LA500A opto comp leveling amp BUILD THREAD 500/51X

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

Postby nenett » Thu Feb 25, 2016 2:07 pm

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 rack that you have +16v at pin 12 and -16v at pin 14 when measured from pin 13 PWR GND 0v. See attachment.

Empty rack power supply test.
black lead pin 13.
Red lead to
pin 12 = ?
pin 14 = ?


Hi Joe, I tested the edge connector again (several times). I get 0V on pin 12 and -16V on pin 14.

When I tested the rack power supply by itself I get +16V on pin 12 and -16V on pin 14

Damir

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

Postby nenett » Fri Feb 26, 2016 5:55 pm

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

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

Postby Joe Malone » Fri Feb 26, 2016 7:03 pm

nenett wrote: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 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 LA500 pcb.

Let me know what you find.

You should be able to measure a low ohm between pin 12 & pin 13 of the edge connector with the module unplugged
Joe :-)
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nenett
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Re: LA500A opto comp leveling amp BUILD THREAD 500/51X

Postby nenett » Mon Feb 29, 2016 12:10 pm

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 LA500 pcb.

Let me know what you find.

You should be able to measure a low ohm between pin 12 & pin 13 of the edge connector with the module unplugged


When I disconnect the ribbon cable I measure -6.7V on the pin 12 of the edge connector. Pin 14 is still measuring -15.7V.

The resistance between the pin 12 and pin 13 when the module is unplugged seems to be going up and down (?). It seems to be going down and stops at 44.3 kilo ohms, then
starts rising again. On another occasion I start measuring 17 kilo ohms, and it starts rising straight away. not sure what that means.

Damir

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

Postby Joe Malone » Mon Feb 29, 2016 1:18 pm

nenett wrote:
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 LA500 pcb.

Let me know what you find.

You should be able to measure a low ohm between pin 12 & pin 13 of the edge connector with the module unplugged


When I disconnect the ribbon cable I measure -6.7V on the pin 12 of the edge connector. Pin 14 is still measuring -15.7V.

The resistance between the pin 12 and pin 13 when the module is unplugged seems to be going up and down (?). It seems to be going down and stops at 44.3 kilo ohms, then
starts rising again. On another occasion I start measuring 17 kilo ohms, and it starts rising straight away. not sure what that means.

Damir


OK unplug OPA2604AP & JLM99v and see if power rail goes back to +15v ?
Joe :-)

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

Postby nenett » Mon Feb 29, 2016 9:09 pm

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 LA500 pcb.

Let me know what you find.

You should be able to measure a low ohm between pin 12 & pin 13 of the edge connector with the module unplugged


When I disconnect the ribbon cable I measure -6.7V on the pin 12 of the edge connector. Pin 14 is still measuring -15.7V.

The resistance between the pin 12 and pin 13 when the module is unplugged seems to be going up and down (?). It seems to be going down and stops at 44.3 kilo ohms, then
starts rising again. On another occasion I start measuring 17 kilo ohms, and it starts rising straight away. not sure what that means.

Damir


OK unplug OPA2604AP & JLM99v and see if power rail goes back to +15v ?



When I unplug OPA2604AP & JLM99v the voltage on pin 12 goes to 0V

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

Postby Joe Malone » Tue Mar 01, 2016 9:59 am

nenett wrote:
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 LA500 pcb.

Let me know what you find.

You should be able to measure a low ohm between pin 12 & pin 13 of the edge connector with the module unplugged


When I disconnect the ribbon cable I measure -6.7V on the pin 12 of the edge connector. Pin 14 is still measuring -15.7V.

The resistance between the pin 12 and pin 13 when the module is unplugged seems to be going up and down (?). It seems to be going down and stops at 44.3 kilo ohms, then
starts rising again. On another occasion I start measuring 17 kilo ohms, and it starts rising straight away. not sure what that means.

Damir


OK unplug OPA2604AP & JLM99v and see if power rail goes back to +15v ?



When I unplug OPA2604AP & JLM99v the voltage on pin 12 goes to 0V


Do you have any other working 500 module available to try in the 500 rack and see if the +15v stays there under load?

As either there is a solder short on the LA500 PCB. So clean the bottom of the PCB with isocol and an old toothbrush and send me a very clear large in focus photo of the bottom of the PCB to check over again.
Or the 500 rack power supply is faulty.
Joe :-)

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

Postby stuartpre » Fri Mar 04, 2016 10:05 am

Hi Joe, I built the kit a few months back, it worked fine, nice...then....

Then i put it away and when I next used it, i noticed the GR vu setting had dropped off, dead needle. So i turned it off and on again and it worked as normal.

Fast forward a month I go to use the unit and again no reading on GR meter setting. It passes audio fine, but as far as I can tell does not compress.

So I check the calibrations. I adjust VU, ( there is a minor issue with that too the inputs on my Focusrite scarlette distort, so I set the levels for no distortion and try to adjust the vu meter for a nominal oVU setting, but the meter pot runs out at -5db vu)

Back to the main issue: I check the GR pot, I go full rotation until clicking sound in both directions, the needle stays limp and lifeless on the -20db line.

What should I do next?

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

Postby Joe Malone » Mon Mar 07, 2016 12:12 pm

stuartpre wrote:Hi Joe, I built the kit a few months back, it worked fine, nice...then....

