Differential pair should be 2N5961
Wound up doing TO-220 drivers and they have new mica pads under them
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Absolutely butchered 250M
- Thread starter goldswimmerb
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- marantz 250m
Differential pair should be 2N5961
Wound up doing TO-220 drivers and they have new mica pads under them
I think I may have just been stupid, will see in a bit. Had my bias Transistor backwards from the looks of it.
You can probably print the meter dial face on transparent inkjet paper and stick it over
a white plastic piece -
https://www.amazon.com/Printable-Transparent-Sticker-Paper-Printers/dp/B01LDJJLE2
You could probably make the meter backing out of a plastic lid -
https://www.homedepot.com/p/HDX-Versa-Tainer-1-qt-Plastic-Lid-RG515H/202802887
a white plastic piece -
https://www.amazon.com/Printable-Transparent-Sticker-Paper-Printers/dp/B01LDJJLE2
You could probably make the meter backing out of a plastic lid -
https://www.homedepot.com/p/HDX-Versa-Tainer-1-qt-Plastic-Lid-RG515H/202802887
Just an update:
Meter backing arrived today, thanks so much @NikonSP the 250M and 501M both use the exact same back plate.
The reproduction is pretty much indistinguishable from the OEM part, aside from the black being a bit less "bold". They look stellar though.
Mine actually weren't too bad from what @wlhd1610 has shown me, but you can see they are quite yellowed. May try taking some retrobrite to them just so I can see if there's a solution. Looks like the plastic they used just yellowed with age, similar to what happened with the Nintendo SNES.
Installation was super easy, though I did have to careful bend one needle upwards a bit to keep it from lightly scraping the backing.
Only thing I wish we had were omnidirectional LED lamps, as all of the current made fuse style lamps for cause a bit if "hot-spotting" on the 250Ms
So here's the before picture:
Nice and green...
After:
Both images used warm white LEDs. As you can see, quite an improvement.
And just for anyone in the future, I did find that when YELLOWED, cool white LEDs will work nicely IF both meters are equally yellowed. I found this on accident while testing bulbs, if you don't mind the red seeming a bit more black the cool whites tend to cancel out the yellowing and give a proper blue color as well.
BUT even with what I mentioned above, there is absolutely no replacement for doing it right and I am much much happier knowing that these new backings not only fit multiple models, but look fantastic.
Really not sure what I was so scared of going into the rebuild, Transistor matching is easy and once that is done it's just a simple matter of checking resistors and any other potentially burnt components. A very straightforward repair and I honestly look forward to the next 240/250/250M that comes across my bench.
And just an observation, the predrivers seem to be more critical to match than the drivers, my MJE15033 Is a bit high (like 30-40) on HFE but the unit is rock solid stable, even at maximum load.
Meter backing arrived today, thanks so much @NikonSP the 250M and 501M both use the exact same back plate.
The reproduction is pretty much indistinguishable from the OEM part, aside from the black being a bit less "bold". They look stellar though.
Mine actually weren't too bad from what @wlhd1610 has shown me, but you can see they are quite yellowed. May try taking some retrobrite to them just so I can see if there's a solution. Looks like the plastic they used just yellowed with age, similar to what happened with the Nintendo SNES.
Installation was super easy, though I did have to careful bend one needle upwards a bit to keep it from lightly scraping the backing.
Only thing I wish we had were omnidirectional LED lamps, as all of the current made fuse style lamps for cause a bit if "hot-spotting" on the 250Ms
So here's the before picture:
Nice and green...
After:
Both images used warm white LEDs. As you can see, quite an improvement.
And just for anyone in the future, I did find that when YELLOWED, cool white LEDs will work nicely IF both meters are equally yellowed. I found this on accident while testing bulbs, if you don't mind the red seeming a bit more black the cool whites tend to cancel out the yellowing and give a proper blue color as well.
BUT even with what I mentioned above, there is absolutely no replacement for doing it right and I am much much happier knowing that these new backings not only fit multiple models, but look fantastic.
Really not sure what I was so scared of going into the rebuild, Transistor matching is easy and once that is done it's just a simple matter of checking resistors and any other potentially burnt components. A very straightforward repair and I honestly look forward to the next 240/250/250M that comes across my bench.
And just an observation, the predrivers seem to be more critical to match than the drivers, my MJE15033 Is a bit high (like 30-40) on HFE but the unit is rock solid stable, even at maximum load.
