Resistance Checks [resolved]

thoven0215 · 12806

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Offline thoven0215

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Reply #15 on: May 01, 2022, 10:24:04 AM
I also notice that the left side of the leds on the pcb did not light up if that helps at all.



Offline Paul Birkeland

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Reply #16 on: May 01, 2022, 10:32:33 AM
OK, so the measurements on everything didn't go to 0V ;)

You'll need to do a whole voltage check and just let us know which terminals are 0V.

Paul "PB" Birkeland

Bottlehead Grunt & The Repro Man


Offline thoven0215

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Reply #17 on: May 01, 2022, 10:40:15 AM
Terminals 1, 2, 6, 7, 21, 22, 24, 25, 27 all shouldn't measure at 0 but measure at 0. I also measured 41-45 and 41 comes at 0 as well.



Offline Paul Birkeland

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Reply #18 on: May 01, 2022, 10:45:01 AM
Does 34 provide a proper measurement? How about 30?

Paul "PB" Birkeland

Bottlehead Grunt & The Repro Man


Offline thoven0215

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Reply #19 on: May 01, 2022, 10:49:56 AM
30 measures at 425, which is about 7% more than the 398 listed. I just attempted to measure 34, and the same pop happened. I just turned off the amp.



Offline Paul Birkeland

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Reply #20 on: May 01, 2022, 10:51:47 AM
I would look for loose components around 34.  In the original photos you posted, 35L doesn't look to be well soldered, and those wires moving around could make a pop.

Paul "PB" Birkeland

Bottlehead Grunt & The Repro Man


Offline thoven0215

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Reply #21 on: May 01, 2022, 11:32:15 AM
I soldered them again, and now I think the pop has taken out the right side too. 19 and 20 measure at 3 volts. 31 measures at 450. 34 measures at 3 volts. 36, 37, 39, 40 all measure at fractions of a volt. 41 measures at 0. 42 measures at 225. 43 measures at 0. 44 measures at 450. 45 measures at 223. Everything else measures at 0.



Offline Paul Birkeland

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Reply #22 on: May 01, 2022, 11:38:42 AM
Loose and/or damaged 130 ohm resistors and/or loose black wires leaving the 41-45 terminal strip will do this.  Did you go through the amp and wrap all the connections and resolder them?

Paul "PB" Birkeland

Bottlehead Grunt & The Repro Man


Offline thoven0215

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Reply #23 on: May 01, 2022, 11:59:24 AM
I did, and how can I tell if the resistors are damaged? The resistors are not loose, and I just reflowed the terminals 41-45 again just to make sure nothing is out of order.



Offline Paul Birkeland

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Reply #24 on: May 01, 2022, 12:18:06 PM
I did, and how can I tell if the resistors are damaged? The resistors are not loose, and I just reflowed the terminals 41-45 again just to make sure nothing is out of order.
You have the correct voltages on 41-45, so I would suggest leaving those alone for now.  A damaged resistor will measure OL with the amp off and discharged if you try to use your meter to measure it.

Paul "PB" Birkeland

Bottlehead Grunt & The Repro Man


Offline thoven0215

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Reply #25 on: May 01, 2022, 12:29:48 PM
I attempted measuring them, and both of the 130 ohm resistors measure at infinity.



Offline Paul Birkeland

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Reply #26 on: May 01, 2022, 12:31:29 PM
You can unsolder one end of each and double check them with one end poking up and not connected to anything.  Most meters will measure these in circuit, but some will not.

Paul "PB" Birkeland

Bottlehead Grunt & The Repro Man


Offline thoven0215

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Reply #27 on: May 01, 2022, 01:08:08 PM
I disconnected them and measured again, but their value just keeps going up until my multimeter can't measure them anymore.



Offline Paul Birkeland

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Reply #28 on: May 01, 2022, 01:25:33 PM
OK, they are probably blown and need to be replaced. 

When you get them replaced, you can tape over the metal tip of your red meter probe so only the metal point sticks out, and that should help avoid potentially shorting a terminal with 400V on it to a terminal with 0V on it next door.

Paul "PB" Birkeland

Bottlehead Grunt & The Repro Man


Offline thoven0215

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Reply #29 on: May 01, 2022, 01:49:55 PM
Just out of curiostiy, is it possible that it could have also been a power transformer issue? Further, I was using alligator clips to measure, and I thought I made sure to not touch other terminals. Could there be an alternate reason for them shorting when I test the terminal? Also where would you recommend me buy resistors? Nevertheless, thank you very much for your help Mr. Birkeland. I will update once I get the resistors.