broken UCD400AD :(

[cowanrg]

well, i have a broken UCD400AD. im curious if it can be fixed or if i just need a new module.

basically, as long as the amp has power, it puts out 57vdc at the binding posts. thats not good. this happens when the amp is on or off, as long as it has power going to it. thats also the same voltage as the rails.

now, i have 4 of these modules, 2 2-channel amps. all the other modules are just fine and play music just fine with TINY dc offets. ive hooked this one up in place of the others, and it still does the same thing, and the others worked when hooked up in the defective one's place. so, its bad for sure.

so, whats wrong? why is it giving me rail voltage at the binding posts? can i get it fixed, do i just need a new one?

[BWRX]

Sure sounds like the high side output FET failed and is shorting the positive rail to the output. Best case scenario is that only the FET is fried. It's more likely that there are more components that went with it though.

Have you probed around the module (disconnected of course) with a multimeter to see if anything else is shorted out?

Any idea what caused the module to fail?

[cowanrg]

thanks.

there are no visible problems on the board, it looks just fine. nothing blew (at least spectacularly...). i have NO idea what happened. one day i just tested it and it didnt work.

i havent touched it yet, i didnt have a clue what to look for, other than visible problems. ill check the fets and see whats going on.

[BWRX]

Hmm... if nothing blew spectacularly then something else might be wrong with the module. Definitely see if there is anything wrong with the FETs first.

Was the module hooked up to a speaker when it had full rail voltage on the output? Was the speaker damaged?

[cowanrg]

Originally posted by BWRX
Hmm... if nothing blew spectacularly then something else might be wrong with the module. Definitely see if there is anything wrong with the FETs first.

Was the module hooked up to a speaker when it had full rail voltage on the output? Was the speaker damaged?

nope, no speaker damage. very very strange. one day, i kicked on the amp (when they were just in the prototype phase), and it made a loud buzzing, i kicked off the amp before anything happened. i thought nothing of it and went back to working on the amps. now that they are being completed, i hooked everything back up again and its bad.

i havent hooked up a speaker to it to see how it reacts to a load, but i really dont want to know

the amps were on my main system (with ribbon speakers!) and i used them daily for about a month or so. one day, i just went to listen to some music (as i did several times a day), and it just started buzzing when i turned it on. nothing seemingly changed. i also use power conditioners and surge protectors on all my stuff.

[Tekko]

Theres your problem, no wonder it failed if you kicked it

[icewall]

How strange!

I have two UcD 400 that shows the exact same behavior as yours. I get the same voltage on speaker outputs as i have on my rails. Similar to you I heard a noice fom the amplifier and shut it down.

I have used my UcD400 for two years, since january they have been driving the woofers in my Orion system.

On my boards I can see something pointing towards heat problems, but I'm not sure.





My question is the same as yours, buy new ones or is it something that can be fixed. Have tryed to mail Hypex for help.

[cowanrg]

well, ive been working on getting these done for years now, and im a bit anxious to be totally done with it. ill email hypex today and see what they will do. it broke while it was just sitting there. it was mounted to a heatsink, and in open air (it was just a prototype setup). so, i cant see how mine overheated. it COULD have been a power surge, but use dual furman power conditioners.

ill see what hypex says and post it here, ill even point jan-peter to this thread.

[cowanrg]

icewall,

what version is yours? mine is V5.

[icewall]

Mine are 2.0
Bottom of board says 06-12-2004

I've had them for alsmost two years. If it was a heat problem I'd like to know so I can correct the heatsinks. In the next version of amplifier I don't want this to happen again I have also mailed Hypex about this but no answer yet.