OK, I'm pretty clueless about switching supplies. And the unit I'm using as a crossover has one, albeit an antique. It's built into a Berning TF-10 preamp. Schematic is here.
The supply doesn't want to start up; when I flick it on, I can see the LED start to fire, then poop out immediately. I replaced the high speed diode called out in the "parts likely to fail," with no help. Now, here's the funny thing- I replaced the 2N2222 (also called out in the "parts likely to fail" section) with a plastic version (PN2222?) and the supply started up. It also screeched like an owl. If I shut the preamp down and plug the old 2N2222 back in fairly quickly, it starts up and runs quietly. If the preamp has sat around for a while and I stick in the old 2N2222, another 2N2222, or a 2N2222A, the supply won't start up.
Before I pull and replace the HV TO3 jobs, any suggestions as to a likely culprit here? If it helps, the deterioration was a slow one- for a while, the unit would start up if I pulled the tubes out, but now it doesn't even do that.
The supply doesn't want to start up; when I flick it on, I can see the LED start to fire, then poop out immediately. I replaced the high speed diode called out in the "parts likely to fail," with no help. Now, here's the funny thing- I replaced the 2N2222 (also called out in the "parts likely to fail" section) with a plastic version (PN2222?) and the supply started up. It also screeched like an owl. If I shut the preamp down and plug the old 2N2222 back in fairly quickly, it starts up and runs quietly. If the preamp has sat around for a while and I stick in the old 2N2222, another 2N2222, or a 2N2222A, the supply won't start up.
Before I pull and replace the HV TO3 jobs, any suggestions as to a likely culprit here? If it helps, the deterioration was a slow one- for a while, the unit would start up if I pulled the tubes out, but now it doesn't even do that.
Hi SY
This could be a tough one.
What I usually do without even trying to understand how this whole thing works is changing caps in the primary section.
I can see C705/6 and perhaps also C703 apart from the ones I missed.
I would check some resistors like R706 and the two-watters.
Next are the caps in the secondary.
If that doesn't help I usually stop in commercial applications.
Not with antique...
There is of course the possibility of leaky zeners and transistors.
That's why it could be a tough one.
Change the caps first!!
/Hugo
This could be a tough one.
What I usually do without even trying to understand how this whole thing works is changing caps in the primary section.
I can see C705/6 and perhaps also C703 apart from the ones I missed.
I would check some resistors like R706 and the two-watters.
Next are the caps in the secondary.
If that doesn't help I usually stop in commercial applications.
Not with antique...
There is of course the possibility of leaky zeners and transistors.
That's why it could be a tough one.
Change the caps first!!
/Hugo
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