Speedball Second Voltage check low

messiach21 · 1285

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Offline messiach21

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on: February 28, 2018, 04:59:59 AM
Hi,

Hoping someone can point me in the right direction here.

I got the small board connected, mounted, and voltage checks were correct - unit was operating at temperatures I'd expect.

I've got the big board on now and the voltage check revealed low voltages:

OA - 94-95v
OB- 53-54v
G- 2.4mv (I think this is OK, close enough to 0)
B+ 82v

In addition, the two 270ohm resisters get so hot, I have to do my tests in short bursts or I'm afraid they'll just burn up.

I've checked and reflowed a few of the wires going off the lug connectors to the board.
I've also checked and reflowed a few of the joints on the big board.
I've double checked to make sure I have the heat sinks and TP50s screwed together correctly (film is between the TP50 and the heat sink).

I also went ahead and started checking the small board again and I can already see the voltages are off now too:

OA - 40v
IA - 96v
B-A/B - 2.4mv
IB - 94v
OB - 80v

Also:
- All LEDs light up
- I checked IA on the small board just before the leds on the big board lit up and the voltage was in the correct range (220v my reading). As soon as the big board leds lit up, it dropped back to 96 and fluctuated.

Anyone run across this before?
I feel like it's still a weak solder joint somewhere but not sure which one - there's a few that have quite a few connectors (instructions for Crack seemed to want to put ones at the top of the lugs when they should be at the bottom to install the speedball without a lot of joints together).

« Last Edit: February 28, 2018, 05:15:15 AM by messiach21 »



Offline buldogge

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Reply #1 on: February 28, 2018, 06:36:24 AM
Where is the 2nd set of LEDs on the big board (on the lower end, in the pic)?

-Mark in St. Louis



Offline Paul Birkeland

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Reply #2 on: February 28, 2018, 07:40:00 AM
Can you post photos of each TIP50 as it's mounted to the heatsink.

I can almost assure you that one of them is not mounted correctly and is making metal to metal contact with the heatsink.

Paul "PB" Birkeland

Bottlehead Grunt & The Repro Man