Help diagnosing boot issue SWTPC 6800

[Chris Elmquist]

You should also verify that you have solid +8V and +/- 12V on the
backplane.

In one of my SWTPC 6800 machines, I found that the white Molex connector
on the power supply filter board had degraded contacts that over time
(a long time!) where heating and actually melted some of the connector
shell, made the contacts further crappy and resulted in too much drop
in the +8V rail so that all the downstream regulators weren't happy.

I replaced the on-board connector with one on wires, repaired the toasted
PCB and now the machine runs fine again.  The new connector floats in
the air a few inches above the PCB and this actually makes it easier to
plug and unplug if needed.

Chris

On Monday (01/01/2018 at 02:17PM -0800), Brad H via cctalk wrote:
> 
>     
> I had that happening on mine.. came down to a bad RAM board.
> 
> 
> Sent from my Samsung device
> 
> -------- Original message --------
> From: Nick Allen via cctalk <cctalk at classiccmp.org> 
> Date: 2018-01-01  10:32 AM  (GMT-08:00) 
> To: cctalk at classiccmp.org 
> 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.
> 
> https://www.youtube.com/watch?v=Ci4vhPn-3PE
> 
> Thanks in advance!
> 
> -Nick
> 
> 
> 
> 

-- 
Chris Elmquist