Acoustic B600H Repair

[hesamadman]

I am trying to repair my Acoustic b600H. It turns on but no sound. I have inspected all boards, top and bottom. It is very clean still. No obvious signs. On the power amp board there is a relay that seems to not be reading continuity. There is an identical relay on the power supply board and it is reading continuity fine. Im not 100% certain that this is the problem but I am assuming it may be. The problem is, I cant find it anywhere. I was hoping someone could help me locate a replacement. It is a JQX-105F-2


http://www.alldatasheet.com/datasheet-pdf/pdf/143538/ETC1/JQX-105F-2.html

[shooter]

but I am assuming it may be

a schematic would help, but, what does the *suspect* relay switch?, mute?.  Can you just *force* (tack a wire, cut a trace) the contacts to *normal* position as a test and see if you're looking down the correct rabbit hole?

[hesamadman]

Here is the schematic.


http://el34world.com/charts/Schematics/files/acoustic/Acoustic_Schematics.htm


I removed the relay and just connected a wire to bypass it. Im just getting a hum now that I did that. So now im wondering if there is something else wrong in addition. Everything powers up fine. There is an identical relay on the power supply. I cant think of any other way to bypass the relay other than how I did it but maybe you can give me some suggestions.

[shooter]

Everything powers up fine

meaning you have + & - 75vdc? + &- 15vdc, +24 etc?
do you have a scope or listening amp, sig gen and ALOT of patience
I downloaded the pdf, i'll try and print it out and mark it up because there is no, j2 goes to page 5 section e4! kinda info.   

IF all the volts test good, and I would do that both at the PS section and pick random points in the schematic to verify they *got where there're going*, then it's time to stick a sig in and see where it goes. 
quick things you can do , verify the mute turns on and off the LED, jack a signal source into the RET jack and see if you get something besides hummmm.

[shooter]

Sooo, I printed out the schematics, It appears the *problem* relay is controlled by a *blackbox* Ic, IC1 on the PA board, (A 4-5).  one qualifier is the temperature section (A 3-4). Another qualifier seems to be an unlabeled line coming from J1-1 (A1-2).  Power out (Pout) might also be a qualifier.

Now my brain hurts, so it's green beer time

[hesamadman]

im slacking on this 


Just now getting around to it again and I have checked preamp. Good to go. Checked FX loop. Good to go. That leaves power supply and power amp. Unfortunately I dont have a scope yet. Are you suspecting these IC's as possible causes? How would i check those?

[shooter]

Are you suspecting these IC's as possible causes? How would i check those?

what I'm *seeing* is the line labeled RELAY, pin 6, IC1, should be low to pull in the relay and send the PA out to spkr.   It *becomes low* based on *qualifying inputs* to IC1.  So if pin 1 is HI, the relay doesn't activate.

you can probe pins 1 - 8 of IC1 to see how many inputs are *wrong*, like 2,4,7,8 probably should be HI.  7&8 appear to detect 24vdc present.  pin 2 wants to see POUT high from the PA section.  Based on the shemo pin 4 wants a HI.  the TEMP line I'm still mulling over, it appears to also cycle the fan based on temp.

These are ALL *protection* monitoring for the amp, so you have to figure out if the protection circuit is protecting, or causing, the problem.

[hesamadman]

What sheet are you seeing IC1? I cant seem to find what youre referencing.

[hesamadman]

i see it. a very long connector.

[shooter]

i see it

is it *labeled*, like LM3900?