Crack + Speedball started making noise in left channel

illusineer · 1116

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Offline illusineer

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on: July 14, 2023, 09:44:34 AM
Hi, I built my crack back in 2020. I've been using it for a while and about a week ago noise started coming the left channel. I tried to troubleshoot with the manuals and went through checking connections and reflowing crappy joints. I reflowed everything on the boards save the LEDs which all light up.

small board
OA 76
IA 184
B-A/B 0
IB 182
OB 172 *

big board
OA 171 *
OB 102
G 0
B 182

notes: The LED on the 9 pin socket further from the center of the chassis lights up slower than the one closer to the center when plugged in. I think I replaced the big board and all components on the big board back in either 2020 or 2021 suspecting that I burned through a trace. Might have banged my amp a bit moving it a few weeks back?

Thanks.


Offline Paul Birkeland

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Reply #1 on: July 15, 2023, 11:45:54 AM
How is the solder joint at A4/A5?  Do both halves of the 12AU7 glow?

Paul "PB" Birkeland

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Offline illusineer

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Reply #2 on: July 15, 2023, 05:42:32 PM
Looks like it's lighting up ok


Offline Paul Birkeland

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Reply #3 on: July 16, 2023, 05:26:17 AM
Was this built with lead free solder?

Paul "PB" Birkeland

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Offline illusineer

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Reply #4 on: July 16, 2023, 05:53:45 AM
No, it's regular leaded 60/40 solder.


Offline Paul Birkeland

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Reply #5 on: July 16, 2023, 05:57:36 AM
I would review this:


A brief look at your photos shows joints that haven't been heated enough to flow out properly.  If you have an adjustable soldering station, definitely turn the temperature all the way up.

Paul "PB" Birkeland

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Offline illusineer

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Reply #6 on: July 16, 2023, 09:36:12 AM
I reflowed them at 350C. The joints are shiny..


Offline Paul Birkeland

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Reply #7 on: July 16, 2023, 10:53:35 AM
Those are not well flowed solder joints.  To some degree there's also too much solder on many of them.

It would definitely help to see what the bottom of the smaller C4S board looks like.

Paul "PB" Birkeland

Bottlehead Grunt & The Repro Man

Offline illusineer

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Reply #8 on: September 09, 2023, 09:15:31 AM
I restored the amp to stock and checked resistance and voltage and found T5 and T9 to have voltage higher than the 15% tolerances in the manual (around 130v). I noticed one of the LEDs on the small socket was lighting up slower and wasn't as bright as the other one when powering on and narrowed it down to the 12au7 tube and replaced it with a 12au7a tube. Voltages on T5, T9 and everywhere else checked out great after that. Amp works, and much less noise than the first time I assembled it. Great!


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