5 Nov
2019
5 Nov
'19
7:34 p.m.
On 2019-11-05 13:50, rescue wrote:
I haven't dug into this one yet, but I did get it
booted in trsdos,
and the letter I on the keyboard wasn't working.
I shut it off, disconnected and removed the keyboard. I desoldered
and removed the APLS switch, opened it up, cleaned up the carbon pad
and the contacts below it, reassembled it, tested it with my DVM, all
good to go. I soldered it back into the keyboard, put the keyboard
back, powered on the system....
I get CRT glow, system reset button will cause the floppy drive to
seek, but nothing on the screen, and pressing return after inserting
TRSDOS does not boot the drive (i.e. testing for a working core
system
with no display....).
I do need to test the power supplies and make sure I have not lost a
power rail on one of the two supplies. I presume the one I need to
check is the one on the backside of the cpu board, as the one on the
side of the drive 'cage' powers the drives and the drive controller
board, and on power up and reset, the drives are motor on and
tracking, so I think that supply is at least providing +5/+12V.
Well, it is something with the supplies. I tried the floppy power
supply in place of the system one, and got a Cass? prompt !
Then I switched back, and got a Cass? prompt ! GRRRR ! I'm still
digging.... maybe something failed and if I mount it back up it will
stop working again (once the ground pads are grounded on the back of the
supply ?).
I'm still hunting for the issue, it's either intermittent or something
flaky with the power supply that fails when it is grounded.
Now to go off and find out which.
At least the mainboard didn't go 'poof'.
-- Curt
Seems odd that putting the keyboard back in resulted in a non working
system. I unplugged it, same behavior with no keyboard plugged in.
I
did not connect the kb connector off by one pin or one row.... so as
best as I can tall, Murphy has struck, and it isn't 'operator error'
:-).
Any tips from Model III experts welcome.
-- Curt