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rjarratt on KDA50 and Some SDI Disks Prof Greg Egan on KDA50 and Some SDI Disks rjarratt on H7826 Power Supply Repair… S. Kraus on H7826 Power Supply Repair… rjarratt on MicroVAX 3100 Model 95 Power… Archives
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Author Archives: rjarratt
Bad DSSI RF72 Hard Disk
I have a number of RF72 hard disks. These are 1GB DSSI disks (DEC rather grandiosely called them Integrated Storage Elements, or ISEs). Most of them work well, but I have one that will not spin up. The console firmware … Continue reading
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KDA50 and Some SDI Disks
A few years ago I acquired a KDA50, which consists of 2 modules, the M7164 and the M7165, an RA72 disk, two RA70 disks, an RA60 disk drive, an operator control panel (OCP) and some big cables, with one I/O … Continue reading
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VAXmate Flyback Transformer
Recently I fixed the power supply of my VAXmate, but found that there was a problem on the monitor board, which may be what caused the power supply to fail in the first place. My suspicion immediately fell on the … Continue reading
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MicroVAX 3100 Model 95 Power Supply
I have a MicroVAX 3100 Model 95 that I acquired some years ago. At 32 VUPs it is one of the faster MicroVAXen. Some time ago I stopped using it because memory modules would suddenly stop working. At the time, … Continue reading
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VAXmate H7270 PSU Fixed, But No Video
In previous posts I have been describing my attempts to find a fault in the H7270 power supply of my VAXmate. After a long time studying and testing it I finally found the fault. It was a shorted diode (marked … Continue reading
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Partial Re-cap of H7109-C PSU for a VAXstation 4000 VLC
Recently I had occasion to dig out one of my VAXstation 4000 VLC machines. Before using it I decided it was prudent to check the power supply, a H7109-C, to make sure there were no leaking or bulging capacitors. It … Continue reading
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Memory for a DECstation 2100
Recently I bought a set of 8 memory modules that were advertised as “DEC VS4000”. They had a part number of 50-19464-02. This is one of the modules: I had assumed this was for the VAXstation 4000 VLC, but it … Continue reading
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H7874 Power Supply
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
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
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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