Trimmer Not adjusting Voltage

[thdewitt]

So,

I just finished building my paramount.  When I go to follow the step to adjust the 10K trimmer, nothing seems to happen.  The voltage stays at 112V.

All the resistance checks seem to be fine except for B2 which reads OL instead of 8.2K.

For voltages I get the following errors:
terminal 1 421 V
terminal 5 67.2
t9  111.5
t16 444
t19 1112

a1 71K
a2 423
a3 0
a4 66.3

C4s
Kreg a  2.5V
Kreg b 10.25
Oa  301
ob 111.7

Any help will be appreciated.  I checked all the solder joints thoroughly.  I will reflow in the morning if I can't find anything else.  I rechecked my connections.  Problem is that some of the materials and pictures don't match anymore so it is a little tricky.

Thanks,
Tom

 

[Paul Joppa]

The 10K potentiometer (R4) and the 4.99K (R3) resistor are on the outer end of the "A" side of the board. They are in series on the board, with the 431 chip in parallel. The ground end goes to -reg on the "A" end, which should go to signal ground. The hot end of this combination goes to  kreg on the "A" side, which in turn goes to the tube socket pin B2, There is a problem with one of these connections.

Based on the 2.50 volt reading at kreg (A side) I suspect the 10K pot is OK but the 4.99K resistor is not connected at one end. Measure the resistance of the resistor itself to be sure the right part is being used, then check the solder connections.

 

[thdewitt]

Paul,

Thank you so much for your quick response.  You were exactly correct.  For some reason I had left out R3 on both of my boards.    Thank you so much for your help.

Regards,
Tom DeWitt