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

[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.

 

[Paul Birkeland]

I think you'd need to drill a new locating hole.

 

[Colonl_Charisma]

Right on. I found this PEC pot that was linked in another BH forum post. I think I will pick this one up. It's much cheaper, and I may not have to do any manipulation of the chassis with it.

Linking below for anyone else interested:

https://www.digikey.com/en/products/detail/KKA1041S28/KKA1041S28-ND/770961

 

[Deke609]

A drill, jeweler's saw or tiny file will all do the job - which one's faster or cleaner will depend on whether the new hole overlaps with the existing one. If it is in a totally new spot or if it more or less perfectly overlaps the existing hole but just needs to be bigger, a metal drill bit (or even a wood one if you don't care about it getting dull) will do the job in a matter of seconds. But if the new hole needs to be centered on the edge of the existing one, a file or jeweler's saw is the better way to go.

cheers, Derek

 

[Colonl_Charisma]

Thanks Derek! I really appreciate the tips. I should get the PEC pot in a couple of days. I'll know for sure then if I will need to tweak the chassis. In the meantime, I will disassemble my current volume pot.

 

[Colonl_Charisma]

PB would it be okay if we kept this thread open until I install my new PEC pot? It should arrive by Tuesday.

I was able to easily desolder all wires from the old pot, and I removed the old pot from the chassis.

For clarification, What should my resistance checks show once I solder the wires on the PEC pot?

 

[Paul Birkeland]

Are you putting the resistors back on the PEC?  Resistances should be consistent between the levels of the pot.

 

[Colonl_Charisma]

Yes, I will put the resistors on the PEC pot. Haha the volume is a bit loud without them. I couldn't really turn the volume past 9 o'clock, and I was getting channel imbalance at the low levels

Theoretically the resistances on the new pot should be:
U and L left lugs = 75K (due to having the 75K resistors connecting the L and R channels to the PEC pot)
U and L middle lugs = ?
U and L right lugs = 0 (this should be 0 because it is the ground connection)

What should the resistance for the middle lugs be?

 

[Paul Birkeland]

If you have one probe on ground, the upper and lower outer lugs will be about 24K, the inner lugs 0, and the middle lugs variable depending on where you have the pot positioned.

I would not even bother to measure this, just install the new pot and listen to it.

 

[Colonl_Charisma]

Will do haha. Do you think I used too much solder causing the old pot to burn out?

I looked at the old one after I removed it, and it looked rough with all the flux everywhere.

 

[Paul Birkeland]

The flux can get in and disrupt the connection the solder lug to the carbon track in the pot.  That isn't really possible with the PEC.