Bottlehead Forum

Bottlehead Kits => Mainline => Topic started by: chienbleu on October 22, 2024, 11:58:43 AM

Title: HELP with mainline - PSU voltage too high!
Post by: chienbleu on October 22, 2024, 11:58:43 AM

Hi, I'm all assembled and at the final voltage check, BUT getting 326v instead of 275 at the +275 pad on the PS board.

I double checked the transformer settings, voltage 120vac at 31 and 32u.
I double checked all the components/visually confirmed solder joints on the PS board.  All seems ok.
Additional Voltage Checks:
KREGs are 26 and 28v respectively
BREGs are both 0
IA is 324.8
IB is 323.6

Where do you suggest I look next?

Thx, Robert

Title: Re: HELP with mainline - PSU voltage too high!
Post by: Doc B. on October 22, 2024, 12:31:17 PM

It sounds like the tubes are not conducting. If you turn the lights down can you see the tubes glowing?

Title: Re: HELP with mainline - PSU voltage too high!
Post by: chienbleu on October 22, 2024, 12:45:42 PM

R and L tubes look good, glowing.  12AU7 was very difficult to physically insert and is just barely glowing when I turn out all the lights

I just swapped in a newer 12au7, short plate.  Getting a better glow, but voltage still 320.

Title: Re: HELP with mainline - PSU voltage too high!
Post by: chienbleu on October 22, 2024, 02:14:51 PM

SOLVED - Noticed the resistor connected to BREG wasn't in circuit to anything else.  Rechecked that part of the manual and discovered I had somehow skipped installing all the jumpers on that page! (Duh)

Getting better voltage now, but it's still only 261vdc instead of 275vdc.  Is that within tolerances?

Thanks for steering me in the right direction.

Robert
 

Title: Re: HELP with mainline - PSU voltage too high!
Post by: Paul Birkeland on October 22, 2024, 02:23:39 PM

That is plenty of voltage for the circuit to function properly.

Title: Re: HELP with mainline - PSU voltage too high!
Post by: chienbleu on October 22, 2024, 02:34:13 PM

Thanks!  Sounds GREAT!