🚀 go-pugleaf

In article <43.1188.uupcb@satalink.com> michael.feeley@satalink.com (Michael Feeley) writes:
>
>        Last night the ribbon power cable that goes from the
>    power supply to the motherboard on my Rainbow 100B started to
>    melt (wire 6 from the right on the power supply end).  I have
>    a replacement cable from a 100A and will attach it as soon as
>    I can "air dust" the unit.
>    
>    Questions:
>    
>        1)  Are there any particular reasons for wire 6 frying?
>    
>        2)  Any way(s) to prevent a recurrence?
>    
>        3)  Any reason I shouldn't use the 100A cable (it looks
>    OK)?
>    
>        4)  One solution that comes to mind is to get a monitor
>    that doesn't draw on the Rainbow power supply.  I have a
>    Rainbow RGB cable.  Would anyone know of reasonable
>    (new/used) monitor brands (in addition to the DEC VR-241)
>    that function with a Rainbow?
>    
>    Thanks in advance.
>    
>    Mike
>    
	I have had a similar experience with a Micro PDP-11/73 (The 
connectors are similar). What happens is this: Due to low contact pressure
a small carbon deposit begins to form between a pin and the contact
in the connector, thus reducing the amount of current it carries. Because
the power wires are paralleled, this places more of a load on the others,
in fact to the point that the contact rating is exceeded. At some point
one wire carries most of the load and it burns down.
	Repair for this problem was quite simple for the PDP's. I cleaned
the pins and installed a newer revision connector (It had a much higher
contact pressure), although using the same rev cable will probably work
for the next ten years anyway.

					Brian.