stereomour 2A3's not glowing

[Paul Birkeland]

Yes, either there is a break in the wire, or the solder joint is not complete.

-PB

[Grainger49]

With a bad connecting wire you never know if it is the from part of the wire not making connection or the to part of the wire.  Try touching up the destination first, 11.  Then try the interconnection.

[azrockitman]

well, I fixed the cold solder between the A socket and the power transformer.  I now have continuity between those two points.  It was just a bad solder and 4 or 5 seconds with some fresh solder on the soldering iron tip solved that.

So far, I can only find one thing amiss on the Active Load PC board...and it's the wire from GND on the Power Supply PC board to the -REG hole.  I had two problems....one, it was a bad solder.  I wiggled it and the solder popped right off.  So that's easy enough to fix. But here's the rub:  I couldn't install it in the correct hole...I accidentally filled that hole with solder, and I couldn't get the hole cleaned out....it was run-off from the top side black wire solder that comes from the bB side.  So, my GND from the power supply is/was soldered to the empty hole right above the "g" in the "-reg" section.   I do have continuity between those three holes:  a)the hole above the "-", b) the hole that resides above and between the "r" and "e" and c) the hole above the "g", where I have the GND wire soldered.  Is that ok?  (in fact, I have continuity between the 4 successive holes in that area the 4th one being the one closest to the "C" next to the "Cc" label.) 

If that's all ok, I can simply resolder that GND connection on the active PC board and hopefully have my problem fixed.  If it must be soldered to that 1st hole above the "-" then I'll have to figure out a way to remove the solder runoff filling that hole.

Thanks

[Paul Birkeland]

You can use one of the other holes that you found with your continutity test.

-PB

[azrockitman]

That will make it easier.  Thanks!

[azrockitman]

We have ignition.   

[azrockitman]

I'm much closer    but I only have audio on the left channel.  (I love the sound out of that one channel though.....can't wait to sort this out)

The problem is not a tube, not interconnects, not speakers, not speaker wires.  Swapping any of those items only confirms the right channel is not working.  My biggest red flag left, other than a couple of odd voltage readings, is that I can't get any reading when I try to do the hum balance exercise.  If the hum pot is defective or wired incorrectly, will that kill sound out of that channel?  or is that irrelevant.

Below are my original voltage readings, todays readings and the S.B. readings.  I see the biggest differences on terminals 2, 4, 12, A3, C3, OA.  The rest look either spot on or close enough.  Is there anything here that would point in one direction? 

PC boards, HV+, both read 374

[Doc B.]

Since the solved problems were related to cold solder joints, one easy approach is to simply go over every joint in the amp (or at least on the bad channel) and watch closely to make sure the solder flows, penetrates the connection and forms a good concave fillet around the joint. Adding just a little bit more solder when you redo each joint is helpful.

[Paul Birkeland]

If OA is zero, then no voltage is getting through that C4S.

You know you have voltage at IA, so the options are:

1.  Cold solder joints on the PC board
2.  A miswire from OA (it should go to pin 1 or pin 6 on the 9 pin socket, I don't remember which off the top of my head)
3.  A short from OA (measure resistance to ground, it should be hard to read at all or very high, but nowhere close to zero)
4.  A backwards LED

Let us know what you find,
-PB

[azrockitman]

Thanks Paul,
I don't believe I have any cold solders on the PC Board
OA is correctly wired to pin 1
I believe I might have had a solder bridge between pin 1 and pin2 on the 9 pin socket, so I moved 2 slightly out of the way.  But now I get 380 volts at OA, which is clearly too much by my interpretation...and it also seems to immediately cause a new problem below;.
My LED's are correctly positioned but where they worked prior to me moving the #2 pin away from pin #1.....now the pair of LED's on the A side no longer light.

[Paul Birkeland]

380V at OA is more correct than 0V.

How is your Kreg votlage on that same side?

If those pins were touching, get in there with your wire cutters and trim everything down so that can't happen again.

-PB

[azrockitman]

OA is at 372   KREG on same side is about 22V   
The other oddities at the moment are Terminal 2 is 370 instead of 230, terminal 4 fluctuates between 16 and 35mV, terminal 12 is around 33mV.

All others, including socket A and C appear normal/within tolerances. 
OB is at 202   KREG on that side is correct at 2.5V

-REG is correct 0.0 on both sides

IA is at 373
IB is at 372

The two HV+ terminals are about 371 each

And I'm still scratching my head at what I did to cause the A side LED pair to stop lighting.  B side remains fine.

Thanks for your help

[Paul Birkeland]

The TL431 is not working on the offending side, that could be the entire problem.

Can you double check that the jumpers are wired up properly?  If so, you'd probably just need to yank and replace that 431, then the LED issue an output issue and OA issue may fall into line.

-PB

[azrockitman]

Both TL 431's are wired with the flat side facing away from the center of the PC board, and the round side facing in towards the center.  And the three solders on the underside for the TL look good/solid and clean to me.

I would suspect Fry's has them....as long as there is nothing especially unique about these, I can try to find one there first....looks like they're cheap. 

[azrockitman]

Fry's had none marked TL431, but the webernet implies that the NTE999 is equivalent.  Can you confirm if it is or not?

http://www.nteinc.com/specs/900to999/pdf/nte999.pdf

Thanks