Hi,
I have a Sanyo VCR 7200 that locks up when a Betamax tape is inserted.
https://www.youtube.com/watch?v=_IZMfejzyJg
I found these videos from The Betamax Man that show a unit with similar behavior. Capacitors, a transformer, and the STK7217 voltage regulator had all failed on the power supply.
https://www.youtube.com/watch?v=UyxD3rqAwvc
https://www.youtube.com/watch?v=vVeFcjUMFBk
https://www.youtube.com/watch?v=fPF9Uri1sEE
I've just tried replacing my STK7217 with one from eBay, seems to be an old stock part with no difference in plastic packaging from the original. It still isn't outputting 9 and 12 volts.
Here is a picture of the power supply schematic as taken from the
service manual.
Here are voltages measured from the power supply under no load:
- V IN OK
- Reg. 9V & 12V missing
- Always 10V = 14V
- AC 2.7V OK
- Time Base = 20V
- Always -24V OK
- Always 5.8V OK
- Always +33 = 64V
- Always 9V = 15V
- Reg. 9V from IC5101 missing (as it's generated from reg. 12V)
So the only problems are that the STK7217 still isn't working (perhaps DOA?) and Always +33 is 64V? Not sure why it is double. I pulled C5105 and it tested good.
Will check the PW2 board for problems but if the "new" STK7217 is really DOA I'll just have to try and design a replacement for PW2 with modern power regulators.