EPROM VPP voltages

[James Sweet]

How critical is the accuracy of the VPP voltage? I have one of those Willem
EPROM programmers which worked fine but now I can't get it to program 2732
chips that use either a 21 or 25v vpp. I checked and the voltage at that pin
comes up a bit low at 18 and 22v respectively. Anyone ever come across this
before? It goes through the programming cycle but the chip remains blank.

Also what should Vcc be set at?

 

[budgie]

On Sat, 14 Feb 2004 19:55:53 GMT, "James Sweet" <jamessweet@hotmail.com> wrote:

How critical is the accuracy of the VPP voltage? I have one of those Willem
EPROM programmers which worked fine but now I can't get it to program 2732
chips that use either a 21 or 25v vpp. I checked and the voltage at that pin
comes up a bit low at 18 and 22v respectively. Anyone ever come across this
before? It goes through the programming cycle but the chip remains blank.

Also what should Vcc be set at?

Usually the required tolerance for Vpp is cited in the (eprom) manufacturer's
data sheet. Typical is +/- 0.5V max. Your figures are way out of spec for
every 21v/25v device I know.

 

[James Sweet]

"budgie" <me@privacy.net> wrote in message
news:jnht20tt24549rhovdamskedccdteao76d@4ax.com...

On Sat, 14 Feb 2004 19:55:53 GMT, "James Sweet" <jamessweet@hotmail.com
wrote:

How critical is the accuracy of the VPP voltage? I have one of those
Willem
EPROM programmers which worked fine but now I can't get it to program
2732
chips that use either a 21 or 25v vpp. I checked and the voltage at that
pin
comes up a bit low at 18 and 22v respectively. Anyone ever come across
this
before? It goes through the programming cycle but the chip remains blank.

Also what should Vcc be set at?

Usually the required tolerance for Vpp is cited in the (eprom)
manufacturer's
data sheet. Typical is +/- 0.5V max. Your figures are way out of spec
for
every 21v/25v device I know.

Yeah I found a 10k resistor that according to a schematic I found should be
15k, though on the board it's labeled 2.2k, I replaced it with a 15k and the
voltages are pretty close now, it once again programs 2732's, I guess they
must have installed the wrong part and it was close enough to work until it
was used a bit, hard to complain for a $45 unit, works wonderfully other
than that snag.