UCD400 and speaker fried - why?? - diyAudio
Go Back   Home > Forums > Amplifiers > Class D

Class D Switching Power Amplifiers and Power D/A conversion

Please consider donating to help us continue to serve you.

Ads on/off / Custom Title / More PMs / More album space / Advanced printing & mass image saving
Reply
 
Thread Tools Search this Thread
Old 31st October 2006, 08:27 AM   #1
diyAudio Member
 
Join Date: Jan 2006
Location: Land Canaan
Unhappy UCD400 and speaker fried - why??

I recently bought two UCD400 modules. Have the parts for a dual mono setup, but I hooked the two modules up to one supply for testing yesterday.

The modules are the "standard" version, NO MODS, so the inputs are AC coupled. (single ended)

I ran the modules WITHOUT heatsinks for about 10min, at relatively low listening levels. After this time, (I was in the kitchen) I heard a very loud **POP** - I ran to the living room, heard the right speaker still playing and saw the left diaphagm looking to pop out of the chassis.

I ran for the power cord, but didnt make it in time, the speaker fried first

I disconnected the blown speaker and repowered the amps. The amp LEDs still work, and the "right" amp/speaker combo sounds fine.

The right amp's heatsink gets warm, the left heatsink stays cold. However, I know that the modules get warm without Load, so I was a bit suspicious at this point.

Later I hooked up the working speaker (have no instrumentation at home) to the left amp.
The speaker outputs were apparently at PSU voltage, because the resulting pop and spark was quite energetic.

The drive transistor(s) are in fact shorted out. (Am at work now, have access to all necessary equipment) The amp must have gotten very hot, because the ESD pad i left the amp on had a melted imprint of the 5mOhm shunt resistor... this could also be from current AFTER the FET shorted though.

I suspect the amps got too hot, after running them without cooling surface.

Anyone with tips or experience? Is it reasonable to just replace the transitors or should I expect other problems? The MOS-drive transistor measures fine...

Thanks,

Mike

PSU:
Trafo: 40Vsec, 500VA
Caps: 2x Epcos Sikorel 10mF, bypassed w 100nF film
Dual rectifiers
Unloaded Voltage = 55.4V

Load:
8ohm CSS FR125 10cm Fullrange, 7L sealed.
  Reply With Quote
Old 31st October 2006, 09:20 AM   #2
diyAudio Member
 
Join Date: Jan 2006
Location: Land Canaan
also, what are opinions on replacing the FDP42AN15A0 with an different part, possibly with lower RDSon?

How tolerant is the UCD drive circuit on drive transitor parameters such as gate charge?

Would the developers care to drop a line?

thanks,
mike
  Reply With Quote
Old 31st October 2006, 12:01 PM   #3
ghemink is offline ghemink  Netherlands
diyAudio Member
 
Join Date: Jun 2004
Location: Japan
Quote:
Originally posted by madstamm
also, what are opinions on replacing the FDP42AN15A0 with an different part, possibly with lower RDSon?

How tolerant is the UCD drive circuit on drive transitor parameters such as gate charge?

Would the developers care to drop a line?

thanks,
mike

You could contact Hypex directly, in my experience they are very responsive. It is indeed a no-go to use the modules without any heatsinking. They do not need much but they do need some.

Best regards

Gertjan
  Reply With Quote
Old 31st October 2006, 12:11 PM   #4
mitch90 is offline mitch90  Canada
diyAudio Member
 
Join Date: Sep 2005
Hello madstamm.

Sorry to hear about your speaker.
As far as I know UCD gate drivers are
matched with MOSFET they drive.
Best approach would be to use same device
'FDP42AN15A0' as replacement.

Regards,


MITCH.
  Reply With Quote
Old 31st October 2006, 12:49 PM   #5
lucpes is offline lucpes  Europe
diyAudio Member
 
Join Date: Dec 2003
Location: Iasi
Send a message via Yahoo to lucpes
Default Re: UCD400 and speaker fried - why??

Quote:
Originally posted by madstamm

I ran the modules WITHOUT heatsinks for about 10min, at relatively low listening levels. After this time, (I was in the kitchen) I heard a very loud **POP** - I ran to the living room, heard the right speaker still playing and saw the left diaphagm looking to pop out of the chassis.
I know, the speakers you used do not draw much power, but I have noticed that hypex says DO NOT run the modules without a heatsink...
__________________
Deep down inside.
  Reply With Quote
Old 31st October 2006, 01:01 PM   #6
diyAudio Member
 
Join Date: Jan 2006
Location: Land Canaan
I realize of course that I was not "supposed" to run the modules w/o heatsinking -

it is not a question if I have done the right thing or not, I certainly havent

I am curious if running w/o a heatsink will *typically* cause the output transistors to "melt" or not, and if I should be concerned that other parts have been destroyed as well.

again, i would think that hypex has some experience in thermally destoying their modules, (i did write them an eMail a few min ago), but has anyone else cratered their amps?
  Reply With Quote
Old 31st October 2006, 02:09 PM   #7
BWRX is offline BWRX  United States
diyAudio Moderator Emeritus
 
Join Date: Jan 2005
Location: Pennsylvania
They shouldn't blow up if you're running them at lower power levels without a heat sink.

Something else probably happened, especially since your other amp still works fine.

I fried one of my 180 modules due to what I believe was a short from output to ground right at the fast on terminals. I checked some parts and fried more than just the output fets.
__________________
Brian
  Reply With Quote
Old 31st October 2006, 02:18 PM   #8
Pierre is offline Pierre  France
Banned
 
Join Date: Nov 2004
Location: Paris
Aren't UcD modules protected against output shortcircuit?
  Reply With Quote
Old 31st October 2006, 02:21 PM   #9
diyAudio Member
 
Join Date: Jan 2006
Location: Land Canaan
hm, that sound unreasonable in my case - there's no chance that a short could have occurred..

I *did* have the modules sitting on the ESD pads that they shipped with. A flukemeter measures them at 10+MOhm though with the meter pins 5mm apart... couldnt imagine..

other ideas?
  Reply With Quote
Old 31st October 2006, 04:18 PM   #10
gl is offline gl  United States
diyAudio Member
 
Join Date: Dec 2003
Location: Sierra Foothills - California
Hi madstamm,

I would suspect one of two things: 1) a wiring error (I know you'll swear it isn't so, but that's what usually happens to me), or 2) it's a grounding problem. It's easy to get ground loops with two channels being run off one supply.

I've seen both of these cause huge problems when first turning on new amps of all types. I have to admit though, I haven't heard many stories about new amps frying speakers.

Good luck with this.

Graeme
  Reply With Quote

Reply


Hide this!Advertise here!
Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Similar Threads
Thread Thread Starter Forum Replies Last Post
Fried X-over Zen Mod Multi-Way 24 24th November 2006 12:12 AM
I think I fried an amp mashaffer Car Audio 1 20th July 2004 12:54 AM
$5 SE amp... but is it fried?! SHiFTY Tubes / Valves 3 18th January 2004 03:13 PM


New To Site? Need Help?

All times are GMT. The time now is 07:06 PM.


vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2014 DragonByte Technologies Ltd.
Copyright 1999-2014 diyAudio

Content Relevant URLs by vBSEO 3.3.2