No sound from left channel after working without issues earlier in the day.

[Colonl_Charisma]

Sorry, I did do the res and vol checks lol. It definitely worked! Both channels are working, and the amp sounds amazing again.

[Paul Birkeland]

Sorry, I did do the res and vol checks lol. It definitely worked! Both channels are working, and the amp sounds amazing again.

No, that's not to fix the amp, it just makes the amp into a mono amp.

Do both channels work with just the jumper on the volume pot?  (this needs to be on without the jumper between 6 and 10)

[Colonl_Charisma]

Gotcha! Yes, both channels work with the jumper on the U and L middle lugs of the volume pot. I have not installed any other jumper cables.

[Paul Birkeland]

That tells you that the problem is between the RCA jacks and the volume pot, which eliminates 90% of the amp.

It is actually possible to destroy the pot if lots of solder gets into it (and the flux with it).  You can remove that jumper, then measure...

What's the DC resistance between the outer top lugs of the pot?

What's the DC resistance between center pin and shell of the left RCA jack?

What's the DC resistance between the left RCA jack center pin and the upper outer lug on the volume pot?

[Colonl_Charisma]

I hope that I have not destroyed the volume pot haha.

Resistance of left upper lug of vol pot = 32.6 ohms
Resistance of right upper lug of vol pot = 00.1 ohms

Resistance between center pin and shell of left RCA jack = 107.2 ohms (I think I measured this correctly)

Resistance of left RCA jack center pin and upper outer lug of vol pot = 107.2 ohms (again, I believe I measured the correct thing)

[Paul Birkeland]

Resistance of left upper lug of vol pot = 32.6 ohms
Resistance between center pin and shell of left RCA jack = 107.2 ohms (I think I measured this correctly)
Resistance of left RCA jack center pin and upper outer lug of vol pot = 107.2 ohms (again, I believe I measured the correct thing)

32.6 ohms or 32.6K ohms?

I'm guessing those are all K ohms, can you put the pot in the middle of its rotation and tell me the resistance between the center lug on each level of the pot and ground?

The 107K between the left RCA jack center pin and the upper outer lug of the volume pot would be a problem.  You have a 75K resistor between those places, you should see 75K for that resistance measurement.

[Colonl_Charisma]

You are correct those are all in K. I forgot to add that in my post. Regarding the 75K resistor. I see a 75K resistance drop. Isn’t that what is supposed to happen or should it be 75K exactly? I think I may have measured the wrong spot.

I measured the left U lug of the volume pot = 32.6K
I then then measured where the white wire connects to the 75K resistor which measured the same as the RCA jack = 107K

Volume pot set to noon position:
U center lug= 11.58K
L center lug= 10.78K
U ground = 00.1
L ground = 0

[Paul Birkeland]

I measured the left U lug of the volume pot = 32.6K

That would indicate your pot is damaged.

[Colonl_Charisma]

I uploaded a photo of the vol pot to make sure we are talking about the same places. There's a 75K resistor between those two spots.

[Paul Birkeland]

Yes, if you measure the bottom outer pot lug I bet it shows 24K.

[Colonl_Charisma]

Yep, that is what it measures. What should I do? If I get a Alps Blue vol pot will that also give me better volume range like the vol pot mod?

Or is there a way for me to get the original volume pot? That resistor modification worked beautifully by increasing the volume range.

[Paul Birkeland]

You should replace the pot.  An Alps Blue is a bit annoying because it requires a PC board mounted to it and that often requires cutting a little relief in the wood base. 

You could get the TKD, PEC, or Noble pots and those would work nicely.  You can use those same resistors on a new pot as well if you like the increased range you get.

[Colonl_Charisma]

Thanks for your help PB!

I found a store online selling a TKD pot. Does this look like what I would need for a Crack?
https://www.partsconnexion.com/TKD-64187.html

One last question. I should not have to manipulate the chassis in any way to install this TKD potentiometer, correct?

[Paul Birkeland]

You may need to snip off the locating pin on the TKD, but otherwise it should fit properly.

[Colonl_Charisma]

Thanks PB. If I need to would it be difficult to file the locating pin hole so that the TKD potentiometer would fit without snipping the pin? I think snipping the pin could cause me trouble down the road.