No Sound from Rt Channel after Speedball Upgrade

[Paul Birkeland]

Woah, 4V at full volume?  That'll be great for these tests!

The next step is to measure the AC voltage between ground and pin 2 on the 9 pin socket, then pin 7 on the 9 pin socket.  These are tough measurements to take, but the amp should be off for this testing anyway and the volume pot on the Crack should be all the way up.

We'll keep working our way through the circuit tracing this 60Hz tone. 

-PB

[cfschill]

The next step is to measure the AC voltage between ground and pin 2 on the 9 pin socket, then pin 7 on the 9 pin socket.  These are tough measurements to take, but the amp should be off for this testing anyway and the volume pot on the Crack should be all the way up.

I randomly get a chunk of time to work through the steps; please forgive the delays.  At first I measured with the tubes in and noted zero measurements.  Then guessed you must have meant with the 9-pin tube removed & noted:

=> 0.8V across ground and pin 2
=> 0.0V across ground and pin 7

Looking forward to the next step in solving this riddle.  As always, I appreciate your expertise.. THANK YOU.

[Paul Birkeland]

The AC voltage should be present with or without the 12AU7 installed.

With the volume pot all the way up, getting 0.8V at A2 and 0V at A7 means that the signal voltage isn't making it to the 9 pin socket properly.  This could be because something is touching A7 that shouldn't be, because two lugs on the pot are shorted, or perhaps there's a broken or poorly soldered wire.

The Speedball itself won't cause a problem like this.

-PB

[cfschill]

OK.  I am now at 4.2V, both pins A2 & A7, with the volume pot all the way up on both the pre-amp & headphone amp.  What's the next plan of action, o captain my captain?

[Paul Birkeland]

Did you end up needing to do anything to get 4.2V at pin A2?

The next test is to turn the amp on and measure the AC voltage at terminals 6 and 10 with a pair of headphones connected (always use a spare pair of inexpensive headphones for testing) and the volume about 1/4 of the way up.

-PB

[cfschill]

Did you end up needing to do anything to get 4.2V at pin A2?

The next test is to turn the amp on and measure the AC voltage at terminals 6 and 10 with a pair of headphones connected (always use a spare pair of inexpensive headphones for testing) and the volume about 1/4 of the way up.

I discovered I was measuring from the wrong pin. Then when testing A2 it read 4.2V.  (still fighting a rookie learning curve)

Regarding the next step in measuring: I assumed you meant from ground to terminal 6, and from ground to terminal 10, as shown in the attached snippet.  If I got it correct, the DMM gave me nothing (0.00V) with the volume approx 1/4 way up, cheap headphones plugged in, on both ground to 6 & ground to 10.

[Paul Birkeland]

Turn the volume all the way up and repeat (again still on AC volts, not DC).

[cfschill]

3 weeks after your last instruction, and I still haven't been able to get to the next step. Life's had a few changes (all for the better), and I have minimal time to troubleshoot.

It appears you're following a flow chart for the troubleshooting process.  If so, would you mind sharing the flowchart, and I could simply report back w/ any questions, concerns &/or comments(?)  Seems it would be a more efficient way to go at it, right?

[fullheadofnothing]

The steps will vary depending on results. So you need to do the test to find out what the next step is.

The nice thing about forum posting is it allows all parties to look back over the previous results, so even with long lag times, the thread can be followed. As long as the thread is followed, of course...

[Paul Birkeland]

  If so, would you mind sharing the flowchart, and I could simply report back w/ any questions, concerns &/or comments(?)  Seems it would be a more efficient way to go at it, right?

It's somewhere in the gooey mass between my ears.  We are just following AC voltage through the amp; this is something that has come up on the forum before, but not all that frequently.

[cfschill]

I appreciate the response & now understand.  Beyond not having much time, I have to transform my work desk to a work bench when I do carve out some time.. my first world problem.  I'll report back when done with the last instruction.  Cheers

[cfschill]

I've reached my threshold.  I simply don't have the time.  What's the process/procedure for sending in for repair?

[fullheadofnothing]

Repair service.