Electronics > Repair

Marantz model 26 receiver: Almost done

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Alex_Baker:
Hello All

I just picked up a nice specimen of a Marantz model 26 stereo receiver for a good price since it needed work. I have already fixed what was wrong with it but I thought I would ask this question to some of the more experienced techs out there.

What I would like to know is if there are any capacitors that should be replaced due to their age, as this amplifier is bearing down on 50 years old. I will list the brands and types of caps in case anybody wants to know that.

-Nippon Chemi-con, Nichicon, and Elna : Aluminum Electrolytic  (I have always worked under the assumption that these are good brands).
-Mallory: Aluminum Electrolytic
-Matsushita (the triangle logo?): Aluminum electrolytic as well as some plastic purple ones labeled as electrolytic.
-Unknown brand : polyester type
-Unknown brand : Ceramic (I generally assume that these don't go bad)
-unknown brand : mylar type (the flat green ones)

I would love to hear you peoples opinions on cap brands and types, as well as my assumptions stated in parentheses. I know capacitors is a common topic so I hope I am not beating dead horse here, but hopefully I will learn something new!

The below pictures are of the various boards and should show all the different types of caps.
[attach=1]

bob91343:
If you insist on fixing what isn't broken, I would limit the shotgun replacement to the power supply filter capacitors.

If you get more ambitious than that, you risk making errors.

David_AVD:
I agree. I've seen too many perfectly working vintage amplifiers mangled by bulk cap replacement.

Some had traces torn off while others had created dry joints all over the place.

Also, sometimes totally inappropriate replacements were used (low ESR or normal instead of low leakage).

All of this makes getting the unit working so much harder and time consuming than repairing any original faults.

Better to check for visible signs (corrosion / leakage) and maybe remove a couple of example types for testing first.

floobydust:
I would replace all the small electrolytics. Why? I find the grey Elna electrolytic capacitors are pretty much end of life, they must be 45+ years old. They dry out and go low value, usually the small guys under ~220uF. Just test some to confirm.
What I do is make a spreadsheet with a list of the caps, for each board. Or, go to eBay and see the cap kits for the 26. Small 1uF and 2.2uF it's common to use Wima film caps instead. Pic related, that guy gives new small transistors as well. The loudspeaker protect relay usually has badly oxidized contacts and need cleaning without breaking it.
If you haven't done this before, or don't have a decent desoldering tool, patience and tenacity, then I would not do it.
Touch the dial cord with a soldering iron and it's destroyed. Forget a cap location or polarity, and screw up the board (hint: take lots of pictures). Clumsy soldering and you'll ruin the PC board.

I have a Marantz 2252b to recap, just haven't had the time and the dial lights are extra work.

beatman:
just replace all caps with good quality brand same capacitance and when not found the same voltage you can do with bigger.16v can be on his position 25v.i do  a lot old complicated devices 25-35 years with succsess.just be very carefully when desolder don t made anny damage on traces and take care for the right polarity of the new caps.

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