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... and running of Nostalgic Obsolete Products. (NOP's). The poster was made by the DECUS NOP SIG to mark the 20th anniversary of the PDP-11 in 1990. The poster shows three generations of the PDP-11. ...
The MS11-JP (M7847-DJ) is a MOS memory board for Unibus PDP11's. In the PDP11/04 I am restoring there are two fully populated boards, each with 32K words of dynamic memory.... and neither board works ...
4. M9301 Repair
(JAQ/BLOG)
The M9301 is a ROM/Terminator board for Unibus PDP11's.  In the PDP11/04 the PROMs on this board provide the boot loader and programmers console code. The PROMs are mapped into two address ...
The KY-11LB Programmers Panel had been working well and being critical to testing the various boards in the PDP-11/04 it was disappointing to power it up and find the 7 segment displays not updating ...
This board was accessible from the front panel when installed in the PDP11/04 but the values read from the receive and tramsit data registers were not as I expected. On initial power up the receive ...
When installed in the PDP11/04 this board caused bits 4, 5 and 8 on the data bus to be set for any Unibus requests.  The schematic shows that these bits are part of the interrupt vector ...
... saw the write up by Henk at www.pdp-11.nl on his SBC6120 build. Following his lead I visited a number of automotive and specialty paint suppliers to try and find a suitable paint at a reasonable ...
  With the 74175 replaced and the track fixed the front panel now correctly displays the values entered on the keypad.     Small steps but I will take everything I can ...
... http://www.retrocmp.com/tools/pdp-1134-programmers-console on using the KY11-LB to test other Unibus boards which I am going to try.... particularly the memory and serial board.    ...
I may have got to the bottom of the front panel problem.   Initially I thought that it was related to the scanning technique that is used to read the keypad and update the 7 segment displays ...
The power supply modules are all back in the mounting box with the transformer and this is reattached to the chassis. I powered up the machine from the front panel on the weekend.  This machine ...
I am continuing to make progress with the power supply modules for the PDP 11/04. This weekend I got a chance to test the modules. One of the H7441 +5V supplies worked fine. The ...
The failed capacitors are replaced so the regulators are ready to test on the upcoming weekend. The 11 has three regulator modules.   2 x H7441 5V regulators are switching ...
An interesting study in the changes in capacitors over the last 25 years.  The new one is 2000uf less (22000uf v 24000uf) than the original but otherwise the specs are the same as best I can ...
Only three modules left..... the next 2 are H7441 5VDC regulator modules. Finally something faulty... it proves that the slow and steady approach works.   One of the two 24000uf ...
With the power control, main transformer and fan assembly operational the next module in the power supply is the 15VDC regulator.  This mounts on the other side of the power control box and is ...
The next module to be tested is the main transformer/fan assembly.  This takes the switched 240VAC output from the control box.  The fans run at 120VAC and the main transformer provides a ...
... it is pretty heavy). Made a start on the PDP-11 by testing the Power Control box.   This is where the 240v comes into the power supply and it has a "lower" voltage circuit that goes ...
Sometimes the unexpected happens.... I got an email from a retrocomputing enthusiest who was leaving the country for a couple of years and wanted to know if I wanted to look after his PDP-11.   ...

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Contact Andrew Quinn

jaquinn@ihug.co.nz http://twitter.com/jaquinn