MauriceH
Experienced Member
As for any with problems PDP8M(/E) The tricky M837 Failure.
Here the debug of the last struggle I had with Booting the PDP8M to OS8.
And thanks for so many help I found here.
The systems seems to work as all Toggle test programs were running.
Have a 8k Core memory so only field 0 & 1.
If I set bit 6-8 to 001 then "Ext Addr Load" , the EMA light to field 1 (001).
Then select addr 0000 "Load Addr" and toggled in test prog.
Run program with no errors. My assumption was that MEM was working both fields,
in fact it wasn't.
When Booting I noticed at the moment it reaches field 1 (EMA 001) System hangs.
With program DUMPREST in Cygwin64 Terminal I could sent RIM files to the PDP8.
So with the help of Don,AK6DN, he suggested the test Maindec-8e-DHKMA.RIM.
That should test the M837 Time share. see Photos.
When SR is set to 0007 , the program should auto recognise the amount of Fields in the system.
It did not and came with 8 Fields. I have only 2.
At run system halted at addr 0725 MD 7402
Reading about that M837 time sharing there were 2 modes, manual and auto.
As looking in the program arguments and when system halt, should be something with IO Transfer.
Debugging the logic I stumbled on a defect E17 74H74 FlipFlop.
Changed out for 74HCT74 and there it went BOOTING OS8.
I got the PDP8M back in 2011 completely dead on arrival.
With also a bunch of Tennecomp cards inside.
M8300 8/E Major Register For KK8-E, Replaces M830 when used with M8310, Quad
M8310 8/E Register Control for KK8-E, Replaces M831 when used with M8300, Quad
M8330 8/E Improved M833 (See M8347), Quad
M837 8/E Memory Extention Control for PDP8-E , Also time Share
M8320 8/E Bus Loads for 8/E, Replaces M832, Quad
G111 (G111c) XML 12 Bit 8/E Sence & Inhibit, 8.5 x Quad
H212 8/E 8k 12 Bit H211, MM8-EJ, PS-3010654
G233 (G233c) 8x X-Y
TP 023B 8/E Tape I/Face
TP 018 Tape Control
TP 017E Tape Read - Write
TP 34 PDP 8E Autoloader
Seems to be cards for the TP-1371 Tape recorder. (If any one have a spare?
)
TP 33c Rotochem ADC and Control Interface (ADC-Kaart)
TP 31c PDP8E Printer and Keybord Interface
Sadly no Serial cards, back cover mention at delivery they where there, but systems seems to been converted
and former owner knew it had been used with some kind of medical instrument.
Over the years I managed to get some extra cards, M8650 (completely defect and still not running), M6855 after repair running.
A second M6850 I borrowed for now. SO still have to get that M6850 to debug.
A M8357 and a M847 with RX01 Bootstrapping.
Problems in Order of repair:
-Power supply, Checked and main Capacitors replaced, adjusted voltages.
-Front pannel, some defect logic, Paraty encoder E3 and E11
-M8310 E17,E40, E50, All 7474's defect. and E44 replaced with 7420 and converter PCB.
Mostly debugged by hand with tracing logic paths outside PDP8.
-M8330, No CLOCK, logic around that E03, later on the X-Tal it self dead, replaced.
As there were still problems with running a program I was not able to debug further.
I could not run any program, only could fill memory.
With help of Roland we figured out it was the M8330 that still had a failure,
Borrowed a Spare M8330 from Roland so I at least can run some programmes to test PDP8 further.
-M6850 Lots of struggling and still not running properly.
-M6855 logic 7404 and M1489
-M8330 I finally found the problem E17 8881 it was the problem maker.
E17 Defect_1nov2021 ; i/o PAUSE Data, 5 6->4 no output signal.
-M837 could not go to field 1 in Time share mode when booting OS8. E17 74H74
-M847 with RX01-Bootstrap
-M8357 RX28 working
From Roland I borrowed the M847E card, and what a fun to have that card.
Build the RX02 Emulation with Arduino 2650 .
Ordered M847E to build.
Also a struggle was to get all that software running as a newbie on LInux UBUNTO,Simh etc.
Had to read lots of forum threats,
Now time to build system further.
Have the TU60 cassette unit, and rebuild the M8331R card, but Logic on TU60 seems to have problems.
As I borrowed the RX02 Floppydisk system from the PDP1123 my brother, I manage to get a hand on both
driver card and cpu, M7444 and M74445, with a Shurgart SA801 I am going to try to build a RX02 system.
Have the RK05 card-set RK8E_RK05-M7104-7105-7106, some diskspacks, So only need the real thing, some day.
Then I go see if I get that Tennecomp card running TP 34 PDP 8E Autoloader.
See if I get it going , but that card is in poor shape, missing logic, I know what it should be.
And figure out this card: TP 31c PDP8E Printer and Keybord Interface
Terminals VT100 or VT220,VT320,Vt420,
ASR33 Teletype ,working.Only needed to replace the rubber puncher.
Facit 4040 Tape Reader, working
So still lots of work to be done, but as for now I finally have a working PDP8M machine that
can boot from real RX02, RX1 disks, RX02 Emulation.
