Mcintosh C28 restoration

guys, sorry if I am seeing something different, but I still have no clue what to do. RG, to me, your very first pic of this cap shows it in a different position that the pic showing it "after". my pic of my original unit location is different than yours.
I have the schematic, but I am not very good at reading them. I guess I may try to learn it so I can figure this out.
I still see 3 different hookups in 3 different pics.??
The first pic that rg3117 posted (post #73) is hooked up the same as yours it is just physically in a different location.
 
The first pic that rg3117 posted (post #73) is hooked up the same as yours it is just physically in a different location.

again, not trying to argue, but RG's first pic is not hooked up the same as mine, his first pic appears to have it hooked up to the glass diode, and silicone diode. mine is not hooked up that way. mine is hooked to the glass diode, and then a screw terminal.

is my hookup correct? or should it be hooked to both diodes??
 
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If you look closely, the silicone diode is also hooked to a screw terminal which is the other mounting screw for the transistor. Yours is correct.
 
I confirm that this was a mistake, thanks JeffV and Hunted11 for catching that. I have now corrected. This actually looks better too with the components aligned.
 

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Thanks guys, so on that note, does anyone have a component location picture/drawing of the underside of this unit showing where everything in the C "300" range is located? I received some of those capacitors yesterday, and I want to get them installed, but I am not positive where they go. For instance, C301 a, b, and c. where are those? same with 302, 305, 308...

The service manual is a great guide showing component placement, but it does not show anything in the 300 range.
 
These are the aluminum cans for the power supply. Some are multi-section capacitors (a, b , c, ...). You will find them on the Power Supply diagram in the service manual (page 16 and 17 in the Pdf section), not on the drawings.
 
Yes, I see them on the diagram, but I am not versed enough at reading the diagram to know what goes where.
The "drawings" on page 3 of the manual are what I need.
 
You will need to match the values from the parts list to the indications on the capacitors themselves. This should be straightforward for single capacitors. On the multi-section capacitors, there are little symbols underneath the capacitor (square, triangle, etc.) that match the label on the side of the can. The first number is the capacity, the second number is voltage rating.
 

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Grounding

Well, I kept the best part of the end... Fixing these ground drains is a pain, but needed to be done.

I believe that I did all of them. I counted 4 underneath and 15 at the back.

I had to pull some of the cables through the chassis to the underside to be able to work on them, and then push them back through the plastic bushing. Nerve-racking!

The problem is well known and appears in many posts (mostly from c_dk):
http://audiokarma.org/forums/index.php?threads/c28-power-supply-caps.440727/#post-6162247

http://audiokarma.org/forums/index.php?threads/mcintosh-c28-is-flaky.738581/

http://audiokarma.org/forums/index.php?threads/picked-up-a-c28.729433/#post-9870338

http://audiokarma.org/forums/index....e-mcintosh-experts.610370/page-2#post-8097026

I am adding a few pictures taken during the work.
 

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DOB would have us do these during and after every amp clinic. It was a shane that the tri metal interaction was not discovered until 7 or 8 years after production was started after the second mode selector was installed with this new wiring harness as a warranty upgrade during the production run. The "better" idea was not so much better.

Actually it probably is a 4 metal interaction what with the 100% aluminum shield, the tinned drain wire, the drain wire extension and the brass ferrule crimp. Too complicated of interaction for this chemistry minor to sort out.

Certainly a PIA part of any restoration but needs to be done to insure reliable future use.

Make sure to get the ones for the output and phono level under the partial top plate.
 
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DOB would have us do these during and after every amp clinic. It was a shane that the tri metal interaction was not discovered until 7 or 8 years after production was started after the second mode selector was installed with this new wiring harness as a warranty upgrade during the production run. The "better" idea was not so much better.

Actually it probably is a 4 metal interaction what with the 100% aluminum shield, the tinned drain wire, the drain wire extension and the brass ferrule crimp. Too complicated of interaction for this chemistry minor to sort out.

Certainly a PIA part of any restoration but needs to be done to insure reliable future use.

Make sure to get the ones for the output and phono level under the partial top plate.
Thanks C_dk! By underneath the top plate, do you mean these four that goes to the Treble adjustment board?
 

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Oh my, I just realized that these 8 underneath need to be done also! How many of these are they?!
 

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I needed a break from all the ground drain work, so I drilled through the rivets of the phono input plate. Gave me a much better access indeed. The two solder lugs coming from the main ground terminal and the phono plate are touching, so I am thinking of simply soldering the two together.
 

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I noticed that the rivets were isolated by some kind of plastic slieve, and the low level input plate is separated from the chassis by a grey cardboard piece. Is the plate supposed to be isolated from the chassis? In that case I will need to find special fixings, as metal bolts would make contact with the chassis on one side and the phono input plate on the other side. I am not sure if that makes sense given that the purpose of the mod is to improve grounding.
 
So I answered my rather silly question myself. Given that the grounding bolt in the corner of the plate is already touching on both sides, I figured that it would not hurt if the bolts in the 3 other corners did the same. Found some pretty nice black hex mini-bolts at my local DIY store, to match the color of the chassis.
 

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Grounding

Well, I kept the best part of the end... Fixing these ground drains is a pain, but needed to be done.

I believe that I did all of them. I counted 4 underneath and 15 at the back.

I had to pull some of the cables through the chassis to the underside to be able to work on them, and then push them back through the plastic bushing. Nerve-racking!

The problem is well known and appears in many posts (mostly from c_dk):
http://audiokarma.org/forums/index.php?threads/c28-power-supply-caps.440727/#post-6162247

http://audiokarma.org/forums/index.php?threads/mcintosh-c28-is-flaky.738581/

http://audiokarma.org/forums/index.php?threads/picked-up-a-c28.729433/#post-9870338

http://audiokarma.org/forums/index....e-mcintosh-experts.610370/page-2#post-8097026

I am adding a few pictures taken during the work.
What kind of shielded cables are they? Brand? Size? And where did you get them?
 
What kind of shielded cables are they? Brand? Size? And where did you get them?
Sorry for the late reply, only saw your message today. I did not change the cables, I reused the ones that were already there, and simply fixed the grounding (I hope).
 
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