Laney TT50H No Outout

[ca7922303]

No, those wires from the OT secondary could not cause a 'no power' fault.
Did you measure the main fuse with your meter?
Some of those fuse holders that are in the AC cord socket are reversible. One way is for 120VAC, the other way is for 240VAC, any chance it's that type and the holder is in upside down?
Have the wires on the AC cord socket ever been removed?

Measured fuse(good), I have not ever had to remove AC cord socket wires. Don't think it's the reversible type but will double check this evening when off work. I don't see anything I've pulled loose from the board being removed. I've had to resolder midi board to main power board a few times in the past. P40 something once, but they're all good right now and have never had a no power issue before. Anymore tests I could run to find where the power is stopping at? Thanks

[g1]

I guess it does not have a 'power' light? So we are just looking for heaters or the channel lights to be lit when power turned on?
Look at pg.4 of schematic, the one that says 'for 115V operation'. Coming out of the power switch should be a brown and blue that go to the power transformer. Check that you measure 120VAC there when switch is on.

[ca7922303]

That's correct, no power light. We I'll check brown and blue wires from power transformer this evening. Thanks.

[ca7922303]

Put all boards back in, have 123vac@brown wire, .085vac@blue wire from main power switch/on/off /standby switch. Now have heater voltage around 6vac. R43(447/374vdc), but no channel switching lights, no output.

[g1]

Check DC volts at all 3 pins of U1 and U2 regulators.

[ca7922303]

Check DC volts at all 3 pins of U1 and U2 regulators.

U1(5/0/8vdc), U2 is a 14 pin, which pins to check for DC volts?

[g1]

There must be more than one U2. I think you are on the midi board.
These are probably on the main board. The U1 and U2 I mean are 3 pin regulators. One is a 7815 and one is a 7915.

[ca7922303]

There must be more than one U2. I think you are on the midi board.
These are probably on the main board. The U1 and U2 I mean are 3 pin regulators. One is a 7815 and one is a 7915.

U1(23v/-.7mv/15vdc)
U2(-.8mv/-24v/-15vdc)
For no good reason channel switching lights came on, but will not switch channels and now no heaters. Didn't touch a thing from last readings except mains and standby on/off.

[Enzo]

Oh, I can't resist...

400

[Jazz P Bass]

Send me the amp!!!

[ca7922303]

There must be more than one U2. I think you are on the midi board.
These are probably on the main board. The U1 and U2 I mean are 3 pin regulators. One is a 7815 and one is a 7915.

U1/U2 look good? On top of board(pin side, l took readings in order from right to left. Wondering why the positions aren't lining up with the numbers.

[g1]

U1/U2 look good? On top of board(pin side, l took readings in order from right to left. Wondering why the positions aren't lining up with the numbers.

The readings are good. The positive regulators have a different pinout than the negative type, that's why the order is different.
Are the heaters still up? You have an intermittent problem with heaters for V1 thru V5. Did you resolder V6 socket? That's where the feed comes from. Resolder V6 socket on component side of board.
The channel lights must also be intermittent if they are sometimes on and sometimes off.

[ca7922303]

The readings are good. The positive regulators have a different pinout than the negative type, that's why the order is different.
Are the heaters still up? You have an intermittent problem with heaters for V1 thru V5. Did you resolder V6 socket? That's where the feed comes from. Resolder V6 socket on component side of board.
The channel lights must also be intermittent if they are sometimes on and sometimes off.

No heaters and channel 3, master volume lights up, but no switching. Have soldered V6. Anything I can take readings on midi board? That was the situation with channel switching before all the work that was done on midi board. Thanks.

[g1]

I guess for the channel switching go back and read through what we checked for that same issue last time around. I'm trying to help, but I don't really have the time to go through the same thing over again?
For the heaters, measure AC volts between pin4 of V5 and pin4 of V6 (one probe to each). Then do same for AC volts between pin9 of V5 and pin9 of V6. If the connections are good, there should be zero volts between. If you find voltage between, there is a break in the connection between the 2 tubes. Follow the trace and look for cracks or burns.

[ca7922303]

I guess for the channel switching go back and read through what we checked for that same issue last time around. I'm trying to help, but I don't really have the time to go through the same thing over again?
For the heaters, measure AC volts between pin4 of V5 and pin4 of V6 (one probe to each). Then do same for AC volts between pin9 of V5 and pin9 of V6. If the connections are good, there should be zero volts between. If you find voltage between, there is a break in the connection between the 2 tubes. Follow the trace and look for cracks or burns.

Pin #9s V5-V6(0.0vac)
Pin #4s V5-V6(7.0vac)

I've taken this board out so many times I wonder if I've caused problems along the way, so I'm trying to not take it out again if possible but I see no traces on pin side of board connected #4 pins to V5 & V6.;Looking at schematic, I can't tell if it's possible to do anything without removing board. Any idea from schematic.