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With the finished schematics of backplane and decoder it is on with the hardware itself : fixed mains switch and tempguard, reconditioned main caps, checked main transistors, and presto : +5V is present ! Sometimes its easy.... But always keep in mind that the design is really very dangerous...

Apologies, that error was coming from my side. I mixed up the script that generates the ROM binaries. Sorry for the timewaste ...

Yep, that seems to be the problem. The printer driver software is shifted by 4K. Other potential pitfall : the 6850 needs to be the 2MHz variant, i.e. 68B50. If alls fails : a very quick hack to obtain a programmable bit : add a 74ls74, with set and reset coupled to the 68B50. Reading/writing...

I will look into creating a guideline for using the RS232 interface. However if you are only interested in toggeling a pin there is a wholly different approach possible : take a look at my 4052 RAMpack design, there I control the TTL counters directly from my 4052 machine. You have a RAM pcb...

And the final installment of my re-engineering efforts : schematics of the backplane, the decoder_iii and an updated schematic of the mainboard. Changes are mainly to do with naming consistency across the different schematics. Also, for completeness sake, some pictures of the backpanel. Note...

Hi Christian. would you happen to still have software / documentation for that system ? I am located in Koblenz/Aargau and have the exact same setup here... Jos Dreesen

Not sure what you mean by boot-routine. The initial loading from a mass storage device ? The manual describes this as the "restart" operation ( appendix A) There we will need to check the firmware to locate that call. The machine I took the ROM from does not have tapes, therefore there must be...

I do have a spare monitor, but sending it to the US is not a practical proposition,,,,

Sorry, have missed this. These manuals are now with me, as I have a running CPT9000 system. I suppose I could scan this material. As already mentioned elsewhere on VCFED, i have some of the 9000 systemsoftware on my FTP site ftp://ftp.dreesen.ch/CPT Looking for a CPT9000 keyboard. It does run...

...and the rest... ( yes the bootboard only has a switch on it...)

Decoder, Keyboard driver, display board....

....memory boards...

Some pics of the mainboard....

Got sidetracked by other projects.... Aren't these jumnps described in the 5500 hardware manual, page 10 ?

Just a reminder : the design for the Ceres-1, a NS32032 machine with 1000x800 display, running the Oberon system, is out there, including all schematics, software, PAL equations for EP610's used. Designed by ateam under the lead of Niklaus Wirth, who just passed away last month. The followup...

My first PDP8/E came out of an ECRM scanner, and yes it was a /e, not a /m. Mine also came with a TU56H, placed externally. I do have the driver software for the ECRM as a papertape should anyone need this.

Hi Roland, as mentioned in the PM : the issue with my machine was a short in the backplane connector. It is now OK again, both RTC chips and GAL's were OK. more per PM. BR Jos

Hi Anthony, Roland's system now resides with me. The CPU box has indeed dual Z80 CPU, and there is room on the PCB for a third Z80. The cartridge diskdrive does belong to the system, as my Trivector has a suitable controller for it on board. Also a cartridge came along with it. Do you have...

So, in the unlikely case anyone here has a need for it : this is the reconstructed schematic of the Rolm s375 control panel interface . This is strictly the interface itself, no added functionality as the 1642 board has . It also is not 100% compatible with the 1642, but should be close enough...

The ROM's are MMI6301-1, and yes, tristate and OC are indeed mixed... There is the additional "decoder iii" board that also contains some of the clocking circuitry, still need to draw out that. I can send you the Kicad project if that eases things. Z61 and Z62 as an entrypoint generator is...