moving cleanout - partial DECmate I / VT278

couryhouse couryhouse at
Mon Jul 20 00:45:33 CDT 2015

What are you going to do with it?Looking. For a wt78 but.... this fell in our lap....

Sent from my Verizon Wireless 4G LTE smartphone

-------- Original message --------
From: Brent Hilpert <hilpert at> 
Date: 07/19/2015  9:29 PM  (GMT-07:00) 
To: "General Discussion: On-Topic and Off-Topic Posts" <cctalk at> 
Subject: Re: moving cleanout - partial DECmate I / VT278 

Further to my earlier message today, something else to go:

	DECmate I / VT278 monitor & CPU

	This is the VT100 monitor/housing with the 6120-PDP8-microproc-based CPU board in one of the logic slots.
	Sadly, missing the keyboard and floppies unit, so it's not complete.

	IIRC, I faked a keyboard-present signal at the keyboard-jack some time ago and got it to produce some boot text on the screen.

See for example:

. . found my notes about it from 2011:





	• LSI PDP-8 in VT100 case.
	• 6120 microprocessor (D1-6120-9 8)
	• 6 * SIP memory modules w 4 chips each (21-17559-AA / 8252 DP)
	• 2 * 6402 (UART)
	• 2 * 6121 (PIO)
	• SND 5027 D (video controller)

Pros & Cons:

	• CON: Missing disk drive.
	• CON: Missing keyboard.

2011 Jul: Powered up. PWR-OK and CPU-OK LEDs lit, CRT filament lit. No raster. Schematic obtained from bitsavers. No video or sync signals from processor board to monitor board. CG CHAR CLK to CRT Controller chip is present (1.5MHz), but no sync signals out from CRT Controller. ROM, CPU, CRTC socketed chips rocked for contact, no change. CRT Controller may not be getting initialised in initial ROM boot process.

Connecting ring (data) to tip (+12V) on keyboard connector after power-up brings up SET-UP message and flashing cursor after several seconds. 


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