Altair 8800b received - test-drb@ccmp.vtda.org

9 Jun 2005

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Subject: Re: Altair 8800b received
   From: "Randy McLaughlin" <cctalk at randy482.com>
   Date: Wed, 08 Jun 2005 22:22:38 -0500
     To: "General Discussion: On-Topic and Off-Topic Posts" <cctalk at
classiccmp.org>

From: "Richard A. Cini" <rcini at optonline.net>
Sent: Wednesday, June 08, 2005 8:39 PM

  All:

 Today I received the Altair 8800b that I won on eBay last week. I
 honestly say that this is the first machine that I'm honestly afraid to plug
  in. It was billed as "working but in need of
a good cleaning" which is an
 understatement. The interior is filled with greasy dust.

 Among the other atrocities buried therein:

 *  two bus connectors (out of 10) have destroyed pins
 *  poor repairs/lifted traces on the display control board
 *  repairs on the other boards (CPU and two memory boards) in need
 of a solder reflow
 *  the main filter cap was replaced with two smaller (but equivalent
 uF) caps which were unsecured,
 banging around the inside. These broke one of the card
 supports.
 *  the top cover has three 3/16" holes drilled into it

 I've asked the seller to give me a rundown of the history of the
 machine if he knows it. On a positive note, the switches appear to be intact
  and the panel graphics seem to be OK.

 Now, I remember someone asked me to look at the CPU board for some
 sort of identification. The CPU board has the following designation: "MITS
 8800b CPU REV 0".

 For those who keep track, this unit is labeled SN#5400280K.

 Rich

 Rich Cini
 Collector of classic computers
 Build Master for the Altair32 Emulation Project
 Web site: http://highgate.comm.sfu.ca/~rcini/classiccmp/
 /************************************************************/ 
Just in case you are unfamiliar it is best to take a pair of vise grips and
break up the bad S100 connectors.  After that you can remove the pins one
pin at a time.  It is very very bad to heat up the Motherboard and by
removing the plastic and just leaving the 100 metal pins that means you need
to apply less heat.  This even applies if you have a desoldering station.
Trying to remove multiple pins at once is near impossible, 100 pins is
impossible. 
Some are of softer plastic and dont crack.

I hate impossible.  ;)  My solution to pulling bad S100 connectors was a 
copper bar of the correct dimensions to heat all 100 at the same time.
The correct dimension is wider than the solder pins and slotted to 
recieve the pins.  Takes three ungar 47watt elements to heat it 
evenly and a special Teflon handle for the whole mess.  The whole 
mess sits in a copper trough of solder to keep it tinned. Works very well.

Why do that?  Back when some of the vendors used tinplate and gold 
over copper for edge connectors.  Some socket vandors also cheaped out
using nickle.  For those that don't know gold over copper requires a 
nickle over copper first or you get old that turns greenish black in 
a while and high resistance contacts. Metal ion migration is a bad 
thing. The end result was shakewell disease.  Shakewell is when to 
get the system to run you have to pull and reinsert every card 
before every use or the system crashes. I learned of this after the 
S100 connectors of the NS* Horizon were contaminated by this.  I had
to replace all the connectors, and junk out 5 8k and one 16k memory 
card, and some of the MITS (tinplated connectors) PIO cards I'd used 
that caused the grief.  The only connectors that were ok had the CPU,
MDS disk controller and my VDM-1.  

I've had to do a backplane replacement really nice ATI S100 I'd 
aquired due to this. plus tossing scrapping the board in it.  When 
I pulled them out the pins of some connectors and most  of the boards
were greenish black.

The only thing more annoying is some brands of IC sockets that loose
their spring or also get a surface corrosion, very difficult to 
troubleshoot the intermittnt signals or worse.

Allison