My Mainline voltage / LED issue

[Tarquinflimbim]

- for future readers - make sure you fit all the valves before doing the tests on page 73.  Doh!


So to follow protocol - here is the description: Resistances check out fine.  Terminal Voltage (DC)
+275vDC on the Power Supply Board 275V - Mine - 295V
+6.3vDC on the Power Supply Board 6.3V - Mine 6.29V
IA on the A side C4S Board 275V - Mine 290V
IA on the B side C4S Board 275V - Mine 290V
Breg Regulator Board (both sides) 220V - Mine 220V
-reg Regulator Board (both sides) 0V - Mine 0 or nearly 0
Kreg Regulator Board (both sides) 8-12V - Mine 4.3V and 3.8V

Both A side LED's are lit on both C4S boards, both B side LED's are dark.

I resoldered the middle board (BIAS regulator board) and confirmed that I had connected the legs together on the adjustment pot.

I have removed the central board three times now, so I'm beginning to think my error may be elsewhere!  Any help appreciated.

Tarquin Flimbim.

 

[Doc B]

Posting good clear pictures of the boards often helps.

 

[Tarquinflimbim]

Left - A Channel LEDs come on after a few seconds, B 's stay dark.

 

[Tarquinflimbim]

Power board (right won't upload for some reason)

 

[Tarquinflimbim]

Back of boards - Left

 

[Tarquinflimbim]

Right side front and back.  Same behaviour as the Left.  RED led's come on for A channel only.

 

[Paul Birkeland]

I'd love to know what you're seeing on OB on the big C4S boards, as well as OA/OB on the small center board.

Your high voltage regulated power supply is working beautifully, and the low voltage at Kreg seems to confirm that the 6C45 isn't drawing adequate current.

It's also worth confirming that the R1 resistors on the big C4S boards are correct, with the 10-ish Ohm resistor on the "A" side and the 14-ish Ohm resistor on the "B" side.

-PB

 

[Tarquinflimbim]

OK - I went through the entire build instructions again; all of it.  Turns out that the line "Insert a 12AU7 into the center socket and a 6C45Pi tube into the left and right sockets" is important.

In case anyone else makes the same mistake, I had only the center tube fitted.

I *did* find one unsoldered connection - which was a drain wire to a ground tab, and was crimped pretty hard, so I'm sure it was connected.  Anyway, I guess that now I am really sure everything is soldered right!

Now listening - sounds lovely with my Beyerdynamics T1's

Tarquinflimbim.

 

[Tarquinflimbim]

Oh - and a couple of hours in.  If you can afford a Crack, you can sell it, and find the money for the Mainline.  I have one of the best Cracks ever built (by Doc), and the mainline is worth the extra.

I have the green crack for sale if anyone is interested.  It's a full spec crack with speedball, painted green hammerhead.  There are a couple of extra upgrades - ALPS pot I think. (Clicks as you change volume).  It's great - but you should buy a mainline.

Let me know if you are interested.

TQFB


 

 

[Paul Birkeland]

Oh man, I hadn't ever even considered the possibility that not all of the tubes were installed!  I'm glad you got it sorted, and I agree with your comparison of a Mainline against a Crack.

-PB

 

[Tarquinflimbim]

The Mainline

 

[Tarquinflimbim]

So - just in case it helps anyone else - I was mentally at the "check everything is OK" stage.  I assumed that you needed a valve to power the middle board, then you test the voltages.  I have now read the instructions a couple of times.  I was wrong.