ADA Preamps > MP-2

Back from the dead!

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Shibiwan:
I've had an MP-2 in my parts pile for over 15 years, and by parts pile, I meant literally "in parts". Never got around to putting it back together until a couple weeks ago when I was cleaning out my storage closet and came across the parts. It helped that I had another MP-2 main board in the pile to salvage parts off, and also did the regular maintenance mods (modded noise mod, also put in a battery holder)

Thanks to the resources and people (especially MarshallJMP) in this forum that have kept this info alive for so long, I managed to put it all together and have finally gotten it working very nicely.

Here's some pics of the rebuild:



Battery holder mod (CR2032)


Almost there...


IT'S ALIVE!!!

rnolan:
Very cool, nice to see it come together.  Did you get to replace R913 yet and, if so, did it get rid of the hum.

Shibiwan:
R913 was the issue. The one I pulled out was dead - literally an open circuit. This allowed the HV line to float without feedback/regulation and thus rose to 245VDC, also causing the hum.

Posted the noise mod updates here:
https://adadepot.com/index.php?topic=1014.msg30024#msg30024

rnolan:
 :whoohoo!: :thumb-up:

Shibiwan:

--- Quote from: rnolan on January 28, 2022, 06:34:37 PM --- :whoohoo!: :thumb-up:

--- End quote ---

Hmmm. Perhaps I spoke too soon.

I was giving it a more thorough test after installing the missing XLR jacks (bought some new Neutrik ones) today. Noticing that there's still a some low 50hz hum in voicings 8/9/10 when I turn off the noise gate or set it to fader...same hum even if nothing's connected. It's silent with the noise gate on and isn't noticable at all when playing.

Is this normal due to the high gain of these voicings?

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