7 Jun
2002
7 Jun
'02
9:27 a.m.
Most of the Hayes modem platforms required AC because the negative voltage
for the RS-232 was generated from it, along with the negative voltage rail
for some op-amps. In the case of a Hayes modem, it shouldn't have affected
basic off-hook and command functions, but audio would be pretty bad, DTMF
synthesis may or may not work, and RS-232 would be out of spec (but probably
workable, since most RS-232 will work at GND and +5)
--John
-----Original Message-----
From: cctalk-admin(a)classiccmp.org [mailto:cctalk-admin@classiccmp.org]On
Behalf Of r. 'bear' stricklin
Sent: Friday, June 07, 2002 17:10
To: Classic Computer
Subject: Re: [OT] measuring DC wall wart
On Fri, 7 Jun 2002, Chris wrote:
I think I am going to dig out the modem it goes to,
and test the voltage
with it hooked to that. That will at least give it real use load (the
modem powers up just fine, it just fails to respond to all AT commands
except for getting the firmware, and it won't attempt to go off hook or
dial... I'm not 100% convinced the modem is really "dead" so much as it
just doesn't want to co-operate).
Hey, you know what? I missed the beginning of this thread, but this is
exactly the sort of behavior you get from a modem which requires a 9V AC
power supply, when you run it with a 9V _DC_ supply.
ok
r.