Laney TT50H No Outout

[g1]

When the preamp tube heaters are not lit, the tubes don't work. If they don't work they don't draw any current through R43 so the same voltage appears at both ends of it.
In post #155 you had already replaced R43 but the voltage was 442/370 at the two ends of it. The preamp tubes will have been lit at that time.
It's just coincidence that it happened after you replaced R43, once you get the heaters working the voltages will go back to where they should be.

Most likely cause of heater problem is as The Dude stated in post #164.

[ca7922303]

When the preamp tube heaters are not lit, the tubes don't work. If they don't work they don't draw any current through R43 so the same voltage appears at both ends of it.
In post #155 you had already replaced R43 but the voltage was 442/370 at the two ends of it. The preamp tubes will have been lit at that time.
It's just coincidence that it happened after you replaced R43, once you get the heaters working the voltages will go back to where they should be.

Most likely cause of heater problem is as The Dude stated in post #164.

Now w/Variac: R43(431/361vdc)
hum balance pot(11.7/11.7vdc)
R52(0.0/0.0mv)
V1(#1-227-#6-247vdc)-#9-#4/5(6.3vac)
V2(#1-307-#6-191vdc)-#9-#4/5(6.4vac)
V3(#1-361-#6-214vdc)-#9-#4/5(6.3vac)
V4(#1-307-#6-243vdc)-#9-#4/5(6.5vac)
V5(#1-361-#6-199vdc)-#9-#4/5(6.6vac)
V6(#1-233-#6-223vdc)-#9-#4/5(6.9vac)
Problems I found was V5, R43, and C37 solder.

[ca7922303]

When the preamp tube heaters are not lit, the tubes don't work. If they don't work they don't draw any current through R43 so the same voltage appears at both ends of it.
In post #155 you had already replaced R43 but the voltage was 442/370 at the two ends of it. The preamp tubes will have been lit at that time.
It's just coincidence that it happened after you replaced R43, once you get the heaters working the voltages will go back to where they should be.

Most likely cause of heater problem is as The Dude stated in post #164.

Ran sound test, no sound with signal in instrument jack and running to another amp. Still only able to get signal running into return fx jack and line out or record out to other amp or speaker out to speaker.

[g1]

So all the preamp tubes must have their heaters lit now as the voltages look normal.
Are you able to check all 3 channels? It seems you said something before about it being stuck in one channel. If that is the case, the switching problem should be fixed first to find out if the preamp is not working right for just one channel or all of them.

[ca7922303]

So all the preamp tubes must have their heaters lit now as the voltages look normal.
Are you able to check all 3 channels? It seems you said something before about it being stuck in one channel. If that is the case, the switching problem should be fixed first to find out if the preamp is not working right for just one channel or all of them.

At full voltage, only channel three(3) lights up. When turning Variac up from zero(0), channels 1 & 2 light up at about 50v and then go out and channel 3 thens lights up somewhere around 75v maybe. Channel 3 volume works on signal when signal is run into return fx. Channel 1 & 2 volume controls do not work. The signal sent thru return fx works all the way down to about 25 volts then cuts out.

[g1]

When you are using the instrument input (not FX return) you have to turn the FX mix down to zero. Have you tried that?

[ca7922303]

When you are using the instrument input (not FX return) you have to turn the FX mix down to zero. Have you tried that?

Tried fx mix @ zero with amp at full power and has no effect. Turned Variac to 60v and channel 3 light goes out and number 1 & 2 light up. Have signal on channel 1 with fx mix @ zero, channel 2 has a hum which increases as volume and gain controls are turned up. Channel 3, which now light will not come on when pushed is non functional. Only signal I can get at full power, is thru return fx.

[g1]

Channel 3 volume works on signal when signal is run into return fx.

Do you mean one of the 2 volumes near the left end of the amp? Or do you mean Ch.3 master?

[ca7922303]

When you are using the instrument input (not FX return) you have to turn the FX mix down to zero. Have you tried that?

Tried fx mix @ zero with amp at full power and has no effect. Turned Variac to 60v and channel 3 light goes out and number 1 & 2 light up. Have signal on channel 1 with fx mix @ zero, channel 2 has a hum which increases as volume and gain controls are turned up. Channel 3, which now light will not come on when pushed is non functional. Only signal I can get at full power, is thru return fx.

[ca7922303]

Do you mean one of the 2 volumes near the left end of the amp? Or do you mean Ch.3 master?

One of the two volumes near the left end of amp.

[ca7922303]

One of the two volumes near the left end of amp.

The two volumes near left end both work when at full power and plugged into return fx jack. Can switch between the two. Channel 1 at left end works with channel 1 volume on right end of amp at 60v with signal plugged into instrument jack. Channel 3 does not work at all and channel two has a hum which increases with gain and volume controls turned up while at 60v with signal into instrument jack.

[g1]

Turned Variac to 60v and channel 3 light goes out and number 1 & 2 light up. Have signal on channel 1 with fx mix @ zero, channel 2 has a hum which increases as volume and gain controls are turned up. Channel 3, which now light will not come on when pushed is non functional. Only signal I can get at full power, is thru return fx.

Is there any time that the channel select buttons work?
Has this switching problem always been there or did it start up some time during the repair?

[Enzo]

Running the amp at 60v really doesn't tell us anything useful.

[ca7922303]

Is there any time that the channel select buttons work?
Has this switching problem always been there or did it start up some time during the repair?

Got it like this, and no they have never functioned. The only thing I've observed is that depending on what voltage the Variac is set at, will light up the switches but they do not work. I way say that the two volume switches to the left that you asked about has a volume 1/volume 2 switch that does switch between those two at full power. I realize that the half power doesn't tell you anything, but trying to make any observations I can to pass on. Thanks.

[g1]

Ok. I'll default to 120V AC line settings unless otherwise noted. On the midi board the is an IC called U2 that is a 74HCT08. If it is smaller surface mount type you will have to be extremely careful not to short any pins together. Measure DC volts at each pin and post results.