DOA Brown Deluxe

[MacGwyn]

Have a Brown Deluxe clone that was working perfectly for hours - but was recently dead at power-up.
Speaker and connections are fine, fuse is fine, pilot light is on... normal voltages on all plates, filaments and the bias, but there is no sound at all... no hum, no hiss, no signal output.   I've swapped out all tubes and have run out of ideas on "what to check next".   Bet someone has an idea!  I'm thinking output transformer, but don't know how to check that.

[Paul1453]

I'm thinking your signal is shorted to Ground somewhere.

Input and or Output jacks could have shorted to ground maybe.   

If all your voltages are good, your OT's primary winding must be good.
The OT's primary winding is more likely to fail than the secondary.
I'd guess your OT is still good if your voltages are good.   

[Platefire]

Speaker leads connected?

Maybe try another speaker!

Standby on?

Check Ground connections

[Paul1453]

Speaker leads connected?

Maybe try another speaker!

Standby on?

Check Ground connections

More good KISS suggestions by Platefire.

[MacGwyn]

Speaker leads connected?

Maybe try another speaker!

Standby on?

Check Ground connections

Tried several speakers... and there is no standby switch on this amp.  Ground connections could be the problem... planning to trace audio through the amp next for clues.   By the way, both channels and all inputs are completely dead.  I'm thinking the problem must be past the preamp stage.

[tubenit]

When you checked the voltages on the plate/s of the phase invertor,  .............. did the speaker make any noise at all? 

IF so, then the problem may be in the preamp section or input jacks.

with respect, Tubenit

[HotBluePlates]

... recently dead at power-up. ... normal voltages on all plates, filaments and the bias, but there is no sound at all...

Check voltages in this pattern:
- Output tube plate, then output tube grid.
- Phase inverter plate then phase inverter grid.
- Next earlier preamp tube plate, then grid for that stage.

With the amp on, as you check the voltages at each of these points, there tends to be a click or pop at the moment you probe with the meter. Even without an actual signal generator/signal tracing (in which you typically work from the input jack forward to find where the signal stops), you can get an idea of a passing of signal working from the output backwards. Typically, as you work backwards the pops get louder due to greater amplification of the momentary voltage disturbance from probing.

[mresistor]

If it has a shorting jack on the speaker output, could it be shorting even with the speaker plugged into it? IOW malfunctioning?

[MacGwyn]

If it has a shorting jack on the speaker output, could it be shorting even with the speaker plugged into it? IOW malfunctioning?

Checked that... the ground switch is well clear when the plug is inserted.

[MacGwyn]

... recently dead at power-up. ... normal voltages on all plates, filaments and the bias, but there is no sound at all...

Check voltages in this pattern:
- Output tube plate, then output tube grid.
- Phase inverter plate then phase inverter grid.
- Next earlier preamp tube plate, then grid for that stage.

With the amp on, as you check the voltages at each of these points, there tends to be a click or pop at the moment you probe with the meter. Even without an actual signal generator/signal tracing (in which you typically work from the input jack forward to find where the signal stops), you can get an idea of a passing of signal working from the output backwards. Typically, as you work backwards the pops get louder due to greater amplification of the momentary voltage disturbance from probing.

That test points to V2, second stage pre and vibrato.  Plate voltage on the vibrato side jumps around in the 170 to 200+ range and the grid is silent (no pops).  On the other side of the same 12 AX7, I get 194v on the plate (with a pop) and on the grid, little if any volts and a loud hum.  On V1, I get pops on both plates... no sound on the grids.  PI and power tubes seem normal to me.

[MacGwyn]

GOT IT!   A broken ground wire to the V1 bias cap/resistor.  That's where the hum at V2 was coming from... and where the music died.  Thanks everyone for your excellent input... this is such a great service to the hobby!

[HotBluePlates]

Good job!

You probably already realized the tremolo side of V2 is not directly in the signal path, so probing the plate/grid didn't result in the pop you got from the rest of the audio path.