DiY AMI U47

[iturnknobs]

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?

 

[Tim Campbell]

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

Yes. Dirt at the edge or center terminal, a pinhole in a membrane or even a dirty pcb at the capsule's connections.

 

[iturnknobs]

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.

 

[vinylwall]

Just in case anyone is interested, I have one of AMI's U47A's for sale on eBay.  It was the last one Oliver shipped himself before he passed away.  https://groupdiy.com/index.php?topic=52965.msg895062#msg895062

 

[Bdkauff1101]

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!

 

[doqmemory]

built the kit more recently

I built a P2P U47 using the schematic at AMI and it works great, but I am using a Matador PSU board.

 

[Bdkauff1101]

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?

 

[jazzcrisis]

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?

I built the AMI U47 with local pattern switching recently and it turned out perfectly. No issues to speak of. Sounds great. Just be meticulous and take your time--you'll be fine!

 

[doqmemory]

Specifically some of the issues AusTex64 pointed on back on page 3?

I don't know what the schematic was back when page 3 was made, but the 2019 schematic on the AMI website is correct. The other cautions about keeping the high impedance nodes clean is true for any such microphone.

 

[Bdkauff1101]

I don't know what the schematic was back when page 3 was made, but the 2019 schematic on the AMI website is correct. The other cautions about keeping the high impedance nodes clean is true for any such microphone.

Great, thanks! Yeah I figured if there were issues they've long been sorted. Any chance you made any layout drawing for yourself for placing components/wiring? I'm waiting for the kit to arrive and can't find any hi-res images of the AMI boards. Trying to get a jump on things!

 

[doqmemory]

Sorry, I made my own layout on a prototyping board, not the kit from AMI. There's not many components, if you're not building the power supply, so it should be pretty straightforward.