McIntosh MC-240 restoration.

gogofast · Feb 16, 2011

I've thought really hard while looking at this what feels like a 70 pound monster. bought a new chassis from an AK member, but I'm not sure if I wanna go through all that to replace the chassis. I mean it looks like a crap load of work. Plus, I kinda like the look of pitting chassis.... maybe that's my lazy a** talking, but for now, I've decided to just begin the internal restoration.

I paid for a copy of Sam's, but the electronic copy is just too horrible to even make out what's what. So, I thought I'd label all the parts on the tag board first.
All resistors test pretty close to spec except for some, but all will be replaced with PRP 1% resistors from partsconnexion. I'll also replace all the caps with combination of Mallory, orange drop, and a few oil caps here and there.

Bluelobster · Feb 16, 2011

Since your still thinking why not take a look at the power supply kit Jim McShane offers for the MC240. I have a similar scheme in my Citation amp and it works well.
http://pages.prodigy.net/jimmcshane/citpage.htm#parts.htm

gogofast · Feb 16, 2011

Bluelobster said:
Since your still thinking why not take a look at the power supply kit Jim McShane offers for the MC240. I have a similar scheme in my Citation amp and it works well.
http://pages.prodigy.net/jimmcshane/citpage.htm#parts.htm

thanks for the suggestion! but actually, i got all my parts in already. i'm gonna use 32/32 & 100/100 multi section for the filter caps. finding the muti can with exact values all in one was impossible. there was a source that custom made those for about the same price, but couldn't wait that long. i've almost finished the resistors last night. i'll snap some pictures later and post.

perchdog · Feb 16, 2011

hmm,

i was just surfing this thread

http://www.audiokarma.org/forums/showthread.php?t=87157&page=8

you may find posts #116 & #119 interesting

gogofast · Feb 16, 2011

perchdog said:
hmm,

i was just surfing this thread

http://www.audiokarma.org/forums/showthread.php?t=87157&page=8

you may find posts #116 & #119 interesting

thank you for directing me to that thread!

i've heard others say same thing about the black beauties in MC240. i'll leave them alone and give it a listen, and then another listen after replacing them. i'll report back what i hear. terry must know what he's talking about.

so, mylar/foil caps never go bad usually? and oil caps do? (further down the thread they talk about it.) i thought it was the other way....

audiodon · Feb 16, 2011

I'm kind of in the same spot about whether to gut and replace or redo with some amps. I'm trying to work my way up to gut and rehab through successive amps starting from ones in better shape and graduating to ones in worse shape.

gogofast · Feb 16, 2011

audiodon said:
I'm kind of in the same spot about whether to gut and replace or redo with some amps. I'm trying to work my way up to gut and rehab through successive amps starting from ones in better shape and graduating to ones in worse shape.

that's a good idea. to build your confidence and motivation.

i'm gonna try to clean all the sockets, and if they work ok, i won't try to replace the chassis. if not, i'll go ahead and use the new chassis top. i'll have to drill the tube sockets out to replace them, and if i go that far, might as well overhaul the darn thing.

drillher · Feb 17, 2011

I hope that your Mc240 restoration goes well.I went over my Mc240 last year and replaced the bumblebees with Russian K-40's from Jim McShane.I did a power supply rebuild as well.I left the 160P's,black beauties as some advise here.I see that you are going to listen to your amp for a time with them in,and then replace them and compare.Please let us know your impressions of those 160P's.Most of my resistors are original,but I need to go back in and re-measure voltages.Good luck,
Dave

Westy56 · Feb 17, 2011

This thread has eliminated a bunch of stupid questions from my end.
Great info for any 240 owner, thanks. :thmbsp:

Steve

gogofast · Feb 17, 2011

drillher said:
...and replaced the bumblebees with Russian K-40's from Jim McShane.

Please let us know your impressions of those 160P's.
Dave

did you replace all bumblebees with K40? or mixed it with any other type?

i will definitely let you know how it goes.:thmbsp:

Westy56 said:
This thread has eliminated a bunch of stupid questions from my end.
Great info for any 240 owner, thanks. :thmbsp:

Steve

thanks! i will post some details as i go...

gogofast · Feb 17, 2011

not much...but just a little bit of progress.

what i've taken out so far...and insulated K-40 and some other parts ready to go in. :music:

you definitely need a good de-soldering iron...

spaceman · Feb 17, 2011

Good luck, I hope it turns out well. :thmbsp: I'll also be interested in what you think about the cap swap.

Westy56 · Feb 17, 2011

I know what (not) to look forward to. They really have those components tied in.

Nice work. :tresbon:

Have you been checking the caps and resistors as you remove them? Were they close to spec?

Steve

diamondsouled · Feb 17, 2011

gogofast said:
thank you for directing me to that thread!

i've heard others say same thing about the black beauties in MC240. i'll leave them alone and give it a listen, and then another listen after replacing them. i'll report back what i hear. terry must know what he's talking about.

so, mylar/foil caps never go bad usually? and oil caps do? (further down the thread they talk about it.) i thought it was the other way....

Actually one of the only molded caps that usually is good is the red labeled Black Beauty and the only oil cap which is consistently bad are the Suzukis which were used in Sansui tube amps and other Japanese amps. Hermetically sealed PIOs made in the USA, as well as Russian K40Ys, rarely go bad; I've tested several hundred NOS of both and have yet to find a bad one.

Cheers

Lar

drillher · Feb 17, 2011

I replaced all of the bumblebees with K-40's and left the 160P's.Are you sure that all of your resistors need to be replaced?
Dave

junkaudio · Feb 17, 2011

now i wish i had a mc240 :smoke:

Steve O · Feb 17, 2011

gogofast said:
not much...but just a little bit of progress.

what i've taken out so far...and insulated K-40 and some other parts ready to go in.
you definitely need a good de-soldering iron...

Actually, IME all four 12K-2W resistors usually warrant replacement.

gogofast · Feb 17, 2011

Steve O said:
Actually, IME all four 12K-2W resistors usually warrant replacement.

i'm actually gonna replace them all.

i'm just working little by little while removing the capacitors from the other side of the tag board.

Westy56 said:
Have you been checking the caps and resistors as you remove them? Were they close to spec?

Steve

only few are right on spec and most are 15-30% off.

drillher said:
I replaced all of the bumblebees with K-40's and left the 160P's.Are you sure that all of your resistors need to be replaced?
Dave

while i was measuring them more than half way through, most of them were off spec 15-30%, and though there were few right on spec, thought it'd make sense to change them all with 1% resistors.

gogofast · Feb 17, 2011

as you can see, the chassis IS in pretty bad shape....

drillher · Feb 17, 2011

Is it possible to measure the resistors while they are connected?Is it better to measure voltages with the amp powered up?
Dave

McIntosh MC-240 restoration.

Addicted Member

Well-Known Member

Addicted Member

AudioDouchebag

Addicted Member

Addicted Member

Addicted Member

Super Member

A symphony of paradox

Addicted Member

Addicted Member

Registered Lunatic

A symphony of paradox

Recycle belly button lint!

Super Member

Super Member

Super Member

Attachments

Addicted Member

Addicted Member

Super Member