Laney TT50H No Outout

[ca7922303]

Has the boost switch been installed or not?

No haven't installed boost/xpand piggyback switch yet.

[ca7922303]

Has the boost switch been installed or not?

Installed boost/xpand switch, installed midi board on back of chassis, now no output at any location and 311vdc@hum balance pot?

[g1]

Double check your work around the switch. Something you did has stopped Ch.1 from working. Also check for arcing around where you did that repair under the socket. That is what was putting the DC on the hum balance pot before.

[ca7922303]

Switch looks ok, before I pull the main board again, took readings of V5-#1(369v)#2(213v)#3(214v)#4(314v)#5(312v)#6(210v)#7(0mv)# 8(1.2v)#9(313v). Can you tell from these readings that there a problem under socket? Thanks.

[g1]

No, can't really tell from those readings.

[ca7922303]

No, can't really tell from those readings.

Was able to see V5 socket by pulling tube and measured start of copper wire than I ran to pin#5. Getting 0.0 ohms resistance and not able to see any door or burn marks from arching?

[g1]

Measure resistance from that wire to pin #1.

[ca7922303]

Measure resistance from that wire to pin #1.

134k ohms

[g1]

Did R52 or the hum balance pot burn again? If there was really 300+V across them, something would burn.
If they are all okay I suspect you have lost a ground somewhere. One end of R52 should be grounded, and that end should measure zero ohms to the grounds on the other circuit boards.

[ca7922303]

Did R52 or the hum balance pot burn again? If there was really 300+V across them, something would burn.
If they are all okay I suspect you have lost a ground somewhere. One end of R52 should be grounded, and that end should measure zero ohms to the grounds on the other circuit boards.

Hum balance pot has not melted like previous one and haven't seen it glow thru adjustment hole in board. R52 reads 98.3 ohms and reads 0.0 ohms on one end to various ground points. I noticed when looking at hum balance pot underneath board that bottom side of INPUT P1 has disconnected. Could this be causing issue? Will have to remove main power board to resolder.

[g1]

You have the amp, we do not. You can see what INPUT P1 is, but we only have the schematic. If you can locate it on the schematic and tell us what area it is in, that is very helpful. Or post pictures.
If it's related to the input jack, that is probably why you have no sound using instrument input jack (all 3 channels).

[ca7922303]

You have the amp, we do not. You can see what INPUT P1 is, but we only have the schematic. If you can locate it on the schematic and tell us what area it is in, that is very helpful. Or post pictures.
If it's related to the input jack, that is probably why you have no sound using instrument input jack (all 3 channels).

It's right next to hum balance, V1, R6, it goes to main preamp board plugs into component side, in front of input jack. I haven't taken out main power board since channel one was working. Not sure how that wire came loose, but wondering if it could cause the 310v on hum balance pot along with channel one working and two and three not working?

[g1]

I thought all channels were now not working, even Ch.1
If so, yes this wire being off (if coming from input jack) would mean the input jack would not work.

[ca7922303]

I thought all channels were now not working, even Ch.1
If so, yes this wire being off (if coming from input jack) would mean the input jack would not work.

I am extremely grateful for all the help. Reconnected P1 and now have output from all three channels. Really appreciate it. Not to damper the situation, have 313vdc@hum balance pot(same voltage reading at V1-V6 at pins 9 & 5/4) and slight hum on channel two at all volumes. Thanks.

[g1]

Measure DC volts directly across R52 (one probe at each end of resistor).