Hoffman Amplifiers Tube Amplifier Forum

Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: chuggy on October 12, 2013, 04:01:20 pm

Title: Reverberocket 2 volume falls when trem turned up
Post by: chuggy on October 12, 2013, 04:01:20 pm

The volume of a vintage Reverberocket 2 GS12 R decreases a lot when the trem intensity is turned up and also the trem is weak.  I have replaced the .047 mfd caps and 25 mfd cathode cap.  Would a bad trem module do this?  Any other thoughts on the cause?
Thanks
Jim

Title: Re: Reverberocket 2 volume falls when trem turned up
Post by: terminalgs on October 12, 2013, 08:20:51 pm

Quote from: chuggy on October 12, 2013, 04:01:20 pm

The volume of a vintage Reverberocket 2 GS12 R decreases a lot when the trem intensity is turned up and also the trem is weak.  I have replaced the .047 mfd caps and 25 mfd cathode cap.  Would a bad trem module do this?  Any other thoughts on the cause?

my bet is on the optocoupler unit.  The LDR is strapped across the 4M intensity pot,  if the unit isn't functioning properly (be it the bulb or the LDR) the pot is really just a variable resistor that is the top half of voltage divider,  at the full 4M switch its a big divider (attenuator).

If the bulb is getting a weak oscillator voltage, it'll only emit enough light to lightly trigger the LDR, so its possible there isn't enough voltage to light the bulb. 

But it seems unlikely. Any difference if you turn the the intensity knob all the way and click the intensity accent switch?

Does it do this when the trem is both switched ON and OFF at the footswitch?

which .047 and 25 are referring to?

Title: Re: Reverberocket 2 volume falls when trem turned up
Post by: chuggy on October 13, 2013, 11:58:58 am

.047 and 25 mfd are values for some caps in the trem circuit.  Schem link is below courtesy of Hoffman amps.

http://www.el34world.com/charts/Schematics/files/ampeg/Ampeg_GS12R.pdf (http://www.el34world.com/charts/Schematics/files/ampeg/Ampeg_GS12R.pdf)

Thanks
Jim

Title: Re: Reverberocket 2 volume falls when trem turned up
Post by: terminalgs on October 14, 2013, 12:09:14 pm

Quote from: chuggy on October 13, 2013, 11:58:58 am

.047 and 25 mfd are values for some caps in the trem circuit.  Schem link is below courtesy of Hoffman amps.

So your oscillator should be working.  If you have a scope, you can check for the AC oscillator signal (If not, with a analog volt meter).   Otherwise, you'll need to pop for a new trem unit.   The fender trem unit works too, if you have one handy.