8 Nov
2011
8 Nov
'11
4:10 p.m.
I've seen a couple of blown-up 1489s through bad grounding of a cabinet (I didn't
do it, it was there and I figured that out after the fact). -- Ian
________________________________________
From: cctalk-bounces at classiccmp.org [cctalk-bounces at classiccmp.org] On Behalf Of
Tony Duell [ard at p850ug1.demon.co.uk]
Sent: Tuesday, November 08, 2011 3:26 PM
To: cctalk at classiccmp.org
Subject: Re: CMD CQD-220TM problems
On Nov 8, 2011 1:00 AM, <cctech at vax-11.org> wrote:
I doubt it. I'v got hundreds (literally) of 1489s in use here, and I've
neer had one die by being connected to an active RS23 line while
powered-down. And I've done that often enough...
I thought the RS232 spec required that you cna conenct any pin (even an
ouptu) to any valid RS232 voltage level without damaging anything, even
if the device is powered down.
-tony
One particular TTL <--> RS232 chip (I forget the PN) had the really
annoying
problem of blowing up if it was connected to a powered-up terminal
while the chip was powered down. This may be the cause of your dead UART.
Beyond that I don't have any suggestions.
Clint
Is that the 1489 line receiver? I've had many a 1489 lose its magic smoke
this way when I had an 11/750... ended up socketing that chip and ordering
a dozen or so extras from JDR Microdevices.