S.E.X. 3.0 Kit: Right headphone driver is significantly quieter [resolved]

[Paul Birkeland]

It might help to see some more photos of the build on the A side of the circuit.

[Jet]

Here are some pictures of side A.

[Paul Birkeland]

5L needs more heat and more solder.

9L had leads that should be trimmed off.

10L needs more heat so the solder flows out.

11L needs more heat so the solder flows out.

10L had leads that need to be trimmed back.

The STP wiring that goes to the 12 pin socket needs to be as close to the chassis plate as possible.  I see one piece of it and it looks like the foil from the STP is touching the lead of the black Solen cap it's next to. Both of these wires are also installed over the 680 ohm resistor, which is incorrect.

[Jet]

I've now made all of those changes to my wiring and I rearranged the STP wires, both of them now go under the 680 ohm resistor. The foil from the STP wiring wasn't making any contact with the black Solen cap.

[Paul Birkeland]

Is there any change to the performance of the amp?

[Jet]

The left headphone driver is still much louder than the right although I do hear a significant hum in the right driver now which I think is new.

[Paul Birkeland]

Are the DC voltages still correct?

[Jet]

All the voltages are normal except for terminal 18 which is reading about 0.023 volts DC when I should be getting 0.

[Paul Birkeland]

This is likely to be a solder joint issue or a component touching something it shouldn't be.  If you'd like to send it in for repair, you can contact Eileen at queen(at)bottlehead(dot)com regarding getting a repair box. 

Otherwise reflowing all the solder joints on the A side of the amp, moving the Solen cap up a bit so the body of the cap isn't touching anything, and ensuring that all your component leads are trimmed should get your amp into working order.

[Jet]

Thank you for your assistance, I've sent Eileen an email about a repair box.

[Jet]

I sent an email to Eileen about a repair box on Sunday but I haven't gotten a response?

[QueenBottlehead]

Hi Jet, I don't seem to have an email from you requesting a repair box. Do you mind sending it again to [email protected]? Thanks so much, Eileen

[Jet]

The request should've come from Geoff Spear

I've received the box and I just packed up the amplifier, it should be ready to ship out tomorrow.

[Paul Birkeland]

Today I got this SEX amp on my bench.  The 220 ohm resistor between A10 and A8 was poorly soldered and creating a major part of the channel imbalance (about 20dB). Two of the jumper wires on the output transformer got hot enough during soldering to melt together and short out, which effectively reduced the output of that channel to nothing.

Either problem on its own wouldn't be that difficult to track down, but the intermittent nature of the loose 220 ohm resistor made sorting all of this out rather difficult.

Once these two issues were dealt with, I discovered that one of the 6FJ7s was not super happy about operating with these issues, but I have a loose replacement that's a match for the remaining good tube.

[Jet]

Thanks so much for the update and letting me know exactly what was wrong with the amp, it's nice to know that the issues are being taken care of.