mikey99
Active Member
I started talking about this 2500 in another thread, and decided since this isn't
a quick fix ......to start a separate thread. Also to keep a log of what all has been
done , hopefully might help someone else in the future. Sorry for the long post
but I need to catch up from the other thread.
I recently inherited a Marantz 2500 from my father.
I remember when he got this used from a friend many years ago, probably around 1990.
The receiver did work at that time, and my father listened to it occasionally.
At some point the receiver started blowing the main fuse and my father set this
aside. He did buy a service manual and spent a few hours looking at it but
never really got too enthusiastic about fixing it.
Fast forward to a few months ago.
I brought the 2500 home and started looking at it.
The P800 PS board was removed so I don't know if there was some indication of a problem there.
So far I have done the following:
Transformer checkout: Checked resistance on all transformer windings...primary and secondaries
....all appear good. With the P800 board disconnected , attached it to a dim bulb tester, and
measured the secondary voltages, all appear good, slightly low due to the DBT.
1) Put the P800 board back in , still attached to a dim bulb tester, powered on
and the fan came on and stayed at high speed.
2) Found that the soft start resistor had opened.....not sure if that happened
when I powered on or it was already open.
3) Started checking for shorts, found that the rail voltage terminals on the right (outside)
amp board were shorted.
4) Disconnected both channels amp board rail voltage, replaced the soft start resistor
with a 12 ohm 10 watt.
5) Powered on, fan came on high speed, then switched to low speed. Basic panel functions
like lights, source select, and source indicators work okay. Nothing on the scope.
Recapped the P800 board (hate that glue) and reinstalled it.
6) Reconnected the left channel (inside) amp board rail voltage.
7) Powered on hoping to get sound from the left speaker but no luck. This time I heard another
click which I think came from the speaker protection relay.
8) Attached an antenna and also noticed the Stereo light does not come on while tuning.
9) Attached my ipod to the Aux input, still no sound output.
10) Attached the ipod to the left channel 'Main In' on the rear panel and I do get sound.
However, bypassing the preamp ..... so cannot really tell much from this.
11) Decided to fix the short in the right channel amp board.
12) Removed the amp tunnel assembly....removed the right channel amp board.
13) There appear to be three shorted output transistors QM11 (D555) and QM09/QM08 (B600)
Looks like Emitter to Base AND Collector all shorted.
At this point I can replace these three transistors, and recap the P700 boards.
Are there other components that should also be replaced in the amp section?
Don't want to replace these three and have them blow again. Does anyone recommend
to replace ALL the transistors ? Wondering if its common to have multiple shorted transistors like this.
Obviously something catastrophic happened here to blow three transistors.
Have not tried cleaning switches or pots, hopefully that will solve some of the other minor issues.
a quick fix ......to start a separate thread. Also to keep a log of what all has been
done , hopefully might help someone else in the future. Sorry for the long post
but I need to catch up from the other thread.
I recently inherited a Marantz 2500 from my father.
I remember when he got this used from a friend many years ago, probably around 1990.
The receiver did work at that time, and my father listened to it occasionally.
At some point the receiver started blowing the main fuse and my father set this
aside. He did buy a service manual and spent a few hours looking at it but
never really got too enthusiastic about fixing it.
Fast forward to a few months ago.
I brought the 2500 home and started looking at it.
The P800 PS board was removed so I don't know if there was some indication of a problem there.
So far I have done the following:
Transformer checkout: Checked resistance on all transformer windings...primary and secondaries
....all appear good. With the P800 board disconnected , attached it to a dim bulb tester, and
measured the secondary voltages, all appear good, slightly low due to the DBT.
1) Put the P800 board back in , still attached to a dim bulb tester, powered on
and the fan came on and stayed at high speed.
2) Found that the soft start resistor had opened.....not sure if that happened
when I powered on or it was already open.
3) Started checking for shorts, found that the rail voltage terminals on the right (outside)
amp board were shorted.
4) Disconnected both channels amp board rail voltage, replaced the soft start resistor
with a 12 ohm 10 watt.
5) Powered on, fan came on high speed, then switched to low speed. Basic panel functions
like lights, source select, and source indicators work okay. Nothing on the scope.
Recapped the P800 board (hate that glue) and reinstalled it.
6) Reconnected the left channel (inside) amp board rail voltage.
7) Powered on hoping to get sound from the left speaker but no luck. This time I heard another
click which I think came from the speaker protection relay.
8) Attached an antenna and also noticed the Stereo light does not come on while tuning.
9) Attached my ipod to the Aux input, still no sound output.
10) Attached the ipod to the left channel 'Main In' on the rear panel and I do get sound.
However, bypassing the preamp ..... so cannot really tell much from this.
11) Decided to fix the short in the right channel amp board.
12) Removed the amp tunnel assembly....removed the right channel amp board.
13) There appear to be three shorted output transistors QM11 (D555) and QM09/QM08 (B600)
Looks like Emitter to Base AND Collector all shorted.
At this point I can replace these three transistors, and recap the P700 boards.
Are there other components that should also be replaced in the amp section?
Don't want to replace these three and have them blow again. Does anyone recommend
to replace ALL the transistors ? Wondering if its common to have multiple shorted transistors like this.
Obviously something catastrophic happened here to blow three transistors.
Have not tried cleaning switches or pots, hopefully that will solve some of the other minor issues.
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