LA500A opto comp leveling amp BUILD THREAD 500/51X

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Taperocket
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Re: LA500A opto comp leveling amp BUILD THREAD 500/51X

Post by Taperocket »

Hi Joe,

Not seeing any voltage across the LEDs. I took it apart today to look for shorts, measured the resistors which were fine, checked the header orientations and everything looked good so I’m at a loss. Pics attached. Thanks,
BB3A1504-0337-4799-8D93-453BB1454A5B.jpeg
2DFA11A2-CA26-415D-BFBD-861C1D05136D.jpeg
F4186741-32E5-496B-93E6-131AD42A9071.jpeg
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Joe Malone
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Re: LA500A opto comp leveling amp BUILD THREAD 500/51X

Post by Joe Malone »

Taperocket wrote:
Thu Sep 09, 2021 11:01 am
Hi Joe,

Not seeing any voltage across the LEDs. I took it apart today to look for shorts, measured the resistors which were fine, checked the header orientations and everything looked good so I’m at a loss. Pics attached. Thanks,

BB3A1504-0337-4799-8D93-453BB1454A5B.jpeg2DFA11A2-CA26-415D-BFBD-861C1D05136D.jpegF4186741-32E5-496B-93E6-131AD42A9071.jpeg
Need to see a photo of the main pcb top and bottom in focus helps.

You are pulling the makeup and threshold pots outwards so they switch on the leds?
Joe :-)
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Taperocket
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Joined: Mon Sep 06, 2021 11:24 am

Re: LA500A opto comp leveling amp BUILD THREAD 500/51X

Post by Taperocket »

Yes. I will have to reopen tomorrow to take some additional pics, sorry about the focus issue on the last few.

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Re: LA500A opto comp leveling amp BUILD THREAD 500/51X

Post by Joe Malone »

Taperocket wrote:
Thu Sep 09, 2021 12:03 pm
Yes. I will have to reopen tomorrow to take some additional pics, sorry about the focus issue on the last few.
The main thing to check if it is back together is that you have +/-15v to 16v on the 2 x 10R at the end of the LA500SC pcb.

Can you calibrate the comp ok? Like does the meter light in VU or GR mode?
Joe :-)
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Taperocket
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Joined: Mon Sep 06, 2021 11:24 am

Re: LA500A opto comp leveling amp BUILD THREAD 500/51X

Post by Taperocket »

Here are the pics of the main PCB that you requested, Joe. My phone camera seems to struggle with focus on the back of the boards - I hope this works.

I ordered a 500 series extension cable to assist with further testing because I can't access the board with my test probes as is. All other functionality seems normal - the unit calibrated fine and meter lights on both GR and VU modes and works as it should as does the compression/makeup gain.
processed-d7efd685-c3fc-41ef-b961-22a541f32c8a_Opqt7d5Z.jpeg
processed-47950647-8c1c-4e53-abde-944b921d0683_NQOgSKEL.jpeg
processed-817d405f-acb8-43d1-bece-0f275a81264f_YQ3aaJ49.jpeg
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Re: LA500A opto comp leveling amp BUILD THREAD 500/51X

Post by Joe Malone »

Taperocket wrote:
Fri Sep 10, 2021 8:18 am
Here are the pics of the main PCB that you requested, Joe. My phone camera seems to struggle with focus on the back of the boards - I hope this works.

I ordered a 500 series extension cable to assist with further testing because I can't access the board with my test probes as is. All other functionality seems normal - the unit calibrated fine and meter lights on both GR and VU modes and works as it should as does the compression/makeup gain.

processed-d7efd685-c3fc-41ef-b961-22a541f32c8a_Opqt7d5Z.jpegprocessed-47950647-8c1c-4e53-abde-944b921d0683_NQOgSKEL.jpegprocessed-817d405f-acb8-43d1-bece-0f275a81264f_YQ3aaJ49.jpeg
Do the 2 LEDs test dead short?
Joe :-)
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Taperocket
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Re: LA500A opto comp leveling amp BUILD THREAD 500/51X

Post by Taperocket »

No, checked for continuity between them and they did not short together.

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Re: LA500A opto comp leveling amp BUILD THREAD 500/51X

Post by Joe Malone »

Taperocket wrote:
Fri Sep 10, 2021 12:31 pm
No, checked for continuity between them and they did not short together.
You are pulling the makeup and threshold pots outwards so they switch on the leds?
Joe :-)
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Taperocket
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Re: LA500A opto comp leveling amp BUILD THREAD 500/51X

Post by Taperocket »

Yes, I regularly keep the threshold pot pulled out for slower attack.

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Re: LA500A opto comp leveling amp BUILD THREAD 500/51X

Post by Joe Malone »

Taperocket wrote:
Sat Sep 11, 2021 4:45 am
Yes, I regularly keep the threshold pot pulled out for slower attack.
If you remove the leds and have the pots pulled what voltage do you see across the led pads?
Joe :-)
JLM Audio
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Taperocket
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Re: LA500A opto comp leveling amp BUILD THREAD 500/51X

Post by Taperocket »

Looks like the issue resolved itself when I pulled the boards last time and reassembled. I'm guessing it's related to the ribbon cables somehow - either a loose connector on one of the headers or an intermittent lead. Either way, both LED'w are lighting now without any changes.🤔

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