Model 500 Restore.....
- Thread starter jstang
- Start date
jstang
Honey,I can't hear you...
What I have left is not the best matched set of 10/10. They would work fine and would be closer than a random new set.
But are interested in a closer matched set? I can order some more and than test/match them for you. I would match npn/pnp left/right... I label every xtor and would give a spread sheet of the values.
For an amp like the 500 with so many outputs it's well worth the effort.
What about 2n5415 and 2n3440 ? Do you want them match too? I have them too. Matching all 3 of the diffy pairs and pre-drivers in each channel makes DC balance very easy and very stable over time. Mine holds between 0 and 2mvs... That might be more the Dmm drifting.
This amps had a bad reputable for being unstable....but that is far from true if they are set up right with good xtors.
JohnK
But are interested in a closer matched set? I can order some more and than test/match them for you. I would match npn/pnp left/right... I label every xtor and would give a spread sheet of the values.
For an amp like the 500 with so many outputs it's well worth the effort.
What about 2n5415 and 2n3440 ? Do you want them match too? I have them too. Matching all 3 of the diffy pairs and pre-drivers in each channel makes DC balance very easy and very stable over time. Mine holds between 0 and 2mvs... That might be more the Dmm drifting.
This amps had a bad reputable for being unstable....but that is far from true if they are set up right with good xtors.
JohnK
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Imike16
Active Member
I am in contant with a man who has belong curve tracer in Hungary
http://www.hobbielektronika.hu/forum/topic_4545.html?pg=8
http://www.hobbielektronika.hu/forum/topic_4545.html?pg=8
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jstang
Honey,I can't hear you...
Lot numbers are what Onsemi provides on them and yes you are likely to receive the same lot numbers from Mouser.
However, the beta match within a lot number still varies. You can and should do better.
Jk
However, the beta match within a lot number still varies. You can and should do better.
Jk
jstang
Honey,I can't hear you...
Here is the diode trace of the MZ2361. It show a two junction voltage drop, ~ 1.4v. No surprise. The horizontal is the forward voltage.
I do not have the trace for the Sz51066K. The key with that one is the temperature co-efficient. If get a chance to test that one, I will.
I suspect it is typical, however the 500 uses the hot carrier diode FH1100 which has a reverse temp co-efficient....
Be cautious in your crossing and avoid hear say.....
I do not have the trace for the Sz51066K. The key with that one is the temperature co-efficient. If get a chance to test that one, I will.
I suspect it is typical, however the 500 uses the hot carrier diode FH1100 which has a reverse temp co-efficient....
Be cautious in your crossing and avoid hear say.....
jstang
Honey,I can't hear you...
I think you will be very close.... The actual implementation of how you mount the diodes is very important to the thermal sensitivity.
With that said you should be ok and you should test/adjust carefully.
My main 500 came to me with one channel's temp comp diodes nonfunctional due to a broken connection. The previous owner was blowing outputs xtors over and over, he ruined that channel's meter because of the issue.
So test/adjust carefully and use the exact correct Fuses Marantz specified for the rail fuses. Do not substitute the fuses, no substitutes!!!!!.....
Set up right, they are bullet proof....and mind blowing. :yes: These amps are the Boss 429s Mustangs of the audio world....
With that said you should be ok and you should test/adjust carefully.
My main 500 came to me with one channel's temp comp diodes nonfunctional due to a broken connection. The previous owner was blowing outputs xtors over and over, he ruined that channel's meter because of the issue.
So test/adjust carefully and use the exact correct Fuses Marantz specified for the rail fuses. Do not substitute the fuses, no substitutes!!!!!.....
Set up right, they are bullet proof....and mind blowing. :yes: These amps are the Boss 429s Mustangs of the audio world....
jstang
Honey,I can't hear you...
Ok... Yesterday I swapped out my MZ 2361s with the 2x1n4148 on one amp board and then spent an hour trouble shooting a blown rail fuse.
I was not in the mood to trouble shoot to see what caused the blown fuse with the 2x1n4148s in the circuit. Not realizing the fuse blew, I spent a hour lifting leads to try to understand why the 18v was not working. Then after track it down to the blown rail fuse, I normalized everything and put the MZs back in. Everything was fine. I was more interested in testing some different feedback cap combos. I swapped every other semi using my curve tracer characterization, first issue I have had with this amp's semi conductors and never blew a rail fuse with this process before. Need to look more closely at what is going on here.
May be the 2x1n4148 is a good replacement for 500's MZ2361s.... Maybe not.... Maybe I did some thing wrong installing the 2x1n4148s... Maybe not....
I usually double & triple check things and inspect closely my soldering, there were no issues... The fuse blew a little after power up and while I was checking voltages. I did not short anything with probing....
So I am thinking its back to drawing board on using 2x 1n4148s on the 500's amp boards.
Mike are you still blowing rail fuses?
I was not in the mood to trouble shoot to see what caused the blown fuse with the 2x1n4148s in the circuit. Not realizing the fuse blew, I spent a hour lifting leads to try to understand why the 18v was not working. Then after track it down to the blown rail fuse, I normalized everything and put the MZs back in. Everything was fine. I was more interested in testing some different feedback cap combos. I swapped every other semi using my curve tracer characterization, first issue I have had with this amp's semi conductors and never blew a rail fuse with this process before. Need to look more closely at what is going on here.
May be the 2x1n4148 is a good replacement for 500's MZ2361s.... Maybe not.... Maybe I did some thing wrong installing the 2x1n4148s... Maybe not....
I usually double & triple check things and inspect closely my soldering, there were no issues... The fuse blew a little after power up and while I was checking voltages. I did not short anything with probing....
So I am thinking its back to drawing board on using 2x 1n4148s on the 500's amp boards.
Mike are you still blowing rail fuses?
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