Left channel out (still causing trouble!)

[Paul Birkeland]

Without getting too confused by batter orientation, you can just flip the D-cells around and remeasure the voltages.

When they are in the proper orientation, the plate voltage pops right down where you want it.  If they are flipped, you barely get any voltage at all.

In the new version of the Quickie, the PJCCS actually won't operate with the batteries in backwards (a good thing).

-PB

 

[denti alligator]

Voltages with D-cells reversed:


1  0
2  1.59
3  0
4  1.55
5  0
6  16.41
7  24.59
9  8.2

A1  3.128
A2  23.55
A3  0
A4  23.56
A5  1.59
A6  23.55
A7  3.127

B1  3.063
B2  22.88
B3  0
B4  22.88
B5  1.572
B6  22.96
B7  3.066

Are these OK? Looks like pins 5 and 6 are a bit low.

 

[Paul Birkeland]

Those voltages would be consistent with 9V batteries that are somewhat low, but a circuit that is otherwise working.  How does it sound?

 

[denti alligator]

Those voltages would be consistent with 9V batteries that are somewhat low, but a circuit that is otherwise working.  How does it sound?

Pretty good!

 

[Paul Joppa]

Excellent! Now the numbers look right.

 

[denti alligator]

Thanks for your help, guys!!

 

[denti alligator]

Turned on the Quickie for the first time since solving this and the L channel is out again!

This is what happened last time: I reflowed some connections, it worked, then didn't work after a couple days.

It's not as if I'm a bad solderer... might there be something else at play here?

By the way, voltages all look to be OK.

 

[Paul Birkeland]

It's very likely a loose connection that's moving around as you're using the preamp.

 

[Paul Joppa]

IF the solder joints are good, then consider the tube socket.

 

[denti alligator]

Thanks, guys. A quick reflow job and it's working again. But I'm doubtful it will last long... We'll see.

Interesting here is how much better I like the sound of my SEX amp with the Quickie! I really miss it when it's out of the chain. That's kind of surprising.

 

[denti alligator]

Well, sure enough: it started OK today, but now the L channel is fading and barely audible. I don't know how many times I can reflow these solder joints. It doesn't quite make sense to me why this keeps happening.

 

[Doc B]

The troubleshooting procedure never changes. If it is going out on one side, measure the voltages. Check the D cells. Make sure the solder joints are actually continuous, not just looking like they ought to be, and rock the tubes in the socket to see if there is a bad socket contact.

 

[Wanderer]

Rock the D cells too. Clean the D cell battery contacts. 

 

[denti alligator]

This hasn't gone away, I've just had less time to listen to music

Left channel only. I can listen for about an hour and then the left channel starts fading. Brand new batteries. What could be doing this to the left channel only, such that when I leave it be over night I can play it again for an hour without problems before it starts up again.

 

[mcandmar]

Sounds like a bad battery.  I had a set of D cells that would die after an hour and measure around .4v when the music faded out.  Leave them overnight and they would measure 1.5v again and play for another hour or two before fading out.

 

[denti alligator]

Sounds like a bad battery.  I had a set of D cells that would die after an hour and measure around .4v when the music faded out.  Leave them overnight and they would measure 1.5v again and play for another hour or two before fading out.

But then I should be able to switch batteries and get the same problem in the right channel. I haven't tested that yet, but I'd bet anything that the problem will still be in the left channel.

 

[mcandmar]

Theory is sound, try it.  I only mentioned it as my set were also new from the store and showed a healthy 1.5v with a meter, it was only under load when they gave up.  I think that phenomenon is caused by a bad cell inside the battery.

 

[denti alligator]

Not the batteries. I switched the D cells and still have the left channel problem. Curiously I got about 10 minutes of decent sound before it began to fail. What could this be?

If it were a bad solder joint it should sound bad all the time, not get increasingly worse, or? Ditto with the tube, though I've switched these and no difference.

 

[denti alligator]

All voltages check out. I'm stumped.

 

[mcandmar]

Hold on, your getting no sound and the voltages check out?