Resistance check failure on 7, 9, B3, and B6 after new stepped attenuator?

[pickles3201]

Hi, I recently tried to upgrade the volume pot on my Bottlehead Crack (with Speedball) and it passed the resistance/voltage checks when I first built it. After removing the volume pot and installing a Valab 23 stepped attenuator, all the terminals passed the resistance checks except for 7, 9, B3, and B6. On my multimeter they all say 1 (open loop) when they should be measuring 2.9k ohms.

The things I changed (regarding the Crack) was new wires for RCA and ground (since they weren't long enough), new red wire for the red socket wire going to the output of the attenuator, and I extended my one ground wire by soldering additional black wires onto it.

Here is a picture of my stepped attenuator, with my RCA wires going into input, and the socket wires going to the output. I know my ground wire is mad janky, but I didn't think that it would have made a difference electrically since it's just a reference (correct me if I'm wrong?).
Any help is appreciated, thanks!

[diynewbie]

I have to wonder if the jumper from input ground to output ground is necessary.  Do you know that the those two grounds are not connected via the circuit board?  It might be worth a pulling the jumper and checking.  Perhaps someone with that attenuator can chime in.

I think that B3 to T7 thru the 3k resistor to T3 (also B6 to T9 thru 3k resistor to T3) should be the path to ground.  Terminal T3 connects directly to the chassis via the mounting screw.  I assume you saw 0 ohm at T3, so I would probably start by re-flowing the T3 solder joint for the 3k resistors.  The Bottlehead crew will give better help.

[Paul Birkeland]

Hi, I recently tried to upgrade the volume pot on my Bottlehead Crack (with Speedball) and it passed the resistance/voltage checks when I first built it. After removing the volume pot and installing a Valab 23 stepped attenuator, all the terminals passed the resistance checks except for 7, 9, B3, and B6. On my multimeter they all say 1 (open loop) when they should be measuring 2.9k ohms.

These resistances change when you remove the 3K (2.9K) resistors and install the Speedball.

[pickles3201]

These resistances change when you remove the 3K (2.9K) resistors and install the Speedball.

Oh so did my Crack pass all resistance checks? And will anything be different for the voltage checks or am I good to go?

[Paul Birkeland]

You should perform the voltage checks.

[pickles3201]

You should perform the voltage checks.

oof a new problem has arisen. Both tubes glow and all red LEDs are on. All voltage checks pass except for at 1 and at OA (they're connected). They both read 175v on my multimeter. It might have something to do with me replacing the red wire going from the pot output to the socket (A7 I believe). A6 should go to 1 and I made sure that A6 and A7 aren't touching.
Do you (or anyone) know what's up? Thanks!

[Paul Birkeland]

Are the LEDs glowing on the 9 pin socket?

Either OA or OB on the big PC board (and 7 or 9) is going to be way, way off if terminal 1 is 175V. 

Normally I expect to see 175V on terminal 1 when the Q2 that's feeding it isn't properly soldered, but certainly an error in installing the new attenuator that resulted in no ground reference could also cause some strange issues.

[pickles3201]

Are the LEDs glowing on the 9 pin socket?

Either OA or OB on the big PC board (and 7 or 9) is going to be way, way off if terminal 1 is 175V. 

Normally I expect to see 175V on terminal 1 when the Q2 that's feeding it isn't properly soldered, but certainly an error in installing the new attenuator that resulted in no ground reference could also cause some strange issues.

Ah it seems that I have impaired vision. The LED attached to A3 is glowing, but the one attached to A8 is not. And I forgot to mention that OB was measuring a bit lower, at around 65v ma bad.
What seems to be the cause?

[Paul Birkeland]

The LED attached to A3 is glowing, but the one attached to A8 is not.

Good, that makes more sense.

And I forgot to mention that OB was measuring a bit lower, at around 65v ma bad.
What seems to be the cause?

Well, the LED at A8 and OB are in the same part of the circuit while the LED at A3 and OA are in the same part of the circuit.  You mentioned that OA is at 175V, which is a problem, and the LED that would be lit by the A side of the C4S passing current is illuminated, while OB is a little lower than expected and not lighting up its associated LED.  Did this Speedballed Crack work properly before you put the attenuator in?  (And by working properly, I mean that it passed its voltage checks perfectly)

If you have the Speedball 1.1, now would be a good time to go back to page 20 of the manual for debugging.

[pickles3201]

Did this Speedballed Crack work properly before you put the attenuator in?  (And by working properly, I mean that it passed its voltage checks perfectly)

If you have the Speedball 1.1, now would be a good time to go back to page 20 of the manual for debugging.

From what I remember, it did, but I couldn't hear a difference between the speedballed Crack vs a solid state amp so I assume there is a problem.

The resistance measured 237, and the mje-350s and the pn2907s have the proper orientation, but as previously stated one LED is not lighting and the 12AU7 tube is indeed glowing.

I also tried resoldering some of my joints and now t1 reads 600v and t5 reads 226v...

[Paul Birkeland]

How does the solder joint look where the black wires meet on the headphone jack?

I would suggest putting the stock volume pot back in, then rechecking things.

[pickles3201]

Aight so never mind about the voltage change, t1 is still 175v and t5 is still 65v (bad multimeter)
But yes the headphone jack ground joint is fine and has continuity to the original ground point.

Is retracing my steps my only option? I have the stepped attenuator (worked fine) that I originally replaced the stock pot with, but I have destroyed the original stock pot (don't ask why lol, but I think I found a very similar one on parts-express).

I believe something went wrong during my speedball installation as I think everything was fine (from what I remember...) with my regular crack.

[Paul Birkeland]

The Speedball 1.1 has instructions for testing the small board before installing the large board.  Did yours pass these checks?