21 Nov
2001
21 Nov
'01
9:12 p.m.
On Thu, 22 Nov 2001, Tony Duell wrote:
Guess it comes with collecting eh?
At the time I thought the particular lead might have not been used, and or
someone damaged it when installing the chip. I had never seen a chip with
its lead corroded off like that. There's no visible water/moisture damage
on the rest of the board either, which seemed very odd.
Have you thought of trying a similar cable made from the newer plastics?
Teflon seems to be very very tough compared to whatever kind of plastic
they used in those older cables. What kind of current goes thru these
cables? Would it be possible to use one of the more flexible carbon types
instead of tin plated copper?
That's exactly the problem mine suffered from.
Well, if this is the machine that would not even turn on, that could
explain something...I know the factory seals had already been broken. I
wish I could get to these machines right now, I sure want to have another
look and fix em :P
-Toth
It's more
a matter of room than time right now, as my old "shop" is packed
floor to ceiling with computers, parts, and so on. My benches are also
currently covered up with even more parts and boxes.
I know exactly what you mean.... :-) I seem to
remember one of these machines had a chip in one of the ram
banks that was missing a pin. It looked like it had corroded off. It was a
ceramic package with gold plated leads.
Ah, if you have a visible problem like that, then you'd better fix it
;-). The machine is unlikely to work if a chip is missing a pin. Once
you've fixed that, you can start the real troubleshooting... replace it
with either a similar cable, or an IDC cable, as you suggested.
I've not found a source of the original type of cable. And I don't like
it much anyway (it seems to have reliability problems, which get a lot
worse if the cable is inserted and removed a few times). What I normally do is unsolder the connector from the
PCB. Replace it
with an SIL header (maybe just a row of pins, maybe one of the 'box
headers used with the IDC sockets with one row of pins removed). Then use
IDC cable/sockets to link the headers. Make sure you use the same row of
holes in both sockets, of course. I've done this in several machines and
not had any problems.
Could also use an SIL amp/berg connector and crimp pins to ribbon cable.
Might look a little more original, but it would take allot more work to
assemble then pressing on an IDC connector.
My model
1's keyboard cable had the same problem, and I replaced it with a
short bit of ribbon cable soldered directly to the boards. I'm planning to
replace that again with something better the next time I work on it.
The origianl M1 keyboard cables was a solid-core ribbon cable soldered to
both PCBs. It breaks if you unfold/reassemble the boards a few times. A
piece of normal ribbon cable seems to be a suitable replacement. I think I saw
some sort of temperature alarm/sensor plugged into the
output of one of the supplies in one of these machines. Was that a 3rd
party add-on or something that came standard?
If that's what it is, it's certainly not standard.
But disk-based M4s have a sound board. A small PCB with a 74LS74 chip, a
transistor and a beeper-thing on it. It has 4 wires coming off it, ending
in a 4 pin 0.1" Molex socket. It looks as though it could plug into a PSU
output connector, but it doesn't (doing so will kill the '74 at least).
It connects to a 4 pin plug on the CPU board just above the keyboard
connector. If yours was plugged into the PSU when you got the machine
then the previous owner was terminally clueless, and expect all sorts of
other problems!