[RESOLVED] Some voltage readings double manual

bp2u · 1540

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Offline bp2u

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on: May 26, 2020, 08:18:58 AM
Resolution: 
1. I turned up my soldering iron and reflowed every solder connection along the ground buss.
2. Replaced both LEDs between A8-A9 and B8-B9 (Probably only A socket LED was toasted)

Root Cause:  My soldering skills are shit.
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So Ive looked at a lot of "voltage issue" posts, and looked at various fixes, but I cant seem to find/fix my issue:
(I have no previous electronics experience. Successfully built a Crack)

All resistance measurements are correct as per manual.

All voltage checks are as per manual except:

Terminal 7:   158
Terminal 13: 155
Terminal 14: 155
Terminal 15: 155

Terminal 31: 157

These readings are basically double what they should be, which tells me I missed something obvious.
Let me know if specific images would be helpful.

Thanks.
« Last Edit: June 01, 2020, 07:31:43 AM by bp2u »



Offline Paul Birkeland

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Reply #1 on: May 26, 2020, 08:29:26 AM
I am guessing you have a bunch of LEDs that also aren't lit? 

This is very likely to be a bunch of loose solder joints in the amp that are causing this.  Do both the tubes glow? 

Paul "PB" Birkeland

Bottlehead Grunt & The Repro Man


Deke609

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Reply #2 on: May 26, 2020, 08:37:43 AM
Just a shot in the dark: If you have 110-120 VAC coming out of your wall, wiring a universal power transformer for 220-240 VAC could result in double the expected voltages.  Easy to check, and if that's the problem, equally easy to fix.

cheers, Derek



Offline Paul Birkeland

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Reply #3 on: May 26, 2020, 09:42:54 AM
Just a shot in the dark: If you have 110-120 VAC coming out of your wall, wiring a universal power transformer for 220-240 VAC could result in double the expected voltages. 
No, that will result in half the expected voltages.

Paul "PB" Birkeland

Bottlehead Grunt & The Repro Man


Offline bp2u

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Reply #4 on: May 26, 2020, 09:50:31 AM
I am guessing you have a bunch of LEDs that also aren't lit? 

This is very likely to be a bunch of loose solder joints in the amp that are causing this.  Do both the tubes glow?

Both LEDs between A8 - A9, and B8 - B9, do not light.

Both tubes glow.

Ill check the solder joints at those locations, and the next couple connections inline, and report back. thanks.

UPDATE:  Ordering 2 new LEDs now..  :| I touched A8 with the soldering iron and one of the legs of the LED just fell off. Ill also double check the buss wire.

BP
« Last Edit: May 26, 2020, 10:08:44 AM by bp2u »



Offline Paul Birkeland

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Reply #5 on: May 26, 2020, 09:53:07 AM
Yeah, so on many of the Reductions that I have repaired, the bare buss wire that snakes through the kit often times is loose in spots.  Sometimes people miss that the solder lug washer on each RCA jacks needs to be right under the nut, and instead they will have it somewhere else, and that causes problems.  Other loose connections will also make similar problems.  Rarely does this actually have anything to do with an LED itself.

Paul "PB" Birkeland

Bottlehead Grunt & The Repro Man


Deke609

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Reply #6 on: May 26, 2020, 10:03:09 AM
No, that will result in half the expected voltages.

Apologies! Meant the opposite. 220 in, wired for 110.



Offline Paul Birkeland

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Reply #7 on: May 26, 2020, 10:08:14 AM
Apologies! Meant the opposite. 220 in, wired for 110.
And that will make the 220uF 250V caps explode and the fuse will blow.

Paul "PB" Birkeland

Bottlehead Grunt & The Repro Man