C29 love...

I had a couple of preamps dropped on my doorstep a few weeks ago. A C20 and a C29. The C20 was first up and needed new power supply caps and a couple of signal caps changed then worked as new.
The C29 worked but needed the switches cleaned up and the push button indicator LEDs were not working. After taking off the covers I discovered some of the solders were looking rather old and tiered. Rather than fool around with them I finally decided to just get out the solder wick and redo most of the solders. Bingo the LEDs were now working.
So I connected it up and gave it a listen. Not bad but it sounded slightly dated and a little thin compared to the current models. Should we update?

Thanks,
Ron-C

ron-c said:

So I connected it up and gave it a listen. Not bad but it sounded slightly dated and a little thin compared to the current models. Should we update?
Ron-C

Click to expand...

My C29 turned 27 years old last month, I sent it to Terry for its first ever upgrade.
Should I update? I think I will as soon as find a C15.

Well of course update. Here is the recipe that worked for me. First off get $100 to blow on parts...
Order 6 new low noise ON semi ICs from Mouser, part number NE5534ANG. These are the same ICs as originally used but are the low noise versions where the originals were only low noise for the two phono. I figured replace them all since they plug in. These are like $1.20 each so no big deal.
Next up replace C163 and 164 which are 10uf , 25 volt NP- Non Polarized capacitors. I tried new electrolytic ones here but preferred to substitute box poly caps which I had on hand. This change will fill out the bass end of things. Parts on hand were no cost.
The power supply, replace all three power supply caps, C201,202,and 205, 3,300 uf @ 35 volts.. I used new Nichicons from the local surplus store, $1.30 each.
The headphone section has two 1000 uf 25 volt caps and I used Silmic audio grade about $4.00 each. There is one other cap in this circuit which should also go, C168 which is 220 uf 25 volt and I used a $.050 Nichicon from surplus.
All of the original caps were Nichicon. Interestingly the new power supply caps are about twice as heavy as the old ones. Wonder what was in them?
Now we are left with a whole bunch of 10 Uf NP caps in the signal path. I used 8 Rubycon Black gates 10 uf 50 volt N type or non polarized. These are $4.25 each and should be used in C123, 124, 101, 102 phono section and c139, 140, high level and C601 and 602 on the bass switch PCB.
C127 and 128 were also changed with 100 uf Nichicon Muse which are $1.50 each.
C165 and 166 were also changed to Nichicon Muse 10uf 50 Volt at $0.65 each.
C206, 47uf, 35 volt, C207 10 uf 35 volt, and C208 100UF 25 volt were all replaced by new Nichicons for about $1.00 each as these are for the regulators and their supply.

The hardest part was tracking down all the parts. The Black gates and Nichicon Muse all came from Micheal Percy Audio, mpercy@pacbell.net but there may be other sources.

So how does it sound? Very modern of course! I was more than pleased in that the sound is very much out of the box with better imaging and depth. Oddly the stereo separation seems greater which I guess is just the precision of the sound. The Rubycon Black Gates deliver the goods for a price. Normal audio grade Nichicon or their better Muse caps can be used but the Black Gates seemed to improve the depth more.

One thing nice about the C29 is that the switch quality is much more modern than the earlier series such as C28 and C26. I am curious to have a go at a C33 and C27 some time. The C29 does use an LDR for switching so no FETs.

I do not think the excellant NE5534 ICs are the limitation on these older preamps but the old caps can be a liability. Using the Low noise version of the ICs is a good idea.

Thanks,
Ron-C

Vahe,

A remote control is a nice upgrade.

Thanks,
Ron-C

Nice write up and pics, thanks for sharing with us. Sure looks pretty.


Carl

I'm nearly speechless.

Great write up Ron. I've never seen a '29 so it was interesting to see what it looks like inside. Much more modern than a C-28 - it sort of looks like a stripped down C-32/33?

Thanks for posting all the pics!

Murray

Great stuff.Thank you .

Great post; thanks Ron.

With this detailed information, my C-29 might get looked into before any of my amplifiers (MC-60's and 240's).

Mike

-edit- couldn't get the schematic from Berners, I'm not a sponsor (although I've got a bunch of service manuals sent to me by Davy O'brien himself) I don't see Berners needing any of them. I'll look, I've probably got an original at home. With what Ron's provided, I can replace all those components, but I'd like to learn more about the circuits in the preamp while doing so. Anyone got another source I can use here at work?

Thanks. Mike

Ron,

Awesome post! Thanks for sharing.
awprint:

Mike,

You can purchase the service schematic from the parts department. It should be used as there are running production changes in the C29 so you will need to use the correct schematic for the version you have. They are all covered in the service manual.

Thanks,
Ron-C

Murray,

The C29 is in the same family as the C30 and C33/34. The C33/34 use FET switching though but do share many of the same circuit designs. Compared to the C28 the C29 has a much cleaner layout inside.

Thanks,
Ron-C

Ron,

Could these updates be performed on a MA 6200? I am supposing so.

Thanks,

Stephen

Sure, any unit that is 30 years old is due for a freshening up. You might want to consider sending it off to Terry for a tune and lube.

Thanks,
Ron-C

c29 love

Next up replace C163 and 164 which are 10uf , 25 volt NP- Non Polarized capacitors. I tried new electrolytic ones here but preferred to substitute box poly caps which I had on hand. This change will fill out the bass end of things. Parts on hand were no cost.

ron-c

Where did you source the box poly caps? and are they the same value as the electrolytic ones? :scratch2: Thanx, Mike.

Mike,

The ones I had on hand were 10uf at 60 volts and were the same green box type as used in the rest of the preamp when new. I picked these up years ago at one of the surplus stores.
You could use a non polarized Nichicon Muse electrolytic as this may be easier to find and will fit. Most of the 10uf polys are huge since they are rated 200 to 600 volts. The Black Gates just were slightly thin in this position. Maybe too much of Black Gate thing. All signals go through these two caps so they are somewhat critical.
The picture posted still had the Black Gates which are the two that straddle the selector shaft.

Thanks,
Ron-C

Just did similar things with a C28 - 2 of them, as a matter of fact. They both came in sound quite 2-dimensional. That is, they had lost that effect of having the stereo image appear to come from beyond the speakers. Put another way, the presentation had collapsed into the speakers.

I redid the power supply caps with new ones for safety sake as much as anything else. Then, I went through the line level stages and, liking the results so much, went back through the phono preamp section using foil-and-film caps.

I had experienced the results of redoing a couple of MX-110s with new instage coupling caps but didn't expect the same resuts from a SS amp.

I agree, if its pretty much 20-30 years old or older, have it in for serious servicing, if my results are any indication.

Cheers,

David

recap c27

hi ron,

did you ever get a chance to update a c27 ?

thanks

A.

You know, I would really love to do something like this myself. I just think I would need to take a class or some kind of crash course. Is there anything like this that is offered to people, as opposed to enrolling in school?

-Mike

The C29 has continued to perform great since the tune up. Had a flacky regulator transistor that powered the push button LED indicator voltage line. It would fade in and out. Replaced it with a modern part from McIntosh parts, less than $2.00 retail and all is well now.

thanks,
Ron-C

The C29 lives in the bedroom system with some tables, tuners, and an originnal MC275.

thanks,
Ron-C