[rescue] sun2 monitor repair

John Hudak jjhudak at gmail.com
Wed May 1 16:27:25 CDT 2019

You need to identify what subsystem is non-functioning.  There are two
general categories: Circuitry to light and scan the CRT, Circuitry to
process the incoming digital data and interface it to the CRT.
Easiest thing to check is the CRT - does  the cathode in the neck glow? or
more directly, does the front of the CRT light?
If not, you need to start there.  Does the unit allow for any other input?
e.g. external analog signal of any sort? if so, try that input and see if
anything is on the face of the CRT.  Do you have a HV probe to check the
anode voltage of the CRT? (for a 19" CRT, about 20-25KV - not necessary to
check this initially, but if you did, and you had low/no voltage, this
would suggest a flyback transformer or a voltage multiplier problem)

Make sure the brightness and contrast is turned all the way up..you should
at least be able to see some retrace lines (most likely)
On the data side, make sure you are sending data in the correct format it

This may be of help
I've found Sam's documentation to be fairly helpful
Good luck

On Wed, May 1, 2019 at 3:36 PM Walter Belgers <walter+rescue at belgers.com>

> Hi,
> Ib ve rescued my second(!) Sun 2/120. It did not work, due to a
> malfunctioning PSU. I got a new PSU (that apparantly has been a spare for
> all
> these years - it looked new!) and now the system starts up. But, there is
> nothing on the monitor. I have tried another monitor that did output
> something, so it is definately the monitor and not the graphics card or
> cable.
> The monitor is a Sun2/Monitor part 540-1062-01. The transformer is
> outputting
> two voltages (both about 60VAC) that goes to a rectifier. That in turn goes
> into a PCB that connects to the high-voltage unit and a PCB hooked up to
> the
> tube. All components look fine. I have resoldered all joints on the large
> PCB,
> which had no effect. I see nothing coming from the tube (also not close to
> the
> foot). I hear a slight hum that seems to be coming from the PCB hooked up
> to
> the tube.
> Does anybody know common failures of these kinds of monitors? Or a link to
> a
> (generic) repair guide/flowchart? I understand the safety precautions
> w.r.t.
> working with the high voltages in the monitor that keep there long after
> being
> turned off.
> Walter.
> _______________________________________________
> rescue list - http://www.sunhelp.org/mailman/listinfo/rescue

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