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This is terrible.

paul79 said:
I'll have to bring the 250 manual home with me tomorrow but my money is on the Darlington transistors. Bet you got crazy stuff going on under load right? Loads of distortion? No bias? Also, seing how it is coming out of protect (I assume??)is the kicker. Here are the parts you need to change: MPSA65, MPSA43 are available at Newark, and MPS6519 is un-available but substitute with BC557 (pin-out is the same) available at Digikey. Buy 10 of each or so and replace all of them on both channels. If you have one good channel, swap em out and see!! There is no way that I have found to check them properly so I just change them. Replace all the electrolytics as there is only a hand full in the whole amp.
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Thanks for your help! i found all the model you've given me.
I'm going to order them new. as soon as possible.
:thmbsp:
 
Arkay said:
I've seen a few horrific "hack jobs", even much worse even than that. I don't know what these people think they are doing. The worst is that often this is done by 'professiona;s' who charge people money for screwing up their gear that way.

I'm an "amateur tech", too... but I make it a point of pride to work carefully and methodically, to do research first (as/when needed), use good materials and tools, etc... and I usually get good results that I'm reasonably proud of. If I do a soldering job that doesn't look good enough to me, and I can't re-flow it nicely, I'll suck it out and start over again. If I have doubts about any component, I'll get a meter out and check it, or replace it. If I'm re-capping, I'll check ALL resistors and transistors, too, and re-mount transistors with fresh grease, etc...

It's just a matter of personal integrity and pride in one's craftsmanship, of having to live with what I've done, every time I look at the gear or use it. If I did 'hack jobs', I'd quit trying to fix anything, if not for my own peace of mind, then for the sake of the gear!

So why can't all 'professionals' do the same? If we were talking about some huge investment of time, I could understand. It would be un-economical. But it takes no more time, really, to install a proper component than a wrong one, or to solder well instead of poorly, etc...

At least this poor, abused example is finally in the hands of someone who will make it all right again. Looking forward to seeing the progress through this thread!
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Damn straight! that's the way I do it too. I like it to look perfect, even though I'm probably the only one to see it. Not enough people take pride in their work, especially in this hobby. I too look forward to seeing it in it's original glory.
 
paul79 said:
I'll have to bring the 250 manual home with me tomorrow but my money is on the Darlington transistors. Bet you got crazy stuff going on under load right? Loads of distortion? No bias? Also, seing how it is coming out of protect (I assume??)is the kicker. Here are the parts you need to change: MPSA65, MPSA43 are available at Newark, and MPS6519 is un-available but substitute with BC557 (pin-out is the same) available at Digikey. Buy 10 of each or so and replace all of them on both channels. If you have one good channel, swap em out and see!! There is no way that I have found to check them properly so I just change them. Replace all the electrolytics as there is only a hand full in the whole amp.
Click to expand...


Which darlington do you mean?
There are no darlington transistors present.
Nobody noticed that...................??!!!
 
Not the guy's from Newark.
This is the mk1 version dude and in this design there are NO darlington transistors present. :smoke:
No offence but i would take a better look next time before giving any advice at all.




Part list:

2N-4250
sps-1928 (diff amp)
sps-1951
sps-1952
2n-4143
2n-4125
sps-1950 (sense)
SS en SJ (drivers + outputs)
 
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You are correct!! Thanks 4 the heads up! (tucking tail and running)
 
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Deja Vu ..... all over again.... I think this darlington transistor comes up every 6 months...

Deja Vu means "Transistor Transistor, all over again" :D

Get it? As in Darlington transistor..... You do know the transistor was invented just 2 miles from where I live.....

(:scratch2:Hello, is anyone out there? I hear Crickets and hedge hogs........).

jk
 
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LOL! I have only seen one mk 1 and several mk 2's. Are there two different 240's also? I think I have two different manuals for that one also, but have only ever seen the one with the darlingtons in it.
 
Yep that's correct.
The older 1200 integrated is a mk1 and the 1200B is the mk2.
further more you have 240's en 250's mk1 and 2.

The model 250M is mk2 only.
 
Well i've done it! i finished repairing the marantz 250 main amplifier.

lot of bad components, works great now!

The VU meters are broken :tears: i need new ones for this piece.

CIMG2943.jpg

broken transistors in left channel, one fall appart.

CIMG2944.jpg

Green board, someone already tried to service it.
CIMG2946.jpg

VU board was not 100%, i connected another meter on this board, and i didn't work.

I've replaced the caps and transistors, also two glass diodes next to the big (hot) resistors.
CIMG2947.jpg


CIMG2953.jpg

everything works fine. And looks a lot better then before.

CIMG2948.jpg


CIMG2950.jpg


The 250 gave +- 185Watts at 8 ohm a channel stable for over half a hour.
 
That's some fine work, Hal. It's great to see a damaged old Marantz brought back to glory. :thmbsp: Model 250 is a beauty, love it. :drool:
 
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