need troubleshooting help

[aragorn723]

What about A6?  That voltage is 29.97 and should be 9-21.  A5/B5 are a little low.  Is there another issue here?  Can the Quickie be safely run this way, or should I still be troubleshooting?

Dave

 

[Paul Birkeland]

I would put in a fresh set of 9V batteries, then remeasure your voltages.

 

[aragorn723]

With new batteries:

IA/IB    36.76v/36.5v
A6/B6    36.3v/23.54v
A5/B5    1.869v/1.795v


Dave

 

[Paul Joppa]

Back on the first page, I see you did not have this problem; both plates were at a suitable voltage. From that I conclude the PJCCS is, or at least was, working correctly. If the PJCCS were shorted on the A6 side during the preceeding page+ of discussion, you would get these measurements. Not saying that's the problem, just trying to get some perspective.

 

[aragorn723]

Hi Paul,

Any suggestions where a short could be?  Maybe by accident during probing (an accidental bridge from pin to pin on the socket tube maybe?)  One thing worth noting, the only joints I touched were the connections for the bias caps.  I tried to pull the original caps out without using a solder removal tool, and heated it up quite a few times to do this (probably not the right thing to do).  Could it be that the 1k got thermally overstressed and that's why the cathode voltage is off?  (Would this impact A6 potentially too?)

Thanks,

Dave

 

[Paul Joppa]

Sorry, the last note was quick without looking closely.

A5 and B5 are the correct value, indicating that the current source is working properly. If you swap the tubes, do you get the same result? It may be a weak tube, or one not yet run in.

 

[aragorn723]

Hi Paul,

Here are the voltages with swapped tubes:

35.6v / 35.62v
35.48v / 21.7v
1.86v / 1.73v

Thanks,

Dave

 

[Paul Joppa]

This makes no sense to me! Must be missong something.

Try swapping the PJCCS outputs that go to A6 and B6 - if it's not the tubes, it must be the plate load (?)

 

[aragorn723]

Just want to make sure i got this right-desolder a6, and jumper that wire to b6, then desolder b6, and jumper that wire to a6?  Thanks,

Dave

 

[Paul Joppa]

Sorry, I didn't look at the manual so that wasn't clear. I want to move the PJCCS wires to test whether the current source is at fault.

In the manual, OA goes to A2 and OB goes to B6 (pins 2 and 6 both go to the tube plate). Just swap those, OA to B6 and OB to A2. Check voltages at A2/6, B2/6, A5, and B5. Better check A3 and B3, too - these are the grids and should measure near zero volts but let's be sure.

 

[aragorn723]

gonna check later today.  I borrowed a capacitor checker too, so that will give another data point on whats up with those.

Dave

 

[aragorn723]

Hi Paul,

These are the measurements with the pjccs outputs moved.

A2/A6    21.39v/21.4v
B2/B6    22.74v/22.74v
A5          1.697v
B5          1.712v
A3          0v
B3          0v

Thanks,

Dave

 

[aragorn723]

Here are the capacitance measurements for the 150uf caps:

90uf
85uf

Is that normal to be that far off 150uf?

There are the measurements for the 220uf caps:

110uf
110uf

Dave

 

[Paul Joppa]

Well, the problem seems to have gone away.

Are you still hearing only one channel?

 

[aragorn723]

I haven't tried hooking it back up yet, looks like it would be safe to do that now.  The one thing that I did besides disconnecting the PJCCS outputs was disconnect A6 (from one of the posts further up), and after realizing that was the wrong wire, re-soldered it (it comes from the terminal strip on the A side).  Maybe it was just a marginal solder joint.

Dave

 

[aragorn723]

Hi,

Just tested the Quickie, and both sides work!  Guessing I should probably solder the pjccs wires back in (to their original locations).  What about the black gate caps, think i can put those back in too?  It definitely sounds better with them (there was a little bit of a grainy sound without having any caps in that location). 

Dave

 

[Grainger49]

Dave,

Do that one step at a time.  Swap the PJCCS back first.  Then after verifying it works put the BG caps back.

 

[Paul Joppa]

The PJCCS does not care which side is which, but I would restore it just so that next time there's a question, you know the wiring matches the manual.

Yeah, put the caps back - making sure they are oriented correctly.

 

[aragorn723]

Thanks everyone, its good to go  8)