29 Apr
2012
29 Apr
'12
3:23 p.m.
On Mon, 30 Apr 2012, Terry Stewart wrote:
I concur. I bought one of these dirt cheap ones from
China too. Forget
the documentation and go for what's written on the circuit board.
It worked for almost everything I wanted to do (Mostly 27xx work). I say
almost everything because for some reason it couldn't cope with 2716 CMOS
EPROMS? (standard 2716 was fine).
Interesting. That's exactly what it wouldn't do reliably for me. It
seemed fine for CMOS EPROMS that used 12.5V Vpp but had significant
problems with those needing, e.g. 21V. The onboard charge pump did not
have the moxie for older NMOS devices and could program + verify only
about 1 in 4.
Apparently this was well known in the Willem community. I ended up buying
a little kit to replace the wimpy pass transistor and step-up with an
adapter that used an external supply. At this point it worked, but was so
inconvenient that I retired it.
As always, Caveat Emptor, past performance is no guarantee of future
returns, look both ways before crossing the street, etc, etc.
Steve
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