-Have to finish the OS8DiskServer.
Here the debug of the last struggle I had with Booting the PDP8M to OS8.
And thanks for so many help I found here.
The systems seems to work as all Toggle test programs were running.
Have a 8k Core memory so only field 0 & 1.
If I set bit 6-8 to 001 then "Ext Addr Load" , the EMA light to field 1 (001).
Then select addr 0000 "Load Addr" and toggled in test prog.
Run program with no errors. My assumption was that MEM was working both fields,
in fact it wasn't.
When Booting I noticed at the moment it reaches field 1 (EMA 001) System hangs.
With program DUMPREST in Cygwin64 Terminal I could sent RIM files to the PDP8.
So with the help of Don,AK6DN, he suggested the test Maindec-8e-DHKMA.RIM.
That should test the M837 Time share. see Photos.
When SR is set to 0007 , the program should auto recognise the amount of Fields in the system.
It did not and came with 8 Fields. I have only 2.
At run system halted at addr 0725 MD 7402
Reading about that M837 time sharing there were 2 modes, manual and auto.
As looking in the program arguments and when system halt, should be something with IO Transfer.
Debugging the logic I stumbled on a defect E17 74H74 FlipFlop.
Changed out for 74HCT74 and there it went BOOTING OS8.
I got the PDP8M back in 2011 completely dead on arrival.
With also a bunch of Tennecomp cards inside.
M8300 8/E Major Register For KK8-E, Replaces M830 when used with M8310, Quad
M8310 8/E Register Control for KK8-E, Replaces M831 when used with M8300, Quad
M8330 8/E Improved M833 (See M8347), Quad
M837 8/E Memory Extention Control for PDP8-E , Also time Share
M8320 8/E Bus Loads for 8/E, Replaces M832, Quad
G111 (G111c) XML 12 Bit 8/E Sence & Inhibit, 8.5 x Quad
H212 8/E 8k 12 Bit H211, MM8-EJ, PS-3010654
G233 (G233c) 8x X-Y
TP 023B 8/E Tape I/Face
TP 018 Tape Control
TP 017E Tape Read - Write
TP 34 PDP 8E Autoloader
Seems to be cards for the TP-1371 Tape recorder. (If any one have a spare?
)TP 33c Rotochem ADC and Control Interface (ADC-Kaart)
TP 31c PDP8E Printer and Keybord Interface
Sadly no Serial cards, back cover mention at delivery they where there, but systems seems to been converted
and former owner knew it had been used with some kind of medical instrument.
Over the years I managed to get some extra cards, M8650 (completely defect and still not running), M6855 after repair running.
A second M6850 I borrowed for now. SO still have to get that M6850 to debug.
A M8357 and a M847 with RX01 Bootstrapping.
Problems in Order of repair:
-Power supply, Checked and main Capacitors replaced, adjusted voltages.
-Front pannel, some defect logic, Paraty encoder E3 and E11
-M8310 E17,E40, E50, All 7474's defect. and E44 replaced with 7420 and converter PCB.
Mostly debugged by hand with tracing logic paths outside PDP8.
-M8330, No CLOCK, logic around that E03, later on the X-Tal it self dead, replaced.
As there were still problems with running a program I was not able to debug further.
I could not run any program, only could fill memory.
With help of Roland we figured out it was the M8330 that still had a failure,
Borrowed a Spare M8330 from Roland so I at least can run some programmes to test PDP8 further.
-M6850 Lots of struggling and still not running properly.
-M6855 logic 7404 and M1489
-M8330 I finally found the problem E17 8881 it was the problem maker.
E17 Defect_1nov2021 ; i/o PAUSE Data, 5 6->4 no output signal.
-M837 could not go to field 1 in Time share mode when booting OS8. E17 74H74
-M847 with RX01-Bootstrap
-M8357 RX28 working
From Roland I borrowed the M847E card, and what a fun to have that card.
Build the RX02 Emulation with Arduino 2650 .
Ordered M847E to build.
Also a struggle was to get all that software running as a newbie on LInux UBUNTO,Simh etc.
Had to read lots of forum threats,
Now time to build system further.
Have the TU60 cassette unit, and rebuild the M8331R card, but Logic on TU60 seems to have problems.
As I borrowed the RX02 Floppydisk system from the PDP1123 my brother, I manage to get a hand on both
driver card and cpu, M7444 and M74445, with a Shurgart SA801 I am going to try to build a RX02 system.
Have the RK05 card-set RK8E_RK05-M7104-7105-7106, some diskspacks, So only need the real thing, some day.
Then I go see if I get that Tennecomp card running TP 34 PDP 8E Autoloader.
See if I get it going , but that card is in poor shape, missing logic, I know what it should be.
And figure out this card: TP 31c PDP8E Printer and Keybord Interface
Terminals VT100 or VT220,VT320,Vt420,
ASR33 Teletype ,working.Only needed to replace the rubber puncher.
Facit 4040 Tape Reader, working
So still lots of work to be done, but as for now I finally have a working PDP8M machine that
can boot from real RX02, RX1 disks, RX02 Emulation.
-Have to finish the OS8DiskServer.
