Mcintosh C28 restoration

I recently bought a Mcintosh C28 preamplifier on Ebay. It looks pretty original from the pictures (original caps, etc.). I like restoring vintage gear, and would like to upgrade it while keeping it as original as possible.

I can see a lot of information on the C28 on Audiokarma, but in many different posts. My goal is to present the work being done on this amplifier, get some help from the community, and insert some links to the best resources I can find as I progressively upgrade this old gear.

My plan is to:
- replace the capacitors, starting with the power supply - hopefully restuff the large cans if I can -, then move on to other electrolytics, and finally mylar caps.
- replace power transistors.
- clean and lubricate all knobs and pot
- replace the broken glass
- replace the light bulbs with LED
- repaint the scratched top cover
- replace all RCAs with gold-plated ones

The C28 is on its way somewhere on a Fedex truck, it should arrive in the next couple of days.

In the meantime, here are some pictures from the Ebay auction.

From first hand experience, if it isn't broke, don't fix it. Mine was original and sounded amazing until the volume control went bad. That part is unavailable and I had to have it rebuilt. It was never the same after.
 
From first hand experience, if it isn't broke, don't fix it. Mine was original and sounded amazing until the volume control went bad. That part is unavailable and I had to have it rebuilt. It was never the same after.

Unfortunately, my C-28 was a bit of a basket case, so everything I am doing including replacing the RCA's is necessary..
 
Unfortunately, my C-28 was a bit of a basket case, so everything I am doing including replacing the RCA's is necessary..

I couldn't live without a working volume control. The weird thing was, I ordered a volume control directly from McIntosh. It was made to the original specs but an aftermarket version. When I installed it, carefully and correctly, it operated in reverse. When I turned it on it was loudest and clockwise made it quieter. I checked and checked and it was wired correctly. Needless to say, I sent the original to Audio Classics and they rebuilt it for me. It works ok but just not the same as it once was.
 
I have finally time to get back to my C28, this time to work on the grounding. I would like to start with the Phono 1 and 2 modification from service bulletin #2. Access to the back of the main ground terminal is really tight, there are a bunch of cables in front of it. Does anyone have a trick? I am posting a picture. By the way, I still haven’t received my glass panel, backordered in January...
 

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I have finally time to get back to my C28, this time to work on the grounding. I would like to start with the Phono 1 and 2 modification from service bulletin #2. Access to the back of the main ground terminal is really tight, there are a bunch of cables in front of it. Does anyone have a trick? I am posting a picture. By the way, I still haven’t received my glass panel, backordered in January...
I drilled out the rivets so the whole phono panel can be moved to a position you can at least work on it.
 
I drilled out the rivets so the whole phono panel can be moved to a position you can at least work on it.
Good idea, thanks. On my C28 there was no solder lug behind the main ground terminal. I am not sure if this is normal, the service bulletin seems to say that there should be one. I was able to add one, putting the bolt back behind was a pain, but now I have a wire coming from the main ground terminal towards the phono panel.
 
1535251908214221034501.jpg question, I am trying to replace the .22uf orange drop in location number C304. the picture in this post is showing the leads soldered to different posts than what is existing in my original(i think) unit. can someone send me a pic of the correct placement?

thanks
 
Good idea, thanks. On my C28 there was no solder lug behind the main ground terminal. I am not sure if this is normal, the service bulletin seems to say that there should be one. I was able to add one, putting the bolt back behind was a pain, but now I have a wire coming from the main ground terminal towards the phono panel.

I just followed the drawing in the service manual. ?
 
View attachment 1265828 question, I am trying to replace the .22uf orange drop in location number C304. the picture in this post is showing the leads soldered to different posts than what is existing in my original(i think) unit. can someone send me a pic of the correct placement?

thanks
Does the attached picture help?
 

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No, that shows it to be different than both the previous pictures...??
The picture in my previous post was taken before I replaced the orange drop, from a different angle than yours. Here is one taken after, hopefully that is a better view.
 

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The cap in pic, post 71 and 73 look to be connected to the same points, just the cap is in a different orientation. the cap in post 75 appears to be connected differently than the other 3 photos. The cap is connected between the base and collector of the transistor.
 
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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 cap in pic, post 71 and 73 look to be connected to the same points, just the cap is in a different orientation. the cap in post 75 appears to be connected differently than the other 3 photos. The cap is connected between the base and collector of the transistor.

where are you getting post numbers from? I am trying to reference the posts you are talking about, but I don't see any numbers.
 
rg3117, In your first pic the cap is connected to the terminals with the glass diode and the silicone diode, which is correct. In your second pic you have it connected to the point with the glass diode and you missed connecting it to the silicone diode. To make it easy just remove the connection on the left and connect it to the bottom terminal with the screw that holds the transistor in place.
 
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