Digitech Twin Tube GFX-1 Power supply making noise

[Dante]

Like a buzzing noise....doesn't sound good

Print on the top of the thing says Shogyo 26-0038-D

Looks like something Digitech used for a few pieces of rack gear. Not sure what to do about that noise tho....ideas anyone?

Here's a vid (sorry about my dad talking in the background)

[rnolan]

Hey Dante, wow, that doesn't sound healthy :-( sounds like some sort of oscillation ?

[MarshallJMP]

Does the unit work?

On the secondary side, are the wires connected to a connector or directly on the pcb?

[Dante]

It appears that everything works with regards to buttons, and the midi is changing patches correctly. However, I get no noise out of the unit....not preamp noise. I do get a very faint oscillation sound on a few patches, I assume that's some effect on in that patch that is just not working

I guess I could keep it for parts, in case I run into another one for cheap

[Dante]

I don't know which side is the secondary, but it looks like all the wires go to 2 clips that attach to the PCB

[MarshallJMP]

If you disconnect the the clip from the transformer that hums, does the humming go away? To be sure disconnect both and just turn it on and see if the hum goes away.

[Harley Hexxe]

Dante,

The Primary side is where the power comes into the transformer which I believe is the side in the 1st pic.

The secondary should be the clips that go to the PC board. To confirm, follow the traces and see if they lead to the tubes. There will be some circuitry along the way, so just be careful not to touch anything that leads to the larger radial caps, as there could be some serious voltage stored there.

[Dante]

I unplugged both clips, turned the unit on, and it still makes the noise. No change

[MarshallJMP]

Ok, and the screws are tight?

[Dante]

Are your screws tight?

Yes, they're all very snug - in fact, the innards of this unit look pretty clean overall

[rnolan]

Hey Dante, I'm not sure if this helps in anyway, but my Digitech IPS33 Smart Shift buzzes/hums which vibrates through the top lid.  It kind of goes away (as in you can't hear it any more) when the lids is taken off.

Whilst this is a different sound to what you posted, seems it could be transformer buzz/vibration??

IIRC the transformer is isolated from the chassis with rubber washers? or am I imagining things...  and I suspect why MJMP asked a bout your screws.

[Dante]

Whilst this is a different sound to what you posted, seems it could be transformer buzz/vibration??

Yeah, that's what it sound like to me too....something vibrating in there. 

I saw a YouTube vid of a guy with a small transformer making a similar noise. He desoldered everything and gave it a "lacquer bath" which somehow fixed it. Here it is:

[Dante]

UPDATE: I landed another unit that was listed as 'parts' for $50....dude said it makes all the right noises, but he can't edit any patches because the display is a jumbled mess. He said he suspected he was getting the factory presets as he was scrolling thru patches, but couldn't be sure

I have a unit that doesn't work, with a sparkling good display.....so, I grabbed that one and took a chance.

I figured the display would utilize a ribbon cable, which would be easy to swap out....nope. It has 16 metal pins soldered to the display board. Rather than unsolder all that, I just clipped the pins. Starting with my busted unit, I clipped them, then the ones in the 'parts' unit. Soldered all 16 pins together (much quicker than puttin all that in the PCB) and it WORKS!!!

Holy sh**, the damn preamp works fine. Just had a display problem. Now, I have a parts unit too, so yay (funny thing, both units have the exact same Groove Tubes in them)

I set up 5 patches....I was able to set up all the patches fine, rename them, and recall them no problem at all. It's good to go (fingers crossed) Then, I put it in a rack full of stuff I don't use....it's a rack full of backup units (except the power amp, I keep switch those out).

How's it sound? It's not bad at all, sounds like a tube preamp. I will admit, there is not much variance in 'gain' tones, but the EQ makes up for that. You can get a nice 'Mesa' V-shaped EQ out of it, which works great. It can get mushy, but the Compressor is nice for tightening that up too. It's a solid backup of a backup of a backup and it's just fun to have several preamps in a rack

[rnolan]

Hey Dante, cool .  You also could have just done a transformer swap .

Maybe try some other tubes in it (hey IIRC you have a bunch). I'm not a fan of groove tubes (rebadged whatever) albeit they work nicely in my Carvin TS100 power amp, very transparent which I like in a power amp. But in a preamp, it's nice to have some character. E.g, I changed out the original ADA tubes in my NOS MP-2 with Mullard Long plates, it just brought it alive (for me).

[Dante]

Hey Dante, cool .  You also could have just done a transformer swap .

Maybe try some other tubes in it (hey IIRC you have a bunch). I'm not a fan of groove tubes (rebadged whatever) albeit they work nicely in my Carvin TS100 power amp, very transparent which I like in a power amp. But in a preamp, it's nice to have some character. E.g, I changed out the original ADA tubes in my NOS MP-2 with Mullard Long plates, it just brought it alive (for me).

If I could find a transformer, I'd have done that....those are not common

I'm gonna try more tubes later, I'm focused on getting my modeler up to snuff without a preamp...and I'm very close, but still find the actual tube preamp sounds a bit better