[Premium-Rx] Update on RF-590 display problem

[Gary Mitchelson]

OK, I'm happy to report that the replacing the zener has indeed fixed my
display to be nice and clear. So far so good and am not sure what caused
the problem to start with.

How sensitive is the RF-590 to heat? Pictures in the manuals show no
clearnance between the 590 and other units in a rack, does the 590 need
clearance for proper cooling?

-----Original Message-----
From: Barry Hauser [mailto:barry at hausernet.com] 
Sent: Sunday, November 24, 2002 22:27
To: Gary Mitchelson; premium-rx at ml.skirrow.org
Subject: Re: [Premium-Rx] RF-590 display **Found the problem**


Gary wrote:


> Well I found the problem on why the unused segments had a slight glow,

> there was no 6.2 V Bias to the Display Converter (the sealed box). VR1

> (provides the 6.2 VDC from the 35VDC supply) was toasted causing a 
> short (really about 20 ohms) to ground. Luckily Radio Shack has 6.2 V 
> Zeners in stock so I'll pick one up tomorrow. Everything else in the 
> converter ohms out OK.

Hi Gary & list:

Yup, that's one of the things I mentioned when you first posted.  Yet
another case where it wasn't the display itself, but a supply or ground
problem.  The vacuum luminescent displays don't seem to fail at the same
rate that the LCD's do which largely replaced them.

However, I had suspected it to be more likely a drifted resistor or
failed cap.  Question is now -- what caused VR1 to fail?  It's possible
that it failed on its own, but could be due another component in that
circuit.  Was this heat-sunk to anything?