ampage
Tube Amps / Music Electronics
For current discussions, please visit Music Electronics Forum. New: view Recent Searches.
New: visit Schematic Hell!
The sunn still shines online!

 
Listen to great tunes streaming live right now!

ampage archive

Vintage threads from the first ten years

Search for:  Mode:  
previous: Benjamin Fargen I have two early 60's Fender Showma... -- 10/16/1999 12:42 AM View Thread

Re: Fender Showman vibrato intensity........I need some tips.

10/16/1999 5:31 PM
Dave Stork
email
Re: Fender Showman vibrato intensity........I need some tips.
You tacked-in new caps in the phase shift network, but did you take the old ones out of the circuit first?  
 
In my experience, problems with the tremolo oscillator are caused by bad caps in the phase shift network 90% of the time. Other times, it can be a bad cathode bypass cap, cathode or plate resistors that have drifted high, or a bad tube.  
 
The LDR does go bad sometimes. I suggest you disconnect it from the circuit and connect an analog ohmmeter across it. Set the trem oscillator for the lowest speed. You should see the resistance of the LDR swing over an appreciable range. If not, suspect a bad LDR.  
 
The neon bulb can go bad, too; but when that happens, the symptom is a total loss of tremolo. When the bulb goes bad, I cut open the assembly, replace the bulb and put it back together with a fresh piece of shrink tubing. Cases where both the bulb and the LDR have gone bad are rare, so it shouldn't be necessary to replace the whole assembly. If you do, it's cheap to make your own.  
 
Be sure to check the intensity and speed pots as well, and the ground connections on same and on the LDR.  
 
Good luck.  
 
Dave