No sound - All LEDs suddenly stopped ligthing

sjeffrey · 4357

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Offline sjeffrey

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Reply #15 on: June 25, 2015, 02:54:38 PM
Amp is back up and singing nicely  ;D
Must have been a bad solder somewhere.  Strange that it worked fine for so long.
Makes me have more sympathy for products you buy that suddenly die 3 months after warranty is up.  ???


Offline Doc B.

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Reply #16 on: June 25, 2015, 03:14:25 PM
Did you find the bad solder joint and fix it? If not the chances are very high that it will cut out again.

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Offline sjeffrey

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Reply #17 on: June 25, 2015, 03:23:58 PM
I just reflowed all the joins involved around T12, 20, 21 and others that were easy to get to.
I'm a bit paranoid about getting shocked so I didn't really want to do 1 joint at a time and retest.  I let it sit for an hour before taking the solder tip to them to be safe.


Offline sjeffrey

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Reply #18 on: August 30, 2016, 05:54:30 AM
Quote from: Doc B. on June 25, 2015, 03:14:25 PM
Did you find the bad solder joint and fix it? If not the chances are very high that it will cut out again.

You called it a year ago,
amp cut out again.  Guess it's time to inspect each solder one by one.
Is there a trick to drain the voltage between 20 and 21 so I don't get zapped or have to wait 24 hours before soldering?


Offline fullheadofnothing

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Reply #19 on: August 30, 2016, 06:58:36 AM
A properly built amplifier will drain off voltage in about 5 minutes through the bleeder resistor. If your power supply is incomplete, it may not have that path, so the voltage will remain high for a long time. If you need to know what voltage a point is at, measure it.

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Offline sjeffrey

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Reply #20 on: August 30, 2016, 03:14:08 PM
I just measured the voltage 24 hours later and it's still at 156V.
I know the power supply's path is incomplete somewhere but is it safe to poke around?
I would rather there be no voltage but waiting several days for it to go to 0 is impractical.
What can I do?


Online Paul Birkeland

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Reply #21 on: August 30, 2016, 03:24:20 PM
Do you have the 270K resistor installed?

Paul "PB" Birkeland

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Offline sjeffrey

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Reply #22 on: August 30, 2016, 03:34:26 PM
Quote from: Caucasian Blackplate on August 30, 2016, 03:24:20 PM
Do you have the 270K resistor installed?

I do, from U12 to U13.  The solder there looks fine.


Online Paul Birkeland

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Reply #23 on: August 30, 2016, 05:03:56 PM
What voltage do you have between 12 and 13?

Paul "PB" Birkeland

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Offline sjeffrey

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Reply #24 on: August 31, 2016, 11:19:08 AM
Quote from: Caucasian Blackplate on August 30, 2016, 05:03:56 PM
What voltage do you have between 12 and 13?

Between 20-21 it was still 147V after 48 hours.
I assume you wanted between 12 and 13 with power on and it was .018V and slowly climbing to .022V after about 5 seconds with probe on.


Online Paul Birkeland

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Reply #25 on: August 31, 2016, 01:02:26 PM
Since the voltage isn't bleeding off, either one of the 270 Ohm resistors or the black wires connecting between the striped sides of the 220uF capacitors is missing or not well connected.  If you poke around with a chop stick, you should be able to temporarily restore the connection.

-PB

Paul "PB" Birkeland

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Offline sjeffrey

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Reply #26 on: September 01, 2016, 01:51:53 PM
Quote from: Caucasian Blackplate on August 31, 2016, 01:02:26 PM
Since the voltage isn't bleeding off, either one of the 270 Ohm resistors or the black wires connecting between the striped sides of the 220uF capacitors is missing or not well connected.  If you poke around with a chop stick, you should be able to temporarily restore the connection.

-PB

I'm stomped.  So tapping with a chop stick I was able to restore a connection and therefore drain what was stuck at 20-21.
I looked at all back wires around 12-16, made sure everything was there.  Capacitors are correctly installed.  I couldn't find anything wrong.  I reflowed the solders in that area.  It's really crammed in there.  At first it didn't help but with more tapping around and push of wires it came back to life.  I wish I knew which one is the problem as I reflowed everything and that didn't directly fix it.  I guess I'll be looking at this again next year  :-[


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