Help diagnosing boot issue SWTPC 6800

William Sudbrink wh.sudbrink at
Mon Jan 1 14:25:15 CST 2018

Hi Nick,

The "fatherboard" contacts on the SWTPc can be very intermittent.  This also plagues the OSI bus.  I recommend a two step treatment:

1) brush the pins with deoxit gold
2) force nyogel 759G (or the successor compound, I think 759G is discontinued) into all of the "holes" (pin sockets on the cards) using a toothpick (careful not to break it off) and seat and remove each card several times.

In my experience, this treatment results in a much more reliable system.  I've also used it on a couple of S-100 systems where the cards were exceedingly difficult to remove and insert.

Bill S.

-----Original Message-----
From: cctalk [mailto:cctalk-bounces at] On Behalf Of Nick Allen via cctalk
Sent: Monday, January 01, 2018 1:32 PM
To: cctalk at
Subject: Help diagnosing boot issue SWTPC 6800

Hey everyone, Happy New Years!  I am thankful for an active community that enjoys helping each other learn, and today I am coming with an ask for help.

I have a SWTPC 6800 and ADM3A terminal, I can get it to boot, and when it boots it will continue to boot for several hours.  But getting it to successfully boot takes upwards of 100 power OFF and ON cycles.  The other 99 times, I get a continuous stream of random ASCII characters (see video link below).  It's my first time seeing this type of issue that happens intermittently, and wondering if anyone has any insights in what might be causing this.  I suspect its a faulty IC on the Processor board that resets or controls the OS reset, will need to deep dive and diagnose, but thought I would ask for some direction first.

Thanks in advance!


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