Amp15 will not unmute

[extremewillis]

Hi guys. I'm in need of some help. I finished building my Amp15 today. I powered it up without the chip or the large caps, and everything looked OK. Rail voltages were in the right place and the 5V was OK. So, I put in the chip and the large caps and powered up again. I put the jumpers on JP2 and JP6. The red LED was on. As I put the jumper on JP1, the amp did not unmute.

I turned it off, let the caps discharge. I noticed D3 was a bit hot - too hot to touch for more than a second. Is this normal?

Next, I checked the solder joints on the chip and powered up again. This time as I was measuring I measured the rail voltage on Ch1 output!

Any help would be appreciated. What should I try next?

[extremewillis]

Here are links to 3 pics:

http://www.flickr.com/photos/37185294@N08/3416991776/

http://www.flickr.com/photos/37185294@N08/3416183621/

http://www.flickr.com/photos/37185294@N08/3416184105/

[mikechw]

Double check your D1,D2,D6 and D7 diode...

Wrong diodes were in the first batch...
I measured rail voltage across the output when I had them installed.

If the diodes were right, it means you have a short circuit through one of the mosfet or somewhere along the path.

[extremewillis]

Thanks mikechw - first let me correct - I meant Q3 was hot - not D3.

So I checked D1, D2, D6, D7 and found something suspicious!!

Which Diodes should be in which position? I noticed I have two that are "809 U1D" and two that say "816 1BL3"

The BOM has them both listed for both locations.

Thanks

[V-bro]

Very well possible that there's nothing else fried but the diodes themselves. I would contact 41hz support and get four 200V diodes (or at least two) and try again...

------X-max. can be several meters on any driver, too bad it can be done only once...------

[extremewillis]

Thanks guys. Jan is sending me the correct diodes. I'll install them and see what happens. Hopefully I won't have to get that chip out!

[V-bro]

Knowing Jan, he might send you the chip anyway

------X-max. can be several meters on any driver, too bad it can be done only once...------

[extremewillis]

Haha!!!!! It works!!! I replaced the diodes with the ultrafast and music is playing!!! Thanks. Now, to mount it in a nice case...

[V-bro]

Great news!

Thought so all the way along....

------X-max. can be several meters on any driver, too bad it can be done only once...------