Laney TT50H No Outout

[ca7922303]

So the short you had earlier measured between pin13 and14 is gone now. That is good. There must have been a solder bridge between those 2 pins.
Look very carefully (with magnifier) at the solder of the ribbon cable connector and the footswitch connector. See if there are any more solder bridges anywhere.

With magnifier, don't see any solder bridges at ribbon cable connector or footswitch.

[ca7922303]

So the short you had earlier measured between pin13 and14 is gone now. That is good. There must have been a solder bridge between those 2 pins.
Look very carefully (with magnifier) at the solder of the ribbon cable connector and the footswitch connector. See if there are any more solder bridges anywhere.

U6 pin#3 pad to ground is still (87 ohms). Is that the number were looking for or something else?

[g1]

U6 pin#3 pad to ground is still (87 ohms). Is that the number were looking for or something else?

Yes that is the number we are chasing down. If you haven't cleaned up around the U6 area yet, do that, on both sides of the board. Check the 87 ohm reading again. Any time that reading changes, stop and report the result.

There is one other socketed chip there (U1), but it is the most critical part of the amp and replacement is likely not available (custom programmed part). It is the most static sensitive of all. So ground yourself, remove it, and check the 87ohm reading. Carefully re-install the chip immediately and post the result.

[ca7922303]

Yes that is the number we are chasing down. If you haven't cleaned up around the U6 area yet, do that, on both sides of the board. Check the 87 ohm reading again. Any time that reading changes, stop and report the result.

There is one other socketed chip there (U1), but it is the most critical part of the amp and replacement is likely not available (custom programmed part). It is the most static sensitive of all. So ground yourself, remove it, and check the 87ohm reading. Carefully re-install the chip immediately and post the result.

With U1 removed, U6 pin#3 pad to ground(2.93k ohms). With U1 reinstalled, U6 pin #3 pad to ground(87 ohms).

[ca7922303]

Yes that is the number we are chasing down. If you haven't cleaned up around the U6 area yet, do that, on both sides of the board. Check the 87 ohm reading again. Any time that reading changes, stop and report the result.

There is one other socketed chip there (U1), but it is the most critical part of the amp and replacement is likely not available (custom programmed part). It is the most static sensitive of all. So ground yourself, remove it, and check the 87ohm reading. Carefully re-install the chip immediately and post the result.

Called mouser about R13. They are asking if it is thick film, thin film, size, and tolerance. Any ideas on that? Resistor is labeled 103 and schematic shows 10ksm. Thanks.

[g1]

U1 is toast and the amp may be a basket case without it. Suggest you check with Laney whether it's available before proceeding with any other work on this amp.

[Enzo]

10k resistor. Color code is brown-black-orange. That code reads 1-0-3. The schematic calls for "103" meaning the same thing. In other words 1-0-000. sm means surface mount.

[ca7922303]

U1 is toast and the amp may be a basket case without it. Suggest you check with Laney whether it's available before proceeding with any other work on this amp.

I appreciate all the help on this and other things. I emailed Laney, then googled it and mouser has 224 in stock for $3.60 so I'll be ordering one. You had mentioned earlier about maybe it had some programing fro. Laney involved? Also, I know I need R13 and U2, do you think I need U6, U4, U5? Thanks

[g1]

You need a new U6 also. The resistor you were asking about would be thick film, under a dollar each, check dimensions to the spacing between the pads lines up with the new one.
The U1 parts from mouser are just blanks, you need a programmed one from Laney. That's why it has a sticker on it with version number. I think U4 and U5 should be ok.

[ca7922303]

You need a new U6 also. The resistor you were asking about would be thick film, under a dollar each, check dimensions to the spacing between the pads lines up with the new one.
The U1 parts from mouser are just blanks, you need a programmed one from Laney. That's why it has a sticker on it with version number. I think U4 and U5 should be ok.

Good news, Laney got back quick. Here is the email.

We still have some programmed IC's in stock. Are you sure the PIC has failed? We never saw any fail during the time we built them. Have you checked all the voltages and supplies on the board. Are all the looms connected and working OK. Does any of the switching work?

Kind regards

Peter Smith


UK Service Support

Laney Amplification


Showed this so that I give the correct answers. I've seen some parts depts(ampeg, mesa come to mind), that will refuse to sell parts to inexperienced responses to their questions, so not knowing how Laney is, want to get it right. Mouser has the other components in stock.

[g1]

Good news, Laney got back quick. Here is the email.

We still have some programmed IC's in stock. Are you sure the PIC has failed?

Tell them you measure 68 ohms to ground at the 5V regulator (U6) output and that the 86 ohm reading goes to around 3K when you remove the PIC from it's socket.

[ca7922303]

Tell them you measure 68 ohms to ground at the 5V regulator (U6) output and that the 86 ohm reading goes to around 3K when you remove the PIC from it's socket.

Appreciate that, do you think we can go ahead and fix the HT issue while I'm waiting to get parts from UK(Laney) and mouser to finish midi board? I have T500mAL fuses.

[g1]

Yes you can proceed the the HT issues. See post #240.
I'm really not sure what happened there, whether there will be some fault that wants to blow the fuse again. It seems this happened about the same time as the switching stopped functioning at all? But you never noticed anything?
If I had to take a wild guess I would have thought the midi board fell onto or touched the main board while running.

[ca7922303]

Yes you can proceed the the HT issues. See post #240.
I'm really not sure what happened there, whether there will be some fault that wants to blow the fuse again. It seems this happened about the same time as the switching stopped functioning at all? But you never noticed anything?
If I had to take a wild guess I would have thought the midi board fell onto or touched the main board while running.

Seems like a good guess

[ca7922303]

Yeah, I know that and it can be dealt with later. The HT fuse is blown and it looks like one of the wires that connects to HT spade lug is probably burnt at it's connector. So that lug will need to be resoldered and the connector on the wire may need replacing.

Also see a switch that has been de-soldered in post #232. Which switch is that? Why is it de-soldered?

All traces and wires from HT and FUSE on board read (0.0 ohms) resistance. So I'm assuming that wires back to HT fuse and traces on board are good. Spade lugs under board to pins on top of board also read (0.0 ohms).