Silvertone 1432 No Tremolo

[misterc57]

Need help figuring out why I have no tremolo. I started with all original caps but I can see the tremolo circuit had been worked on in the past. All other functions work great and amp is dead quiet at idle.

I have replaced some resistors and all tremolo caps. Good connections from top control panel to lower amp chassis

Replaced a bad 6AU6. Have 226 V at the plate and 120 V at pin 6.

Schematic attached.

Thank you! MarkO

[g1]

Are you using the footswitch? If not, has the footswitch jack wiring been changed (shorting type jack)?
You replaced the 7 caps and checked all the resistors in the circuit?

[misterc57]

Are you using the footswitch? If not, has the footswitch jack wiring been changed (shorting type jack)?
You replaced the 7 caps and checked all the resistors in the circuit?

I have a footswitch I tried with and without the switch. Checked all resistors and changed the two 330K. Replaced 4 caps C8, C9, C10, C11.

[Jon Snell]

Change R16.

[misterc57]

Change R16.

R16 measured good at 2.2M

[g1]

Replaced 4 caps C8, C9, C10, C11.

C5, C6, C7 should also be replaced.

[misterc57]

I have replaced all but C6 (have to see what I can find in this value).

Still not working. If I compare the schematic to the wiring, things look different at C6 and the R16 2.2M resistor. In the wiring they are connected, in the schematic they are not, however the wiring on this amp matches another 1432 I have.

Any other thoughts as I look for a .00068 cap?

Is there anything that can be shutting off the trem circuit. The foot switch jack is a normal jack and probably original, I have tried with and without a one button 1/4 switch.

Thank you

[g1]

things look different at C6 and the R16 2.2M resistor. In the wiring they are connected, in the schematic they are not,

The schematic shows one end of each connects to ground, so it does show them connected.

Do you have a way to verify the replacement tube is good?

[misterc57]

I may have found the problem. I think the 6AU6 tube is never turning ON.

I suspect the tube socket, heater pin 3 is missing its metal connector and I suspect someone modified it with a section of metal. I do have 6.4 VAC at pins 3 and 4 on both sides of the tube socket.

I tried moving the tube around but the tube never appears to heat up.

[misterc57]

Argh. After some tweaking I can see the tube filament is lit now but I still have no tremolo. The same tube is working in another 1432 amp.

What else can I check?

Thank you

[misterc57]

New info. The 6AU6 plate is only reading about 1.5 V with the tube inserted, if I remove the tube I have about 230 V at pin 5.

The 68K plate resistor is okay.

[Helmholtz]

What is the voltage drop across the plate resistor R13?
What are your PS node voltages?

[misterc57]

What is the voltage drop across the plate resistor R13?
What are your PS node voltages?

243 V drop across R13, leaving about 1 V at pin 5.

264 V at C13
245 V at C12B
215 V at C12A

[misterc57]

C6 is still original

[Helmholtz]

243 V drop across R13, leaving about 1 V at pin 5.

264 V at C13
245 V at C12B
215 V at C12A

So, if R13 is good, something is causing a short across the tube.
Something must have changed since your first post.