|Re: Dead 67 & Woodstock ACT chips & Prevention|
Message #2 Posted by Tony Duell on 17 May 2004, 1:57 p.m.,
in response to message #1 by John Garza
I don't believe it's any external event that kills the ACT. I've never had a replacement fail shortly after fitting it in place of the dead one (if, say, the PSU was the cause, you'd expect it to kill the replacement too). I think it's just old age of the chip (chips do _not_ last for ever, no matter what some people believe).
I also don't believe in blanket recapping (not of vintage valved equipment -- yes, I work on that too -- nor of HP calculators). Certainly replace capacitors that are causing problems, but I don't find replacing good ones does anything at all. I've actually had stuff where some caps have needed replacing several times (and yes, I do use good replacements, I had to replace them every 10 years or so), while others are still the originals.
Alkaline batteries have a higher voltage than the original NiCds. While this shouldn't cause a problem (the power converter is a regulated circuit, and should be happy with 3V rather than 2.5V input), I don't do it. Mind you, I do have the reserve power packs (external chargers) for the classics, woodstocks, spices and topcats :-). If you don't have the woodstock one, just use a junk 21 (say with a dead ACT or ROM chip). All you need is the charger connector, resistor and diode down one side of the PCB, and the battery contacts.
On non-C machines, there is _no_ risk to charging batteries in the machine with the switch turned off. There is then no connection from the +ve side of the PSU or battery to the rest of the machine. I've seen the schematics...