DD DM1500a, randomly blown power supply and output FETs, was told own hooked up subs wrong?
I removed all P.Supply and O.Put FETs, no switching on the tl494c or the lm393, I remove both to see what empty pads are getting/giving and it’s flat lines everywhere but 12.6v where it should be for each to function pins 8, 11, 12 on 494 and pin8 on 393 but 7.5v on pin 3 of 393), amp boots up blue light ok idling at .03a, I tried installing a known good lm393 to see if that does anything anywhere and it changes nothing. 494 gets no triangle wave/gives no waves, same as 393 regardless if good ICs installed for each or not.
Nothing else is probing bad with my DMM, except Q20, Q22 & Q28, Q30 are reading shorted between legs 1&3 with probes one way, same on each of the 4, but not when I reverse probes, so I’m assuming amp is designed as such and they are not actually shorted.
Currently reading up on the tl494 to see what it needs to operate, I know they have 2 comparators that need to run right to function (pins 1&2 + 15&16) and i am assuming the 393 is part of that and needa to function correcrly first before the 494 starts operating as it should.
Seems i have the hardest time with DDs for some reason, although the last i worked on had a bad PIC 😅 Any help greatly appreciated, i finally just got a new GPU and am in the process of rigging back up my watercooled gaming rig, almost ready for that guide, i have never wanted learning material this bad before ...lol
I removed all P.Supply and O.Put FETs, no switching on the tl494c or the lm393, I remove both to see what empty pads are getting/giving and it’s flat lines everywhere but 12.6v where it should be for each to function pins 8, 11, 12 on 494 and pin8 on 393 but 7.5v on pin 3 of 393), amp boots up blue light ok idling at .03a, I tried installing a known good lm393 to see if that does anything anywhere and it changes nothing. 494 gets no triangle wave/gives no waves, same as 393 regardless if good ICs installed for each or not.
Nothing else is probing bad with my DMM, except Q20, Q22 & Q28, Q30 are reading shorted between legs 1&3 with probes one way, same on each of the 4, but not when I reverse probes, so I’m assuming amp is designed as such and they are not actually shorted.
Currently reading up on the tl494 to see what it needs to operate, I know they have 2 comparators that need to run right to function (pins 1&2 + 15&16) and i am assuming the 393 is part of that and needa to function correcrly first before the 494 starts operating as it should.
Seems i have the hardest time with DDs for some reason, although the last i worked on had a bad PIC 😅 Any help greatly appreciated, i finally just got a new GPU and am in the process of rigging back up my watercooled gaming rig, almost ready for that guide, i have never wanted learning material this bad before ...lol
Attachments
If you have the tutorial, refer to #44 on the PS troubleshooting page. If not, look for a group of transistors designated as Q85, 86 and 87. Do you see them?
My apologizes for the late reply.
So the output FETs were heating up without me knowing (I still need a thermal camera and when I did feel them they did not even feel warm) when something went wrong and switching stopped on the output side that’s when I felt them and they were blistering hot :/
needless to say I have new OutPuts and Drive chips coming soon and will report back once I do.
thank you 🙏🏻
So the output FETs were heating up without me knowing (I still need a thermal camera and when I did feel them they did not even feel warm) when something went wrong and switching stopped on the output side that’s when I felt them and they were blistering hot :/
needless to say I have new OutPuts and Drive chips coming soon and will report back once I do.
thank you 🙏🏻