Hoffman Amplifiers Tube Amplifier Forum
Other Stuff => Solid State => Topic started by: hesamadman on December 18, 2015, 11:42:21 am
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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 (http://www.alldatasheet.com/datasheet-pdf/pdf/143538/ETC1/JQX-105F-2.html)
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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?
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Here is the schematic.
http://el34world.com/charts/Schematics/files/acoustic/Acoustic_Schematics.htm (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.
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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 :icon_biggrin:
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.
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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 :blob10:
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im slacking on this :BangHead:
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?
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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.
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What sheet are you seeing IC1? I cant seem to find what youre referencing.
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i see it. a very long connector.
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i see it
is it *labeled*, like LM3900?