More tranny trouble? [solved]

[Karl5150]

Here goes:

2 - With no tone - 143
    With 60Hz tone - 143 to 170+ as input moved from min up

6 - With no tone - 0
    With 60Hz tone - 0 to 0.6 as input moved from min up

10 - With no tone - 0
      With 60Hz tone - 0 to 30 as input moved from min up

I did not do an input level sweep on the RCA pin because of its location, but a static check matched the signal on the left side.
2, 6 & 10 AC voltage readings mirror the left channel equivalents at slightly higher levels.

Karl

 

[Karl5150]

Those are the # on the "ACV" scale set at 200 (I did 'em again cause you got me scared )
I got a low level "sinus 60Hz -10dB" tone running thru my nuforce microDAC2.
They do vary depending on the volume the computer feeds the DAC, it defaults to 100%
Those # are way different than DC values.

 

[Grainger49]

Then you might be reading them wrong.  146V AC in the Reduction would be only at a transformer output to the high voltage rectifiers.

I don't have the reduction or the manual.  But 143V AC is not going to happen in the signal path.  Could it have been 143mV AC?

When you have a meter with different ranges start with the highest range and move downward on the ranges till you have a reading of at least 50% of that range.  A reading of 0.6V or even 30V on the 200V range is unreliable.

 

[Karl5150]

Unfortunately the AC voltage on my meter only reads 200 and 600V scales. 
The meter reads 122.4 from the wall outlet and a third check shows the same #s reported, similar on both channels.
DC reads down to mV, maybe I'll try and pick up a meter that reads AC in the mV range too.
Thanks for the heads up

 

[2wo]

Before you condemn your meter, look again. I bet there is a little mv indicator somewhere along the bottom. easy to miss...John   

 

[Paul Birkeland]

Those are the # on the "ACV" scale set at 200 (I did 'em again cause you got me scared )
I got a low level "sinus 60Hz -10dB" tone running thru my nuforce microDAC2.
They do vary depending on the volume the computer feeds the DAC, it defaults to 100%
Those # are way different than DC values.

100% out of the computer is too high, try 2%.

What I am looking for is for you to feed a fixed 60Hz tone into the Reduction, then to measure the AC voltage at those points without adjusting the level coming in.  If you adjust the level coming in, then you need to start over.

-PB

 

[Karl5150]

Will do
The DAC also has a pot, should that also be set to the minimum?
I have access to a meter that reads AC in mV.
At 100% the test tone only showed a steady output of about 10% on the level meter built in to the volume display on the computer.
As an aside, I'm sure this is frustrating for all on the help end of the forum, just for different reasons than it is for me on the build end, but for me it is much more of a learning experience than the original builds, which went so well.
Thank you for all your time.

 

[Paul Birkeland]

You can measure the signal coming out of your digital setup by measuring hot to cold on each RCA plug. Do your best to set those to 2-5mV. 

-PB

 

[Karl5150]

Got 4mV from the DAC measured on the open end of 0.6m interconnects, plugged them into the Reduction and got:

2 - 2.9V AC
6 - 100mV AC
10 - 2.9V AC
I hope these #s make more sense.
Thanks

 

[fullheadofnothing]

It seems, in my limited experience, that you are putting an AC voltage into a tube, and getting a higher voltage on the other side(it goes from 4mv at the grid of the first triode to 100mv at the anode of the first /grid of second triode, then to 2.9V at the anode of the second triode). In other words: an amplifier...

What is the AC voltage at the center pin of the output jack in this test scenario? If you're losing voltage between 10 and the pin, you've found your bad solder joint.

 

[Paul Birkeland]

These numbers tell us that the right channel is passing signal.

Did I misread your post about no hum, noise, and sound from the right channel? (I read this as the right channel doesn't work at all)

 

[Karl5150]

Paul,
Yes it is the right channel. That has been frustrating on my end, seeing resistance and voltages where they should be, on what had been an opperating system. I guess if it passes signal and the AC numbers (once correctly gathered) weren't too far out of line then at least I got the boards right. (small win?)
Josh,
I probed 10 at 10U with access to 10L limited by the cap, stand off and ground terminal. Maybe a cold solder to the RCA out has shown up from all the physical motion of adding the boards and testing.
I have to put aside my preconception that because it worked properly before, the problem can only be from the upgrade point forward.
I will check the AC V and lift the board to check the solder joints to the RCA out.
Thanks again for all your help with this.
 

 

[Paul Birkeland]

I have to put aside my preconception that because it worked properly before, the problem can only be from the upgrade point forward.

Those are words of sage wisdom!

 

[Karl5150]

I had the guy at work who builds/repairs power amps for motion control look at it and he pointed out several solder joints he thinks are marginal. I will spend some time re-flowing and see where that goes.
Again, thanks for all the time and instruction on this.

 

[Karl5150]

I believe we can marked this one solved.
First, thanks to all, especially PB, for the help. While I am not the most apt pupil, I did learn quite a lot and hope I will remember to apply these lessons in the future.
In the end it wasn't my marginal soldering (although I won't rule it out going forward) that was the source of trouble.
After removing it numerous times from the custom, copper tape lined box it shares with the S.E.X. and reflowing joints, checking the #s, returning it and having it work and then turning it on another time to not work (or vice versa) I realized the common thread:
It always checked-out outside the box. A tight fit, the right C4S board barely touched/barely didn't touch the box. Slightly melt one side of the stand-offs with the iron while applying pressure and the board cants slightly forward. Problem solved. (enter embarrassed emoticon here)

 

[Paul Joppa]

Nice piece of diagnostic work! You are to be congratulated. Figuring out a difficult problem often takes out-of-the-box thinking (sic  :^)