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Digital DECmate VT278

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  Digital DECmate VT278 by Bill Degnan - 10/05/2017 08:10
Digital DECmate VT278
Digital DECmate VT278 Click image for larger view.


EK-VT278 Technical Description

Digital DECmate
The DECmate VT278 is a PDP 8 on a CPU / RAM board installed in a VT-100 chassis. Pictured here is the SETUP screen one sees upon successful boot. Click image for larger view.


Digital DECmate
This image shows the CPU card (left) and Comm port card (right side). Click image for larger view.


Digital DECmate
These are the RAM modules. Note that the rear RAM module was found to be defective and removed. The system should have 32K, I guess removing one RAM module will reduce to 28K, I have not determined yet, but the system will boot without the last RAM module installed. Click image for larger view.


Digital DECmate
Here is a close up of the RAM module removed from the CPU card. Note the missing pin. Click image for larger view.


Digital DECmate
After removing the bad RAM I was able to access terminal mode by pressing "4" from the SETUP screen. Click image for larger view.


Digital DECmate
This is the dual RX02 drive pedestal that came with the DECmate. I need to get cables and software. I don't know if the drives work. Click image for larger view.


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  Items Needed for DecMate by Bill Degnan - 10/17/2017 18:04
I need a 37pin to 25 pin drive cable, DECmate OS/8 disks in RX02 format, and a RAM module.

Tips on making a boot disk:
http://avitech.com.au/?page_id=847

I have a catweasel it may be possible to use that to create disks See cw2dmk on this page:
http://www.tim-mann.org/catweasel.html

Tips on replacing a RAM module:
http://www.vcfed.org/for...um.php...achmentid=2553

I happen to have a 37pin to 25 pin cable that was used in a DEC environment, but it was split to connect to two "somethings" so I will need to check the pinouts from the manual and compare with the cable, hack it to work as a DECmate cable. Here is the pinout of a similar cable:
http://www.pdp8online.com/pdp8docs/rx02pinout.txt

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  Disk Images by Bill Degnan - 02/26/2019 00:18
http://www.pdp8.net/imag...ges/os8/DECmate_I.shtml

Thanks Lou.

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  OS/8 Disk created by Bill Degnan - 02/18/2020 22:06
DECMATE VT-278 rear ports
Pictured is the rear of the VT-278 with RX278 Floppy Drive Interface Connector (drive cable) attached. It's called a RX278 Floppy Drive Interface Connector cable, part number is RC26N-2L. Click image for larger view.


This weekend at the System Source computer museum I used their DECMATE VT278 to build a copy of the OS/8 boot disk for my system. Now that I have a known-working OS/8 disk, I need the cable. I checked page 23 of the ED-VT278-HR-001 Decmate System Architecture Manual for a pin-out to confirm that I don't have the correct cable on hand.

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  Drive Cable Found, but... by Bill Degnan - 02/01/2021 01:17
Finally found a drive cable but alas the drive itself is not working. It responds to a request to boot from disk but the drive just "ding ding ding"'s...indicating probably a snapped or disconnected drive belt. I did make my own cable a while back and I got the same results, so at least I know my homemade cable is probably ok afterall.

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