Repairing an Astro Wars
I had an Astro Wars as a kid and loved it. The VFD display used in toys and cars from the 1980s has a really lovely glow about it. Much richer than an LCD display.
Last year I picked up an old 1981 Grandstand Astro Wars that wasn’t working. I was hoping the issue would be something simple like a corroded battery connector or a broken wire or something. It turned out to be a bit trickier.
I cleaned and checked all the connections and tested that current was getting to the board. No problems there. After that I noticed that the large transistor S02 got quite hot.
I removed the transistor and tested it with a component tester. It seemed to be OK, but then transistors are a dark art - so I decided to order some replacements. It can be tricky finding components that are compatible with the original components. Unsurprisingly electronics have come a long way, companies have folded and the same models are not always available.
A component tester
I then proceeded to test all the other components and replace all the electrolytic capacitors (which I could get at a local electronics store). They are really cheap and it seemed to make sense to replace them while you have the hood open.
The replacement transistors arrived and I replaced the S02 transistor. I turned on the Astro Wars and it worked! I enjoyed playing it, the kids enjoyed it. And then about a month later it stopped working again.
It appears that the S02 transistor had failed again. And the small transistor S03 in the bottom right was also getting hot. So I replaced the S02 again, but it still didn’t work.
Then one day I came across this video on youtube. It suggested replacing the mysterious S06 component - which is a Zener Diode (140v 500mw). Now these things are rare. I ordered some from an ebay seller in the UK.
Eventually they arrived and I replaced the S06 zener diode (and the S02 transistor again for good measure). Now when I power up the device the music starts, but the screen doesn’t turn on. Rats.
Working again
It goes again. It turns out the zener diodes I received were not the correct specification. I ordered more parts from AliExpress. These are the parts I have replaced
- S06 140v 2w zener diodes.
- S03, S04, S05 2SA1175 transistors
- S02 D882 transistor
- All electrolytic capacitors (as labelled)
While only a 500mw zener diode was required (like the 1N5275B), I could only find 2w versions on AliExpress.
Power supply improvements
From reading a number of comments on forums, it seems many of the units are broken when powered from the wrong 6 volt DC power adapter. The daft thing about these Grandstand consoles is that the plug has a reversed polarity barrel plug. This means the outside of the plug is positive. It seems in the ’80s that manufacturers hadn’t quite agreed which way to power devices. What makes it worse is that Grandstand didn’t include a diode for reverse voltage protection. Adding a diode protects against this.
In addition, the device can now be powered from USB with the inclusion of a USB C boost converter. While you can run the device off 5 volts, the screen is not as bright as it is on 6 volts. The boost converter can be configured to output 6 volts. I need to work out a way to mount this without making a hole in the case.