Then i put it away and when I next used it, i noticed the GR vu setting had dropped off, dead needle. So i turned it off and on again and it worked as normal.

Fast forward a month I go to use the unit and again no reading on GR meter setting. It passes audio fine, but as far as I can tell does not compress.

So I check the calibrations. I adjust VU, ( there is a minor issue with that too the inputs on my Focusrite scarlette distort, so I set the levels for no distortion and try to adjust the vu meter for a nominal oVU setting, but the meter pot runs out at -5db vu)

Back to the main issue: I check the GR pot, I go full rotation until clicking sound in both directions, the needle stays limp and lifeless on the -20db line.

What should I do next?


HI Stuart sounds like a missed solder joint to me. I would pull out each PCB and clean the bottom of each with alcohol like isocol and a old toothbrush and check all solder joints. If you are still not sure send to my email clear well lit in focus and cleaned PCB top and bottom photos so I can check it for you.
Joe :-)

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

Postby stuartpre » Fri Mar 11, 2016 4:38 pm

Ok, i pulled it apart, cleaned it and re-soldered all pads. Now it works 8)

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

Postby Joe Malone » Fri Mar 11, 2016 5:11 pm

stuartpre wrote:Ok, i pulled it apart, cleaned it and re-soldered all pads. Now it works 8)


HI Stuart Cool great to hear :-)
Joe :-)

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Joeflyer59
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Cable orientation?

Postby Joeflyer59 » Sun Mar 13, 2016 4:24 pm

Hello!

Pardon the newbie and perhaps OCD question - but I'm hoping someone can clear this up for me? I've a question about ribbon connector orientation -

Specifically, I'm at the place where I'm connecting the transformer. The instructions call out specifically the cable without the lock, however, I've noticed that my cable connectors are not oriented the same as in the instruction guide. Normally, I wouldn't let this type of detail bug me, as I can work with the cable placement - however I can't help but notice that because of one of my connector ends is oriented different, it causes the cable to totally flip flop (notice the red side of the cable on mine versus the one on the instructions in my attached pic).

cable.jpg

I don't know if it makes a difference (I would assume it does), and being a bit of a rookie - I don't know wether this a mistake on the cable sent to me, or if the change is intentional and just not updated in the instructions yet - or if it just doesn't even matter. I just don't want to proceed and take the chance on frying something. Any help is appreciated!! :)

Thanks!

Joey
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Re: Cable orientation?

Postby Joe Malone » Mon Mar 14, 2016 9:41 am

Joeflyer59 wrote:Hello!

Pardon the newbie and perhaps OCD question - but I'm hoping someone can clear this up for me? I've a question about ribbon connector orientation -

Specifically, I'm at the place where I'm connecting the transformer. The instructions call out specifically the cable without the lock, however, I've noticed that my cable connectors are not oriented the same as in the instruction guide. Normally, I wouldn't let this type of detail bug me, as I can work with the cable placement - however I can't help but notice that because of one of my connector ends is oriented different, it causes the cable to totally flip flop (notice the red side of the cable on mine versus the one on the instructions in my attached pic).

cable.jpg

I don't know if it makes a difference (I would assume it does), and being a bit of a rookie - I don't know wether this a mistake on the cable sent to me, or if the change is intentional and just not updated in the instructions yet - or if it just doesn't even matter. I just don't want to proceed and take the chance on frying something. Any help is appreciated!! :)

Thanks!

Joey


HI Joey Yes that cable has the transformer plug on backwards compared to the build thread. But due to the symmetrical layout of the transformer pinout it makes no difference. So will work exactly as designed but you will need to fold the cable down around the side of the transformer like the instructions so it doesn't get caught on the next 500 module.
Joe :-)

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Joeflyer59
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Re: LA500A opto comp leveling amp BUILD THREAD 500/51X

Postby Joeflyer59 » Mon Mar 14, 2016 11:11 pm

Thank you!!

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

Postby nenett » Tue Mar 29, 2016 3:35 pm

Joe Malone wrote:
nenett wrote:
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 LA500 pcb.

Let me know what you find.

You should be able to measure a low ohm between pin 12 & pin 13 of the edge connector with the module unplugged


When I disconnect the ribbon cable I measure -6.7V on the pin 12 of the edge connector. Pin 14 is still measuring -15.7V.

The resistance between the pin 12 and pin 13 when the module is unplugged seems to be going up and down (?). It seems to be going down and stops at 44.3 kilo ohms, then
starts rising again. On another occasion I start measuring 17 kilo ohms, and it starts rising straight away. not sure what that means.

Damir


OK unplug OPA2604AP & JLM99v and see if power rail goes back to +15v ?



When I unplug OPA2604AP & JLM99v the voltage on pin 12 goes to 0V


Do you have any other working 500 module available to try in the 500 rack and see if the +15v stays there under load?

As either there is a solder short on the LA500 PCB. So clean the bottom of the PCB with isocol and an old toothbrush and send me a very clear large in focus photo of the bottom of the PCB to check over again.
Or the 500 rack power supply is faulty.


Hi Joe. I cleaned the bottom of the PCB with isocol as advised. Here are a few photos of it from different angles. Unfortunately I don't have any other modules to test the 500 rack. I couldn't find anyone I know that has a 500 rack or modules to help me out with this. I'm a bit stuck here.
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