• The move to the new server is done. There are some software and database maintenance updates in process. This has us passing the hat around to help out. We appreciate any donations. Seriously, even a dollar helps. The payment page may be found here - https://www.audiokarma.org/support.html

Earlier production C26 restoration - filter cap mounting?

kcvintage

kcvintage

Active Member
I made my first purchase of non-working equipment from ebay - an earlier production C26 (SN 69P98). The seller shipped in a massive wad of bubble wrap but the faceplate still broke - not surprised. We settled up at the price of a new one from McIntosh, which I promptly ordered.

I was able to get it running by (temporarily) replacing one of the power supply multi caps that measured at virtually no reading. I've cleaned and lubed the pots and switches and it sounded darn good with two replacement caps tacked in. My plan is to replace the power supply caps, then move on and recap at least the electrolytics, and probably the mylar caps.

After a few projects where I restuffed original filter cap cans, I'm leaning heavily towards chassis mounting maybe with perf board on aluminum standoffs (ala c_dk's posted C28 restoration). I've read almost all of the C26 posts here on AK, and most of the C28 posts (I also have a non-working C28 I've set aside for the time being...). Does anyone have any suggestions on the best route to take for an under chassis mounting of the four replacement electrolytics?
Thanks in advance for your thoughts!

IMG_0497.jpg IMG_0496.jpg IMG_0495.jpg
 
Register to hide this ad
I do not believe there is enough room under the deck to mount a circuit board in the C26.

I have installed solder lugs, 3 and 5 lug types and laid the caps horizontally. If I remember correctly I drilled out one rivet to screw mount one and reused a screw already there for the other.
 
KC, I’m curious, have you made any progress on the under chassis filter cap mounting? I recently acquired a C26 and one filter cap is a Sprague 066-122 200/50mfd @200/200v; the other is a Sprague 066-123 200/200mfd @200/200v
The schematic I have says these should be Sprague 066-095 160/200 mfd 200/150v
What does your C26 have as filter caps and what are you planning on replacing them with?
My S/N is 71P62
 
Rob - I had the same Sprague P/Ns as you. I decided to restuff the cans. I've attached a few pictures of a recap - I think c_dk - Chris did this one. Two new filter caps in the place of the Sprague cans, and then two new caps underneath. I agree there is not room for all four under chassis.

Keep us updated!
 

Attachments

  • c-26 caps bttm sm.jpg
    c-26 caps bttm sm.jpg
    187.8 KB · Views: 71
  • c-26 caps top sm-1.jpg
    c-26 caps top sm-1.jpg
    115.7 KB · Views: 70
Not my work but even though I can not read all the installed values I am hesitant to go too large in capacitance value while replacing the 45 year old caps.

I have found that going to large seems to add to the preamps turn on noise and "rush" especially the first capin the group.

I do drill out a rivet and install a 5 lug solder mount and and do not depend on the chassis mounted screw for ground but hard wire it back to the origin.
 
c_dk said:
I have installed solder lugs, 3 and 5 lug types and laid the caps horizontally. If I remember correctly I drilled out one rivet to screw mount one and reused a screw already there for the other.
Click to expand...
I like the idea of under-chassis solder lugs on this vintage of units, what are they Gen I solid state amps? for mounting replacement caps even if it means drilling a hole or two. Just use bright stainless 6-32 screws thru the chrome chassis deck. Upgrading old nasty Mc screws with stainless phillips is standard practice here.

-Greg
 
Gregory said:
I like the idea of under-chassis solder lugs on this vintage of units, what are they Gen I solid state amps? for mounting replacement caps even if it means drilling a hole or two. Just use bright stainless 6-32 screws thru the chrome chassis deck. Upgrading old nasty Mc screws with stainless phillips is standard practice here.

-Greg
Click to expand...

I think they're gen 2; the C-24 was SS.

Derail off...
 
I thought about ordering the same hex head style as Macintosh used, but I like the round head look after seeing Gregory's photos...
Gregory - Do you use Mcmaster's "crome plated" or "passivated"?
 
kcvintage said:
I thought about ordering the same hex head style as Macintosh used, but I like the round head look after seeing Gregory's photos...
Gregory - Do you use Mcmaster's "crome plated" or "passivated"?
Click to expand...
If you look at the box of screws a couple posts above, the label says:
6-32 x 1/4" Phillips Pan head Machine Screws - Black Oxide​

The `bright´ ones are:
6-32 x 1/4" Phillips Pan head Machine Screws - Stainless steel​

The originals are called "slotted hex head machine screws" IIRC. I kept all the old screws in a zip-loc if someone later wanted to go original. McMaster is a great source hardware, tools and materials. Ordering and checkout are hassle-free and shipments arrives faster that expected. Engineers and machine/manufacturing shops order from them, for example aluminum stock, drill bits and taps, etc. https://www.mcmaster.com/

Here's another example of replacing nasty old MC 2205 screws with stainless:

MC2205_Love_right_shield.jpg

That is, after using auto polish on the shield. All shiny and smooth now.


-Greg
 
Last edited:
You must log in or register to reply here.
Back
Top Bottom