Incorrect Voltages - Where to start

azmouse76 · 2412

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Offline azmouse76

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on: May 08, 2016, 12:36:35 PM
So I am picking backup a project that I started a year ago and never finished.

Everything is assembled. Apparently something is not perfect.

Resistance test looks good, however when I get to the voltage test on p77, things are off:

Point (Expected) = Actual

Left
kreg (1VDC) = 0.58
breg (100VDC) = 0
OB (100VDC) = 216
bA (0VDC) = 0
OA (170VDC) = 0
IA (225VDC) = 307

Right
kreg (1VDC) = 0.013
breg (100VDC) = 0
OB (100VDC) = 216
bA (0VDC) = 0
OA (170VDC) = 0
IA (225VDC) =307

Any ideas where to start?

Thanks

-dan


Offline Paul Birkeland

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Reply #1 on: May 09, 2016, 06:12:53 PM
Are all the tubes glowing?

Paul "PB" Birkeland

Bottlehead Grunt & The Repro Man

Offline azmouse76

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Reply #2 on: May 10, 2016, 06:04:55 PM
Thanks for jumping in.

No Glow.

The Shunt Regulator Board LED's A-D2 and B-D2 seem about 50% dimmer than the led's on the Plate load boards and the A-D1 and B-D1 are about 75% dimmer than the plate load boards. 



Offline Paul Birkeland

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Reply #3 on: May 11, 2016, 07:38:03 AM
If the tubes don't glow, then you can forget about debugging any of the PC boards except the power supply board at the back.  Do you get 6.3V DC on the two pads labeled as such on the power supply board?  (There was a check for this in the manual early in the manual)

Paul "PB" Birkeland

Bottlehead Grunt & The Repro Man

Offline azmouse76

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Reply #4 on: May 15, 2016, 03:16:09 PM
Thanks, noticed a mistake, swapped the 6922 and 12BH7.

Put in the proper sockets, the 12BH7 glows, however the 6922 does not. Looking at the data sheets, it seems the 6922 could now be bad given the voltages it saw in the 12BH7 socket.

Seem reasonable?

I ordered a new 6922 and will see what happens!


Offline Paul Birkeland

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Reply #5 on: May 16, 2016, 06:30:26 AM
The 6922 can be somewhat difficult to see glowing.  When you had it in the 12BH7 socket, you weren't supplying any heater voltage at all to it, so it may be worth revisiting with the lights in the room off, just to be sure.  I would also check your voltages now. 

Paul "PB" Birkeland

Bottlehead Grunt & The Repro Man

Offline azmouse76

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Reply #6 on: May 17, 2016, 03:42:50 AM
No visable glow with lights on on the 6922.

Voltages are now:

Left
kreg (1VDC) = 0.027
breg (100VDC) = 0
OB (100VDC) = 213
bA (0VDC) = 0
OA (170VDC) = 219
IA (225VDC) = 221

Right
kreg (1VDC) = 0.0
breg (100VDC) = 0
OB (100VDC) = 212
bA (0VDC) = 0
OA (170VDC) = 220
IA (225VDC) =222


Offline Doc B.

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Reply #7 on: May 17, 2016, 05:07:31 AM
Try turning the lights out and check again.

Dan "Doc B." Schmalle
President For Life
Bottlehead Corp.

Offline azmouse76

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Reply #8 on: May 18, 2016, 04:48:02 PM
haha...sorry, lights were off....evidently in more way then one!


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