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-   -   Memphis 1000 Class D with blown capacitor....need some guidance (http://www.diyaudio.com/forums/car-audio/185676-memphis-1000-class-d-blown-capacitor-need-some-guidance.html)

mojo3120 24th March 2011 04:14 AM

Memphis 1000 Class D with blown capacitor....need some guidance
 
I picked up a blown Memphis 16-ST1000D for cheap off Craigslist and looking for some "guidance" on repairing it.

I took lots of pics while disassembling
Memphis Amp Rebuild - a set on Flickr
(to see high res, click the image, click "All sizes" on top right, and click "Original")

Here's what I know.....
Guy said it was working fine, then something inside blew up (like a shotgun) and there was "oil all on the inside" which he cleaned up. So obviously a blown capacitor which I immediately spotted on the audio side when I opened it up.

Used a desoldering gun and solder wick to remove both the capacitors.
http://farm6.static.flickr.com/5265/...5558bba3_z.jpg
http://farm6.static.flickr.com/5022/...8e90c95e_z.jpg
http://farm6.static.flickr.com/5303/...84133a2c_z.jpg

Obviously these will need to be replaced. Should I try to find the original part # (all caps are Samwha), or will any 4700uf capacitor with >= original volt & temp ratings work? (Is "Working Volt" rating = "Volt" rating?) Neither Mouser nor digikey carry the Samwha brand, any recs on a good replacement?

Should I just throw in 2 new capacitors and see what happens or is it likely another component shorted or failed causing the cap to blow? I'm going to try and figure out how to test the mosfets w/ my DMM tomorrow, anything else I should test?

Thanks in advance for any assistance :up:

Perry Babin 24th March 2011 09:47 AM

You don't need to use the original brand. Mouser or Digi-Key should have suitable replacements.

WV = voltage rating.

After installing the capacitors, clamp all transistors tightly to the heatsink and insert a 10-15 amp fuse in the B+ line and power it up. If the fuse doesn't blow, monitor the temperature of the capacitors at idle (no audio). If they don't get hot, the original caps may have failed from driving the amp too hard. If they do get hot or if the fuse blows, you'll have to do a bit more troubleshooting.

mojo3120 24th March 2011 07:14 PM

Quote:

Originally Posted by Perry Babin (Post 2514514)
You don't need to use the original brand. Mouser or Digi-Key should have suitable replacements.

WV = voltage rating.

After installing the capacitors, clamp all transistors tightly to the heatsink and insert a 10-15 amp fuse in the B+ line and power it up. If the fuse doesn't blow, monitor the temperature of the capacitors at idle (no audio). If they don't get hot, the original caps may have failed from driving the amp too hard. If they do get hot or if the fuse blows, you'll have to do a bit more troubleshooting.

ESMH800VNN472MA30T United Chemi-Con Aluminum Electrolytic Capacitors - Snap In

Ordered 2 of these. The originals were 25mm tall, but the shortest I could find was 30mm. It's going to be a tight fit, I may have to modify the back cover or make little spacers or something.

Thanks for your help

mojo3120 10th December 2011 09:11 PM

Finally got around to replacing those caps. Replaced both the large capacitors, reassembled and wired up the power. When remote terminal is jumped I can hear the relay click on, the protect light comes on and power light flickers. Being powered on for about 30 seconds the area circled below and adjacent fets began to rapidly heat up, and I pulled the plug. The fuses remained intact and this was the only area that was hot as far as I could tell (new capacitors on other side remained cool to the touch).

http://www.andrewstallings.com/temp/memphisamp-hot.jpg


Any suggestions on whats next to troubleshoot?

Thanks!
-Andrew

ivkata 10th December 2011 09:42 PM

test all power supply transistors for blown ones .if none reads 0 test all transistors that are mounted to the heatsink ,remove all bad ones and try to turn it on the same way perry says

Perry Babin 10th December 2011 10:35 PM

Did you check/replace the drivers on the power supply driver board?


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