How to slow down tremolo in Ampeg Reverberocket

[punkykatt]

http://el34world.com/charts/Schematics/files/ampeg/reverb_rocket_12rt.pdf

Hey Guys, Did a complete electrolytic cap job, clean and service, check all resistors for spec, check coupling caps for leaking DC, replaced all caps in the tremolo speed circuit on this Reverberocket 12RT.  The tremolo works great but the customer would like the tremolo to be slower. The 500k speed pot  tests good. I know in the Fender circuits changing the last cap of the .02/.01/.01 sequence to .02/.01/.02 will slow the tremolo down. This circuit has .047/.047/.047 sequence. What do I need to change to slow down the tremolo? Thanks in advance for your time and help. 

Stan

[Willabe]

What do I need to change to slow down the tremolo?

Basically the same thing, increase 1 or more of the cap's in the C/R string in value. The LFO's FB from plate to grid causes the tube to oscillate. The charging of the C's through the R's used create a time constant which set the speed of the LFO. Different amp companies used different values for the R's and C's, if you lessen the C value you need to increase the R value, or vice versa, to keep the same speed. Larger value caps take more time to charge up.

So your amp has .047 caps, try a .1 or try putting a 2nd .047 in parallel with 1 of the .047's already installed. If still not slow enough try adding a 2nd .1 instead of what's there now.

You could also try changing the 500K speed pot to a 1M if you have that and not bigger caps, although the 1M might not slow it down as much as a .1 cap or 2. And it might make adjusting the speed a little touchy.   


                   Brad   

[eleventeen]

Short answer: Fatten up the caps! You know that parallel caps add in value. The easy way is to just tack solder more of them across one or more of the existing caps, til you get the speed where you want it.  Then replace neatly with the values you come up with. Or you can leave in parallel caps, that's no sin. They don't especially have to be the same 3 values.


You say you have .047; if you find adding .02's does the deed, go to .068. That's not especially a "laying around" common value though obviously you can go buy them. If that's not enough, go to .1 ufs.

[punkykatt]

Thanks guys for the great info.

[sluckey]

This may be of some value if your customer is interested in a two speed range tremolo...

http://home.comcast.net/~seluckey/amps/RCA/Ampeg_J12B.pdf