Laney TT50H No Outout

[Enzo]

And please please please stop thinking of the variac as a contest. It isn't intended to be turned up until something smokes. We turn it up while we watch mains current. If we see that rising, BACK OFF.

Clearly your B+ is shorted to the heaters.

[g1]

It seemed there was no problem with anything involved with the heaters until you replaced C37. That is when R52 and the hum balance pot started to burn.
Triple check your work looking for any solder bridges, bent tube socket pins, etc. Also check both sides of all tube sockets for any signs of arcing (carbon).
You might even want to remove C37 and check underneath it. I had a Vox AC15 in where they ran a heater trace under the filter cap. The trace arced to the cap lead, but you couldn't see it til the cap was removed.

This is a double sided circuit board, so there are a lot more hidden areas.

[Jazz P Bass]

" Checking dcv on two(2) of the three(3) pins on him balance pot and it's going up to 328v when at 91v on variac, then the red glow and I shut it down."
Wow.
328 Vdc on the heater circuit!

[ca7922303]

12VDC across that resistor makes approx. 1.5 Watts. Not sure what the resistor rating is, but I doubt it is a 2W. And you are only at 40V so far, so it will go much higher.
The 12VDC should not be there. It should be around 6.5VAC maximum at full line voltage if schematic is correct. Something is still putting DC on the heater line.
Remove tubes one at a time to see if you can make that voltage disappear.

Removed all tubes one at a time, and while doing that, I ran variac up to 91 volts and can see red glow thru hum balance adjustment. This is the small circle I first saw when I thought maybe a capacitor was heating up. Checking dcv on two(2) of the three(3) pins on him balance pot and it's going up to 328v when at 91v on variac, then the red glow and I shut it down. Reinstalled all tubes and tried it again and got same results on hum balance pot, 328v @ 91v on variac, 2 of 3 pins, then red glow in hum adjustment hole. Original hum balance pot melted and now the replacement is also heating up.

[Enzo]

And maake sure nothing on the power tube sockets is leaning over and touching the heater pins.

[g1]

12VDC across that resistor makes approx. 1.5 Watts. Not sure what the resistor rating is, but I doubt it is a 2W. And you are only at 40V so far, so it will go much higher.
The 12VDC should not be there. It should be around 6.5VAC maximum at full line voltage if schematic is correct. Something is still putting DC on the heater line.
Remove tubes one at a time to see if you can make that voltage disappear.

[ca7922303]

You will have to verify whether the smoke is coming from R52, or something else nearby. Measure voltage across R52, check both DC and AC volts. Variac up to 60V, same as when you noticed smoke.

Ran variac up to 40v before smoke occurred, 12vdc/0.03vac. R52 still not burnt and @ 100 ohms

[g1]

You will have to verify whether the smoke is coming from R52, or something else nearby. Measure voltage across R52, check both DC and AC volts. Variac up to 60V, same as when you noticed smoke.

[ca7922303]

I suspect V5 has a heater to cathode short (bad tube).
It is a cathode follower circuit. The schematic has an error showing a resistor R20. There is no resistor, V5 pin1 goes straight to C37. That is what you had found earlier when you repaired the connection between C37 and V5 pin1.

Replace R52. If PS2 is bad it will need to be replaced as well. Bring it up on the variac with all tubes installed except V5. Keep checking that R52 is not overheating.
Remember with power tubes installed you will need the load connected.

Installed ps2, all tubes installed except V5, variac up to 60v, then getting smoke near R52. R52 is not burnt and still reads 100 ohms.

[ca7922303]

I suspect V5 has a heater to cathode short (bad tube).
It is a cathode follower circuit. The schematic has an error showing a resistor R20. There is no resistor, V5 pin1 goes straight to C37. That is what you had found earlier when you repaired the connection between C37 and V5 pin1.

Replace R52. If PS2 is bad it will need to be replaced as well. Bring it up on the variac with all tubes installed except V5. Keep checking that R52 is not overheating.
Remember with power tubes installed you will need the load connected.

Replaced R52, ordered a 1k bias pot from tube depot(3-5 days delivery). Also need a piggyback push button switch (one broke on me). Digikey says CIT doesn't show one now(there is a CIT one on internet previously). Not finding one at mouser either. Maybe someone has a link?

[g1]

I suspect V5 has a heater to cathode short (bad tube).
It is a cathode follower circuit. The schematic has an error showing a resistor R20. There is no resistor, V5 pin1 goes straight to C37. That is what you had found earlier when you repaired the connection between C37 and V5 pin1.

Replace R52. If PS2 is bad it will need to be replaced as well. Bring it up on the variac with all tubes installed except V5. Keep checking that R52 is not overheating.
Remember with power tubes installed you will need the load connected.

[ca7922303]

Yes, if power tubes are removed, it can be run without a load.
Without the power tubes installed the main supply voltage will rise. So check that the big filter caps (C22, C23) are not getting more than their rated voltage. This is the only problem that may arise when testing with power tubes removed. In this case it looks like C22 and C23 are rated for 500V. So as long as the voltage on them doesn't go over 500V you are ok to test with tubes removed.

Photos of component side of board and ps1, ps2, ps3.

[ca7922303]

Yes, if power tubes are removed, it can be run without a load.
Without the power tubes installed the main supply voltage will rise. So check that the big filter caps (C22, C23) are not getting more than their rated voltage. This is the only problem that may arise when testing with power tubes removed. In this case it looks like C22 and C23 are rated for 500V. So as long as the voltage on them doesn't go over 500V you are ok to test with tubes removed.

With power tubes removed and no load, variac on about 60v, power on, got 156vdc @ SCR, then smoke(R52 burnt again).

[g1]

Ok, it m ready to test without power tubes installed. Am I able to power on and test without power tubes and without a load? I should know this but can't find anywhere on internet where both are uninstalled for testing? Thanks.

Yes, if power tubes are removed, it can be run without a load.
Without the power tubes installed the main supply voltage will rise. So check that the big filter caps (C22, C23) are not getting more than their rated voltage. This is the only problem that may arise when testing with power tubes removed. In this case it looks like C22 and C23 are rated for 500V. So as long as the voltage on them doesn't go over 500V you are ok to test with tubes removed.

[ca7922303]

Then replace R52, and I would try it with just the preamp tubes. Do you have other power tubes to try? If someone glued the locator pin in the wrong position that could be the problem. Or are these power tubes the known working power tubes you mentioned at the start?

Ok, it m ready to test without power tubes installed. Am I able to power on and test without power tubes and without a load? I should know this but can't find anywhere on internet where both are uninstalled for testing? Thanks.