Reddish 500 EQ

[JMan]

Okay, this sounds good (except that I do think you should increase the level of your test tone, you've currently got it set at -13.8dBu). The slight drop in level across the transformer primaries is likely due to the impedance of the transformer itself.

This likely means that our problem is on the secondary side of the transformer, which basically leaves two possibilities that I can think of. The first is that one or both of the secondary connections is not being made, which would be the ideal scenario since that's probably as simple as fixing a solder joint. The second scenario is that the transformer itself is defective, which although unlikely, is possible - it has happened to me with other projects, as well as others on the forum, to be sure.

Let's test scenario A. With your meter set to measure continuity, test the following:

Place one probe on the second-from-left pin of J1 (the right angle connector), and with the other probe,
-first see if there is continuity to T1 Pin 10 on the transformer mounting PCB
-then check if that same pin of J1 has continuity to the Aud GND pin on the edge connector.

Then, test for continuity between the leftmost pin of J1 and the right leg of R0.

Also, you didn't answer the question about whether you made sure to match the transformer pins to the mounting pcb silkscreen. Can you just reassure us on that?

 

[JMan]

This is an aside that is not (I wouldn't imagine) related to the troubleshooting process here, but I did notice in your earlier pictures that J3 - which is one of the connectors between the main pcb and the pushbutton switch board - is mounted the wrong way around, which has in turn created an awkward angle that does not allow the Keystone 621 to be fastened to the main board. It's possible that this is a non-issue as far as basic function, but you might want to consider fixing that at some point. See the first picture on page 13 of the build guide for how that should look (basically it needs to be mounted the same as the other one on that board, J4).

 

[Forcemusicgroup]

Digging into it now

 

[Forcemusicgroup]

Okay, this sounds good (except that I do think you should increase the level of your test tone, you've currently got it set at -13.8dBu). The slight drop in level across the transformer primaries is likely due to the impedance of the transformer itself.

This likely means that our problem is on the secondary side of the transformer, which basically leaves two possibilities that I can think of. The first is that one or both of the secondary connections is not being made, which would be the ideal scenario since that's probably as simple as fixing a solder joint. The second scenario is that the transformer itself is defective, which although unlikely, is possible - it has happened to me with other projects, as well as others on the forum, to be sure.

Let's test scenario A. With your meter set to measure continuity, test the following:

Place one probe on the second-from-left pin of J1 (the right angle connector), and with the other probe,
-first see if there is continuity to T1 Pin 10 on the transformer mounting PCB
-then check if that same pin of J1 has continuity to the Aud GND pin on the edge connector.

Then, test for continuity between the leftmost pin of J1 and the right leg of R0.

Also, you didn't answer the question about whether you made sure to match the transformer pins to the mounting pcb silkscreen. Can you just reassure us on that?

Yes I can confirm that the transformer pins the two rows are at the top and the Labeling of the board is facing outward displaying the numbers of the pins of the transformer "11" being the left corner pin

 

[Forcemusicgroup]

Okay, this sounds good (except that I do think you should increase the level of your test tone, you've currently got it set at -13.8dBu). The slight drop in level across the transformer primaries is likely due to the impedance of the transformer itself.

This likely means that our problem is on the secondary side of the transformer, which basically leaves two possibilities that I can think of. The first is that one or both of the secondary connections is not being made, which would be the ideal scenario since that's probably as simple as fixing a solder joint. The second scenario is that the transformer itself is defective, which although unlikely, is possible - it has happened to me with other projects, as well as others on the forum, to be sure.

Let's test scenario A. With your meter set to measure continuity, test the following:

Place one probe on the second-from-left pin of J1 (the right angle connector), and with the other probe,
-first see if there is continuity to T1 Pin 10 on the transformer mounting PCB
-then check if that same pin of J1 has continuity to the Aud GND pin on the edge connector.

Then, test for continuity between the leftmost pin of J1 and the right leg of R0.

Also, you didn't answer the question about whether you made sure to match the transformer pins to the mounting pcb silkscreen. Can you just reassure us on that?

there is continuity with second from left pin j1 and pin 10 on pcb
there is continuity on j1 and audio GND

there is continuity on j1 to right leg of r0

 

[JMan]

Okay, unfortunately this basically rules out problems on the PCB as far as I can tell. Can you measure the resistance between pins 7 and 10 on the transformer?

 

[Forcemusicgroup]

Okay, unfortunately this basically rules out problems on the PCB as far as I can tell. Can you measure the resistance between pins 7 and 10 on the transformer?

yes 0.771k ohms

 

[JMan]

Okay, and do you measure the same resistance between the two left-most pins of J1?

 

[Forcemusicgroup]

Okay, and do you measure the same resistance between the two left-most pins of J1?

the two most left pins come to a result of 0.771kohms

 

[Forcemusicgroup]

 

[JMan]

Alright, something is not adding up here. Based on the tests we've done, there is absolutely no explanation that I can see for why you would have no signal at R0. I'll give it some thought after I've had my coffee, but in the meantime, can you repeat the tests in post #377?

 

[inf0]

@JMan Not pre-trimming VR1 wouldn't cause any issues to the relay , would it? Just throwing out a thought

 

[JMan]

It shouldn't, but he also said in an earlier post that he was getting 24v across the relay, so either way I don't think that's the issue. With the unit in, he was able to measure signal at the primaries of the input transformer, so we know the relay is working.

With that being the case, and now having thoroughly tested all of the connections on the secondary side as well, it makes zero sense why there wouldn't be signal at R0.

 

[andia]

ask @Forcemusicgroup to measure voltage at R0 of the good unit.

 

[Forcemusicgroup]

one second I'll compare the working to the non working