DiY AMI U47

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iturnknobs

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Tim Campbell said:
It could be a slight short in or at the capsule.  You could sustitute a small value capacitor (60pf-100pf) capacitor for the capsule or switch capsules and see if the problem persists.

Do you mean shorted from the rear diaphragm to the backplate?
 

iturnknobs

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Aug 2, 2014
Messages
638
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Crystal Lake, IL
Tim Campbell said:
Yes. Dirt at the edge or center terminal, a pinhole in a membrane or even a dirty pcb at the capsule's connections.

I reseated the capsule in the holder, gently dusted the membranes with canned air and cleaned everything I could around the capsule holder and acrylic deck. Not sure what single issue it was, but one of these three actions solved my problem. Thank you for  pointing me in the right direction.
 

Bdkauff1101

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Nov 24, 2021
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Chicago
Hello! Bringing this thread back to life with my first post!

I'm interested in building my own U47 and was attracted to the AMI/Tab kit. After reading up about it on this thread/forum, it seemed like the AMI schematic wasn't quite right and needed tweaks to getting it working. However, the schematic on AMI is now dated 2019, after all the discussion here.

I'm wondering if anyone has built the kit more recently and whether those tweaks to PSU/etc are still necessary? I've reached out to AMI with the same question already.

Thanks in advance!
 

Bdkauff1101

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Nov 24, 2021
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Location
Chicago
I built a P2P U47 using the schematic at AMI and it works great, but I am using a Matador PSU board.
Cool! This will be ambitious for me, so I'll go with the prebuilt PSU.

Anyone else have recent experiences to share? Specifically some of the issues AusTex64 pointed on back on page 3?
 
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