Or buy a can of cold spray, and after its warmed up and working, start
spraying components until you find the area that causes it to go bonkers.
-Lawrence LeMay
> This appears to me to be an intermittent trace on the main board's video
> addressing logic I'd look in the counter chains. Careful examination of the
> boad may enable you to find it.
>
> Dick
>
> -----Original Message-----
> From: Doug Spence <ds_spenc_at_alcor.concordia.ca>
> To: Discussion re-collecting of classic computers
> <classiccmp_at_u.washington.edu>
> Date: Monday, March 29, 1999 4:18 AM
> Subject: Messed up Apple (clone) video
>
>
> >
> >Hi,
> >
> >Along with a dead 4116 (which I recently replaced with a hacked 4164),
> >my Microcom II+ (Apple II+ clone) has a video problem which has kept me
> >from using it for the past few years.
> >
> >Usually when it's cold, the display is a complete mess. As it warms up,
> >the image becomes clear but in four parts. Each quarter (corner) of the
> >screen is a mini-image of what should be displayed on the whole screen.
> >Out of each group of four pixels of what would be displayed normally, each
> >will be displayed in a different quadrant of the screen.
> >
> >After about 10 minutes, the screen becomes normal, with occasional "zaps"
> >and returns to the quartered screen image.
> >
> >Just about everything in the II+ is TTL, so it's probably just a matter of
> >knowing which piece of TTL to replace. Does anyone know?
> >
> >I'm looking at the schematics (for a _real_ Apple II) now, but I have no
> >idea how to locate the problem because there are several lines leading to
> >the video output, and the problem chip may be farther back into the
> >curcuitry and not connected directly to the output.
> >
> >I know that some of you are fairly expert with Apple hardware.
> >
> >I want to get the Microcom II+ working because it's the only machine I've
> >got that's capable of using my Z80 Softcard or my SMC-II Light Pen.
> >Neither will work in my Apple //e.
> >
> >Besides, it also has a better keyboard than the //e, once it's been worked
> >in to cure the 'bounce'.
> >
> >
> >(As an addition note on the machine's history:
> >The machine was repaired at the Microcom store in early 1987, and it came
> >back with a loose, drifty keyboard. I found out the reason was that the
> >keyboard's curcuit board had been cracked and the keyboard only works if
> >it's not screwed in too tightly. I'll get around to looking at that after
> >the video is fixed. It's just one corner that's folded a bit, but there
> >are traces on there! The keyboard tends to report the wrong characters
> >when it's screwed in properly.)
> >
> >--
> >Doug Spence
> >ds_spenc_at_alcor.concordia.ca
> >http://alcor.concordia.ca/~ds_spenc/
> >
>
Received on Mon Mar 29 1999 - 11:49:50 BST