Hi
I had a Marshall AVT150 on my bench for repair. The output amps had blown so I replaced them with some I had in stock from a while back (from a previous AVT repair). When I brought the amp up on a Variac, it came up, worked for about a minute and then the outputs blew again. I purchased a few other TDA7293s when I went thru my stock and had similar problems. Since stock is no longer available, I purchased some "used" chips from I don't remember where and finally got the master to work, but the slave blew up again.
So short story, I tried many different chips (all branded, FWIW) and had many problems with them blowing up. I was very thorough in looking for other possible causes but there were no other problems in the amp or test setup.My main question is: can I NOT Variac the voltage on a 7293? I have seen other posts regarding the authenticity of the TDA7293s on the market so that makes me suspicious but I had either success, no success or limited success with same lot items.
I am a fairly experienced tech, this was one of my most vexing repairs. If anyone can shed some light why I was having so many varied problems replacing these amps I'd appreciate the advice.
I had a Marshall AVT150 on my bench for repair. The output amps had blown so I replaced them with some I had in stock from a while back (from a previous AVT repair). When I brought the amp up on a Variac, it came up, worked for about a minute and then the outputs blew again. I purchased a few other TDA7293s when I went thru my stock and had similar problems. Since stock is no longer available, I purchased some "used" chips from I don't remember where and finally got the master to work, but the slave blew up again.
So short story, I tried many different chips (all branded, FWIW) and had many problems with them blowing up. I was very thorough in looking for other possible causes but there were no other problems in the amp or test setup.My main question is: can I NOT Variac the voltage on a 7293? I have seen other posts regarding the authenticity of the TDA7293s on the market so that makes me suspicious but I had either success, no success or limited success with same lot items.
I am a fairly experienced tech, this was one of my most vexing repairs. If anyone can shed some light why I was having so many varied problems replacing these amps I'd appreciate the advice.
I had a strange fault on a 7293 where the outputs blew up.
When I did a visual inspection I noticed the front legs were touching rear pcb pads.
I fixed it by not pushing 7293 right down to pcb level and so have a gap between front legs and pcb read pads.
When I did a visual inspection I noticed the front legs were touching rear pcb pads.
I fixed it by not pushing 7293 right down to pcb level and so have a gap between front legs and pcb read pads.