Decwriter LA30

Most recent revision date of this page, Dec 23 2019. Some links changed Apr 30 2023.

Introduction

In early 2010, I acquired a DECwriter LA-30P. It was attached to a parallel interface on a PDP-11. In 2011 as shown on this Web page, I evaluated the printer. In 2019, I acquired another print head. I have other DEC produced computer products on a Web page of DEC stuff.

Details of the LA-30P

My Decwriter LA30-P, acquired early 2010.
Decwriter head and paper mechs
Decwriter backplane and H735 power supply from back
Decwriter boards in backplane
Decwriter backplane label - dated June 1973
Decwriter label #7695

Boards in LA30, left to right, top/bottom

[three empty slots dual width]
M7721, dual width "CONTROL LOGIC A, (M7711 WITH BELL LOGIC) LA30"
M7712, dual width "CONTROL LOGIC B FOR LA30" 
M7713, dual width RIBBON CONTROL AND LAST CHARACTER VISIBILITY FOR LA30
M7724, dual width M7714 CHARACTER GENERATOR FOR LA30 WITH 7474'S INST
M7710, dual width "PRINT CYCLE TIMING, LA30 
M7717/16, single width Motor Control/HS50 Motor Translator
M7717/G936, single width Motor Control/Clock Accelerator 
cable/M7715 single width "LINE FEED CONTROL, LA30  
G8004/G380, single width /Solenoid Drivers 
cable/G380, single width /Solenoid Drivers 
cable/G380, single width /Solenoid Drivers 
cable/G380, single width /Solenoid Drivers

parallel to serial upgrade

Dave Fischer's site cca.org has a list from The RetroComputing Society of RI of LA30 modules which match mine, except their unit has the following serial modules, where I have empty slots:

M7389	(dbl)	async serial transceiver
M7731	(dbl)	active buffer/control module
M973	M598	cable connector & opto-isolated I/O card
M7721	(dbl)	control logic A (like mine)
M7712	(dbl)	control logic B (like mine)
...etc

These are SERIAL modules option, for an LA30-S. I have an LA30-P, a PARALLEL interface option. The maintenance manual says "A parallel LA30 interface consists of an 18-twisted pair cable up to 25 feet long and a set of modules to gate parallel data signals on and off the processor I/O bus.".."The parallel cable connects between A06 on the logic panel and the interface module of the system in which the LA30 is to operate."

In Dec 2019, I found a 1974 DEC Field Service manual on bitsavers.org. In this exerpt, there's an in-field upgrade for LA30-P to LA30-S.

In April 2023, it was called to my attention, that the LA-30P (parallel) has a G8004 "power fail" module among the slots for the cables. Whereas, the LA-30S (serial) does not. "Module Utilization" in the LA-30 Engineering Drawings has this notation. Thanks to Mowgli Assor for calling this to my attention. Their LA30 and the RCSRI's are both serial and lack the G8004 module.

Additional LA30 parts

In Oct 2019, I acquired a complete LA30 printhead on cable; as shown in these photos. Note the printed date underneath the head, of "March 16 1977". Other sources say the LA30 was produced as early as 1970. The underside photo of the head, shows how the print pins extend well into the head solenoids (coils). In addition, I have a print head with cable cut off.

Sources for module descriptions, tech info:

A former archive of DEC module documents at Ken Olsen's Microsoft archive "pdp12.lofty.com", is now mirrored at http://dustyoldcomputers.com/

bitsavers.org has PDFs by DEC M-module number here. and in adjacent folders. for G-series, etc. Modern CAD renderings of some of those modules are among CAD documents at so-much-stuff.com.

The rcsri.org Web site, shows a "Decwriter I" in their collection but has no further information as of 2019.

Since 2011, there's a Youtube video of a LA30 in brief operation. He has another video with some inside views. The head on his LA30 is of different construction than the heads I have.

In Feb 2011, I recieved an email from the picture editor of the German magazine CHIP as follows: "In our upcoming issue we are featuring a timeline about printers. In this context we would very much like to show a photo of the LA30 by the Digital Equipment Corporation. May we use [your] photo to illustrate our article?". We provided a higher-resolution photo in response, which they accepted. They agreed to crediting the photo to me by name and with a link to this Web page. However as of 2019, the CHIP magazine Web site insists on showing ads when browsing: I cannot access the site with an ad-blocking browser.

By and large, both in 2011 and in 2019, there's not much available on the Web, about currently existing LA30 terminals. - Herb