Dear All,
I am working on a 250M, both dial plates were yellowish and dim/uneven meter looks,
would some one can share the meter artwork file? CAD data? have chance to remake/or reprint then lamination.?
Dial plate is not the headache, I am not sure where should I post it? in this thread or other thread?
1 year ago, I did fix the 250M from fuse blown issue,
by replacement all Power transistor to MJ21193/94 pair, but with silicone pad, not mica, i am wondering it is a good idea or bad?
I kept the pre-driver/driver to original, seems they measured OK, but I swapped their position based on measured hfe,
recapped electrolytic capacitors, differential pair, Darlington transistor,
it works after the repair!
I can run to max power at both channel with out any issue.
distortion is also within the spec.
but after I did one miss-take, now 250M runs very strange.
after the service , I am thinking about how to make meter dial plate getting better, I got few LED bulb, but still looks badly,
so the top cover is never returned, soomeday, someone clean my room , and stack some heavy item on the amp,
guessed what, R517 and C517 was pushed down so hard, I power on the amp and no noticed some damaged inside,
even powered on, the relay never click-in, after I separate the Left and right channel, I can confirm the Left channel was damaged.
after fix the trace and re-solder the parts, confirm no more broken point.
now the Left channel can make relay energized, however when the output is over ~3.0 AC, the relay will de-energy for few second, then re-energized again,
I try to re-measure Q510/Q511 Q507/Q508, they are OK. they are still stock parts, should I replace them with modern parts like MJE15030/15031 pair?
or where should I start to shoot the issue?
so far I only checked rail voltage, they are good for positive and negative.
the other check point voltage indicated on manual (parts view with some voltage) , should I do it?
where to begin with, if some one can show me a light?
thank you very much!
Chen-shen
I am working on a 250M, both dial plates were yellowish and dim/uneven meter looks,
would some one can share the meter artwork file? CAD data? have chance to remake/or reprint then lamination.?
Dial plate is not the headache, I am not sure where should I post it? in this thread or other thread?
1 year ago, I did fix the 250M from fuse blown issue,
by replacement all Power transistor to MJ21193/94 pair, but with silicone pad, not mica, i am wondering it is a good idea or bad?
I kept the pre-driver/driver to original, seems they measured OK, but I swapped their position based on measured hfe,
recapped electrolytic capacitors, differential pair, Darlington transistor,
it works after the repair!
I can run to max power at both channel with out any issue.
distortion is also within the spec.
but after I did one miss-take, now 250M runs very strange.
after the service , I am thinking about how to make meter dial plate getting better, I got few LED bulb, but still looks badly,
so the top cover is never returned, soomeday, someone clean my room , and stack some heavy item on the amp,
guessed what, R517 and C517 was pushed down so hard, I power on the amp and no noticed some damaged inside,
even powered on, the relay never click-in, after I separate the Left and right channel, I can confirm the Left channel was damaged.
after fix the trace and re-solder the parts, confirm no more broken point.
now the Left channel can make relay energized, however when the output is over ~3.0 AC, the relay will de-energy for few second, then re-energized again,
I try to re-measure Q510/Q511 Q507/Q508, they are OK. they are still stock parts, should I replace them with modern parts like MJE15030/15031 pair?
or where should I start to shoot the issue?
so far I only checked rail voltage, they are good for positive and negative.
the other check point voltage indicated on manual (parts view with some voltage) , should I do it?
where to begin with, if some one can show me a light?
thank you very much!
Chen-shen
eGeezer
New Member
Sadly it's the actual white plastic dial face that is yellowed from incandescent lamp heat.
It's the same effect that you see with the old yellowed vellum in Marantz receivers.
I asked an AK member who makes absolutely spot on replacement lamp housings and he can make the plastic piece but not the silk screen dial scale printing with the two colors.
Maybe someone else can give it a go.
Bob
eGeezer
New Member
Hey Bob, I actually have made my own replacement meter faces as pictured.i scanned the old discolored plastic, used photoshop to make the image white instead of smoke/ burnt and then used a color laser printing onto transparency film or water-slide decal paper(cannot remember).Then I went with warm white surface mount LED backlighting. Looks factory and works very well.they're shown in my profile pic. I hope this helps!
I ordered a pair from @NikonSP and anxiously waiting to receive and install them!
My 250M meters are very green from the plastic heating up. Will think about installing some lower heat warm white LED's when I refit the plastics.
Warm white looks nice with the new meter backings. Cool white should correct most of the issues with how green they are though, or it did in my experience.