1771 floppy controller questions

From: Richard Erlacher <edick_at_idcomm.com>
Date: Fri Nov 23 09:29:55 2001

If you need 4116's, just send me your address. I've got more than I'll EVER
use, believe me.

Dick

----- Original Message -----
From: "Tothwolf" <tothwolf_at_concentric.net>
To: <classiccmp_at_classiccmp.org>
Sent: Friday, November 23, 2001 2:55 AM
Subject: Re: 1771 floppy controller questions


> On Thu, 22 Nov 2001, Tony Duell wrote:
>
> > > 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
> >
> > IIRC, the DRAMs in the model 3 are 16K * 1 4116s or similar. All the pins
> > are used on these chips. If a pin is missing, then you are going to have
> > problems...
>
> I wonder if it would be worth soldering a new pin to what's left of that
> chip's lead? It looked like it had just corroded off, but with no other
> signs of moisture, I was kinda puzzled.
>
> > > 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?
> >
> > In the Model 3/4 it's just logic level signals. There's a separate power
> > connector on the disk controller board. But I suspect that carbon-cable
> > would have too high a resistance to be reliable (if nothing else it's
> > going to delay the signals somewhat due to the RC time constant of the
> > cable and the input capacitance of the chips on the board). Probably not
> > a good idea.
>
> Sounds like I may have to experiment a little once I get some clear bench
> space ;)
>
> > > 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.
> >
> > It's a lot slower to assemble, and it's actually slightly taller. Also,
> > those SIL Berg/Amp/Molex connectors are difficult to find in >10 way
> > sizes (yes, they're made, but nobody seems to stock them). I prefer to
> > use parts I can get in 1-off quantities :-)
>
> I can often find them in large sizes, and use an a sharp X-acto to trim
> them to whatever pin count I need. [If anyone decides to try this, be very
> very careful, those blades are extremely sharp, and will cut thru the
> connector slow at first, then slice thru the remaining material very
> fast.] The leftovers can be recycled for even shorter connectors. This
> would not be economical for more then a few dozen connectors however.
>
> > > 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
> >
> > Argh!. If the sound board has been plugged into the PSU output there's no
> > way of knowing what else has been misconnected and what damage has been
> > done. That's one reason to give a machine a complete visual inspection
> > before applying power, hoping that if things are totally misconnected
> > that the previous owner didn't power the machine up like that (some hope,
> > I know).
>
> I think that machine is the model 4, which I think came from a surplus
> dealer. There is no way of knowing what all someone tried to do to this
> thing before I bought it. The model 3 came from a thrift shop, and seemed
> to be in much better overall shape, and may have still had its factory
> seals intact.
>
> -Toth
>
>
Received on Fri Nov 23 2001 - 09:29:55 GMT