Compressor signal thru only when it's bypassed, no signal when compression engaged

[pl]

Hey everyone, I'm trying to make my question simple.

I bought 2 of AML ez2254 diy kit and built them together and parallelly. The result turns out that 1 works perfectly and another 1 only get the signal thru when it bypasses. There's nothing but silence when it switches to engage. No noise, no low/tiny signal, literally nothing at all. I need a troubleshooting 101 in this situation. Much appreciated if I can get some suggestions from you guys. Thank ya'll.

 

[abbey road d enfer]

Troubleshooting 101 says you need to trace signal from input to output.
What do you have to trace signal?
Ideally, you would use a scope. If you don't have a scope, you must trace using an amp and speaker and follow signal along all the stages, from the input stage to the subsequent ones.
Beware that it could result in very loud signals and bangs so you must protect your ears and speakers by first probing then turning the volume up.
Don't use headphones, they may damage your ears irremediably. Don't use an Ampeg SVT or Marshall 3-stack for that task.
How good are you at tracing the signal path from the schematic?

 

[pl]

Troubleshooting 101 says you need to trace signal from input to output.
What do you have to trace signal?
Ideally, you would use a scope. If you don't have a scope, you must trace using an amp and speaker and follow signal along all the stages, from the input stage to the subsequent ones.
Beware that it could result in very loud signals and bangs so you must protect your ears and speakers by first probing then turning the volume up.
Don't use headphones, they may damage your ears irremediably. Don't use an Ampeg SVT or Marshall 3-stack for that task.
How good are you at tracing the signal path from the schematic?

Thank you for helping. My signal flow is computer - interface - compressor - interface - headphone/speakers
I have no idea how to trace the signal by audition since once the compression function engaged, the signal is cut and lost, meter doesn't move either. It looks like the signal is blocking out at input stage when the compression is on.
I'm ABC level for reading a schematic.
Thank you for your patience.

 

[abbey road d enfer]

Thank you for helping. My signal flow is computer - interface - compressor - interface - headphone/speakers
I have no idea how to trace the signal by audition since once the compression function engaged, the signal is cut and lost, meter doesn't move either. It looks like the signal is blocking out at input stage when the compression is on.
I'm ABC level for reading a schematic.
Thank you for your patience.

You need to identify the signal flow from the schematic.
I can hardly accept that "the signal is blocking out at input stage". I believe the input stage is still active even when the compressor is engaged. The signal loss happens later.
Can you post the schematic and lay-out? We may help you finding the relevant test points.

 

[pl]

You need to identify the signal flow from the schematic.
I can hardly accept that "the signal is blocking out at input stage". I believe the input stage is still active even when the compressor is engaged. The signal loss happens later.
Can you post the schematic and lay-out? We may help you finding the relevant test points.

https://www.audiomaintenance.com/downloads/ez2254_colourbook.pdf
Schematic is from page 58

Thank you very much

 

[abbey road d enfer]

Probe the points in red and report.

 

[pl]

Probe the points in red and report.
View attachment 139368

And layout is page 72. Thank you so much!

 

[Tekay]

Did you put in the screws in the three mic/line transforners? If they're too long they might cause a short inside the transformer.
We asked Carnhill to remove the press nuts on the version we are using as the nut it self caused the problem as well.

 

[pl]

Probe the points in red and report.
View attachment 139368

Hi d'enfer, I tested all 29 resistors.
All pnp/npn showed 0.6v-0.7v range.
Tip3055 transistor showed 1.9v and 0.7v.
BCY70 transistor 1.2v and 0.7v.
7824 voltage regulator showed 0.7v.

 

[pl]

Did you put in the screws in the three mic/line transforners? If they're too long they might cause a short inside the transformer.
We asked Carnhill to remove the press nuts on the version we are using as the nut it self caused the problem as well.

Tekay thank you for the clue. They come with screws attached already. I tested all 3pcs and the number is

First 9046

2-4 183.5
3-5 183.8
7-9 62.7
8-10 63.4

Second 9046

2-4 173.5
3-5 173.4
7-9 73.7
8-10 63.9

9045

2-4 25.5 with buzzing
3-5 25.6 with buzzing
7-9 133
8-10 133.6

 

[abbey road d enfer]

Hi d'enfer, I tested all 29 resistors.
All pnp/npn showed 0.6v-0.7v range.
Tip3055 transistor showed 1.9v and 0.7v.
BCY70 transistor 1.2v and 0.7v.
7824 voltage regulator showed 0.7v.

I don't understand what you mean.
Probe in this specific case means listening to signal.

 

[pl]

I don't understand what you mean.
Probe in this specific case means listening to signal.

will do that and report soon

 

[pl]

Probe the points in red and report.
View attachment 139368

Hi denfer, I made a signal tracer and used my computer as the source and speaker is my output. Unfortunately, I only got sound from compressor's input/output ports and 2 relays. There's no any feedback when probe touched resistors, capacitors and triodes. Same thing happened on the properly worked one. Am I mishandling? Thank you for your patience.

 

[abbey road d enfer]

Unfortunately, I only got sound from compressor's input/output ports and 2 relays.

Even those two?

 

[pl]

Both comps are giving the same result. I took this clip to demo it, please correct me if I'm wrong.

 

[Harpo]

...
7824 voltage regulator showed 0.7v.

Something seems to be drawing too much current/shorting out your +24VDC supply rail (schematic pg.71).
Get this fixed if the 0.7VDC measurement on output of the 7824 vreg is still confirmed.

 

[TheseGoToEleven]

Something seems to be drawing too much current/shorting out your +24VDC supply rail (schematic pg.71).
Get this fixed if the 0.7VDC measurement on output of the 7824 vreg is still confirmed.

The 7824 is supposed to be able to supply 1.5 amps @ 24V, which is a lot more than the 630mA fuse should allow. So if there is really not 24V DC at the output of the 7824, it seems like the problem is somewhere in the power supply.

 

[inkster]

How does 1.9V show up at the 2n3055 when the 7824 is only putting out .7V?
Have you verified pinouts against datasheets?

 

[Harpo]

View attachment 139363

Maybe only optical artifact, but the 7824 voltage regulator doesn't look attached tight to the heatsink by the clip (see colourbook pg.37), so this vreg might be in thermal shutdown.