Laney TT50H No Outout

[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]

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]

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]

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.

[ca7922303]

Should read U2 pin#5 is(5.6mv)

[ca7922303]

Channel 2 is not stuck, R3 is (0.5k ohms)and is getting (5v) at one end. Pin Uncategorized Groups of U2 is (5.6mv) lit up and (1.3mv) when pushed in.

[g1]

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.

[ca7922303]

Channel 3 will light up when pushed, but goes back to channel 2 when released. Flexed board and prided U2 pins, no change. Noticed that all pins on U2, with the exception of 5,6,7 are 5 volts. 5,6,7 are millivolts.

Channel 3 does also have output when pushing button in, but cuts out when released and goes back to channel 2 lighting up and has output.

[ca7922303]

So something in the process of looking at those connections and checking that voltage made the master vol. switching and the Ch.2 light work.
Some kind of intermittent connection. Flex the midi board and prod the connectors to see if you can make the lights go on and off.

Channel 3 will light up when pushed, but goes back to channel 2 when released. Flexed board and prided U2 pins, no change. Noticed that all pins on U2, with the exception of 5,6,7 are 5 volts. 5,6,7 are millivolts.

[g1]

So something in the process of looking at those connections and checking that voltage made the master vol. switching and the Ch.2 light work.
Some kind of intermittent connection. Flex the midi board and prod the connectors to see if you can make the lights go on and off.

[ca7922303]

So in post #412 you have 5V coming out of the 7805 regulator, is solder good at that pin on both sides of board?
The 5V should get to U2 pin14, is it there? If not, follow the trace back to the 7805 regulator and find why it is not getting the connection.

U2 pin #14(5V). Solder is good on both sides of 7805 regulator. Now when I power on, channel 2 lights up only, can switch between both master volumes and have output(channel 2 only).

[g1]

So in post #412 you have 5V coming out of the 7805 regulator, is solder good at that pin on both sides of board?
The 5V should get to U2 pin14, is it there? If not, follow the trace back to the 7805 regulator and find why it is not getting the connection.

[ca7922303]

U2 was replaced, solder connections on it and ribbon cable socket look good. U2 pin #2(0.8vdc), pressing channel one(1)(0.3mvdc).

[g1]

I think U2 on midi board was replaced? Have a look with a magnifier at all the solder connections. Also look at solder on ribbon cable connector and make sure the cable plugs are well seated at both ends.
If nothing obvious, measure DC volts at U2 pin2 and again while pressing ch.1 switch.

[ca7922303]

With only ch.3 running, are you able to switch between the 2 master volumes?
First thing to check on the midi board is whether the 7805 regulator (U6) is putting out it's 5VDC.

Unable to switch between master volumes and U6 reads(8/0/5vdc). Thanks