McIntosh Receiver Recapping

w5hro

Member
This is mainly for the MAC 1500, 1700 and 1900 receivers

I think most people always say to replace the electrolytic caps in these receivers, but it’s not always necessary. McIntosh used very high-quality components and often military or scientific equipment grade components. Believe it or not, many of the electrolytic caps in these old receivers are still good today and do not leak. Unless you are hearing a hum it’s best to just leave them alone until you do.

The main problem in these old receivers are with the old tubular paper caps and it didn’t matter if they were military or scientific grade. Most all of the old paper caps are leaking today and they must be replaced. McIntosh used a ton of the white Mallory paper caps below.

These were recently removed from a MAC-1700 receiver
mallory1.jpg

Most are on the PC boards
mallory2.jpg

Three are on this board below
mallory3.jpg

As you can see most of them are on the PC boards, but not all. You will usually find one or two more on the chassis somewhere.
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c_dk will probably disagree with you. A mil spec capacitor is usually encased in metal with a glass seal and probably cost $10. I worked on radar altimeters during a summer job while in college back around 1968 and dealt with "real" mil-spec parts. I have recapped over 10 different Mac units from the 70's - 90's and all of the caps were standard commercial grade audio with low ESR from well known manufacturers. Back in the 70's, tantalum caps were considered high grade but their main attribute was their capacity/size ratio (ie, tiny). They were not designed for a 30+ year life.
 
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30+ year old elytics are past their prime.
I'm not saying they're all bad or even not good.
If you're inside anyway you might as well change them anyway. It just makes sense.
There are also tantalums, that should be changed and there a films that will fit in these positions.
Testing at voltage may prove cap meets spec and doesn t leak.
If its your gear you may want to leave it.
If it's someone's else's and you don't want come back fixes (with possibly irate customers).
It's 30, 40, 50 years old. Toss em. (My 2c)
 
A lot of that depends on the age and the receiver's environmental storage conditions. If it was stored out in a hot or cold garage, attic, etc. for a number of years then the electrolytic caps should be replaced. However, if it was used indoors and taken care of by a McIntosh user during it’s life then 9 times out of 10 they are usually still good in those 3 hybrid receivers. The quality of the electrolytics used in those receivers were outstanding and they just didn’t go bad very often and even after 40-years. The ones in my MAC-1700 are still good and have not been replaced.

The thing I was trying to point out is those tubular paper caps are the main weak link in the receivers and are more of a problem than the electrolytics.
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40 years is well past the service life of an electrolytic capacitor, even a well made Mil-spec cap.

They all need to be replaced, whilst some may look OK now, you can be rest assured that they are slowly changing from a capacitor into a resistor, or worse they can short out. Its not worth the risk leaving them in units this old.

PIO are known to be bad this far down the track, just like electro caps. You gotta replace them all to ensure a reliable unit which will run for the next 30 years....
 
Fair enough
A 15 would be at least 50
A 17 , 45
And a 19 at least 39
To be fair I had a 1700 about 6 years ago and untouched I thought it performed flawlessly
(No subjective test data)
Even all the lamps still worked.
I restored a 1900 about 2 years ago for my brother.
It seemed to work fine when I got it.
I still changed all the films, elytics and tantalums.
I'm confident if something fails in it, it won't be those.
My brother is in another state.
You may be right.
If I had to pull them all test and reinstall, I just don't see not doing it. Thanks for the tip on the paper caps:thumbsup:
 
It needs to be differentiated between a tech's look at problem solving and a restorers look at extending the service life of a unit.

A service tech is looking to solve a problem, finding the faulty part and replacing it. A restoration involves acknowledging the known part issues and replacing them before they become a service issue.

Most often the time cost of pulling a part to test it will exceed the cost of just replaceing a part that has a known service life issue.
 
40 years is well past the service life of an electrolytic capacitor, even a well made Mil-spec cap.

Not necessarily, I checked all the ones in my 1700 with a high voltage cap checker which checks for leakage with high-voltage applied and they were all fine. However, all of those white Mallory tubular paper caps in the bag in my pic were leaking and I mean every single one of them which is completely normal and that doesn’t apply to only McIntosh stereo equipment. It applies to all consumer equipment made back then that used them.

Again, the point I was trying to make is I’ve seen too many people focus and say you must replace all the electrolytic and they never even bother to replace the ones that are the biggest problem. Either because they simply don’t know and lack the technical knowledge or they just never bothered to check them. When those paper ones leak it loads down the supply and causes other problems like making the electrolytics go bad faster because it greatly increases the ripple current.
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Not necessarily, I checked all the ones in my 1700 with a high voltage cap checker which checks for leakage with high-voltage applied and they were all fine. However, all of those white Mallory tubular paper caps in the bag in my pic were leaking and I mean every single one of them which is completely normal and that doesn’t apply to only McIntosh stereo equipment. It applies to all consumer equipment made back then that used them.

