[rescue] Any 3/110 owners out there?

[Ryan Eisworth]

I also have a 3/110 that has no video output (normally). This machine was stored at the bottom of a pile in someone’s storage unit that reached up to the ceiling of other systems and manuals, and the VME boards were halfway out of the chassis. As a result, the boards in my system are somewhat bowed, and it’s in pretty rough shape. I was surprised it seemed otherwise functional over serial. 

Quite by accident while trying to flex the system board, I discovered that if I touched a certain pin on one of the ICs involved in the video output that the monitor would suddenly come to life and show a perfectly good image for a moment, and then fade back to black over the course of several seconds. As best as I recall, if I kept my finger on the IC for too long the image would eventually brighten to full-white. I found a data sheet for an IC similar to the one on the 110 board and it designated the affected pin as N/C. I couldn’t find a data sheet for the exact IC though. 

It has been many years since I’ve looked at that system, and I can’t find my notes on what IC was involved. I might have some time this weekend to pull the system out and do some further probing. I’m curious to see if I note the same short that you are observing. 

I had intended to just try to tack a capacitor onto the mystery pin of the IC and see if I could get the video output stable but I never made it that far. I could not find continuity between that IC pin and anything else on the system board. My working theory was that this had something to do with termination on the monitor. 

Best,
Ryan

On Sun, Jan 19, 2025, at 11:13 PM, Kurt Nowak via rescue wrote:
> About a year ago I lost video output on my 3/110 and I'm back to trying to
> find the fault. Not so easy on a VME bus machine. Yesterday I noticed a
> short across the large 470 ufd electrolytic capacitor near the battery of
> the CPU board (270-1134-03). I desoldered the cap and it tested fine and
> noticed that the short is across the vias of the cap. Since a schematic of
> this machine is pretty much unobtainable I was wondering if another 3/110
> owner out there would be kind enough to test the continuity across this
> cap. Thanks.
>
> -Kurt
>
> _______________________________________________
> rescue list - http://sunhelp.org/mailman/listinfo/rescue_sunhelp.org