C26 volume control repair

srm51555

AK Subscriber
Subscriber
Hello,

About three months ago I was gifted a C 26 with a bad volume control from my late uncle's estate. When hooking a meter up to the potentiometers, the pot sandwiched in the middle of the power switch and other pot would not read properly until the volume control was at the 10 o'clock position. In another thread a member suggested me taking apart the pots and seeing whats what. Attached are the pieces and I really don't see anything wrong with them. Is there somthing I'm missing?
IMG_6671.JPG

IMG_6674.JPG

IMG_6676.JPG

Thanks,
Scott
 
In your first picture, there appears to be a gap in the carbon track of the left side pot section. If you're lucky, you can find a pot with a 'wafer' (or whatever the term is) of the same basic shape, and replace the bad wafer with it. Good luck!
-Adam
 
Looks like there is some missing carbon.....

The generic control that Mac parts supplies will most likely not work for the C26. I have not tried it but years ago the Count was having all kinds of issues so I did some research.

Alpha branded wafers will fit but finding one with a audio taper might be a challenge.
 
Audio Classics should have that pot. I replaced mine a few years ago and Audio Classics supplied it.
 
Hello

If you're lucky, you can find a pot with a 'wafer' (or whatever the term is) of the same basic shape, and replace the bad wafer with it. Good luck!

no , you can't do that because it is not serious repair . Both cages are adjusted at manufacture when they are made . If you change one by another one you can't get the same result . Y ou will get differences between one channel and the other one ...The better way is to find one replacement volume control . Original one (NOS) or brand new one with the same value (there is no loudness tag on this volume control )

no other serious way
 
Thank you for all of the replies. I was hoping the volume pot McIntosh supplies along with the 47k ohm resistor found here would work.

Has this changed now. I wanted to get this item running again. I always regretted selling mine.

Thanks,
Scott
 
That post was 10 years ago, I am quite sure that Mac part is long gone but you could call the factory and ask.

That said what Count D ran into was a taper mismatch. The generic loudness tapped control Mac has been sending out for 7 different controls is a linear taper, the tap for loudness is used to alter the taper.

The loudness circuit for the C26 is different and so the control needs to be a audio taper.

You are into the dark void of experimentation to find a solution. I myself have been searching for a solution for a 1959 heathkit and a Mx115.
 
Now you know why I got rid of my C-28 and bought a C-29 with the precision tracking volume control. It worked for me for over 30 years with out a VC control issue. Had to clean input, mode , and tone rotary switches semi annually if I were unlucky, once a year if I was. A C-34 is a big improvement.
 
Update:

I purchased a volume control from McIntosh and it works but not very good. I have to turn the dial to the 10 o'clock position to get any sound out of it. Has anyone ever tried this one listed below from tube depot? It doesn't have the power control function but that would be easy to figure out. I may just purchase it and give it a try if nobody objects and post it here for future reference.

https://tubedepot.com/products/alpha-24mm-dual-audio-taper-pot-8mm-bushing

Thanks,
Scott
 
I have to say that I am impressed that anyone would follow up on their 3 year old original post with a possible solution! If the power switch could be transferred to the new pot, you might have a winner if you can transfer the carbon sections to the old switch. There is no loudness compensation tap, and the shaft is all wrong so transfer of internal parts would be the only solution. Is this the same part number as the one in the ongoing Mac1900 sagas?
 
Thanks for the reply. I ordered the volume control yesterday afternoon just to see how it tracks vs the McIntosh replacement. I was unable to find a CTS dual replacement on any of the larger suppliers. I'm not worried about the ON/OFF feature yet. Although I haven't looked at it physically, my plan was to noninvasively remove the center channel or phase switch assembly and place a turn style switch there. I'd really like to find a solution to post because I'm guessing this will eventually happen to all of the C26's. A coworker has a C28 and Mc2100 for possible sale but given it is the same style volume control/OnOff I may just pass.

Per the service manual the 1900 uses a different volume control.

Thanks,
Scott
 
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