Did I fry the headphone input? [resolved]

[Discgo1013]

Greetings...used my home bound free time to complete a SEX kit I got over the holidays. Was fun to build and I had to resolder some of the headphone jack wiring and I think I may have fried the headphone input....I'm not a headphone listener but I have a cheap pair I've used for testing...I only get sound from the right channel with no phones plugged in, if I plug in just the tip of the jack I get sound from both left and right speakers

With phones if I plug the jack in all the way, I only get sound in the right, but if I back it out a click I get both channels.

Excuse this headphone newbie, its not a connection I'm used to...

Any insight here? Thanks in advance and hope everyone is safe & healthly

 

[Paul Birkeland]

If you pull the headphone plug part way in, you will connect the tip and ring of the headphone jack to the tip of the headphone plug.

Do you get sound out of the left and right speaker posts?

 

[Discgo1013]

Yes, I only get both left and right speaker channels audible with the headphone plug partially inserted, like 1 click....maybe it’s mis wired? The jack did get melted quite a bit when I resoldered, especially the middle terminals

 

[Paul Birkeland]

If you use speakers on your amp, do you get sound from both sets of binding posts?

Can you post some photos of the jack? 

How are your DC voltages?

 

[Discgo1013]

Thanks for your help, Paul! Photos and DC voltage readings below, I did have a change from my original readings on terminal 16.

If you use speakers on your amp, do you get sound from both sets of binding posts?

Only if I insert a headphone plug partially in, 1 click

No headphone cable plugged in: hear right speaker only
Headphone cable plugged in 1 click - hear both speakers

I've attached several photos of the headphone jack, after looking at the wiring with more attention, I think I may need to rewire the headphone jack to clean it up...think I should order a new one? Its melted a bit

2 - 80.8V
3 - 18.7V
4 - 12-15mV (this was 0)
5 - 0V
6 - 378V
7 - 398V
10 - 372V

16 - 54.5V (this was 78.2V)
17 - 17.9V
18 - 12-15mV (this was 0)
19 - 0V
20 - 377V
21 - 395V
24 - 369V

H2,H5 - 3.25V
H4, H7 - 3.08

 

[Paul Birkeland]

Your headphone jack is a little melted. 

Even with speakers, you can short the left and right channels by partially inserting a 1/4" plug, so that still doesn't tell us much.  If you horribly melted the jack, you might be able to only get both channels on your headphones, but not your speakers, and you'd see that the contacts that move when you plug in your headphones wouldn't touch with no 1/4" plug installed. 

Your voltage on terminal 16 is a little off. 

In the photo below, you can see what looks like a resistor lead poking out and going nowhere.  That is the kind of thing that will make your SEX amp not work, especially if it touches the chassis or the lead of another component.  If you have lots of untrimmed leads in your kit, you'll want to grab a proper pair of side cutters and trim them back.

-PB

 

[Discgo1013]

Yea, I snipped that wire just after taking the photos, and before the voltage check..good catch

Any thoughts on where to look for the cause of low voltage on terminal 16?

What about bypassing the headphone output all together and attaching the green/brown wires from the output transformer to the RCA jacks directly instead of the headphone jack first?

I'm not a headphone user so don't need that functionality

 

[Paul Birkeland]

Any thoughts on where to look for the cause of low voltage on terminal 16?

See if the low voltage follows a tube if you swap them between channels.

What about bypassing the headphone output all together and attaching the green/brown wires from the output transformer to the RCA jacks directly instead of the headphone jack first?

I would very, very strongly not recommend modifying the amp in an attempt to solve a problem.  What you can do is with nothing plugged into the headphone jack, measure the DC resistance between:

1.  Each black binding post and the two lugs on the headphone jack closest to the chassis.
2.  The right channel red binding post and the two lugs on the headphone jack in the middle level (ring).
3.  The left channel red binding post and the two lugs on the headphone jack up top (tip).

Please post these measurements, then I can let you know if there's actually a problem with your headphone jack.  I am 99.999999999% sure that your headphone jack is working perfectly. 

You might also want to post some photos of your build, as we may be able to spot something that is preventing the signal from leaving the amp on one channel.

-PB

 

[Discgo1013]

I would very, very strongly not recommend modifying the amp in an attempt to solve a problem.  What you can do is with nothing plugged into the headphone jack, measure the DC resistance between:

Thanks for your support with doing things the right way! This is with the amp disconnected from power, correct?

 

[Paul Birkeland]

Yes, it can be unplugged.

 

[Discgo1013]

1.  Each black binding post and the two lugs on the headphone jack closest to the chassis.
2.  The right channel red binding post and the two lugs on the headphone jack in the middle level (ring).
3.  The left channel red binding post and the two lugs on the headphone jack up top (tip).

All resistance readings are 0, I guess this means the jack is fine?

Here's a photo of the entire build, I'm carefully checking each joint in the output wiring again now

 

[Discgo1013]

Could this be a tube issue? I swapped R & L tubes and the issue follows the tube....I can still get both channels by partially inserting a 1/4 inch headphone plug

Its the same tube that gave the low Terminal 16 reading, got the same reading on Terminal 2 when I swapped them

 

[Paul Birkeland]

Your resistance measurements indicate that the headphone jack is functioning 100% and you don't need to zero in on that to discover the source of your channel dropping.

Could this be a tube issue? I swapped R & L tubes and the issue follows the tube....

Did the channel that's out follow the tube?

I can still get both channels by partially inserting a 1/4 inch headphone plug

That just means you have one working channel.  This isn't really helpful information.

Immediately I noticed this piece of component lead circled in red.  If those two terminals touch, your SEX amp may turn into a smoke machine.

 

[Paul Birkeland]

If these leads in the red circles touch, you will lose a channel.

 

[Discgo1013]

I need glasses and better light!

I'm having a real hard time seeing exactly what you've circled in the first photo in the amp...I felt comfortable during the build

Let me get some readers and better light and I'll try to sort this out. Thank you for your help and experienced eyes.

And yes, the channel that is out does follow the tube.

You rock, Paul!

 

[Paul Birkeland]

If the channel that's out follows the tube, I would replace the tube.

Having said that, an intermittent short caused by debris or untrimmed leads may periodically destroy any tube you plug into the SEX if it shorts things out.

In the first photo, it appears that there's a piece of metal between where the blue wire connects and where the striped end of the 1000uF/35V capacitor connects.  If that is the case, you 380V power supply would short to ground through your plate choke, and that will destroy the plate choke.

 

[Discgo1013]

Got it, the light I used to take the photos was different then where I work, very hard for me to see but I clipped it

One the second photo, there is at least 1cm space between those wires

The dead channel 100% follows the tube now so I have ordered a new one.

Can't thank you enough, cheers!

 

[Discgo1013]

New tube came yesterday and the SEX sounds great. All voltages are good and beautiful music from headphone out and speakers!

Thanks a ton, Paul!