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September 21, 2020, 08:02:01 AM

Author Topic: Wrong voltage on speedball big board [resolved]  (Read 292 times)

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Offline illusineer

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Re: Wrong voltage on speedball big board
« Reply #30 on: September 13, 2020, 04:35:30 PM »
What about OA? It doesn't give any reading while the other one did give a reading on my meter.

Offline Paul Birkeland

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Re: Wrong voltage on speedball big board
« Reply #31 on: September 13, 2020, 04:58:25 PM »
One side is reading 4,500,000 ohms and the other side is reading so high your meter can't determine what it is.

The manual says OA and OB on the big board should be several hundred thousand ohms at minimum.

I'm not seeing what the issue is here, I would move on to checking the voltages.
Paul "PB" Birkeland

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Offline illusineer

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Re: Wrong voltage on speedball big board
« Reply #32 on: September 13, 2020, 05:16:09 PM »
OA - 120
OB - 221
G - 0
B+ 246

Offline Paul Birkeland

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Re: Wrong voltage on speedball big board
« Reply #33 on: September 13, 2020, 05:20:21 PM »
Let's go back to pictures of the bottom of the board...
Paul "PB" Birkeland

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Offline illusineer

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Re: Wrong voltage on speedball big board
« Reply #34 on: September 13, 2020, 05:27:19 PM »
Trying my best lol, this pcb soldering stuff isn't as easy as the stripping wires and soldering them to terminals sticking up ig...

Offline Paul Birkeland

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Re: Wrong voltage on speedball big board
« Reply #35 on: September 13, 2020, 05:34:01 PM »
Can you send me a link to the solder and soldering iron you're using?
Paul "PB" Birkeland

Bottlehead Grunt & The Repro Man

Offline illusineer

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Re: Wrong voltage on speedball big board
« Reply #36 on: September 13, 2020, 06:05:01 PM »
I've been using this 60/40 rosin core radioshack solder that's been lying around in my garage forever throughout the whole amp, as for irons I've used this bluepoint soldering gun for about 95% of the time except for just recently with the pcbs I started using this weller iron (I like the soldering gun better).

Offline Paul Birkeland

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Re: Wrong voltage on speedball big board
« Reply #37 on: September 13, 2020, 06:05:47 PM »
I would use the gun on your board.  You can leave the LED joints alone, but use the gun on everything else. 
Paul "PB" Birkeland

Bottlehead Grunt & The Repro Man

Offline illusineer

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Re: Wrong voltage on speedball big board
« Reply #38 on: September 13, 2020, 06:35:47 PM »
OK, reflowed with the gun put the board on again, resistance check, meter didn't read anything, voltage check

OA - 117
OB - 220
G - 0
B+ -226


Offline Paul Birkeland

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Re: Wrong voltage on speedball big board
« Reply #39 on: September 13, 2020, 06:37:32 PM »
Well, at this point I would suggest sending it in for repair and I can fit a new board on it for you, or you can e-mail replacementparts to ask for a new board, or you can pull the LEDs and the two transistors on the bit that's not conducting and replace them.

Board rework isn't super easy though.

It's moderately probable that the big lump of solder that I saw bridging the connections on one of the LEDs would've required enough heat to melt the LED itself, and it may be damaged.  Some meters have a diode check setting that can allow you to measure them, and they should show about 1.57V in one direction and nothing in the other.
Paul "PB" Birkeland

Bottlehead Grunt & The Repro Man

Offline illusineer

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Re: Wrong voltage on speedball big board
« Reply #40 on: September 13, 2020, 06:56:46 PM »
My meter does seem to have a diode check, not sure how to work it though. I'm not super eager to spend more $ to send it back for repair tbh especially having been so close to having everything working  :-\

Offline Paul Birkeland

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Re: Wrong voltage on speedball big board
« Reply #41 on: September 13, 2020, 07:10:21 PM »
Well, you can get some solder braid and wick the solder out of those joints.  I would start with two new LEDs, then see what the results are before yanking out the transistors.
Paul "PB" Birkeland

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Offline illusineer

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Re: Wrong voltage on speedball big board
« Reply #42 on: Yesterday at 02:33:27 PM »
I went ahead and replaced the big board and everything on it with new parts, did the tests and everything works now. Thanks