Bottlehead Kits > Mainline

Mainline Voltage Check

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FS:
Hello,

I have completed my Mainline. The voltage check gave me different values for each side. When the tubes are inserted and the amp powered up, the tube filaments glow on all three tubes.
On the C side of the Amp, the D1 and D2 of the A side of the C4S board glow, D1 and D2 of the B side don't.
On the A side of the Amp, none of the D's glow on the C4S board.

My voltage measurements as per instructions pn page 73 of the manual (tubes are inserted):

+275VDC on Power Supply board: spec is 275V,  reads 243V
+6.3vDC on Power Supply board: spec is 6.3V, reads 5.33V
IA on A side of C4S board: spec is 275V,  reads 243V
IA on B side of C4S board: spec is 275V, reads 243V
Breg on Regulator board (both sides): spec is 220V, reads 3.7V on A, 153V on B
-reg on Regulator board (both sides): spec is 0V   reads 0V on both sides
Kreg on Regulator board (both sides): spec = 8-12V,  reads 2.43V on A, 1.58V on B

Could somebody please pinpoint me to the possible problem?
Thanks in advance.
Cheers,
Falko

Paul Birkeland:
I would start by determining why you don't have 6.3V DC out of the power supply board.  This is most often solder joints.

The 243V on the high voltage side is also odd, but would still be enough for the regulator to work properly.  There may also be a flaky solder joint on this part of the board that's causing some voltage drop that wouldn't otherwise be there.

Breg being 3.7V on A makes me believe that you have a jumper on that board that isn't where it's supposed to be.

The Kreg voltages being so far off also point to jumper issues on the PC boards (you did solder the two legs of each trim pot together as advised in the instructions?).

-PB

FS:
Hi Paul,

Thanks for your quick reply. I have touched all the soldering joints to re-flow the solder on the power board and the regulator board. I did the same on the connections to the power transformer. I checked and retraced all the steps from populating the boards through soldering, everything looks as it was supposed to. And yes, I have soldered the two legs of the trim pots together as instructed. I still have the exact same readings. Are there any other readings that I could take to narrow it down?
Thanks,
Falko

Paul Birkeland:
It might help to put some photos up of your build, as well as to focus on getting 6.3V out of the power supply board when the tubes are plugged in.  This is still most certainly a solder joint issue.

-PB

FS:
Hi Paul,

Thanks. I will work on this tonight. The 6.3V will be my first aim before moving on to the other boards.
Cheers,
Falko

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