Marantz 250M
- Thread starter sanjib
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I think you have an earlier run since the production number looks to be purely sequential. Later models added numerical sequences to include production dates, runs, intended markets and even voltage sources.
I see you have the Pioneer SA-9500ii. I had that amp for about a year or so. How do you like it?
I see you have the Pioneer SA-9500ii. I had that amp for about a year or so. How do you like it?
Thank you!
When I got Pioneer SA-9500II, only the preamp section was working. I just repair the main amp sections and it is now going through a full restoration. So, need few weeks to listen to it!
I believe the manual is correct, I can check with my 250 that's here though.
I would advise pulling the driver, predriver and output Transistors to verify that the gain is within the range that Marantz specifies, I've seen em drift pretty far out making it only a matter of time until the unit explodes.
Yes, I will do all those during the restoration that I will start pretty soon. Currently, it is working when plugged into 100V step-down transformer.
Thank you for your advice and it would be great if you post a picture of the transformer connections of your 250M.
GRonald
Active Member
Unlike the US/European models, those 250M Japanese versions are factory modified, attached some pics of the power board. When I got the first one, I thought some tech had modified only to realize these are factory mods, when I received 2 more of the same, all from serials 30,000+ and above. I restored the first 2 back to the original design, as I could not find any information on these mods. These power boards also have a standard BJT 2SA1124 in place of the PNP Darlington at location Q503. I did a full restore on the first 2, Pics of the first unit.
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GRonald
Active Member
Thank you!
I have completed the project this summer with a full recap and all of the service bulletin works were already factory done. I completed the voltage conversion and a full recap of the main amp and power supply board.
Nice! How are the Audyns working for you?
I like it a lot! I also used these in my Accuphase P-300, love the results!
GRonald
Active Member
A lot more than just the service bulletins are done on these Japanese versions, no available documentation though.
How does it sound?
Is the backside of the PCB modified same as the one I have in the pictures?
What is the transistor in location Q503 on your board?
Do the Japanese serial number models have the same transformer that is multi voltage for 220 and 240v also?
I don't know about all of them but if there is a red sticker on the rear of the top cover saying converted to 100V then it is.
GRonald
Active Member
Yes they are multi-voltage transformer, however I noticed a difference on the DC output,
- On these Japanese version the dc rail voltage is 56.5 volts with the variac voltage set to perfect 240Volts,while the US/European models I have the DC rail voltage is 58.5 Volts. Point to note My 1200B runs at 53.5 volts.
- The current limited variable resistors missing on these Japanese boards and these unit clipped at 125.5 watts in 8ohms load (when unrestored and with the Japanese mods in place).
- On the US/European Models I have, I was able to drive the to 139/142 watts before clipping, of course the adjustment had to be made as per the service manual to clip at 125 watts for protection, which I did after testing.
Thanks for the clarity I have a 240v version with those same mods which look factory initially I thought was a old repair but seeing those boards makes me think it was factory delivered that way
GRonald
Active Member
A close look at the Marantz 500 Model and the 250M, there are so many similarities in the initial stage. To me the 250M is the best at my normal listening volume, My fully restored 510M does come to life and the sound is a lot more pleasing and desirable than the 250M, but at that volume, everyone in the house wants to kick me out. I believe with the right speakers and the right room, the 510M can be unbeatable. It reminds me of two of the statements we had in engineering. " It takes a 1000 watts to accurately produce the sound of a needle falling on the floor". and "Buy your music system and then build a house designed for it".
