Need help with lost right channel on sex 3.0

[Big Bamboo]

Recently I lost my right channel affecting both speakers and headphones. After trying different inputs and head phones, I conclude it was my amp.
Tube swapping and cleaning the headphone jack did nothing. The OA and OB voltages were 77 and 78 volts DC.

So, I did the chopstick test and immediately noted when pushing on the headphone jack lug closest to the top plate, the right Chanel came back. As soon as I released pressure, it went out again. So, I figured great, Ive found the issue….a bad solder joint.
So, I reflowed that joint which didn’t fix it. So I reflowed it a few more times adding a bit of solder and wallah, the Chanel came back. I thought all was good.

But, now my speakers don’t work. I get a low volume static sound with very faint music heard. At first I thought the headphones sounded fine, but after running a L, R, MONO test, I found that the an isolated signal to the right headphone sounded fine on that side, but there was a faint weird ringing echo on the left.

I’m now beginning to wonder if the headphone jack was the problem all along. Did I bugger something when reflowing? I was careful not to overheat it.

Before I consider replacing the headphone jack, I’ll wait for advice.

The picture has a red arrow pointing to the lug in question.

Btw, although you might question it from the picture, the lug in question is not shorted to the middle lug.

Thanks for your help

John

 

[Paul Birkeland]

It would be a good idea to see what the other side of the headphone jack looks like. Generally you'd also want to check the rest of the voltages as well (your measurements indicate that the first stage on each side is working, but the second stage may have an issue).

For the lug you pointed to, does it show continuity to the other terminal across from it? Headphone jacks can fail from excessive heat when the spring contacts pull the lugs through the plastic when they get hot, and this would show as a resistance issue. Do note that you can also add a jumper between the bottom two lugs on that jack if you'd like.

 

[Big Bamboo]

I tested and there is continuity between the two lugs you mentioned. Is that what one is supposed to see in a functioning Jack?
I attached a few more photos as well.
Could you please tell me what other voltages to check or point me to the manual detailing those. For some reason, I thought after the C4S upgrade, the only voltages to measure were OA and OB.
I don’t understand enough about the circuit to get why you suggested putting a jumper between the lower lugs.

Thank you so much.

 

[Paul Birkeland]

Your headphone jack has definitely melted a fair bit, but this won't cause problems with headphones. If you have both channels of your headphones working and one speaker output stops working, then you should replace that jack. Please don't do that now though, as it could introduce another issue while trying to figure out what's going on.

Voltages at 3 and 17 would be useful to know.

 

[Big Bamboo]

thx,

3 16.55 volts DC
17 16.59 volts DC

For clarification,
The headphones play on both channels but do not sound right.
There is some distortion noticed in the left channel when playing both channels simultaneously. If I send a signal to just the right headphone, the right sounds good, but you still hear the shrill noise on the left.

The speakers emit a very low volume of distorted music. Even at full volume, you barely hear it.
Hope that helps.

Thank you
John

 

[Paul Birkeland]

I'd start by replacing the headphone jack since you have a difference between the headphone and speaker sound.

 

[Big Bamboo]

Thank you,

I put an order in for replacement and will follow up later.

 

[Big Bamboo]

I replaced the headphone jack and my problems continue. On headphones the left channel sounds normal and the right channel is silent. On speakers I get a low volume distorted sound out of both channels.
I rechecked the things you had asked about
OA 83 v DC
OB 77.5 V DC
3 16.86 V DC
17 16.59 V DC
there is continuity across the two headphone lugs closest to the top plate

Of note is that when I flipped the amp the voltages were off due to one tube not being lit. I jiggled the tube at which point it lit and voltages were good. When I flipped the amp back over I noticed if I jiggle the one tube, the tube glow would go out, until I pushed it in a certain direction. Cleaning the tube pins and socket did not change the behavior. Swapping tubes showed it was particular to the socket not the tube. I’d guess this is not causing the problem I posted about. I have never seen a case when both tubes weren’t lit when in an upright configuration.

Any additional trouble shooting steps would be appreciated.
I have attached updated photos of the new head phone jack.

John

 

[Paul Birkeland]

It's possible to melt together cat5 wiring if you're not careful. Wherever CAT 5 wires are touching, manually pull them apart so you know the bare wire underneath aren't touching.