Only have audio on left side.

[Demoninja]

So I built my crack a while ago but haven't had the chance to really listen to it. I started it up and only had audio on the right side. I resoldered all the connections to the headphone jack which seemed to solve the problem. Now a few days later the Crack's been sitting on my desk and the last time I used it it was fine. Today I tried listening and I have no audio on the right side. Anyone have any potential ideas? All the voltages and resistances checked out.

Edit: Didn't mention earlier but I did look everything over to  make sure it's all still connected and it is.

 

[Paul Birkeland]

If you performed the shorting mod stickied on the Crack board, there's a possibility that the jack is staying shorted even when headphones are plugged in.  If you didn't perform this mod, I'd be looking really closely at the right RCA jack.  Any solder or conductive debris that gets between the center pin and the shell won't let any signal in.

-PB

 

[Demoninja]

If you performed the shorting mod stickied on the Crack board, there's a possibility that the jack is staying shorted even when headphones are plugged in.  If you didn't perform this mod, I'd be looking really closely at the right RCA jack.  Any solder or conductive debris that gets between the center pin and the shell won't let any signal in.

-PB

Thanks for the help PB.

Something really odd happened, I decided to try again and this time the right channel definitely works. I didn't change anything or resolder anything yet it's definitely working now. At this point I suspect I'm crazy.

 

[Klots]

Had that same problem yesterday. Was listening music in the morning and then went out for shopping and when I came back and started listening to music again, sound was coming only from the left channel. Changed the input tube (from E80CC to stock 12au7), and everything was working well again. Terminal 1 and 7 were 170V with E80CC, so something is messed up with that tube.

 

[kgoss]

Or, it could be a suspect solder joint on the tube socket.  Replacing the tube moved it enough to start working again.
Did you try popping the bad tube back in after both channels started working to confirm it is bad?

 

[Demoninja]

Hey everyone, I solved my problem. I most likely didn't install the headphone jack properly. I got home today, fired up the Crack and plugged my headphones in. No audio on the right channel. On a whim I moved the headphone jack around a bit and I got audio on both sides now. I'll probably resolder it on Sunday since I'm busy until then.

Happy New Years all! and thanks for the help!

 

[Paul Birkeland]

That's a false positive test.  Pulling the plug out half way provides signal to both drivers from one channel of the amp.

-PB

 

[Doc B]

PB is right. Were you pulling it out part way - which would create the false two channel effect - or just wiggling it with the plug fully inserted? If the later, you probably have bent or loose contacts in the jack.

 

[Demoninja]

I just wiggled it around while it was fully inserted.

 

[Demoninja]

I spent most of January away from home and now I'm back and I would like to try and figure this out. When I plug in my headphones I will hear audio on the right side but nothing on the left now. I've tried resoldering the headphone jack. Any other ideas about what could be  wrong? I don't think it's the RCA inputs since originally the issue was on the left side.

 

[Paul Birkeland]

Can you check the voltages against those in the manual?

-PB

 

[Demoninja]

Can you check the voltages against those in the manual?

-PB

I rechecked the voltages just now. I changed the ones that didn't check out in my opinion to red.

1 - 90
2 - 224
3 - 0
4 - 225
5 - 95
6 - Fluctuates around 0
7 - 107
8 - 0
9 - 105
10 - Fluctuates around 0
11 - 0
13 - 195
14 - 0
15 - 207
20 - 0
21 - 222

A1 - 87
A2 - 0
A4 - 0
A5 - 0
A6 - 89
A7 - 0
A9 - 0

B1 - 89
B2 - 194
B3 - 120
B4 - 87
B5 - 194
B6 - 106
B7 - 0
B8 - 0

 

[Paul Birkeland]

6 and 10 are supposed to be 0V, so those don't go on the red list.

B3 and terminal 7 are connected by a piece of wire (or should be), it shouldn't be possible for them to be at different voltages.

 

[Demoninja]

I thought because it said 0 it should settle down on a number eventually. It's okay that it's fluctuating around 0?

And sorry you're absolutely right. I rechecked and B3 and 7 are both coming up at 107.

 

[Paul Birkeland]

You have a perfectly working amplifier in terms of voltages.  What this means is that:

1.  There may be a short at the RCA jacks.  Turn the volume knob all the way up, then measure resistance between center pin and shell.  If one is unusually low, there may be some crud or solder shorting the jack out.

2.  There may be a connection issue at the headphone plug.  With the headphone plugged in, can you look at the contacts and see that things are touching properly?  If you have the grounding mod described on this forum, and the ring isn't moving the jack contact enough, it may leave the jack shorted.  Maybe there is also an issue with the red wire going to the headphone jack from terminal 6.

-PB

 

[Demoninja]

Great that in terms of voltages everything checks out.

1. I turned the knob all the way up and measured the resistance and they both came up around 87K ohms.

2. By contacts do you mean the 3 metal parts that get pushed out when the headphone is plugged in? If so when you look at it from the under side, the "top" contact doesn't seem to move. By top I mean the one the white wire is soldered to from 10L.

 

[Paul Birkeland]

2. By contacts do you mean the 3 metal parts that get pushed out when the headphone is plugged in? If so when you look at it from the under side, the "top" contact doesn't seem to move. By top I mean the one the white wire is soldered to from 10L.

That connection feeds the left channel.  It might be worth double checking that your headphones do send the left channel to the left driver, and right channel to the right driver.

Beyond that, you will want to download a 60 Hz test tone and get the meter back out, then I can help you trace signal through the amp.

-PB