Again, the point I was trying to make is I’ve seen too many people focus and say you must replace all the electrolytic and they never even bother to replace the ones that are the biggest problem. Either because they simply don’t know and lack the technical knowledge or they just never bothered to check them. When those paper ones leak it loads down the supply and causes other problems like making the electrolytics go bad faster because it greatly increases the ripple current.
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Again, if you want reliability for another 40 years, you need to replace PIO, Tantalums, Bumble bee, Electro caps etc etc, I am not disputing they may test fine now, I am looking at the future, they may last another 5 years, or possibly 10, but they wont last another 20-30 years and this is what I am talking about.
I have pulled far too many bad caps from receivers, integrated, tuners, amplifiers etc...to take the gamble that the unit will be okay.
I have even at the request of a customer left the electro caps, only to have him come back a couple of months later with bad electro cap issues....
Electrolytic capacitors have a known service life, end of story.
As I have a small business doing this, I do not have time to pull caps and run a full voltage leakage test, then replace or re-install, it is simply not economical for me or the customer, so they are replaced.

If you have the time to pull and test or take the gamble, that's all good and your choice, but I do not work like that because I am running a business repairing and restoring, so its a matter of economics for me and my customers.
High quality electro caps are so cheap these days, its a no brainer as far as I am concerned.
 
What is your take on the glossy maroon coupling caps used in McIntosh tube gear, for instance used in the MAC1500 and MAC1700?

I see a split opinion on them--with many saying they are important to retain the classic sound and rarely go bad, with others arguing it is just a matter of time for them to fail too.
 
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c_dk will probably disagree with you. A mil spec capacitor is usually encased in metal with a glass seal and probably cost $10. I worked on radar altimeters during a summer job while in college back around 1968 and dealt with "real" mil-spec parts. I have recapped over 10 different Mac units from the 70's - 90's and all of the caps were standard commercial grade audio with low ESR from well known manufacturers. Back in the 70's, tantalum caps were considered high grade but their main attribute was their capacity/size ratio (ie, tiny). They were not designed for a 30+ year life.
I agree with C_dk with reference to the type of capacitors used in the McIntosh line of products. One should note that not all non-electrolytic capacitors leak. Problem with them is that, over the years, they change value and can cause changes in the Sonics of the unit. When we restore a unit, we replace all of the electrolytics and verify the ESR of the main can filters. Mark - McIntosh Service Center
 
Not necessarily, I checked all the ones in my 1700 with a high voltage cap checker which checks for leakage with high-voltage applied and they were all fine. However, all of those white Mallory tubular paper caps in the bag in my pic were leaking and I mean every single one of them which is completely normal and that doesn’t apply to only McIntosh stereo equipment. It applies to all consumer equipment made back then that used them.

Again, the point I was trying to make is I’ve seen too many people focus and say you must replace all the electrolytic and they never even bother to replace the ones that are the biggest problem. Either because they simply don’t know and lack the technical knowledge or they just never bothered to check them. When those paper ones leak it loads down the supply and causes other problems like making the electrolytics go bad faster because it greatly increases the ripple current.
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My MAC 1700 are using black Sprague capacitors instead of Mallory tubular caps. Not sure if these are original or replaced sometime ago. I am thinking about replacing those, particularly the one in power supply leading to phono, as I'm having issue with phono input with periodically losing sound.

Any suggestion on what capacitors to replace these? Hard to find modern axial capacitors matching the specs.
 
I'd do a good contact cleaning before changing caps.
I suspect the spragues are original.
If you need caps, I'd suggest a good polypropylene. (Maybe an orange drop or panasonic).
 
I'd do a good contact cleaning before changing caps.
I suspect the spragues are original.
If you need caps, I'd suggest a good polypropylene. (Maybe an orange drop or panasonic).

Thanks! I have tried deoxit on all pots I can find, which fixed some initial issues of weak left channels and aux inputs.
I can't find Panasonic polypropylene caps meeting the specifications, only the electrolytic ones, which are suggested by someone in another thread.
 
Replaced the 10v filter cap power supply and 4 caps on the power driver boards with Nichicon. The original caps are way out of specs. The 100uf ones tested 150uf, and the 200uf ones tested 370-450uf! I am surprised this thing even still works with the old caps.

This fixed the issue of phono losing sound periodically. However, right channel still has louder background noise in phono when nothing is being played. Not sure if this is caused by higher DC offset in the right channel, which reads about 30mv, while the left channel only has 12mf.

Next step is to replace the others on the pre-amp board...
 
I'd bet its a noisy transistor or possibly a carbon comp resistor or a string of them. A scope is your friend in hunting the noise.
 
Trial and error changing components.
Or shotguning (that is changing all the components)
That isn't without risks. It's not difficult to do more harm than good, doing this.
 
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