Perq 2T1 display fault

From: CRC <technobug_at_comcast.net>
Date: Mon Feb 9 13:21:09 2004

On Sat, 2004-02-07 at 23:35, Jules Richardson wrote:

> Oh, and if anyone's dishing out Perq wisdom there's also a Perq 1 with
> a
> display fault too - on that one the image is centered on the screen,
> but
> squashed into about 80% of the normal width, and maybe 10% of normal
> height. It's also very non-rectangular in nature.

Chatted with my good buddy who still makes a living repairing
terminals. His guess is that the horizontal yoke isolation cap is
leaking/bad. This will definitely make the horizontal squoosh. Many
terminals derive the drive voltage for the vertical from the horizontal
flyback - thereby causing the problem you are seeing.

His recommendations:
1. look for an oversized cap (electrolytic - yup one of those
beasties...) near the horizontal drive transistor (generally
heatsinked) that has a rating between 35 and 60 volts and a value
between 2.2 and 20 microfarads. This is the isolation cap. If it is in
the 2.2 to 4.7 volt range replace it with a film cap - you will never
have a problem again. You can't reform this one since they put AC
(albeit mostly DC) through the cap and once it goes it's gone.

2. Replace any electrolytic near anything that looks hot.

3. Inspect, clean, lubricate, and replace, if necessary, the yoke
connector socket. His experience is that when the cap goes, the current
through the yoke goes up and fries the connector. The bad connection
will cause early failures.

If the vertical problem persists, you probably have a similar problem
with a cap in the vertical drive or a power supply problem.

        Good luck

        Claude Ceccon
Received on Mon Feb 09 2004 - 13:21:09 GMT