G'day Roy,



04 Jun 96 22:46, Roy McNeill wrote to Rod Gasson:



 RG>> Its a Philips VR6740 (similar to the Sharp VC486), and for

 RG>> reasons unknown it keeps blowing the capstan drive IC (TA7267).



 RG>> So far it has blown about 5 of them (over a 3 week period). It

 RG>> has also blown 2 micro's in the same timeframe.



 RM> 2 micro's as well?? Although I don't know vcr's at all (as you



Yeah :-(



 RM> know ) I'd suspect overvoltage, possibly caused by a power

 RM> supply regulator going strange, maybe by losing a 0V reference.



Tis possible, BUT I don't think so.. The last time it blew, I had a

meter hooked up to both the 5v supply for the micro, plus another of

the 12v supply to the drive chip. They were both rock steady at the

time of failure..  I got it on tape :-)



 RM> Given an unlimited supply of ic's,



At $80 each..  not likely.



 RM> I'd start hanging 5 watt zeners

 RM> of suitable values across the power supply and output terminals of

 RM> the ic (do this close to the ic, not at the power supply.)

 RM> Just a thought.



Not a bad idea, but I'm hoping someone, somewhere comes up with a more

positive answer, or at least a suggestion of which component is going

faulty first and taking the others out before I go this route..  I

don't relish the idea of forking out another $80 just to confirm/reject

this possibilty..  but it is certainly on the cards if/when I get other

ideas as to the actual cause of it all.



Cheers,

Rod



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