PL Model 700 Series II with LEDs that just won't work!

[bhuskins]

That looks good. Pin 3 is probably depressed because it is a 1M resistor providing the bias and your meter probably loads it down. Is pin 1 at 7.02V as well?

Yes pin 1 is the same 7.02vdc

Just in case...
pin 4 - 1.1mvdc ground I suspect
pin 5 - 1.00vdc
pin 6 - 1.31vdc
pin 7 - 1.33vdc
pin 8 - 14.2vdc

 

[Gepetto]

Yes pin 1 is the same 7.02vdc

Just in case...
pin 4 - 1.1mvdc ground I suspect
pin 5 - 1.00vdc
pin 6 - 1.31vdc
pin 7 - 1.33vdc
pin 8 - 14.2vdc

So far so good. What does Z301 pin 1 look like if you input a 1Khz sine wave into the input pin of the meter board? I cannot tell which pin that is because my schematic is so bad. I think it goes to R304 as the input. Put a 200mV signal into the input and observe pin 1.

Notice the output and then put a jumper across R320 and notice if the output goes up quite a bit. Pin 1 will be centered around a 7V DC level. If jumpering R320 makes the output go up a lot that tells you the compressor is functioning.

 

[Gepetto]

Yes pin 1 is the same 7.02vdc

Just in case...
pin 4 - 1.1mvdc ground I suspect
pin 5 - 1.00vdc
pin 6 - 1.31vdc
pin 7 - 1.33vdc
pin 8 - 14.2vdc

I should have asked you, do you have one channel not indicating or both channels out?

 

[wattsabundant]

All of the displays issues I've repaired were due to capacitor failures, specifically C304. The same cap is used elsewhere but I've not seen those fail.

C304 is a coupling cap so a failure (open) will result in no response. With an open cap I would expect all DC voltages to check ok.

 

[bhuskins]

I should have asked you, do you have one channel not indicating or both channels out?

Both channels indications are out

 

[laatsch55]

Brent, Joe has a day job. I think might be tonight before he can answer..

 

[laatsch55]

Same with Don...he seems to be the midnight man...

 

[bhuskins]

All of the displays issues I've repaired were due to capacitor failures, specifically C304. The same cap is used elsewhere but I've not seen those fail.

C304 is a coupling cap so a failure (open) will result in no response. With an open cap I would expect all DC voltages to check ok.

The primary LED board with the rectifying diodes has had all electrolytics replaced. The secondary LED has also had C304 replaced...that was the 1st thing I did.

 

[bhuskins]

So far so good. What does Z301 pin 1 look like if you input a 1Khz sine wave into the input pin of the meter board? I cannot tell which pin that is because my schematic is so bad. I think it goes to R304 as the input. Put a 200mV signal into the input and observe pin 1.

Notice the output and then put a jumper across R320 and notice if the output goes up quite a bit. Pin 1 will be centered around a 7V DC level. If jumpering R320 makes the output go up a lot that tells you the compressor is functioning.

The signal input pin is Pin 6 on the board.

So, from my signal generator I set it to 1khz sine wave and adjust the ouput to measure 200 mvdc? By measuring that from the + and - leads of the generator?

Also, I'd assume + goes to pin 6, where should I put the -?

 

[laatsch55]

If you are outputting a sine wave that's AC....200mv 1khz measured with your DMM....

 

[laatsch55]

Other lead to groind...

 

[Gepetto]

Other lead to groind...

As Lee said, to a local ground point

 

[Gepetto]

Both channels indications are out

That is pretty rare I would imagine that both are solid out. Have you tested any of the LEDs in the LED array to ensure you are not chasing your tail with DEDs instead of LEDs?

 

[stuwee]

You're in good hands here bhuskins

I can't help just wanted to say Welcome to the Phoenix Community!!

 

[bhuskins]

So far so good. What does Z301 pin 1 look like if you input a 1Khz sine wave into the input pin of the meter board? I cannot tell which pin that is because my schematic is so bad. I think it goes to R304 as the input. Put a 200mV signal into the input and observe pin 1.

Notice the output and then put a jumper across R320 and notice if the output goes up quite a bit. Pin 1 will be centered around a 7V DC level. If jumpering R320 makes the output go up a lot that tells you the compressor is functioning.

When a 1Khz sine wave is injected into pin 6 of the meter board, pin 1 of Z301 remains at 7.0vdc and I get no reaction from the meter. If I boost the signal up a bit it eventually starts to flash the last 4 LEDs in the array only. When I jumper R320, the same thing occurs. Pin 1 of Z301 remain at 7vdc and the last 4 LEDs flash (no other LEDs react.)

I also pulled all 6 led banks and tested them with a regulated power supply. Sure enough, 2 of the banks are bad..1 of the bad banks came from the board we are testing and it was located in the 1st bank. The 2nd and 3rd bank tested OK. On the board I was testing, I replaced all three sockets with known good LED panels and unfortunately got the same test results when all 3 panels test good.

At minimum, I need 2 LED panels. If there's a reasonable replacement, I'll replace all 6. Any sources?

I still have the issue at hand to deal with as well.

 

[bhuskins]

I stuck in some temp LEDs and it also tested the same (those in the attached pic are blinking/I have R320 jumped)...I have some on the other end too to make sure it didn't change the behavior.9400110200830611212430

Bad UAA170's? All 4 of them??
or Bad RC4558? Both of them??

and of course the bad LED bars

 

[bhuskins]

One other thing...

Let's not forget that this amp was wired for 240v for a long time (likely since new) and ran that way on 120v here in the states. I wonder what damage that could have caused to the light boards?

 

[bhuskins]

I must have had the 2 "bad" LED modules flipped backwards when testing....All 6 modules test good...so, it's not the LEDs for sure.

FYI...the cathode(-) on tha bar graph LED modules is on the label side (labeled FNA12) and the anode(+) on the blank side.

 

[Gepetto]

When a 1Khz sine wave is injected into pin 6 of the meter board, pin 1 of Z301 remains at 7.0vdc and I get no reaction from the meter. If I boost the signal up a bit it eventually starts to flash the last 4 LEDs in the array only. When I jumper R320, the same thing occurs. Pin 1 of Z301 remain at 7vdc and the last 4 LEDs flash (no other LEDs react.)

I also pulled all 6 led banks and tested them with a regulated power supply. Sure enough, 2 of the banks are bad..1 of the bad banks came from the board we are testing and it was located in the 1st bank. The 2nd and 3rd bank tested OK. On the board I was testing, I replaced all three sockets with known good LED panels and unfortunately got the same test results when all 3 panels test good.

At minimum, I need 2 LED panels. If there's a reasonable replacement, I'll replace all 6. Any sources?

I still have the issue at hand to deal with as well.

Did this amp take a lightning strike in its past?

 

[bhuskins]

Did this amp take a lightning strike in its past?

not that I know of...the amp is new to me though