Computer Room

Computer hardware and software; especially vintage machines and retrocomputing.

Aug 162020
Tandy 6000 Power Supply Replacement

I bought this Tandy 6000 computer system back in 2013. It’s the last model in the Tandy/TRS-80 model II/12/16/6000 series. It would not power up, and I began an on-again/off-again project of fixing its power supply spanning over several years while being distracted by all sorts of other shiny objects. I ended up temporarily (?) replacing its power supply with a modern generic power supply in 2018. This is a summary of what I did, in case it might inspire other owners of the Tandy/Radio Shack business computer system line.

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Oct 162016
An S-100 Computer Chassis

A friend of mine just brought me this old rack-mount chassis containing two " half height floppy drives. It turned out to be much nicer than just a box with a couple of floppy drives inside: It also contains a 7-slot S-100 bus backplane! So, now this begins my quest to acquire a set of S-100 cards to turn this back into a working computer.

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Oct 012016
Retrochallenge 2016/10: Convert a DEC RL02 into a Ginormous USB Hard Drive

I have decided to participate in Retrochallenge 2016/10, which is pretty much an excuse to spend the month of October working on a retrocomputing project. Ok, let’s be serious: That doesn’t really make October much different than the preceding or following months for a lot of us retrocomputing enthusiasts. But this month, it’s official!

I’m taking on an ambitious project which will almost certainly remain unfinished at the end of the month: Converting a DEC RL02 into a ginormous USB hard drive, so I can use it for imaging and writing RL02 packs!

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Sep 182016
Wanted: Radio Shack Color TVs for TRS-80 Color Computer

My first computer was a Radio Shack TRS-80 Color Computer which my dad bought for Christmas in 1981. With a built-in RF modulator, it plugged into an antenna switch box mounted on the family color TV. That old Magnavox TV is long gone, but I still have that Color Computer.

A “holy grail” that I seek for my collection is one of the Radio Shack color televisions which were featured in advertisements for the Color Computer. There are two that I’m looking for.

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Mar 142016
Imaging VAX-11/730 Disks

I’ve been looking for a good way to transfer images of the hard drives on my VAX-11/730 over to my modern computers for archival and other fun. My previous attempt to bring up TCP/IP networking on the VAX was not successful, so I tried a different approach this weekend. And it worked! Well, mostly.

Now before digging into the details, let’s describe the computer in question. The VAX-11/730 was small by VAX-11 standards, but it’s still a great big beast of a machine that takes up a lot of room in my little house. It also sucks lots of power and gives off a whole lot of heat, but luckily it was a cool and breezy weekend so I could open up windows to keep the room from getting too hot. My VAX-11/730 has 3M of RAM if I recall correctly. It has a 120 megabyte model R80 fixed hard drive, and a 10 megabyte model RL02 removable-back hard drive. It also has a 1600 BPI 9-track magtape drive, model TU80. The R80 drive came with hobbyist-licensed OpenVMS 7.3 on it, with a node name of PIKE and a node ID of 1.730. The previous hobbyist owner apparently had it clustered with another VMS machine named KIRK.

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Nov 092015
IBM System/32 at the Local Electronics Recycler

A couple of days ago, I learned that there’s an IBM System/32 up for sale at an electronics recycler in Corona, California. This is very close to my home, and I happen to have a bit of free time right now between jobs, so I figured I should go look at it. Even though I’m quite tempted by this beautiful beast, I really shouldn’t spend the money or floor space on it at this time. But, being local, maybe I can help it find its way to its new home, just as another collector helped me acquire my VAX-11/730?

The seller says they got it about six months ago, and it was used for payroll at some small company. He says that the folks that he got it from claimed that it still works, but he hasn’t tried powering it up… which is good, because it probably needs lots of cleaning, careful examination of the power supplies, and other such attention to make sure that the magic smoke stays inside.

It’s a bit dirty, but it looks complete aside from a missing paper rack on the back side. This one has the keyswitch option, which replaces the power toggle switch next to they keyboard with a tubular lock.

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Jun 012015
Cheap HDMI Converter with Apple //c

Retro Computing Roundtable episode 100 began with a discussion of the problems often encountered when trying to connect an 8-bit computer from the 1980s to a modern display such as a typical 16:9 1080p TV or monitor with HDMI input. Open Apple #43 also included some discussion of the out-of-spec video output from the Apple II series, and the resulting problems that can cause with many digital displays.

With that in mind, I decided to try buying an inexpensive composite video to HDMI converter to experiment with. I got it for $19 from Amazon. I’ve heard reports that results vary a lot depending on the particular converter used, the particular version of that converter (i.e., its innards might get a complete re-design without any outward indication… part of the game one plays when buying these super-cheap imported devices), and the particular video source. Thus, my results here may or may not reflect the results you would get.

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Nov 292014
pyMiniCircuits: Python Support for Mini-Circuits Portable Test Equipment

Well, that didn’t take long. As mentioned in my previous post, I’ve just created a Python package providing support for Mini-Circuits brand portable test equipment. Well, more accurately, it just provides support for my model PWR-SEN-4GHS USB-interfaced RF power sensor (and probably the other sensors in that product line), since that’s the only piece of Mini-Circuits test gear that I have.

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Aug 252014
Kaypro II Therapy

This Kaypro II computer has led a hard life, but it’s on the road to recovery now. A previous owner has modified it quite a bit, but some of the modifications are hack-jobs. I’ll probably need some help identifying some of the upgrades to determine whether I want to keep them or back them out, but there are a few changes that are definitely coming out.

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Aug 212014
Word Processing was Expensive in 1980!

In a recent eBay purchase that I made, the seller included a 1980 brochure advertising word processing capabilities of the TRS-80 Model I computer system. The advertised system prices ranged from $2,046.95 for a cassette-based system with a dot matrix printer, to $5492.95 for a system with two 80k floppy drives and a daisy wheel printer. Computers sure have gotten a lot cheaper since then!

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Aug 132014
IBM System/23 Datamaster

I just became the proud new owner of an IBM System/23 Datamaster computer system yesterday. This 8085-based computer is an immediate predecessor to the IBM PC. It has BASIC in ROM, and two 8" floppy disk drives. I don’t have any disks or documentation for it yet, and I would like to get my hands on some of that.

Here are a couple of quick pictures that I took for Big Blue Week over on the RetroBattlstations subreddit.

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