JLM AUDIO

And here are some more photos. Thanks again for your help with this.

OK you have a dead solder short on either the LA500 pcb or the LA500SC pcb. Unplug the LA500SC pcb ribbon cable from the LA500 PCB and retest to see if +15v is back at pin 12 or not. If +15v is back then the short is on the LA500SC pcb. If you still have no power on pin 12 then the short is on the ...

OK you have a dead solder short on either the LA500 pcb or the LA500SC pcb. Unplug the LA500SC pcb ribbon cable from the LA500 PCB and retest to see if +15v is back at pin 12 or not. If +15v is back then the short is on the LA500SC pcb. If you still have no power on pin 12 then the short is on the ...

OK you have a dead solder short on either the LA500 pcb or the LA500SC pcb. Unplug the LA500SC pcb ribbon cable from the LA500 PCB and retest to see if +15v is back at pin 12 or not. If +15v is back then the short is on the LA500SC pcb. If you still have no power on pin 12 then the short is on the ...

just to clarify further to my last post: I measure -14.9V on pin 4 and -1V on the pin 8 of the OPA2604AP on the LAA500SC. Same on the main PCB.

Damir

Ok pin 14 should be -16v and pin 12 should be +16v. They cannot swap. So check you had you black lead on pin 13 all the time you were testing. But looks like you are missing the +16v rail form the rack power supply. So remove everything from your 500 rack and check at the edge connector inside the ...

OK that is the problem. Check voltages using pin 13 as 0v for black meter lead and let me know what voltages you have at pin 12 & pin 14 at the LA500 back edge connector PIn 12 ? Pin 14 ? If they have +16v and -16v then do below check and let me know results Then check OPA2604AP on the LA500 main P...

3.Check you have +16v at pin 8 of the OPA2604AP measured from 0v? Not the case here. The voltage measured is 0V 4.Check you have -16v at pin 4 of the OPA2604AP measured from 0v? Not the case here. The voltage measured is ~44mV. NOTE: I have included the photos of what I understood is the pin 13 of ...

Hi Joe, let me try this again. I was moving house, so my last post was on Dec 15. The LA500A is not working after I put it together. Audio goes straight through, without being affected. Light on the meter comes on when the power gets turned on. Does the meter pin to the right in both VU and GR? => ...

and some more:

And here is some more photos:

More photos and answer all questions below. I need a photo of the underside of the LA500SC PCB and top and bottom of the POT PCB. Always best to send a fully built photo first. Sounds like the bypass circuit is not working. Which is only the VU/GR switch 1k8 resistor and relay but this travels on t...

Plugging a opamp in backwards and powering up will usually kill the opamp or burn one or both the 10R resistors in the same PCB as it. Check the 2 x 10R carbon resistors still measure 10R each and change the OPA2604AP for a new one should have you going. Does the meter light up when switching to VU ...

Hi all, I recently purchased a LA500A opto comp kit. I managed to finish it a couple of days ago. I tried calibrating the unit, but am having some issues with it. When I plug it in the meter goes all the way to the right (+4). I checked that the voltage on the output is 1.23 V. Had to do some adjus...

Hi all, I recently purchased a LA500A opto comp kit. I managed to finish it a couple of days ago. I tried calibrating the unit, but am having some issues with it. When I plug it in the meter goes all the way to the right (+4). I checked that the voltage on the output is 1.23 V. Had to do some adjust...