Laney TT50H No Outout

[ca7922303]

Should read U2 pin#5 is(5.6mv)

[ca7922303]

Is channel 2 button stuck down? It must release.
Look at pg.11 of schematic. Pin5 of U2 goes to R3. Check that R3 is 10K. Check that R3 is getting it's 5V at one end.
If R3 is ok and getting 5V, then pin5 of U2 should be 5V except when ch.2 button is being pressed. If it's not stuck down it could be a bad switch, or something in that line from the switch to U2 pin5 could be getting shorted to ground.

Checking trace from U2 pin 5 to R3, one end is (0.0 ohms), the other end is (0.5k ohms). Also U2 pin 5 to ribbon cable pin connected to R3 is (0.0 ohms). I have some 10k surface mount resistors than Laney sent when I ordered the PIC and the xpand/boost piggyback switch or is R3 reading 0.5k ohms because it's in circuit? Thanks.

[g1]

is R3 reading 0.5k ohms because it's in circuit? Thanks.

It might be. Unplug the ribbon cable and check again. Check with one probe at each end of resistor.

[ca7922303]

It might be. Unplug the ribbon cable and check again. Check with one probe at each end of resistor.

With ribbon cable unplugged and one probe on each end of R3(0.5k ohms).

[g1]

What resistance readings do R2 and R4 give?
Wasn't one of those replaced before, which one?

If R2 and R4 give 10K readings, then de-solder U2 pin5 and recheck R3 resistance.

[ca7922303]

What resistance readings do R2 and R4 give?
Wasn't one of those replaced before, which one?

If R2 and R4 give 10K readings, then de-solder U2 pin5 and recheck R3 resistance.

R2/R4(10k ohms). Will desolder R3 this evening when off work. Thanks.

[ca7922303]

R2/R4(10k ohms). Will desolder R3 this evening when off work. Thanks.

Meant to write desolder U2 pin 5.

[ca7922303]

What resistance readings do R2 and R4 give?
Wasn't one of those replaced before, which one?

If R2 and R4 give 10K readings, then de-solder U2 pin5 and recheck R3 resistance.

R13 I believe without looking(at work now) was the only surface mount resistor that was replaced.

[g1]

Back around New Years I had said a couple times that U2 needed to be replaced. You had the old one removed, did you replace it with a new part?

[ca7922303]

Yes, U2 was replaced.

[g1]

Such small chips are easy to overheat when replacing. If the R3 reading goes to 10K when pin5 of U2 is lifted, you will need to replace it again.

[ca7922303]

Such small chips are easy to overheat when replacing. If the R3 reading goes to 10K when pin5 of U2 is lifted, you will need to replace it again.

Lifted U2 pin 5, R3 now(10k ohms). I'll order at least two(2) this time. Thanks.

[ca7922303]

Lifted U2 pin 5, R3 now(10k ohms). I'll order at least two(2) this time. Thanks.

Also, channel was working, can overheating cause it to go bad over a short period of time like this one did?

[g1]

Yes it's possible. Aside from overheating, it could have been damaged by the ribbon cable going to the wrong socket at other end, or if something funny happened at the footswitch connector.

[ca7922303]

Yes it's possible. Aside from overheating, it could have been damaged by the ribbon cable going to the wrong socket at other end, or if something funny happened at the footswitch connector.

Previous U2 I ordered from mouser(74hct08) is out of stock until 9/22. Can you tell if this one will work in its place? Thanks. 74HCT08D-Q100,118 Datasheet (PDF)