Just finished my S.E.X.

[SilverS]

Alright I desoldered the wires connected to T5 and T25, no sound on either channel now. I'd also like to add I never plan on hooking speakers up to the amp, so trouble shooting the binding posts is at the bottom of list for me.

 

[Paul Joppa]

So, now we trace the wiring to the headphone jack and binding posts. (I am including the speaker binding posts because an error in that wiring could cause problems with the headphone wiring, and I don't want to complicate matters by deviating from the manual.) At every terminal you test, inspect the solder joint while you are there in case the solder hasn't flowed properly.

First check the ground wiring. With one meter lead to terminal 17 or 18, check that there is zero resistance to terminals 17, 18, 15, and 10 (and to A3 on the tube socket). Then check resistance to the lowest terminals on the headphone jack. Finally, you should find zero resistance from this ground to the two black speaker binding posts (one for each speaker).

All OK? Then measure the resistance to ground of the wire that used to go from terminal 5 to the headphone jack - it should be infinite. Do the same for the red speaker binding posts which should also be infinite resistance to ground.

Repeat for the other side, terminals 37, 38, 35, 30, and B3 for ground, and infinite resistance at the wire that used to go from terminal 25 to the headphone jack, and the red binding posts.

If all that is OK, then we will trace the hot leads. With one meter lead connected to the wire that used to go from terminal 5 to the headphone jack, put the other lead on the middle terminal of the headphone jack on the side nearest the volume control - the should be connected with zero resistance. At the other end of the 120 ohms resistor, you should measure 120 ohms. The resistance to the other resistor on the headphone jack (the top terminals) should be infinite. Finally, at one of the red speaker binding posts you should read zero resistance, and infinite resistance at the other red terminal.

Repeat for the other side - meter to the wire that used to go from terminal 25 to the headphone jack, read resistance at both ends of the resistor on the top of the headphone jack (should be zero and 120 ohms) and the other red speaker binding post.

 

[SilverS]

Here are the results of the tests:

All resistances in Ohms
T17 ~ 1.1
T18 ~ 1.4
T15 ~ 1.1
T10 ~ 1.6 - 1.8
A3 ~ 1.6 - 1.8
Black Binding posts (L/R) ~ inf./inf.

T37 ~ 1.1
T38 ~ 1.4
T35 ~ 1.1
T30 ~ 1.6 - 1.8
B3 ~ 1.6-1.8
Red Biding posts (L/R) ~ inf./inf.

As for the wires going from T5 and T25 to the headphone jack, was I supposed to desolder them from the headphone jack or the terminal strips?

 

[Paul Joppa]

Man, it's really hard to describe things fully with just words! Sorry about that, I means to desolder from the terminal 5 and terminal 25.

The ground buss resistances are all low, showing they are connected properly. However, those resistances should not differ by even 0.1 ohm, since they are all connected by short lengths of wire. It may be the solder connections are not good, or it may be that the connection to the meter was not good enough to get that kind of accuracy. It can be quite difficult to get a good, low resistance connection with a meter probe or even a cliplead.

You did not report the resistance from ground to the bottom terminals on the headphone jack, but they should also be near zero. There are two twisted pairs of wire, from the headphone jack, one to each speaker output pair. One of those wires is the ground and should go from the bottom terminal of the headphone jack to the black binding post. You did report that none of the speaker binding posts are connected to ground, but the black ones should be. So there is a failure of ground connections somewhere along that line.

 

[SilverS]

Whats really confusing me is that the speaker posts get their signal from the headphone jack, which means they're getting the right channel from the headphone jack but the headphone jack doesn't appear to be getting the signal in the first place.