It reminds me of MC34063. I tried make one or two MC34063 power boards a long time ago, but gave up after buck or boost boards became widely available. Compared to modern switchers, I might call them nasty (in a fond sort of way of course.)
If it's MC34063 or a work-alike, the waveform would be 33 kHz thereabouts. It's been a long time I fiddled with it and the DS really does not want to tell the whole story, but the thing about MC34063 is that the duty cycle is fixed to about 1:6, see the timing capacitor waveform. So it will burst burst burst with that kind of a waveform to produce either a buck or boost output at the voltage you want. Nasty.![:D]( "Very Happy")
Your DSO pix with almost triangular waveform reminds me of MC34063. And maybe they put in whatever cheapest inductor they could get their hands on. I found MC34063 once in a ADSL modem, runs warm. IIRC I had to troubleshoot it because some power chain caps died. Warm.![:D]( "Very Happy")
Replaced the caps and it worked again.
If it's MC34063 or a work-alike, the waveform would be 33 kHz thereabouts. It's been a long time I fiddled with it and the DS really does not want to tell the whole story, but the thing about MC34063 is that the duty cycle is fixed to about 1:6, see the timing capacitor waveform. So it will burst burst burst with that kind of a waveform to produce either a buck or boost output at the voltage you want. Nasty.
Your DSO pix with almost triangular waveform reminds me of MC34063. And maybe they put in whatever cheapest inductor they could get their hands on. I found MC34063 once in a ADSL modem, runs warm. IIRC I had to troubleshoot it because some power chain caps died. Warm.
Replaced the caps and it worked again.Statistics: Posted by katak255 — Tue Nov 05, 2024 3:33 am