On 10/16/2020 1:37 PM, David Gesswein via cctalk wrote: > Noticed in another thread an 8L is upcoming on the persons restoration > list. Making separate post so more visible. The G228's have a 20 uF 50V > electrolytic capacitor on them. I have had two short. When they short its > a race between the trace on the board burning up or the backplane 30 AWG > wirewrap wire burning up. One was on an 8/I I was restoring where the > backplane wire providing the power burnt up at power on. Wasn't shorted > before power on. The other was I saw one G228 had a burnt track while I was > washing the cards in an 8/L. I had not applied power at that point so that > was old damage. Usage history is unknown. > > As a minimum I would recommend applying current limited 30V to the capacitor > on each card out of the machine before initial power on. Low enough limit may > allow the capacitor to reform without shorting. The same part # capacitor is > still available for protective replacement. The capacitors don't read shorted > before power is applied. Unknown if they will short if the machine is powered > on periodically. > > I've head lots of reports of all the failures in 8/L's. I replaced the > one G228 and some bulbs but otherwise the machine was fine. It did need a lot > of cleaning and I did do my normal power supply reform and checkout. >
Thanks for that warning - my 8/L and likely the PDP-12 as well appreciate it. ;)