PDP-12 Restoration at the RICM

-----Original Message----- From: cctalk [mailto:cctalk-bounces at classiccmp.org] On Behalf Of Cory Heisterkamp Sent: 31 May 2015 15:48 To: General Discussion: On-Topic Posts Subject: Re: PDP-12 Restoration at the RICM Michael, Sounds like you're making some real progress. Next time you're near the ASR33, check the rubber hammer for the print cylinder. These have a

to self destruct and in doing so, destroy the cylinder itself...and they

anytime. There's a fellow on the Greenkeys that has tooled up and is

replacements; same profile as the original and easy to install. Cheap

really. -C On May 31, 2015, at 8:08 AM, Michael Thompson wrote: > We spent some time on the console Teletype that came with the PDP-12. > The platen was nearly impossible to move, so the Line Feed did not > work. We removed the platen, and found that the plastic in the bearing > area had swollen and was binding. We sanded, cleaned, and lubricate > the bearing surface and the platen now turns freely. On reassembly we > found that none of the Control Characters like Line Feed or Bell would > work in Local Mode. We fiddled for quite a while, but did not find a > problem. We speculated that something got bent when it could not move

binding platen. > > We found a bad SN7474 E13 on the M706 Teletype Receiver flip-chip from > the PDP-12. We will repair and test it next week. > > We borrowed the M706 Teletype receiver from the PDP-8/I and connected > the Teletype to the PDP-12. We loaded and ran a toggle-in program that > echos the keyboard to the printer. We were a little surprised when > everything in the Teletype worked OK. We were even more surprised when > the Teletype now worked correctly in local mode. > > We borrowed the console cable from the PDP-8/I and connected my laptop > to the PDP-12. The terminal emulator worked correctly and echoed > characters to the PDP-12 and back. > > We toggled in the RIM loader and then loaded the LBAA BIN loader from > my laptop. We ran the BIN loader and loaded and ran the PDP-8/I > Instruction Test #1. It actually works OK! > > We tried twice to load MAINDEC-8I-D02B-D Instruction Test #2, but > failed both times. Running that diagnostic and others will be the > project for next week. > > Al Kossow posted LOTS of PDP-12 manuals to Bitsavers. One manual > includes the allowable ripple for the power supplies. They allow > 3,000mV of ripple on the -30V supply for the core memory, so I guess > that the 180mV that we measured two weeks ago is OK. > > On Mon, May 25, 2015 at 8:07 PM, Michael Thompson < > michael.99.thompson at gmail.com> wrote: > >> Today we pulled all of the M113 flip-chips and tested them because >> SN7474 and SN7400 ICs seem to be a problem in these early DEC >> systems. The ones in slots J33 and K30 were bad. Replacing them fixed >> the problem with the JMP instruction. We did some more testing with >> the toggle-in programs and found that ISZ cleared the AC. Replacing >> the M119 in slot H28 fixed that. All of the toggle-in tests pass, so

processor is substantially functional. >> >> Core memory in field 1 with addresses X5XX didn't work. We replaced >> the >> G221 in slot D10 to fix that. >> >> We tried the ASR33 Teletype that came with the system. The mechanics >> were sticky from not being used for 30 years, but we got most of it >> free and working. We could send characters to the Teletype, but could >> not receive anything. The M706 receiver failed in the board tester. >> The spare is also broken, so we need to fix both. >> > > > > -- > Michael Thompson