Question re: Power Supply Board [resolved]

[berzerkeleyan]

Hello all. I completed my mainline build a few weeks ago. After reading a some troubleshooting posts on this forum, I was able to get my voltages correct and I was up and running For about a week, things sounded wonderful. Then some static, then my left-channel disappeared. Eventually everything went quiet.

After a lot of troubleshooting, my two questions are this:

• What does it mean when the +6.3vDC solder pad on the power supply board is not supplying any juice?
• what are the symptoms of the +6.3vDC solder pad on the power supply board not supplying any juice?

I get ~350vDC on the +275vDC solder pad of the power supply board, so I'm ultra-confused. All my solders look good, though I've decoupled everything from the power supply until I figure this out.

Thanks.

[Grainger49]

Ok, you don't have the heater voltage so the tube will not conduct.  That makes the voltage stay high on the output of the power supply.  Your problem is in the heater circuit. 

Go over the board looking at anything associated with the 6.3V DC output.  There just might be something that didn't get soldered that worked for a week or two.

[Paul Birkeland]

• What does it mean when the +6.3vDC solder pad on the power supply board is not supplying any juice?
• what are the symptoms of the +6.3vDC solder pad on the power supply board not supplying any juice?

There are two possibilities.  Either you are getting no DC voltage out of the low voltage power supply/regulator (as Grainger mentioned), or you have a short downstream.

Pop the red wire out of the +6.3V pad temporarily, then measure the DC voltage between the two pads.  If it pops up to 6.3V, then you have a short on one of the tube sockets.  If it stays at 0, then there's an issue on the board.

-PB

[berzerkeleyan]

Thanks for the suggestions, guys. I'm sending the forum a quick note to say all is well. I got distracted with work and didn't spend any time troubleshooting after I first posted. I finally went back to the soldering table today and reinspected and resoldered some suspicious connections. After several rounds of voltage testing, I finally got to the necessary values. The final result is a blissfully clean setup.

There's no question this is a very different-sounding amp than the Crack. Now that I've got a stable box I'll be spending a lot of time over the coming weeks comparing the two.

Thanks again!