No vibrato on silver face vibrochamp

ian field

Joined Oct 27, 2012
6,536
Pin 1: .68v
Pin 2: .88v
Pin3: 0v
Pin4: 0
Pin5 : 0
(Those two are connected)
Pin 6: 369
Pin7: .7
Pin 8: 9
Pin 9: 0

That 170v reading must've been a fluke

Could that 470k resistor be at fault
The schematic is a bit smudgy - can you repost with pin function annotated?

The cathode voltage on the cathode follower stage should be a few volts higher than the grid - the data sheet should tell you how many.
 

Thread Starter

Skylar Coy

Joined Apr 29, 2017
133
Well guys, the intensity knob is now acting as a master volume. I replaced the 10uf cap, all resistors in the vibrato circuit. And caps. What do I do next. Do I check for wiring issues?
 

Thread Starter

Skylar Coy

Joined Apr 29, 2017
133
The voltages need re-measuring with the duff 470k replaced.
The schematic is a bit smudgy - can you repost with pin function annotated?

The cathode voltage on the cathode follower stage should be a few volts higher than the grid - the data sheet should tell you how many.
Updated voltages.
1: 352
2: 16mv
3: 3.4
4: 378Mv
5: joined with 4
6: 350
7: 227
8:227

Pin 1 is super high so is pin 7
 
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Thread Starter

Skylar Coy

Joined Apr 29, 2017
133
Could really use the help. I checked all resistors and all are within 10%. What could be causing the vibrato to act like a Master volume. I feel like it has something to do with the high plate voltage.

Maybe a rectifier tube issue. When I turn on the intensity it takes down the volume but also makes it sound like crap.
 
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ian field

Joined Oct 27, 2012
6,536
Well guys, the intensity knob is now acting as a master volume. I replaced the 10uf cap, all resistors in the vibrato circuit. And caps. What do I do next. Do I check for wiring issues?
The vibrato cathode follower adds a varying current to the cathode resistors of one amplification stage. this varies the amp stage cathode voltage relative to the grid and so varies the gain.

I'd hazard a guess that the oscillator might not be oscillating.
 
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