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Jumped in BIG....found a Marantz 2500.

Ok EW.....no worries.......I am working on the amps.......the drivers are 2sb630/2sd610......what is best to use ksa940/ksc2073 or mj15032/15033?

All the main out-puts will be changed to mj's.........

Thanks.....
 
Nothing like a few days of to get some work done.:banana:

Got the amp's and the old fan out...........regarding the old fan..it was rated at 230v......my new fan is rated 115v...will this be a problem? see pic.

I sub'ed the main outputs: 2sb600=mj21193 and 2sd555=mj21194.

(in a couple of threads this is switched around.....I hope I have it correct)

Again, if anyone sees anything non-ok......please , please let me know.....

A few pic's..............
 
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anderslober said:
Nothing like a few days of to get some work done.:banana:

Got the amp's and the old fan out...........regarding the old fan..it was rated at 230v......my new fan is rated 115v...will this be a problem? see pic.

I sub'ed the main outputs: 2sb600=mj21193 and 2sd555=mj21194.

(in a couple of threads this is switched around.....I hope I have it correct)

Again, if anyone sees anything non-ok......please , please let me know.....

A few pic's..............
Click to expand...


Wow! C L E A N! Just curious. Why did you opt to replace those working original NEC outputs?

About your fan. If your receiver is wired like multivoltage like my 2500 is supposed to be with a transformer installed, then that fan will work. BUT if your 2500 is straight 230v, then you got a problem here.
 
My unit is a multi-voltage unit, so my new fan should be okay. Regarding the change in outputs.........on the right channel 2 were non-original.......a tech had been there before me. I have elected to change all the old outputs to modern, beefier MJ's. The old outputs seemed a bit under-spec'ed for the amp as a whole.......

The drivers one the right channel were not original either.........I know from another thread that EW had bias problems with MJ drivers.........I was actually intending to put in MJ's.......have you any suggestions?
 
Been going over the amp boards......all seems ok except the Q731, which is a EQA01-35R(35v/.5W zener) on one board and what looks like a w06b:eek:...on the other! I will change this......only the 35v zener is a hard find.....I guess I will put a 20v and 15v in series........1N4744A and 1N4747A.....should be ok...?
Just confirm for me.......black zener 'bar' to red zener 'end.....
 
When you have to put zeners in series, the best practice is to have them be as close to the same voltage rating as possible. So for 35V, a 17V and an 18V zener would be best.

Learn the terminology...one zener's anode connects to the other's cathode (cathode is the banded end) in order to have them effectively in series.
 
Yes EW...ofcourse you are right...I should use the correct terminology. Ok, I will get hold of some 17v/18v 0.5w zeners and install them.

EW...do you have an opinion on using the mj'15033/32's for drivers?

On the power supply ...I will change q807 to rgp02-20e diode.(2000v.0.5A). q808/809 will be changed to 1n4007's....1000v/1A diodes.
Please confirm this to be okay.....thanks.

After all this....and a triple-check...and a severe cleaning....I should be ready for POWER ON.
 
EW.....went hunting for the correct zeners today.....unable to find 35v......unable to find 17v...I did find 36v(+/-5% tolerance)...would this be okay to use?

I also found 16v and 19v.............if this series method is better...please indicate what is best.......thanks
 
17 & 18V 500mW zeners are a standard size, so why you can't find them is puzzling. If you deviate from the desired 35V, you may have to adjust the gain of the regulator to compensate. If the best you can do is 16 & 19, then it's the best you can do.
 
ok...got a bit more work done on the 2500.......changed the zeners on the amp boards.....got the 'pig' back in the unit........only to find out that the shroud/filter for the fan was contacting the fan.......so when the fan turned, there was a 'fit-fit-fit-fit' sound....anyway...out with the 'pig' again.....adjusted the shroud.....in with the 'pig' and no 'fit-ting'.
De-oxited and and cai-lubed all switches and pots..............got all the friggin' connectors connected up again..........did some cleaning of the chassis.....blew all dust and gunk out with compressed air. I checked all fuses.....all were good except the main fuse on the back.....it was an 8A instead of a 6.3A.....I changed to spec. Also drilled the holes for securing the softstart/fan resistors.......

I have also been going over everything that I can see.......caps, tr's, connectors, new softstart/fan resistor area............all seems good.........almost ready for power 'ON'......will also post a few pictures.

Thanks to catrafter for sending me some decal files...I will print them on sticky paper and put the decals on the main caps and transformer........

Once all has been gone over thrice...I will turn the unit and hope for the best.....I will adjust, dc-offset, idle current an'all....Marantz gets no prizes for making this easy....left amp is easy to adjust...right amp is 'inverted' and not so easy to adjust....

Cant wait............goin' on a trip now..........
 
Back again with the 2500......got it all back together again...now awaiting only correct fuse and amp adjustment.....some pics..........

Rust on the inner chassis will be cleaned and paited as much as possible.....

If anybody sees anything funky....let me know...thanks.
 
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A couple more......Marantz gets no prizes for 'cable-clealiness....it is just a mess in there............what were they thinking:sigh:

I will try to tidy it up a bit with some plastic strips here and there.......
 
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Hello again forum'ers. After checking everything a couple of times.....I decided to pwer up the 2500...........with some trepidation, I pressed the power button and low and behold......the unit came on, relay clicked 8 sec. later. Nothing blew up or smoked......I adjusted all the voltages to spec.....this was quite easy.:banana:

Anyway.....I still have the slight humming problem........it is constant and does not go up/down with volume. The hum is also there no matter what type of input is selected. What could this be? Big caps? If anyone else with a 2500/2600 has had this small problem....please chime in.:thmbsp:

Overall, I am happy that the 2500 is working again and it is now ready for a couple of decades of use.:thmbsp:
 
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hello EW......according to the scat....would it be enough just to disconnect JE02 from the pre amp board?

OR could I just stick 4 rca's(not jumpers) in the main in/pre out connectors....would this infact disconnect the amp and pre-amp? Without destroying something ofcourse.....thanks again........
 
EW...I connected the IC's to the main in jacks...........the hum was definitely much lower with the amp and pre-amp separated. So I guess the hum originates from the pre-amp section...maybe even the filter(sk30a's???)

There are no tr's on the pre-amp board.....however the filter board has a few tr's.........sk30a's and some 2sc1681/2sa841's.......I think I may change all of them to new tr's.........2sc1681 becomes a ksc1845.......2sa841 becomes ksa992.............please confirm this to be a good swap....thanks.

The sk30a's will be new sk30a's.
 
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