Search results

I have been restoring a VT100. I have replaced one of the RAM chips and the sender UART for the keyboard and the main board seems to work, except for the video output. I think the bad video output may be affecting the video driver board, so I have removed it for now. I am using the external...

I have been repairing a VT100, and I have got to the point where the monitor board does not seem to be working (see other threads). While doing so I have at times been comparing the board to one I have in a working VT102. However, just lately the display on the VT102 failed. I have been looking...

I have a non-functioning VT100. I think it is failing in the POST during the RAM check. I don't know for sure because I can't get it to light up the LEDs on the keyboard, however I used my logic analyser (a HP1630G) to see what values were written to the UART to send to the keyboard and I see it...

I thought I had this book but it seems I don't. I would buy a copy but there don't seem to be any available in the UK. Does anyone know if the Files-11 and/or ODS-2 specs (not sure of the difference to be honest) are online anywhere? Thanks

I recently acquired an AlphaStation 250 4/266. I am trying to get into the SRM console but it is currently set to automatically boot from disk. No matter what I do, while the machine is in text mode I get no console output, I just get a non-blinking cursor at the bottom left of the screen. The...

I have an Epson SD-600 5.25" Floppy Disk Drive. The locking lever on the front wouldn't lock and hold in the floppy disk. On inspection I found a plastic cam that holds the drive mechanism in place was cracked and was no longer in the correct position. I have attempted a repair by rotating it...

I have been asked to format some floppies on my Rainbow for use in a DECmate II. I have been sent some Verbatim Single-Sided/Quad Density floppies. When I try to format them in MS-DOS 2.11 with I get "Format failure". Not being sure which way to orient the floppy in the drive I have tried it...

I have just been trying a 32MB module that I acquired recently, in my 3400. When I install it and do SH MEM in the firmware it reports this: I suspect that the error is benign as I have had something similar on a different machine. What is FDM? How might its absence affect anything? Thanks Rob

I have just acquired a VT100 (minus keyboard). As seems normal with VT100s, the pop fasteners that keep the case on are all broken. I have another VT10x with missing fasteners. Has anyone done a 3D model of the fasteners suitable for 3D printing? Thanks Rob

I have acquired an RF71 disk. Using the DUMP command it looks like it could be a VMS volume for VMS 6.0. However it won't mount because it can't find the home block. I tried to see if I could use the ANALYZE command to repair it, but that wants to be able to mount the disk first. Are there any...

I am trying to get some RF30 disks working. I have tried three different RF30 disks, two of them from one source and one from a completely different source, so completely different histories. They all give me the same diagnostic error code, 0x300B, which seems to be too much of a coincidence, so...

Hello, I have an RF72 that won't spin up. The console firmware in a VAX 4000-500 does not see a disk if I do SHOW DEVICES. I have other working RF72s. I have removed the drive module and done some tests. I have learned the following: One or two of the electrolytic capacitors have a fairly...

A while ago I found that the flyback transformer on my VAXmate has failed, in fact I blogged about it here: https://robs-old-computers.com/2020/04/18/vaxmate-h7270-psu-fixed-but-no-video/ and here https://robs-old-computers.com/2020/05/12/vaxmate-flyback-transformer/. I have three ways to deal...

I have a faulty RF72 disk drive (won't spin, not recognised by console firmware). I have other faulty RF disks with controllers that work better, but they aren't RF72 but RF71. Is it possible to swap the controller boards or are they specific to the disk? I am guessing they are specific, but you...

I have a MicroVAX 3400 in a BA213 enclosure. It is all set up for DSSI, but I do have some RA disks, a KDA50 and the Operator Control Panel. However, I don't have the outer plate (called a Media Faceplate in some of the DEC documentation). The part number is 70-24534-01. I have seen it listed on...

I have finally got around to testing my KDA50 with some RA7x disks. I want to install the KDA50 in my VAX 4000-500. This is a BA440 enclosure. I understand that this enclosure only has Q22/CD slots. The KDA50 User Guide seems to suggest that I need to remove Bus Grant jumpers W2 and W3 for this...

Given that it seems unlikely that I will ever be able to replace the flyback transformer in the monitor for my VAXmate, my next option is to try to use an external VGA monitor driven from the I/O board. The I/O board produces RGBI, H and V sync. H sync is 26.4KHz, V sync is 60Hz. The RGBI...

I am about as certain as I can be that the flyback transformer from my VAXmate monitor board has failed. The VAXmate one is a Tai-Ho TH-1802B (DEC P/N 16-27188-01) and according the Technical Description has a primary voltage of +28V and produces auxiliary voltages as follows: +13.1kV @85uA...

I have a POST error on my VAXmate, which I think is related to the hard disk. I get error codes 81 or 82 depending on whether my MFM emulator is running or not. I suspect the hard disk controller may be faulty, because I don't see much activity on the MFM emulator itself (it is the David...

Not so long ago I tried starting up my AlphaStation 200. All I got was some beeps and an LED diagnostic code that suggests the NVRAM test failed, no video output. I swapped the battery, as the old one was dead, but it still refused to work. I have tried connecting to the serial port and got...