Speedball upgrade fail after a month, voltages way off [resolved]

[Paul Birkeland]

What are the DC voltages on each side of each 270 ohm resistor in the power supply?

[goldencalves]

U15 - 124v
U21 - 187v
U13 - 50v

Are these the correct locations? 

[Paul Birkeland]

Can you try again with no tubes?

[goldencalves]

W/ no tubes:

U13 - 237
U15 - 241
U21 - 246

[Paul Birkeland]

Now try just the 12AU7 and post voltages on terminals 1-5.

[goldencalves]

W/ 12AU7 only:

1 - 73
2 - 231
3 - 0
4 - 231
5 - 74

[Paul Birkeland]

This is major progress!

Can you post some photos of the wiring around the octal socket that you have currently? 

[goldencalves]

I'm just glad that its looking like the whole thing isn't toast!

Also: there is only one LED on the octal.  I had some short/issue a little while back and I followed the advice on a post in this forum that swapped out a jumper for the 2nd LED (which worked).

[Thermioniclife]

PB is looking for pics of the other socket. Octal= 8 pins, Noval= 9 pins.
Sometimes photos can be deceptive but check that the jumper you put in on the Noval socket is not shorted to pin 7.
That will give you all sorts of grief. In general you should not have that much uninsulated wire exposed. pin a2 is the way they should be.

[goldencalves]

Of course, thank you, that socket does have 9 pins not 8!

The jumper is currently not shorting to the 7th pin.  I went ahead and wiggled the tube all around the noval and it doesn't appear that any wire is touching nor able to touch its neighbor.

I will pick up some liquid insulator and shore up those exposed bits asap though, thanks for the tip.

[Paul Birkeland]

The wire that's oddly routed at B8 is going to cause problems eventually.

The upper wire on B2 doesn't look to be well captured by solder.


You may find at this point that it's just easier to order a replacement big board + parts. 

[goldencalves]

Thanks Paul, I am about to resolder those two wires on the oct.

Are there any other readings I can take to narrow down the issue on the big board?

[Paul Birkeland]

It's totally possible that the big board just didn't survive the flux event.  What is the DC resistance to ground that you get from OA and OB on the big PC board?

[goldencalves]

Resistance to ground from:
OA - 0
OB - 124.7

[Paul Birkeland]

OK, can you post some photos of how the TIP50 is mounted on the A side?