Marantz 2285 (non B) Restoration

MBuras

Restoration is an Addiction
Just finishing up another receiver right now and then on to my latest acquisition, a Marantz 2285 in very nice condition. Relatively clean inside and out with only minor corrosion inside.

Photo Jul 07, 4 11 22 PM.jpg Photo Jul 07, 4 12 11 PM.jpg

Interesting to note the change in board layout from the earlier 70's models. The AM board is now back on the left side of the transformer. And it has a cover along with the FM MPX board up front. Also note the huge 50mm 13,000uf filter caps. Wow! Great news that the amp boards unplug for ease of removal.

I did note the phono and preamp board uses reddish films (not brown or green or gray). Was wondering if anyone had seen them before and any thoughts on their performance? Here's a pic of the phono board.

Photo Jul 07, 3 32 38 PM.jpg

Of course if you know me you know pretty much everything will be new when finished. But because this receiver is somewhat rare compared to the common 2230/2270, etc I was wondering if others had input or advice. I've been busy confirming component values and will wait until the weekend to place my Mouser order. My first rebuild without a historical template to follow, at least that I could find on AK. Should be fun!
 
Good luck with Mouser. I just cancelled a parts order for the caps to update my 2275's power supply board. One of the caps was BO'd until October so I'm now trying to source the caps somewhere else.
 
I had the same problem when I placed my order for 2230 parts. 4 or 5 of them were BO'd and I got an e-mail saying some would come in Sept and some in Oct. I just ordered those from Digikey and got them in a couple of days.
 
I did note the phono and preamp board uses reddish films (not brown or green or gray). Was wondering if anyone had seen them before and any thoughts on their performance?

Yes, that was a production change.
My 2250B from the end of October 76 has the same updated components on the phono board (and the same 1uf/100v caps on the tone board instead of the grays), however a 2325 from September 76 does not.
Also note that H405 and H406 should be the updated C1775 transistors and H407 and H408 are the updated diodes.
 
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Also note that H405 and H406 should be the updated C1775 transistors and H407 and H408 are the updated diodes.

Yes. I have confirmed both of those are correct. But they still left the VD1212 at H409 so I plan to replace that with the normal 2x 4148's in series.
 
I would replace those films, which are Panasonic/Matsushita, with Panasonic polypropylenes.
 
P800 Power Supply Board:

The place where every good Marantz resurrection starts. This power board was looking sad and dirty. It doesn't show well from a top view but that huge 2200uf cap on the far right was actually installed on stilts because it wouldn't fit on the board. Looks factory. Go figure!
Photo Jul 12, 5 08 08 PM.jpg

So of course I had to document everything, strip down the board and clean it up.
Photo Jul 13, 12 38 09 PM.jpg

And then it gets all new parts.
Photo Jul 16, 12 58 29 PM.jpg Photo Jul 16, 12 58 36 PM.jpg

Yes, I did notice that grounding strap wasn't secured and took care of it after the pics. :)

First thing you'll notice is a brand new shiny Omron MY2-0-DC24 on the right. Also way up top there's a new 7W 150-ohm resistor (old one was 5W) and 2 new On Semi MUR1620 common cathode diodes replacing the original DS131-B's. Any resistors over 1/2 watt were replaced and all new diodes. And a new Bourns 4.7K 1/2 watt trimmer on the bottom left. Transistors are all new as well with Fairchild 2073's taking over for the aging 330 and 331 big guys, while the remaining 5 to-92's were replaced with Fairchild 2383's.

I've marked the caps on the last image for easy identification. All were replaced with Nichicon UPW series with high ripple current ratings. Those tasked with filtering were upsized to fit in the physical space available.
C801 went from 63v/220uf to 63v/1000uf
C802 went from 50v/100uf to 63v/330uf
C804 went from 35v/22uf to 35v/47uf
C805 went from 50v/330uf to 63v/470uf
C806 went from 16v/2200uf to 25v/2200uf (just couldn't get more in the physical size needed - but it is planted on the board now)
C807 went from 50v/10uf to 50v/22uf
C808 went from 16v/100uf to 35v/100uf
C809 went from 10v/220uf to 25v/220uf

More to come soon.
 
Mike, great looking work! I'm curious about the rationale for raising the capacitance on many of the electrolytics. I get increasing the voltage rating, but what is gained in increasing capacitance, and are there any downsides? Just trying to learn. Thanks!
Steve
 
I'm following @Leestereo school of thinking on the power supply section. The idea is that Marantz would have put larger caps in certain areas if physical size wasn't a limitation in the 1970's. Now that technology has made things smaller this is possible.

Here's one of the original threads I followed and pulled ideas from: http://audiokarma.org/forums/index....oration-and-upgrade-of-a-marantz-2325.689386/

I read the post on the power section, compared it to the schematic for that receiver, and then applied that to my receiver which is similar but not quite the same. Did something similar to the last receiver I worked on with good results although I can't say it results in any sound difference. Just long term reliability. And the cost is only a few cents more so not a downside to me.
 
Excellent work being done here, I love using Nichicon PW series in power supplies and some HE when need be.

There is a possible downside and it is surge current. Upon power up the filter caps draw a large surge and that passes through the rectifier diodes. Maybe look into upgrading those to a higher current rating. Then only the power switch and power transformer will be worked harder!
 
Good segue to the power switch topic. I'm probably going to make a separate post on finding a replacement. It's not the normal Marantz power switch and is mounted into a bracket that is integral with other push buttons on the backside of the front panel. Never seen anything like it.
 
