Faulty Left Channel

[Mesz77]

My crack has decided to give out after a year or so. The left channel hasn't been working at all. Whenever I built my crack I got suckered into doing a bunch of mods for it, which included two large film caps at terminals 6&7 and 9&10. I used zip tie mounts to secure the caps to the plate, but after a while the cap connected to 9&10 started to dangle from the plate because the adhesive wore off. Around this time is when the left channel gave out. So I figured it was due to the hanging cap.
I flipped the plate over and turned it on to do a little testing.  I poked both wires coming from the cap and whenever I poked the one leading to terminal 9, the left channel kicked in! So I took the heat shrink tubing off both ends of the capacitor. When I put the capacitors on when I first built the crack I had to solder some extra wire to both ends of the caps since their leads weren't long enough. I figured that there was a faulty connection so I twisted the wires together and soldered them for both ends. I used gorilla glue to secure the caps to the plate and figured I was all good to go. I was not.
The left channel is not working again and I cannot figure out why. All the LEDs are lit up, but the ones on the board without the heatsinks are pretty dim. My voltage checks for both boards are all good. One thing that has occured a few times while messing with the components is that ive gotten zapped even though the amp is turned off and unplugged from the wall. I really want to return to audio nirvana asap so any help is greatly appreciated!!

 

[Paul Birkeland]

Can you post all the voltages from both PC boards?

A properly built/running Crack, especially with the Speedball, should discharge the HV power supply within a minute or two. 

Have you considered just using the 100uF caps we provide with the kit?  Big film caps tend to make for an unreliable Crack.  If you have to have them, there's ample space in the Crack-a-two-a.

-PB

 

[Mesz77]

I have not used the caps that were provided, but if it ends up being the difference between the amp working or not, I will put them in.

Small Board:
OA - 69.2
IA - 181
B-A/B - 0
IB - 181.2
OB - 70.7

Large Board:
OA - 104.9
OB - 102.6
G - 0
B+ - 180.8

 

[Paul Birkeland]

It may indeed be just that.  In the absence of a voltage problem, it tends to be input/output wiring that causes a problem like this (or something outside the amp like cabling).

 

[Mesz77]

I switched out the film capacitor for the stock capacitor and the left channel is still not there. I made sure to solder the banded lead to 10U and the unbanded to 9U

 

[Paul Birkeland]

Can you post some photos of what you have going on right now?

 

[Mesz77]

Let me know if you need more than these

 

[Paul Birkeland]

I see Doc B. has increased the maximum image size we accept on the forum!

So you have an Alps blue pot installed without a PC board.  Those break when you connect wires to the pins.

Is that a pilot light you've added?

The white wire on the headphone jack looks like it might not be super well soldered.

 

[Mesz77]

Lol I didn't realize the images were so huge! The white wire to the headphone jack looked and felt pretty solid, but I reflowed it and still no left channel. I suppose I'll reflow all the pins to the alps pot now. That is a pilot light that I installed since I kept on forgetting to turn the amp off!

 

[Mesz77]

I think I may have found the issue but I want to double check. Whenever a pair of headphones is plugged in, are all three of these pins on the jack suppose to look separated like in the image?
I wasn't getting anything through the left channel after reflowing parts of the alps pot, but while listening I poked the very top pin in the headphone jack so it would touch the plate across from it. It was separated like the other two pins, but not as wide as them as you can see in the image. I got audio in both channels whenever this happened, and the pin went back to being separated like it was before after poking it. The audio remained in both channels so I ran a left/right channel test from youtube through the amp to make sure it wasn't the right channel coming in through both channels. It's definitely working now, but the top pin on the jack concerns me. If I pull a little bit on it to separate it more I lose the left channel completely.

 

[Paul Birkeland]

The tip contact won't separate as much as the ring and the sleeve do.  That's normal and what I see in your photo. If you poked that top contact down so it touches the other side, that will cause your left channel to short to ground and it will drop.

I don't suppose you're using a 1/4" to 1/8" adapter?

 

[Mesz77]

No adapter...

 

[Paul Birkeland]

With your headphones plugged in, you can measure the DC resistance between ground and the tip, then ground and the ring.  They should be about the same. 

The ring is the connection on the HP jack where the red wire lands.

The tip is the connection on the HP jack where the white wire lands.

 

[Mesz77]

Both the ring and tip are around 230 ohms. Both channels are still working, but the tip contact is very sensitive. When I touch it with the multimeter the audio cuts in and out.

 

[Paul Birkeland]

If you wiggle the white wire connecting to the tip terminal does the audio cut in and out?

 

[Mesz77]

It doesn't cut the audio when I wiggle it

 

[Deluk]

Off the wall suggestion. Remove some of the solder on the headphone jack link wires as if you were going to remove them. Plug in you phones and reflow the connections. That may allow the sections to "relax" and re align the contacts. You could try this first with the plug in if you wish. Will it help? I don't know.

 

[Mesz77]

I haven't had any problems with the amp since yesterday, but ive been looking into other headphone jacks. If I were to get the one in the link how would i go about wiring it?

https://www.digikey.com/en/products/detail/153X/153X-ND/1290423

 

[Paul Birkeland]

Well, that's a mono jack, so you'd lose output to the right ear cup under all circumstances.  It's also not insulated, so you would put the chassis plate in the signal path which isn't ideal.