Swr workingman 15 combo

[Eggman]

Does anyone know if Q8 on main PCb is the muting transistor that stops the output? All v+ appear correct..

[Enzo]

2SC4382 in the power amp? No, that is not a mute.

Q1,Q2 form a power up mute circuit. That is a legitimate function, but otherwise there is no one transistor that makes the amp silent.

[g1]

Also, welcome to the board and kind regards to The Walrus.

[Jazz P Bass]

I like the location: From: New Jersey- unfortunately.

[J M Fahey]

Welcome and suggest posting schematic together with question.

The mighty Enzo answers such questions without need to check, unlike us mere mortals

[glebert]

Are Q5 and Q8 mounted on the heatsink on this? On SWR amps, especially combos it seems, there are known problems of broken transistor legs, but I can't remember if the driver transistors are mounted on the heatsink.

[Eggman]

I will check b+ on Q1+2. 5+8 are on heat sink. Signal is good at preamp out but is not controlled by master volume. Injecting signal at power amp in or center of master doesn’t pass. It is attenuated at the 10k resistor off of the wiper of master.

[Eggman]

I believe I have a bad Q13-2n5457 j-get but need to get one

[g1]

Schematic:
(maybe not exact revision but should be close)

[Eggman]

That’s the one I am using. Thanks

[Jazz P Bass]

If you think Q13 limiter jfet is the cause, you can remove it to see if that brings the signal back.

[Eggman]

I removed it but still no output.

[Jazz P Bass]

Stupid question: do you have signal at the Headphone jack?

[J M Fahey]

Q1-Q2 MUTE the amp by fully cutting OFF current to Q5-Q6-Q7 so check what voltage do you have at the R23+R25 junction.

On a working amp, I expect almost full +V there (50-55 Volts?)
On a muted one, some/much less.
Actual value is undefined (for me) because it "floats" and unpredictable leakage currents rule, but it will definitely be more than, say, 2 or 3 V DC away (lower) than +V

Measure it, also what do you measure as +V at the main filter cap C1.

[Eggman]

No signal at udon jack or feed to it. I do have signal thru all IC’s to #7.