S.E.X. 3.0 [resolved]

[Dana Hinds]

sorry I am going to go back through everything ,just getting frustrated.

[Dana Hinds]

I have gone through all assembly to make sure of connections or shorts , found nothing. Wondering if the miissed solder connection on resistor to terminal 16U may have taken out a capacitor or something.Lokking for the next step.

[oguinn]

Probably want to start with running the resistance and voltage checks and listing any that are out of spec here.

[Dana Hinds]

before power up normal ,now here's what I get
Terminal #1-0 #3-891 #4-240 #5-0 #8-0 #9-0 #11-678 #12-0 #14-0
#15-0 #17-218 #18-5.5 #19-0 #22-0 #23-0#25-0 #26-0 #36-0 H1-0 H8-0
looks like 17,18,25, are way off

[Paul Birkeland]

Are those voltages or resistances?

[Dana Hinds]

resistances

[Paul Birkeland]

I would be most concerned about terminal 25 reading 0 ohms.  Two wires, one capacitor, and one resistor land there.  Remove each of those one at a time and recheck your resistances as you go until you don't see a 0 anymore.  I would start with the cap, then the resistor, then the white wire going to the OT, then the white wire going to the socket.

You can stop when you find the connection that's dragging that terminal to 0 ohms and let us know what it was.

[Dana Hinds]

with the cap removed I get 678k ohms

[Paul Birkeland]

Hopefully 0.678K? 

You can actually run the amp with the cap removed to check DC voltages, but if you try to listen to it that side of the amp will be quieter and more distorted than the other side.  In any case, I'd go ahead and replace it.  I can remember getting on SEX amp in the past that had a dead cathode bypass cap like that, and I remember that there was something that I thought could have precipitated the failure, but I can't remember what it was.

[Dana Hinds]

great where is the best place to source one

[Dana Hinds]

I now have voltage readings that are off. all are good except terminal #17 has 63v and #18 has 59v should be 15 and 0

[Paul Birkeland]

So what's going on here really is that the voltage on terminal 18 is not 0V, and that is screwing up everything else and has allowed excess voltage on that cap that's shorted out. 

There's a 249K resistor between 18 and 19, does it still measure as 249K?  If so, take the tube out of that socket and set it aside, then take the tube from the other side of the amp and try it in that socket to see if that same pesky high voltage is there.

[Dana Hinds]

I only get 95k on the resistor

[Paul Birkeland]

I would heat up the solder joint holding one leg of the 0.1uF cap in place and pop one lead of that cap off the terminal strip, then recheck that resistance.

[Dana Hinds]

I now get 249k