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Marantz 2230 Service Bulletins

I uploaded them to HiFi Engine, so they are now available there.

If anyone still wants me to e-mail them the scans, I will.

Rob
 
I have not run across either of these. What are you guys using for the 150 ohm Thermister (25C) when you do need it?
 
I have never seen a 2230 with a blown power amp channel unless someone did something extremely reckless. Many other models use the same basic scheme for bias and they don't seem to have a high failure rate either.

We have nothing to go on as far as the thermistor specifications except for the Marantz part number in the service bulletin, which probably won't cross to any modern part, and the fact that it is 150Ω at 25°C. If someone had the listed thermistor and the equipment necessary to determine the B25/85 characteristics, perhaps an exact substitute could be found. (see page 10)

This 150Ω 25° NTC thermistor has a B25/85 of 3560 which means it is 150Ω at 25°C, 60Ω at 50°C and 20Ω at 85°C. If this is used in place of the one in the bulletin, it will definitely reduce the bias if H755 gets hot, may be not enough, may be too much.

This looks like something I will never have enough time to fully investigate, anyone need a science project?:D

Tom
 
Tom thanks for the additional info, after a 2230 rebuild I always monitor heatsink temp and board temp on the amps, have never seen anything above 25C (78 deg.) so may or may not ever be a problem. I have a spare amp board here with the thermister but have yet to need it.
 
catrafter said:
. . . If the input and output coupling caps (C701, C702) are electrolytic types, replace them with 1uF/250V film types, Panasonic ECQ-E2105KF. If they and the output coupling caps are .47uF, you might gain a few Hz on the bottom end if you change them to 1uF/250V types like the later models have. . . .
Click to expand...

I'm resurrecting this thread for a little clarification.

My P700 board has the big, brown lima bean caps at C401 and C402. I have been leaving these alone on other boards.

I've seen threads saying that the lima beans contribute to the "warm Marantz sound." I've seen other threads saying that films are preferred on inputs and outputs because they don't color the sound. I get the impression that replacing lima beans with films at C401 and C402 will result in a marginal improvement in bass, at best.

It seems like the lima beans aren't failure prone, so I'm leaning toward leaving them in. Sounds like the safe way to go.

Thoughts?
 
They are film caps and do not need to be replaced, and by the way they sound very very good!
 
Y
Robisme said:
I uploaded them to HiFi Engine, so they are now available there.

If anyone still wants me to e-mail them the scans, I will.

Rob
Click to expand...
Yes please, I know this is an old thread but I have 2 units of 2230 that will start restoration soon. Hope you don't mind to email me, Rob.
Thank you in advance.

Best Regards,
Elsuhan
(Email: elsuhan@yahoo.com)
 
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