Phil Allison wrote:


In the example on my bench, it looks like an intermittent solder joint in the feed to the -15V supply did the job. The amps test just fine.

One 10uF bi-polar cap would have saved the horn diaphragm and a simple triac crow bar would have saved the woofer. A couple of dollars worth of components.


** I have now added a 20uF, 250VAC cap to the horn feed and an active relay board to the woofer amp. The NC contacts short the speaker while unpowered and open about 2 seconds after AC power is applied, the NO contacts then close and the amp is connected. If more than +/- 9VDC is detected the relay drops back to it's rest condition. There is a 7Amp fuse in series with the relay contacts in case of an arc developing to ground from the 80V rail.


.... Phil