glitch
Veteran Member
I picked up a PDP-11/34a after VCF East this year, it's one I actually worked on back in 2017 for its previous owner, who sold it to me as he wanted the space it required back for other machines. I of course jumped on the opportunity to buy it, since it'd be a much more capable Unibus machine than my PDP-11/10. I put it on one of the benches this week to clean it and get any parts ordered ahead of VCF MW, so that they're hopefully in by the time I'm back. I have some upcoming customer work that'll be easier to complete on the PDP-11/34a vs. the 11/10. Started with taking panels off and dusting out the cobwebs:
It's pretty much how I remember it being in 2017, just with a little more dust and spider houses. I will be going through the H765 power system again, and disconnected it first:
I'm going to add a fuse for the 5411086 board (the one in my PDP-11/10 shorted a bridge rectifier and blew traces off the board), replace some of the known problem capacitors (so long, Sangamo!), generally clean everything out, etc. The power distribution board had a lot of greasy, caked-on dust, so it got a hot soapy water bath and a trip through the drying cabinet. I'll test and repair the regulator modules out of chassis, I made harnesses for that when I worked on the PDP-11/10's power system.
The 9-slot expansion backplane has a fault in it, I didn't get it working in 2017 and just left it disconnected, since it wasn't needed at the time. I want to try and isolate the fault and repair it, though I've heard it's sometimes bad wire wrap pin plating or bad soldering from DEC, and that it's often a nightmare to find under the wire wrap jungle! Backplanes, from the bottom:
All of the boards will get a thorough cleaning and get some likely problem caps replaced -- I already found one epoxy sealed Sprague 8uF electrolytic that's starting to leak past the epoxy. The chassis itself will get a deep cleaning, since I don't expect to have it this far apart after it gets racked for a good long while. I may respray the metal programmer's panel surround, since it has little rust spots all over it. At the moment, the chassis is fully stripped down of unboltable parts:
It's pretty much how I remember it being in 2017, just with a little more dust and spider houses. I will be going through the H765 power system again, and disconnected it first:
I'm going to add a fuse for the 5411086 board (the one in my PDP-11/10 shorted a bridge rectifier and blew traces off the board), replace some of the known problem capacitors (so long, Sangamo!), generally clean everything out, etc. The power distribution board had a lot of greasy, caked-on dust, so it got a hot soapy water bath and a trip through the drying cabinet. I'll test and repair the regulator modules out of chassis, I made harnesses for that when I worked on the PDP-11/10's power system.
The 9-slot expansion backplane has a fault in it, I didn't get it working in 2017 and just left it disconnected, since it wasn't needed at the time. I want to try and isolate the fault and repair it, though I've heard it's sometimes bad wire wrap pin plating or bad soldering from DEC, and that it's often a nightmare to find under the wire wrap jungle! Backplanes, from the bottom:
All of the boards will get a thorough cleaning and get some likely problem caps replaced -- I already found one epoxy sealed Sprague 8uF electrolytic that's starting to leak past the epoxy. The chassis itself will get a deep cleaning, since I don't expect to have it this far apart after it gets racked for a good long while. I may respray the metal programmer's panel surround, since it has little rust spots all over it. At the moment, the chassis is fully stripped down of unboltable parts:
At least it's relatively easy to work on!