Vox Berkely 2 schematic

[Enzo]

Hey, I need this for a repair. The thing is different enough from the various SS Vox drawings I already have. The amp goes unstable wuth signal, makes audio modulated RF at the output.

ANy help?

[52 Bill]

I have a lot of Thomas Organ VOX schematics, do you know the model number? It will be a V-???? number. If not I'll let you know which Berkeleys I have.

[xFallen]

Hey, I need this for a repair. The thing is different enough from the various SS Vox drawings I already have. The amp goes unstable wuth signal, makes audio modulated RF at the output.

ANy help?

What frequency or band? Maybe you could rebrand it and sell it as an amateur radio transmitter.

Not helpful, I know...seriously though, I am curious to know for my own curisoity how you go about detecting that situation in a guitar amp thta gets plopped on your bench.


Barry

[Enzo]

It is a V1081 s/n 1034600, thanks.

My email is: tmenzo at msn dot com

I don't think there is room on the panel for "Halicrafters."

How does one detect this? The sound is very tinny and weak coming out. WHen amps oscillate they often sound that way. So I was suspicious already. Though not so much here, they also often sound hummier than usual. On the bench, I connect amps to my speaker patch panel, and I have a dedicated scope input for that panel, so I usually connect a scope to the speaker terminals in the process. That way I can look at what is coming out.

RF oscillation is instantly obvious on a scope. Instead of a waving thin line, you see a wide band of light with little modulation peaks along the edges.

In this case the amp is stable sitting there, even with the controls up. But when signal is present, it turns it into muck.

[xFallen]

Cool, thanks. I need to play with my scope a bit more and spend some time looking at my amps with it. I have a function generator I built a ways back and a simple two tone oscillator I built intended for measuring SSB IMD but have never actually used it.


Barry

[52 Bill]

I have sent it to you.

Hope it helps.

[Enzo]

Thanks, looks like what I need.

[R.G.]

It's probably dry electrolytic caps. Whatever you do, don't replace the one or two caps that make it quit oscillating and call it good. Get the owner to go for a full cap job. If that's done, it's good for another few decades. If it's not, the amp will fail soon no matter what you do.

[Enzo]

I'm with you. This is a pretty simple amp anyway, one channel with trem and reverb - not all that many ecaps to strat with.

[aymecor]

I have sent it to you.

Hope it helps.

i found the berkeley 2 schematics diagram and user notice
i have a us version i think with the serial number :1034447 year????
thank's for tour answer

[vintagekiki]

Vox Berkely 2 V1081

http://www.schematicheaven.com/voxam...y_II_v1081.pdf