Cheap DIY 200 Vibrato Speed Mod

[velo-hobo]

Thought I would share a mod I made to my 200 after overhauling the amp.

R32 is the main resistor which sets the vibrato rate.  Normally the value is selected at the factory to set the rate around 5.75Hz.  Mine had an 18k resistor, at the low end of the range on the schematic.

I played around with some parts and found that for my amp, a 15k 1/2w resistor in series with a 25k linear taper pot worked pretty well as a rate control.  The adjustment range is not huge but definitely usable and musical.

One has to be careful selecting component values as the oscillator will stop working if there is too little or too much resistance at R32.

There was a little bit of thump at the slow end of the rate knob, which pretty much disappeared when I got around to replacing the three .12uF caps with new ones.  Tweaking the value of C39 a little might help solve this problem too.

After I was satisfied with my component arrangement, I soldered in two leads to where R32 was on the board, custom-made a bracket for the rate pot, and installed a 3-knob faceplate from Ken Rich Sounds, normally sold with their custom 200 amp and vibrato unit.  They were able to sell me the faceplate for the same price as a 2-knob version.  I had an extra 200-style knob laying around, so it looks very seamless.  Will try to put up photos of this at some point.

Also, R32 could also be replaced with a trimmer or internal pot, if you don't want to mod your case but still want to be able to control the vibrato rate, say for a specific recording, etc.

The whole mod cost less than $50, and most of that was for the new faceplate.  The speed range available is not as impressive as the Warneck VariVib or Vintage Vibe's new custom amp, but for the low cost and ease of installation, I think it is pretty good.

[Abraham]

thank you for posting your findings, some recordings or even video would be REALLY appreciated. This would be definitely useful for showing out whether this 'non impressive' rate tweaking is worth the job -and money- (which btw Im sure it does!)