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Marantz 2285B - a tour

M

MatthewK

Active Member
As part of the LED lamp project I decided to go all-out and fully restore my Marantz 2285B. I decided on Deoxit / ProGold treatment for the controls, and replacement of the caps in the entire preamp / amp pathway.

So here are some shots of the work - first, the insides of the receiver from above and underneath.

Top view, top row left-to-right: tuning capacitor, transformer, power supply capacitors. Power amp board runs down the right side with black heatsinks. Inboard of that is the relay board, also mounted vertically. To the left is the tuner board (brown PCB) and the long narrow green board below that is the array of switches. The lamp housings (beige) can be seen below that.

From beneath: the tone board is at the top (it's been freed from the front face by undoing the nuts from the controls). It's partially in front of the underside of the tuner board. Along the bottom we see the input selector switch (it's at the rear of the unit, normally connected to the front control by a long shaft which I had removed by this point); the underside of the transformer and PS caps, and the power amp on the right side.
 

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Second up - the re-cap jobs on the selector board, tone board and power amp board. In each image "before" is at the top; below, "after".

Also an extra-special thank you to Dan Simon from this board, who gave me precious information about setting the bias currents and offsets for the power amp - the community spirit here is wonderful!

I used stock components from my local electronics supply - I figure the original design was based on standard grade components and I may upset things by using exotics. As a result the whole job cost under ten bucks in parts, and took about five hours. The replacement caps are smaller, have higher temperature (sometimes higher voltage) ratings, and I figure they should give the amp another thirty years. One power amp cap was a bit swollen so I think I did it just in time.

The receiver was reasonable to work on - surprisingly the power amp board was easiest, you just disconnect the connectors at the bottom and undo four screws to lift it out. That allows access to the relay board, wish I'd known that six months ago.

So - after a warmup and a listen the sound is wonderful - I had a "front wall disappears" experience through my VAF Ultra 7s (an Australian budget hi-fi floorstander D'Appolito array with a tweeter, 2 x 6" woofers and a reflex port, self-assembled). I don't really ascribe this to the caps themselves (though they may be closer to design rating) but more to the bias setting that Dan enabled - it was way off, and by different amounts, on both channels. All controls are now noise-free and the switches are reliable.

Anyway, I've given a new lease of life to a classic, and you can't ask much more than that. Next project, the Phase Linear 700!
 

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MatthewK said:
Second up - the re-cap jobs on the selector board, tone board and power amp board. In each image "before" is at the top; below, "after".

Also an extra-special thank you to Dan Simon from this board, who gave me precious information about setting the bias currents and offsets for the power amp - the community spirit here is wonderful!

I used stock components from my local electronics supply - I figure the original design was based on standard grade components and I may upset things by using exotics. As a result the whole job cost under ten bucks in parts, and took about five hours. The replacement caps are smaller, have higher temperature (sometimes higher voltage) ratings, and I figure they should give the amp another thirty years. One power amp cap was a bit swollen so I think I did it just in time.

The receiver was reasonable to work on - surprisingly the power amp board was easiest, you just disconnect the connectors at the bottom and undo four screws to lift it out. That allows access to the relay board, wish I'd known that six months ago.

So - after a warmup and a listen the sound is wonderful - I had a "front wall disappears" experience through my VAF Ultra 7s (an Australian budget hi-fi floorstander D'Appolito array with a tweeter, 2 x 6" woofers and a reflex port, self-assembled). I don't really ascribe this to the caps themselves (though they may be closer to design rating) but more to the bias setting that Dan enabled - it was way off, and by different amounts, on both channels. All controls are now noise-free and the switches are reliable.

Anyway, I've given a new lease of life to a classic, and you can't ask much more than that. Next project, the Phase Linear 700!
Click to expand...

I almost want to cry after reading your post. I badly wish that I could do my own capacitor swapping and repairs like that.

Did you remove the power board to do those recaps? (looks like it?)
 
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