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 tendency to self destruct and in doing so, destroy the cylinder itself...and they can go at anytime. There's a fellow on the Greenkeys that has tooled up and is producing replacements; same profile as the original and easy to install. Cheap insurance, 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 the 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.thomp...@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 the 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