apeculiar PA100 problem

sith · 23rd February 2006, 12:00 PM

Just finished, PA100 using Alexw schematics and layout, and Carlosfm snuberized regulated PSU.
Testing one chanel (board) everything is beautiful, rail voltage is steady +/-27V, dc-offset 15mV, testing other the same thing... Absolutely beautiful...

Now the funny part, when I connected both channels(boards) to a PSU I got massive voltage drop and negative LM388 got too hot to touch... I used a single power tranny (separate windings), a single PSU, two rectifiers (ready made, rated 7A) LM388 regulators... So, every board works perfectly, but when they are both in system sh.. hits the fan...

Alexw amp.
http://shine7.com/audio/pa100.htm

Regulated psu , nuuk's pages http://myweb.tiscali.co.uk/nuukspot/...ainclone6.html

sith · 24th February 2006, 09:06 AM

what??? No one???

C'mon ppl help me out with this one!!!!

tiltedhalo · 25th February 2006, 03:20 AM

LM3886 insulated or non-insulated, is the heat sink grounded and no insulator? PS properly connected for each channel?? Could you give more details??

Eva · 25th February 2006, 02:16 PM

I built a similar symmetrical regulated power supply around LM338K eight years ago, it was intended to power four TDA7294 ICs. I had planned to put both regulators in the same heatsink, but that caused parasitistic oscillation issues that by that time I did't know how to solve. The only working solution that I found was to put each regulator in a separate heatsink, without any electrical coupling between them, and also without any coupling to to the case or to the heatsinks of the chip-amps.

sith · 25th February 2006, 06:48 PM

Quote:

LM3886 insulated or non-insulated, is the heat sink grounded and no insulator? PS properly connected for each channel?? Could you give more details??

Insulated, separate heatsinks, sure is connected properly, only one amp board in system, works perfectly, together they make problems....

23rd February 2006, 12:00 PM	#1
sith diyAudio Member Join Date: Nov 2003 Location: Split	apeculiar PA100 problem Just finished, PA100 using Alexw schematics and layout, and Carlosfm snuberized regulated PSU. Testing one chanel (board) everything is beautiful, rail voltage is steady +/-27V, dc-offset 15mV, testing other the same thing... Absolutely beautiful... Now the funny part, when I connected both channels(boards) to a PSU I got massive voltage drop and negative LM388 got too hot to touch... I used a single power tranny (separate windings), a single PSU, two rectifiers (ready made, rated 7A) LM388 regulators... So, every board works perfectly, but when they are both in system sh.. hits the fan... Alexw amp. http://shine7.com/audio/pa100.htm Regulated psu , nuuk's pages http://myweb.tiscali.co.uk/nuukspot/...ainclone6.html __________________ There is no spoon...there is a fork!!!

24th February 2006, 09:06 AM	#2
sith diyAudio Member Join Date: Nov 2003 Location: Split	what??? No one??? C'mon ppl help me out with this one!!!! __________________ There is no spoon...there is a fork!!!

25th February 2006, 03:20 AM	#3
tiltedhalo diyAudio Member Join Date: Sep 2005 Location: Melbourne Florida	PA 100 LM3886 insulated or non-insulated, is the heat sink grounded and no insulator? PS properly connected for each channel?? Could you give more details??

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25th February 2006, 02:16 PM	#4
Eva diyAudio Member Join Date: Oct 2003 Location: Near the sea	I built a similar symmetrical regulated power supply around LM338K eight years ago, it was intended to power four TDA7294 ICs. I had planned to put both regulators in the same heatsink, but that caused parasitistic oscillation issues that by that time I did't know how to solve. The only working solution that I found was to put each regulator in a separate heatsink, without any electrical coupling between them, and also without any coupling to to the case or to the heatsinks of the chip-amps.

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