP and get it all done, mod board, noise mods etc.
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MarshallJMP

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Re: Bass setting not saving
« Reply #11 on: Time Format »

are you confident it would solve the problem? if so i would order two chips, the eprom v2.01 and a tube board simultaneously. deciding between 3.666 and 3TM. thinking i might prefer the tone of the 3.666 but if it adds no gain then i would go the 3TM as i would really like a bit more gain and its easy to shape the tone with eq etc. thank you for all your help!

Send me an email and we'll get this sorted out.

Now since you swapped the TC's and the problem also swapped I'm almost 100% sure that replacing the bad TC will solve your problem.

Does the faulty one gets hot?I have seen these chips pull down the whole power supply and get really HOT.
That's why ADA put 200 ohm resistors between the +15V and the TC,so it couldn't pull that much current anymore.So the early MP-1's don't have this resistor.(A,B and early C rev).So it can cause start up problems.

Now i must say that's the first time i encounter a problem like this.In most cases when the TC9170 goes down it gets hot and the tone section won't work at all (at least either bass and presence or treble and mid).

Well the pic is from a UK unit.You can tell because it has a different transformer.For some reason the UK distributor changed the original 110V transformers with transformers that were (i guess special made)made in the UK and retrofitted in the mp-1's.then they put a sticker with 220V on the back.Problem with these was that the high voltage winding breaks down easily.
« Last Edit: Time Format by MarshallJMP »
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rnolan

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Re: Bass setting not saving
« Reply #12 on: Time Format »

Well the pic is from a UK unit.You can tell because it has a different transformer.For some reason the UK distributor changed the original 110V transformers with transformers that were (i guess special made)made in the UK and retrofitted in the mp-1's.then they put a sticker with 220V on the back.Problem with these was that the high voltage winding breaks down easily.
 :facepalm: My guess was wrong LOL, I saw a transformer.. sounds like it needs a MDRT..Nice clear pic BTW, I could read the IC numbers.  So was it a timing thing ? we got 240v models in Australia from ADA (I assume you did in Europe to),why do a local tranny swap out ?
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MarshallJMP

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Re: Bass setting not saving
« Reply #13 on: Time Format »

Don't know why they did a tranny swap.This was only done in the UK as far as i know.Maybe the distributor wasn't happy with the original trannys :dunno:
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rnolan

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Re: Bass setting not saving
« Reply #14 on: Time Format »

Hey Revhed, the guy who used to work on ADA gear for pro audio is no longer around, there's a guy Shamrock Electronics 02 62947080 (33 Altson Cct Condor ACT 2906) who's happy to work on your MP1 as long as he has instructions schematics etc (which we can get).  This guy has a good reputation in the valve hi fi field (done (good) work for a good mate of mine) and is super keen to get his mits into my old 1972 Marshall 50 (loves this stuff apparently).  So you could give him a go.
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