[Tech]Need some pointers on fixing SW Upright

[John Bennett]

[ukvac] [Tech]Need some pointers on fixing SW Upright

Hi guys,

I finally got a new AVG/CPU/Sound combination for my upright Atari Star
Wars (the old one was fragged to hell after a major soldering accident
(please don't ask) ).

Anyway - the new board was fully tested and working, and has shown up a
few problems on my machine that I hadn't noticed (because the old board
was only ever partially working).

I haven't had a really good look at the machine yet (other than
installing the new board), so there might be some obvious thing that I
haven't spotted yet...

1. I am completely missing the colour green. I think there is a single
green dot in the center of the screen, but I can't be sure (it's very
dark)

2. The intensity of the red/blue guns appears to fade in proportion to
the amount of stuff on screen. When the machine is first powered on,
the brightness is very very low, and it takes a while to get up to
normal - but then begins to fade when there is a lot of text or action
on screen.

I will take a closer look at all the boards at the weekend, but I was
hoping that some kind vector experienced soul could point me at some
specific things to look at/for

Thanks for your help.

Dave

(one step closer to finally owning a working SW

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DATA Imported from archives: originally posted by David Cowan (david.cowan@vissci.com)

 

[LukeWells]

Re: [ukvac] [Tech]Need some pointers on fixing SW Upright

Those faults sound like monitor falts not pcb fautlts for a start.

In this case you can treat the monitor troubleshooting in exactly the same
way as you can a raster monitor.

1) try swapping the green and red input wires to the monitor. If you now
have green and red is missing then its definatly a monitor fault....
continue here..... do the same with the neckboard wires, swap over green and
red and see if the missing colour changes again. If it does change then the
fault lies on the deflection pcb where the input comes in. If the missing
colour does not change then the fault lies in either the associated colour
transistor, the neck socket or the tube.

2) Thats a common case of poor voltage regulation. I would start off by
rebuilding the regulation section before even trying to diagnose anything,
you only need a few caps and a couple of transistors, and possibly some
rectifier diodes, see the schematics for your particular monitor.

HTH

Luke

 

[peterbudduk]

[ukvac] Re: [Tech]Need some pointers on fixing SW Upright

I agree with Luke that it is more likely to be a monitor fault but I
would first check the RGB outputs on the AVG board and the circuitry
around them to see if everything is OK there.

Note that if the AVG board is not sending out green then swapping red
and green inputs to the monitor will produce a lack of red on the
screen and it is *NOT* the monitor at fault.

Peter

 

[John Bennett]

RE: [ukvac] Re: [Tech]Need some pointers on fixing SW Upright

Thanks guys... I'll take a good look at the weekend. It might be the
connector board that connects the AVG and Mainboard to the rest of the
system... It's been very loose, and the picture will black out if the
board is just moved even slightly.

Any tips on how to tighten edge connectors?



DATA Imported from archives: originally posted by David Cowan (david.cowan@vissci.com)