Power chord for SEX amp 3.0? (and other questions about SEX) [resolved]

[slankoe]

Don't use your amp if it does not pass the voltage tests!

Curiosity got the better of me, but you are right. There is no warranty on a human life.

 

[Doc B]

Check to see if the 1000uF capacitor connected to terminals 11 and 12 has perhaps been installed backwards. Black stripe side should be connected to terminal 12. Also make sure white wire from the OT-2 output transformer terminal 10 has been properly connected to terminal strip terminal 11 and not some other terminal by accident.

 

[slankoe]

Check to see if the 1000uF capacitor connected to terminals 11 and 12 has perhaps been installed backwards. Black stripe side should be connected to terminal 12. Also make sure white wire from the OT-2 output transformer terminal 10 has been properly connected to terminal strip terminal 11 and not some other terminal by accident.

Capacitor polarity is correct, white wire from OT-2 terminal 10 is going to terminal 11. Re-soldered the terminal strip 11 connection because it looked like it possibly wasn't correct, but that didn't change test results.

 

[slankoe]

Right channel still dead, left channel still... sounds fantastic.

Hey wait so get this. Not sure if this is normal. Not sure if anything is normal, but I unplugged the left RCA input channel from the source to the amp, and kept the right one plugged in. I heard very quiet sound coming in. As if the right channel was crossfeeding a bit into the left. Still zero sound on the right. Does this mean anything?

 

[Doc B]

It means that the signal is getting partway through the right side circuitry, enough to bleed into the left. Maybe try disconnecting the 1000uF cap at terminal 12 and see if that changes the voltage reading at terminal 10. Also, posting an image of the circuitry around that socket and strips might be helpful.

 

[slankoe]

I'll try to get to that before I leave for work, thank you. Will update soon.

 

[Paul Birkeland]

The voltage for terminal 2 is good (85 or so), but then terminal 3 is completely weird. It goes in the millivolt range, between 200mV and 2mV sometimes there is a minus for example 02.4mV was just measured. The number keeps changing. what the hell is going on?

Terminals 3 and 17 are wired together at the cathode of the output triode of that 6FJ7.  Getting 0V there means that either the tube isn't conducting or a part is loose/damaged and not permitting conduction.

 

[Paul Birkeland]

I plugged it all in and my headphones make sound out of the left ear only

Not passing your voltage checks means that your amp shouldn't be used.  We will not respond to any commentary on what you do or don't hear from your headphones until you pass your voltage checks and the amplifier is safe to operate.

 

[Paul Birkeland]

Did all my voltage checks again. All were pretty normal looking. Except much of the 385V were bumped to 400V and likewise the ones that were supposed to say 400 were closer to 425. The only one that isnt normal is terminal 3 which shows in the millivolt range, which is not ZERO, but then again all the ones that were supposed to say zero as per the manual actually are close to zero, but none of them are zero. I'm assuming this is just because of the sensitivity of the volt meter or what?

When you post your voltages, it should be a list of the terminal, the voltage you have, and the voltage you're supposed to have.  Having 400V where you're supposed to have 385V is an issue, but you haven't actually told us at which terminals you have that issue.

 

[slankoe]

I got back from work and went to a meet. I had a third party with amp building experience re-check the wiring diagram. Turns out I was missing one little wire. Problem solved. Works like a beauty now.

 

[slankoe]

Successfully installed C4S update, sounds good! Noticeable improvement in reduced noise (nearly silent background where there was a slight hiss at max volume with no music playing).

Thanks to all who assisted me during this build and thanks to Bottlehead for making such cool kits available. It was a really neat first build experience, despite the hiccups (simply caused by missing one step)  ;D

Maybe someday I will make another order, 'till then I shall enjoy my lovely SEX AMP.