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Marantz 2275, 2285 and more - MPX board P300 - service manual discrepancies

Mjölnir

Mjölnir

New Member
I'm upgrading my Marantz 2285 after a failed upgrade attempt by a previous owner. I'm about 75% through and one of the last boards to complete is the P300 MPX board. I've been trying to rely on the service manual for component values but eventually I ended up with serious differences between the actual PCB and the service manual. This seems to affect 2285, 2275 and other receivers from the 22xx series using the same P300 board. The schematic, actual board, PCB layout and the component list at the end of the manual. My initial guess is that there are several revisions of the board over the years and also revisions for the same board (some PCB component locations aren't populated). On top of everything the component list doesn't seem to match neither actual PCB, schematic or the manual PCB layout. I have checked my service manual vs service manuals online and they are identical. I would appreciate input from anyone as to if and with what values the PCB (reflecting the latest revision) should be populated with the capacitors C339 through C344.

My P300 board vs. the service manual:

P300..jpg
 
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@thxdave has a very comprehensive thread about his 2275 rebuild, including a spreadsheet of all parts replaced. The only cap on your list that is also on his list is C342. That leads me to believe it is the only one populated, or at least the only one he thought needed replacement. That one was a 10uF 16V that he replaced with a 10uF 50V

https://audiokarma.org/forums/index.php?threads/2275-rebuild-project.735510/page-6#post-11997561

He has pretty good before and after pics of the board here. Maybe you can compare.

https://audiokarma.org/forums/index.php?threads/2275-rebuild-project.735510/page-5#post-10322425
 
Thanks for the link. Although thxdave doesn't specify what components he replaced on his P300 board it looks like from the picture that he replaced C340 with 10uF/16V and left the position for C339 unpopulated. For the C341-C344 his thread doesn't say anything but his end result seems to be fine. This means that the manual should include only the C340 cap and omit all other caps from my C339-C344 list. I guess these caps are remnants from earlier incarnations of this board. I wish there is a later version of this manual or an errata list available somewhere.
 
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If you have any uncertainties, I have a 2275 on the shelf that I can open up and inspect if you need it. But it has been recapped - not original.
 
Thanks, I would appreciate that if it's not too much hassle. I have to assume that if your board works fine and you just replaced present original caps on the board (not added or removed caps) then it should be like original. Could you please also confirm my findings re. the caps on my list.
 
I opened up the 2275 to check the caps on the 300 board with quite a bit of frustration (see my new thread “No good deed goes unpunished”). C339, C340 and C341 are unpopulated. C342 has a new 10uF 35V electrolytic cap and C343 is an original “greenie” film cap. Hope this helps,

IMG_3563.jpg

IMG_3564.jpg
 
It seems that our boards are slightly different. Since you have a 2275 then my 2285 board is probably a later revision. Mine doesn't have a C342 location at all. Neither does the 2275 service manual (see pic below) which indicates that the manual was written for the first 22xx using this board and was never updated after that although the physical boards changed over time. The 2275 and the 2285 are identical for this board. The bottom line is that from C339-C344 only one 10uf/16V is to be used. I am now confident in replacing this existing cap only and not worry about the rest. Thanks for your help!!!

Pics from the 2275 manual marantz_2275_P300_1.jpg marantz_2275_P300.jpg
 
I didn’t check C344, but C343 is definitely present in the form of a film capacitor. It’s that green cap right next to the mounting hole in my second pic.
 
Everything I changed or upgraded was at the behest of Ben "leestereo" who very patiently told me why each part was in need of change. He might jump into this thread to answer questions. I'm not smart enough yet to offer much info except to say that I had a blast doing the 2275. Just to update, my source selector switch has developed a dirty spot and lets signal drop out occasionally. So, I need to open it up again!
 
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