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Marantz 2500 on the bench

if from mouser they do not include insulators. but i dont think any of the big dog suppliers include anything other than whats listed.
 
mikey99 said:
Next step is to determine why I have no sound from AM/FM or the AUX inputs. Almost seems that the preamp
isn't working at all or I have some very dirty switches.
Click to expand...

Check if you have signal on BOTH sides of the balance slider, I had the same issue with my 2385, the slider was dead...dead...dead nothing. Bypassed it problem solved.
 
Separating the amp tunnel channels

IMG_4918.JPG IMG_4919.JPG IMG_4920.JPG IMG_4921.JPG

Closeup of the bad channel outputs.....not much dust in here at all.

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Be careful when you remove the screw that has the QM01 (Varistor STV-4H) and QM02 sandwiched together. The part is brittle and when you turn the screw it can fracture.
 
Pulled the suspect output transistors and confirmed they are in fact shorted.
Insulators are used between the transistor and the heat sink, but its not obvious
if there was any type of thermal compound/grease used.
I'm planning on pulling all eight and replacing with the MJ21193/MJ21194.

Will this cause any type of sound mismatch with the other channel which still has the original outputs ?

Now I need to decide if I should pull all eight at the same time and totally separate the circuit
board from the heat sink for cleaning etc. Doesn't look dusty at all so I'm leaning towards just
replacing the outputs one at a time.

Also for the TO-220 devices I think I have the following two correct:
D610 (2SD610A) crosses to 2SC4793 or MJE15032G
B630 (2SB630A) crosses to 2SA1837 or MJE15033G

Its difficult finding time to work on this with the beautiful weather we've been having and all the outdoor yard work that needs to be done.
 
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txturbo said:
Be careful when you remove the screw that has the QM01 (Varistor STV-4H) and QM02 sandwiched together. The part is brittle and when you turn the screw it can fracture.
Click to expand...

Thanks for the tip, still debating on changing these two, but I probably should. Kind of strange the way these two are stacked like this.
 
catrafter said:
There are a couple of excellent threads on the repair and restoration of the 2500/2600 here on AK that it would be prudent to look through.
I have and would replace all the output devices in the shorted channel. Be sure to check the TO220 drivers.

Tom
Click to expand...

Would you recommend changing all the output transistors in the other working channel too ?
While I have this disassembled......They are fairly easy to replace, and only about $40 in additional parts.....

I'm not sure how well the other channel is working, I did get sound when attaching my ipod
to the Main in....not very loud but I'm sure the ipod output level is much lower than a preamp.
 
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Recapped both P700 amp boards and the PX01 board today. Measured some of the old caps
and most measure about 1.5X marked values. Waiting on the output transistors.....
MJ21193G and MJ21194G from Mouser.com.

I also ordered TO-220 devices:
D610 ---- MJE15032G
B630 ---- MJE15033G

And ten of the KSC1845FTA, hopefully can match two pairs of these.
 
It's been awhile !!! :) ...... but I finally got everything back together and the 2500 is now working !!!!!!!

To summarize:
I replaced all 8 output transistors in the shorted right channel heat sink.....QM05->QM12
Replaced all electrolytic capacitors in both of the P700 boards and PX01 board.
I replaced the two TO-220 devices in the center of the heatsink......QM02 and QM03
I replaced two additional blown (open) transistors on the right amplifier board P700 ....Q711 and Q712

Last time I had this powered up back in October....only the left channel main amp was working
by feeding my ipod output into the MAIN AMP on the rear panel. The entire front end appeared
dead at that time. Nothing was seen on the scope at all.

Well today after reassembling everything.....testing with a dim bulb tester.....no shorts.
Plugged it in and hit the power switch.....both channels work AND the front end is working.
AM and FM work great and the scope even works ! Its not clear what I did that caused the
front end to start working.....guess its just my lucky day.

Initially I was concerned that replacing one channel outputs with the On-Semi devices would
cause a sound mismatch between the two channels. Doesn't appear to be an issue at all,
at least my ears can't tell any difference.

Eventually I plan to recap the remaining boards including the tuner, and remove the preamp
boards to recap and clean the controls. But for now I may just sit back and listen for awhile.....
 
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One issue I've noticed is the PEAK indicators are always on....even when the volume is turned down.
I think these are controlled by the PX01 board. Seeing as how both are on, it must be something common
to both channels causing this.
 
Beautiful receiver and great work. Unless you have the equipment needed and the knowledge on dealing with a tuner readjustment, it would be advisable to leave the tuner be, or find one of the few people who do that any more. You should feel pretty proud knowing that you saved a true classic receiver.
 
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