Hi guy's. So I recently ran into a problem, my newly accuired SA-7500's input differentail pair decided to die the other day with a loud bzzzz in the left channel, the differential pair tested fine on my multimeter but seemed to be breaking down in circuit causing DC on the left channel. No problem I thought, I put in a pair of KSA992FBU's, all voltages are good and I was back to the races. Or so I thought... About two days later the same thing happens, BZZZZZ *click*. Okay. Maybe one of the 992's was a dud, so I replaced them both again and again after about two days. BZZZZZZ click. Now today I decided to rob a pair of 2SA970's out of a spare amp I have, thinking maybe the lower collector current rating of the 992's was my downfall. So I power it up with the 970's in it and it worked on my DBT, powered it directly off the mains all was good. Hooked up my 8ohm test load and it ran for a few minutes idle before dying yet again... When it's working all my voltages on the transistors are fine and pretty much match the right channel and the schematic. I've got some KSA1015's coming as I was told these would be a better sub for the 726's but I can't help but feel that these are going to pop too. Nothings oscillating and it's nothing in my system that's causing it. I'm currently considering stealing a pair of 726's out of my SX-737 but if those blow I won't be able to use it. Any insight and suggestions are more than welcome. Thanks.