Laney TT50H No Outout

[Jazz P Bass]

G1 gets the "all saints award" for mulling through this fiasco of a repair.,

[ca7922303]

The sleeve (neg.) terminals of the speaker jacks are all connected together going to circuit ground which also connects to chassis ground. Then there is that black wire which also goes directly to chassis from the sleeve terminals of the spkr. jacks. I guess the connection is duplicated to prevent burning of the narrow trace on the board that goes from those jacks to ground.
The black chassis wire got moved from the sleeve terminal to the tip terminal of the 4 & 8 ohm jacks. That shorts them out so they can barely work. The tip and sleeve of those jacks are now both going to ground, so the only reason you can hear anything is the tiny resistance of the traces themselves.
The 16 ohm jacks would still sort of function because the 4 or 8 ohm tap would serve as ground for it, and it's tip did not get grounded with the others..
With barely any output, you would have had to really crank the level. That much signal along with the oscillation is probably what caused the arc over at the preamp tube socket.

Thanks again for everything, your the best!

[Helmholtz]

The 16 ohm jacks would still sort of function because the 4 or 8 ohm tap would serve as ground for it, and it's tip did not get grounded with the others..

The 16 Ohm output shouldn't work either, as shorting one (part of a) transformer winding essentially shorts all other windings including the primary.

[g1]

The 16 Ohm output shouldn't work either, as shorting one (part of a) transformer winding essentially shorts all other windings including the primary.

I think we have seen on several occasions where the practical results do not match up perfectly with the theory. A shorted turn or winding will not necessarily kill the output 100%. In this case the output was very weak and distorted, but the 16 ohm output was louder. That's why I said the 16 ohm output 'sort of' worked. I should have said it gave more output.
Sometimes we have reports of weak output from OT's (or PT's) that fail the neon bulb test due to shorted turns. They still have some output.
Definitely something that could use some actual data under test conditions, if anyone were to feel inclined.

[Helmholtz]

I think we have seen on several occasions where the practical results do not match up perfectly with the theory. A shorted turn or winding will not necessarily kill the output 100%. In this case the output was very weak and distorted, but the 16 ohm output was louder. That's why I said the 16 ohm output 'sort of' worked. I should have said it gave more output.

It will depend on the effective shorting resistance which is composed of the winding DCR + external wiring DCR.
Assuming a shorting DCR of say 0.2R at the 4 Ohm winding, the 16 Ohm output will appear loaded by 0.8R parallel to the speaker.
Consequently output power could be up to 5% of nominal.
But as the tubes will see a very low Raa, which allows for only little voltage swing, output power should be much less than 5%.
Nevertheless a few hundred mWs of output power seem possible.