Welcome back to the Depot! 

Quote from: rnolan on Today at 01:01:00 AMWhilst 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:

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.

Great to have you back   and warm greetings from Australia 

Good morning everyone. Please forgive my absence and delay in replying in this time, but life has a lot of surprises in store. Now I am operational. First of all I want to thank "Sparker" who shared the GFX1 schematic with me about 5 years ago. I am starting to consider it a great device again. I will also reply to those who wrote to me privately. Thanking everyone and apologizing for my English. A big hug from Italy. Rock 'n' roll.

Are your screws tight?

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

Ok, and the screws are tight?

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

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.

Thanks Richard,

  I have an original here I believe. I keep all my ADA manuals together, so I know where to find them.

  Just in case I don't find it, thanks for posting the links to the manuals.

  You know, it's kind of funny, I've had the MB-1 for at least 25 years, but like you, all this time I assumed it operated like the MP-1. Just a preamp with a lot of cool voices. Now, I have to look at it all over again and try out this configuration. With the B500B, and the Basslines HX cabs, this should sound pretty damned good.

   The true test of a good bass amp for me is if it will try to rattle the windows out of their panes around the house.