Good segue to the power switch topic. I'm probably going to make a separate post on finding a replacement. It's not the normal Marantz power switch and is mounted into a bracket that is integral with other push buttons on the backside of the front panel. Never seen anything like it.

Many models used a similar mounting method, the 2275 is a good example. If you pry up the fingers on the mounting bracket holding the old switch, you may be able to insert a new switch in place of the old.
Here are a couple of really bad pictures of this method.
Power switch bracket.jpg Power switch mounted.jpg

Alternately, If there are screw holes in the front chassis, you may be able to cut the end off of the old bracket and mount a new switch utilizing the bracket on the new switch.
Tom
 
Very nice work MBuras.

Note that the P800 board of the 2285 is nearly identical to that used in the 2235B (some capacitors values are different), and a restored and upgraded example of the latter can be found here: Power Supply/Relay Board (P800) Restoration.

RBuckner is correct in stating that the increase in charging and turn-on surge current should be taken into consideration when increasing capacitor capacity ratings. The 2-3 fold increase in capacity of small (e.g. <1000µF) capacitors is not really problematic for the silicon diodes when one considers that even 1A silicon diodes are typically spec'd to momentarily withstand ~30A of current. The increase load on the power transformer winding should also be also considered, but unless the original rating was marginal, this should not be a problem for a 2-3 fold capacity increase. The power switch in a high power receiver does take a beating and this is due to the initial charging of the main capacitors, which are typically >10,000µF each. Accordingly, this current surge is much larger than the current draw from the comparatively tiny board capacitors.
 
Note that the P800 board of the 2285 is nearly identical to that used in the 2235B

Interesting read. I never looked at that receiver for a comparison but they are indeed very close in build style. Thanks for the heads up and further inspiration.

If you pry up the fingers on the mounting bracket holding the old switch, you may be able to insert a new switch in place of the old.
Alternately, If there are screw holes in the front chassis, you may be able to cut the end off of the old bracket and mount a new switch utilizing the bracket on the new switch.

Good info on that power switch. I'll be digging into that shortly.
 
Be Careful of 2 caps on the preamp board. They are marked wrong. I forgot the numbers

Note: This issue exists on the B unit, I am not sure if your unit applies...
 
PE01 Preamp & Tone Board:

Sorry I don't have any before photos on this one, but I will start with the stripped down version. All components were documented and no errors were found, surprisingly enough.
Photo Jul 14, 8 59 26 AM.jpg

Good news is the board has a modular connector so no pins were harmed in the removing/replacing of this board.

And here's the finished product.
Photo Jul 14, 10 04 27 AM.jpg

All electrolytics and ceramics were replaced along with a few films, along with all transistors.

HE03/HE05 received new Fairchild 1845's while HE04/HE06 got new Fairchild 992's.

CE39 was a 35v/220uf and replaced with Nichicon UPW series 50v/470uf to increase filtering ability.

CE09/10 were 10v/100uf electrolytics and were replaced with Nichicon UPW series 35v/100uf. I noted at 8mm they are slightly too large to sit comfortably together. Next time I would order something slightly smaller.

CE11/12 were originally 35v/10uf polar electrolytics and were replaced with Nichicon UES series bipolar 35v/22uf. Once again I noted these were slightly too large and I would order something slightly smaller next time.

CE13/14/33/34/35/36/37/38 were all replaced with WIMA polyester films.

CE05/06 were originally those funky red films and were replaced with Panasonic polypropylene films of the same value.

CE07/08/31/32 were original ceramics and replaced with modern C0G MLCC's.

And of course all controls were cleaned while they were out and easily accessible.
 
PH01 Filter Amp Board:

This little board is tucked into the bottom in the center where the preamp is on many of the smaller 22xx series receivers.
Photo Jul 14, 2 30 07 PM.jpg

And here's the final board.
Photo Jul 14, 3 01 03 PM.jpg

CH01/02 were greenie films and replaced with Panasonic polypropylene films of the same value.

CH03/04 were low noise electrolytics (identified by orange color) and were replaced with WIMA polyester films.

CH05/06 are hidden behind those big WIMA films. These were factory ceramics and replaced with C0G MLCC's.

All four transistors we're replaced with Fairchild 992's and 1845's. There weren't any issues with these but at 15 cents each they're quick and cheap to replace.
 
PC01 FM Dolby Board & PS01 Dolby Board:

PC01 Before: Not much on this board except those ugly blue tantalums.
Photo Jul 17, 3 12 05 PM.jpg

After:
Photo Jul 17, 5 59 40 PM.jpg

Pretty easy work on this one. I replaced all 25v/1uf tantalums with 50v/1uf WIMA films.

PS01 Dolby Board:

I don't have pictures on this one because its in the worst place possible and I suspect most except the most dedicated techs would access this board. It's located under the meter lighting housing, ahead of the MPX board and access to components below is blocked by the 48-headed hydra otherwise known as the function switch. Access required pulling screws for all button assemblies, all tape/headphone jacks, and removing screws that hold the inner face to the frame. Pull the inner face out just enough to clear the function switch stem and then carefully move the function switch ever so slightly. Don't want to break any of those wires off!

CS01/02/03 were 35v/4.7uf electrolytics and were replaced with Nichicon UPW series of the same value.

CS04/05 (by far the hardest ones to get at - helps to trim the leads on the replacements) were 16v/10uf electrolytics and were replaced with Nichicon UPW series of the same value.

HS01/02 to-92 transistors were replaced while I was in there with Fairchild 2383's.
 
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