Author Archives: rjarratt

H7874 Power Supply

Posted on March 29, 2020 by rjarratt

The H7874 is the power supply  used in the BA4xx and R400x enclosures, such as several machines in the VAX 4000 series. I have a VAX 4000-500 in a BA440. I had some problems with this power supply that seemed … Continue reading →

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Further Analysis of the VAXmate H7270 PSU Failure

Posted on March 28, 2020 by rjarratt

I have been doing further analysis of the failure of my VAXmate’s H7270 PSU. To start with the schematics are now greatly improved. I am still not sure how correct they are, but here are the latest and greatest: I … Continue reading →

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Possible Cause of VAXmate H7270 PSU Failure

Posted on January 12, 2020 by rjarratt

Now that I have acquired a DSO (a Rigol DS1054Z), I have been doing more work to understand the failure of the H7270 PSU on my VAXmate that I first blogged about here. I still don’t fully understand the problem, … Continue reading →

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VAXmate PSU (H7270) Failure

Posted on December 31, 2019 by rjarratt

While I was using my newly working VAXmate the other day, it suddenly failed. I had left it running for a few minutes and when I came back there was a smell and the machine was not running. I wondered … Continue reading →

Posted in Retro-Computing | 6 Comments

VAXmate

Posted on December 21, 2019 by rjarratt

I acquired a VAXmate earlier this year. The VAXmate was the successor to the Rainbow. It is PC compatible and runs MS-DOS. It was the first commercial diskless PC, although mine came with an expansion box containing a Seagate ST225 … Continue reading →

Posted in Retro-Computing | 4 Comments

MUSL Compiler Builds a Simple MU5 Program

Posted on May 2, 2019 by rjarratt

I have been slowly working on getting a MUSL compiler that targets the MU5 emulator, with the ultimate goal of compiling the MUSS source code to run on it. The first step is to build a cross compiler that works … Continue reading →

Posted in MU5, MUSS, Retro-Computing | 2 Comments

Teletype Model 33 ASR Ribbon Feed

Posted on March 17, 2019 by rjarratt

In November last year I attended DEC Legacy 2018 and as usual I took along my treasured Teletype Model 33 ASR. I hooked it up as usual to the PDP10 simulator in SIMH to run DEC’s TOPS-20 operating system. You … Continue reading →

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DECstation 5000/240 With the TURBOchannel Extender

Posted on October 7, 2018 by rjarratt

Recently I repaired the H7826 power supply in my TURBOchannel Extender. So now I wanted to get it working with the DECstation 5000/240 it came with. The trouble is, I don’t have the cable to connect the Extender to the … Continue reading →

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H7826 Power Supply Repaired

Posted on September 23, 2018 by rjarratt

After a spell of concentrating on other things I have finally got round to looking again at the H7826 power supply from my TURBOchannel Extender. When I left it back at the beginning of the year I was waiting for … Continue reading →

Posted in DECstation 5000/240, Retro-Computing | 3 Comments

Flocoder FLIP Now Processes Its Own Source

Posted on August 12, 2018 by rjarratt

I am at the stage with my MUSS restoration that I can process the Flocoder FLIP source code with my own implementation of FLIP written in Flex and Bison. My MUSL compiler can’t process all the Flocoder source files yet … Continue reading →

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