Marantz 300DC

Autobahn

Autobahn

Active Member
I'm the proud new owner of a 300 DC amplifier now. It was stated that it was checked out by a reputable shop here in Germany last June, and that everything was in spec.
Well I got it here yesterday. Tried it out, and it sounds like it isn't quite putting out the power it should.
Take off the cover to take at look at the inside. It will need to be re-capped. See some swollen caps. Also see that the relay has been changed, and the board was hacked to make it fit. Not too happy with the relay work.

Has anyone made a cap list for the 300 DC?
If not I'll see about making one as I re-cap it, and share it here. ( Could be awhile though, other projects being worked)

Mike
DSC00014.jpg DSC00008.jpg DSC00012.jpg DSC00010.jpg DSC00009.jpg
 
I'm starting on a 300DC restoration,probably next week, just as soon as I finish this 2385 restoration.
I ordered the parts from Digikey last week.
I'll go back and look them up.
Also, AK'r KutzlerTrans has a thread on his that he's been doing a resto on.

Bob
 
Hey Mike, Congratulations:banana:
There isn't a whole lot of caps in these, compared to a receiver, but i am not sure if i ever seen a dedicated list.
Do you have the service manual? You should be able to cob some answers from that. I know Bob,(whld1610) is rebuilding one right now, he may have a list.
I used the 36DA style Chemi-Con 100v 12,000 filters. They are a perfect fit!
I changed a few 1uf electrolytic's to films. The boards unplug, which is good, because the wiring is rather short and routed tight.
The correct relay is a Omron my2-02 relay. I cut the two extra unused pins off.

Transistor subs were fun to find, but i bought a pile of original diff pair transistors on ebay
http://www.ebay.com/itm/171396617383?_trksid=p2060353.m2749.l2649&ssPageName=STRK:MEBIDX:IT
The bridge rectifiers were upgraded to 25amp units on the unit i am working on. My unit is almost finished, but the project had to take a back seat to more pressing needs.
Make sure you take a lot of pictures and document your wire colors and plug orientation, because the wires break off easy;). John
 
I'm not sure about the 300DC but with some units there isn't a drop in replacement relay available anymore. With one of my amps I had to open the relay and swap wires inside.
 
Lavane said:
I'm not sure about the 300DC but with some units there isn't a drop in replacement relay available anymore. With one of my amps I had to open the relay and swap wires inside.
Click to expand...

That's for the 250/250M amps.

The MY2-02-DC24 is a perfect fit drop-in replacement.
DigiKey P/N Z2633-ND

I'm going with the caps John quoted or the 15,000uf 80V 105C 50mm x 63mm CDM's which also are a perfect sized drop-in that fit the clamps like the oem caps.

Bob
 
300 DC cap list

P700 board(x2)

1 50V 10uf
2 16V 22uf
2 35V 22uf
2 100V 22uf
Differential input pair - 2sa879

P800 board(x2)

2 100V 1uf
2 100V 22uf
1 35V 47uf
2 25V 100uf
2 100V 220uf

PN00 board(only one)

2 50V 3.3uf
1 100V 10uf
2 16V 47uf
1 16V 330uf

1 MY2-02-24VDC relay


Bob
 
wlhd1610 said:
300 DC cap list

P700 board(x2)

1 50V 10uf
2 16V 22uf
2 35V 22uf
2 100V 22uf
Differential input pair - 2sa879

P800 board(x2)

2 100V 1uf
2 100V 22uf
1 35V 47uf
2 25V 100uf
2 100V 220uf

PN00 board(only one)

2 50V 3.3uf
1 100V 10uf
2 16V 47uf
1 16V 330uf

1 MY2-02-24VDC relay


Bob
Click to expand...

Thanks! That matches what I figured out this morning. I pulled the boards from the left side, and matched them against the service manual.
I also have a 16V 10uf electrolytic capacitor on the P700 board (C701) that is grounded thru the board to the heatsink.

Mike
 
That question is going to illicit a mixed response pretty much like religion and politics.
My feelings are that it can't hurt to install them since they are not detrimental to the sound and some claim to actually hear an improvement.

Bob
 
wlhd1610 said:
That question is going to illicit a mixed response pretty much like religion and politics.
My feelings are that it can't hurt to install them since they are not detrimental to the sound and some claim to actually hear an improvement.

Bob
Click to expand...
Yeah, I thought so. I did it on one of my 2270s, and really did not hear a difference.
On the other hand, I have a bag of those film caps. Wont hurt to try it out.

Mike
 
I would try it. Most of time I felt bypass caps had a negative effect sound wise on cap coupled units though. worst case you could always snip them out.
 
Some bypass caps appear to make a difference and some do not. If you are not sure, hook up a switch on one leg of your experimental cap. I have found a difference in caps of the same value. Some will work better than others. They will clean up any high frequency noise in your line and send it to ground. usually 1/100th of the filter. I believe texas instruments did a study on this. With all the crap on our power lines, i do hear a difference, but i will be doing a detailed experiment with my 300dc using a switch and a pile of different capacitor brands, hopefully within the next month.
Its best to just do it, rather than listen to someone that never tried it tell you its voodoo.
I can say for a fact that my input capacitor tester did indeed give different results, with 90% of the test caps making no difference in the sound. The 10% that did were oil caps and a few interesting others, but this test was not the same as bypassing a filter cap, though.

It proved to me that somethings going on. Most changes were very subtle and showing up mostly as an enhanced sound with more depth.
The crazy part was some days it was more pronounced than others. My main goal was to determine whether or not the Panasonic films were better than the stock grey Marantz films, and there was a definite change in sound with the :thumbsup: going to the Panasonic ECQ units. Oil motor start caps beat them all, hands down,, but they were too big to fit into the unit, and bypassing any of them with a .01 made the biggest difference in clarity as long as certain kinds were used.
I found the best decoupling cap to be the Russian k77 .01uf green jobs for the input cap bypass on my 2325 pre amp board. it may not be the best one for a filter bypass though.

What i did not document was the direction the bigger films should be installed, because they can act like little antenna's if installed backwards due to the outer foil. if in doubt, try holding one twix the fingers and try it on a tape input. Just guessing here, but i would think that you may notice the difference.
 
Last edited:
(update)
Still awaiting parts. I have a military APO address here. So it's a little slower than shipping within CONUS.
 
Finished!:beerchug:
Been running it all morning. Bias came out at 48-49mA. Power supply at 70.1 VDC. DC Balance at 0.00 - 0.01mV.

Mike
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