Re: Caps a poppin!

[heuser.marcus@freenet.de]

Tristan Mumford schrieb:
> heuser.marcus@freenet.de wrote:
> >
> > Can you provide a good photo of the mainboard?
>
> I took one. Not sure if I'd call it good per se, but it's the best I could
> do. http://images1.filecloud.com/333356/2clone.jpg

It is a good picture: It's good enough to confirm that your
mainboard looks practically identical to the one in my clone!
(I had this suspicion after I saw your keyboard...)
Perhaps the clone of a clone? ;-)

I have no schematics but I guess that all chips/parts/traces
"should" be the same. So if you need any data - ask away.


> > Which caps did you replace?
>
> Going by the silkscreened coordinates they are at roughly D14
> (At the edge. No silkscreen for 13 or 14) and E9. The obviously
> pre-replaced ones (may be others that I didn't spot) are at C3
> and D3.

After seeing the photo I had bet on these, too - so the picture is
proven to be good enough ;-)

Is D3 a tantal cap?

> > Did you try to reseat/exchange the RAM or other chips?
>
> I reseated some of the ICs. I'm going to go through and do the
> whole lot.

My theory is that more of the chips could be fried - some of the
caps are next to them and are used as "buffers". The event which
caused them to explode may have been strong enough to kill
them, too.

In this case reseating obviously won't help much.


> I don't believe I actually have any compatible RAM chips
> anymore, which is a pity because I think I killed one.

You may take RAMs from the language card for tests.
They should be compatible IIRC but somebody needs
to confirm this.

My first suggestion would be to take it out anyway as it
complicates more than it helps, IMHO.

The fact that you actually get a video signal isn't too bad -
the question is which circuits are affected. (Video)RAM,
video scanner, video generator...

Is the on-screen garbage the only defect of the board or
are other functions affected?

Does the machine beep when turned on?
Did you try to boot from diskette?
Does it respond to keyboard input?
Did you try to change the video mode?
Do the usual BASIC video mode commands (GR, HGR, TEXT)
show a reaction?


> > What monitor do you use?
>
> My C= 1084S. The type with the D9 and RCAs.

The 1084 should work but the Videx clone card may be
defective, too. I don't know if this card works in a IIe but
this could surely be answered by other people in this group.


> I remembered last night in one of those awful half-awake states
> that I have a couple of RCA connectored mono monitors in the
> shed. One is some generic  one, which I think has selectable
> termination resistance. The other is one of the Apple mono
> monitors where the inside of the case pivots for vertical screen
> angle adjustment.

Some monitors have a switch for 80-column-mode next to the video
input. Other than that I guess the majority of all monitors should work
with the card without any special settings, like the Apple monitor.

It may be a good idea to test the video card with one of these.

bye
Marcus