Laney TT50H No Outout

[g1]

That's all good now and ready to test. I don't know your level of experience as far as amp usage, so I will say that 'presence' control is not as obvious as other tone controls. It just puts some sparkle or brightness into the upper midrange frequencies. Probably most noticeable with overdriven tones which are rich in harmonics.

If presence works backwards, or there is loud squeal right when you turn it on, you will need to swap the green and blue wires at the lugs marked 'grids'.

[ca7922303]

That's all good now and ready to test. I don't know your level of experience as far as amp usage, so I will say that 'presence' control is not as obvious as other tone controls. It just puts some sparkle or brightness into the upper midrange frequencies. Probably most noticeable with overdriven tones which are rich in harmonics.

If presence works backwards, or there is loud squeal right when you turn it on, you will need to swap the green and blue wires at the lugs marked 'grids'.

No presence or damping function. Low distorted output, oscillation only on channel 3 when boost or xpand is engaged.
Swapped grid wires, oscillation on channel 2 & channel 3 but if either boost or xpand are engaged , oscillation stops, but low distorted output seems the same

[g1]

Measure DC volts at both sides of R34, and both sides of R44.

[g1]

No presence or damping function. Low distorted output,

This pic is from post # 466 a couple days ago. Where does the black wire at the top of the picture go?

[ca7922303]

This pic is from post # 466 a couple days ago. Where does the black wire at the top of the picture go?

Chassis ground and back to board(photo)

[ca7922303]

Measure DC volts at both sides of R34, and both sides of R44.

R34(12.9v/-0.2mv)
R44(12.9v/41v)

[ca7922303]

R34(12.9v/-0.2mv)
R44(12.9v/41v)

Anything to test on xpand/boost switch? It was replaced with PIC. Maybe remove it and retest?

[g1]

Chassis ground and back to board(photo)

Ok, we are almost there now. Take a pic of where the 16 ohm jack black wire meets the board.

[ca7922303]

Ok, we are almost there now. Take a pic of where the 16 ohm jack black wire meets the board.

16 ohm jack black wire to board.

[g1]

16 ohm jack black wire to board.

Ok. Someone moved the black wire going to chassis. From the very first pics on pg.3 from a year ago, it was already in the wrong place. Whether it was like that when you got it, or you moved it there, it was the fatal mistake.

Move the black wire to the yellow arrow point in the picture below.
With nothing connected to output jacks, put your black probe to that black wire and measure resistance to point marked R. Then measure from black wire to point marked 4. The difference will only be a fraction of an ohm, maybe .1 or .2 difference. Repeat several times until you are sure one is consistently higher than the other, post result.

[ca7922303]

Ok. Someone moved the black wire going to chassis. From the very first pics on pg.3 from a year ago, it was already in the wrong place. Whether it was like that when you got it, or you moved it there, it was the fatal mistake.

Move the black wire to the yellow arrow point in the picture below.
With nothing connected to output jacks, put your black probe to that black wire and measure resistance to point marked R. Then measure from black wire to point marked 4. The difference will only be a fraction of an ohm, maybe .1 or .2 difference. Repeat several times until you are sure one is consistently higher than the other, post result.

Moved black wire to yellow arrow R(0.6 ohms)
4(0.4 ohms)

[g1]

Moved black wire to yellow arrow R(0.6 ohms)
4(0.4 ohms)

That means the red and brown wires to the 4 and 8 ohm lugs are in the right place, so you won't have to flip the board again.
Of the green and blue wires going to the lugs marked 'grids', judging by the oldest pictures, the green one should be on the grid lug closest to the lug marked 'GND'.
If it's not that way, swap the green and blue around.

Test it out but be careful because it will probably be 100 times louder than it was before.
If presence works backwards, swap the green and blue at the 'grid' lugs around.

[ca7922303]

That means the red and brown wires to the 4 and 8 ohm lugs are in the right place, so you won't have to flip the board again.
Of the green and blue wires going to the lugs marked 'grids', judging by the oldest pictures, the green one should be on the grid lug closest to the lug marked 'GND'.
If it's not that way, swap the green and blue around.

Test it out but be careful because it will probably be 100 times louder than it was before.
If presence works backwards, swap the green and blue at the 'grid' lugs around.

Your a genius! No ocillation at any point, output is normal on all channels. Really appreciate it. Apologize for wrong wires soldered, etc., etc. Can you summarize what you recall about the how and why it got completed? Thanks again.

[nosaj]

Your a genius! No ocillation at any point, output is normal on all channels. Really appreciate it. Apologize for wrong wires soldered, etc., etc. Can you summarize what you recall about the how and why it got completed? Thanks again.

I know you can't be asking him to give you what to put on the service ticket are you?
nosaj

[g1]

Can you summarize what you recall about the how and why it got completed? Thanks again.

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.