GB retro hobbyist pleased to make your acquaintances!

[SirMorris]

Hello fellow vintage computer enthusiasts!

SirMorris here, AKA Charlie. I'm very pleased to have been given the keys to the door, so to speak. Thanks Terry!

I am pretty much always up to my elbow in some project or other. At the moment I have a sick System 80 (UK version, 'Video Genie 3003') so I am alternately prodding it with various test instruments and working on the 'expansion port tickler' - a device which will hopefully fulfil the function of the tester hinted at in the technical manual. I don't know if the tickler is a displacement activity itself designed to keep the harder task of fixing the thing at bay Or maybe that's just how the hobby works for me...

Anyway my main machine has to be the ZX81. I'm usually found on the Sinclair ZX World forums spouting some rubbish or other. I also like Acorn machines, especially the Atom, the forerunner of the venerable Beeb. If anyone suggested a game of Sea Dragon on the Atari 800 then I'd definitely be up for that. Unlike most brits I don't have a soft spot for the Spectrum or C64. I was still blowing up Atoms while everyone else got on with the gaming. I was more a programmy type. Still am.

Although I dabble in electronics I'm not very good at it, well certainly not a natural at any rate. More of an enthusiast, like my avatar namesake. I can make a mean circuit board, though. It's just making the things that go on it work, there's the rub

Anyway enough twoddle from me. See you over in the repair forum!

C

[Audronic]

Welcome SirMorris

Do you have a link to the document that talks about the 'expansion port tickler' ?? .

Good luck
Ray

[tezza]

Welcome to the forums Charlie!

There are a few System 80 hardware gurus here (I'm not one), but Andrew Quinn (alias TRS80) is a guru's guru. If he doesn't spot you repair posts regarding the System 80 be sure to alert him with a personal message.

[SirMorris]

Thanks! I'll be sure to do that once I get going.

There is a schematic in the technical manual & service guide which shows a device consisting of switches and LEDs on the address, data and a selection of control lines. It is attached via the expansion connector, and isolates the processor from the bus by asserting the bus disable lines. I think you use it by setting up memory addressing states on the switches in order to probe around and/or see the results of the operation on the blinkenlights.

I can't be arsed wiring up 28 switches and LEDs, so I'm spending much more time and effort on bringing this up to date..!

I have a USB/HID device that I built ages ago which I'll be up-cycling to talk to a small interface board. The firmware for the device is all open source and pretty easy to use, so I figure having a little project like this, which will save me from having to start the real business, would be well worth while It'll do what the switchy thing does but all from a cosy computer UI.

I'll be happy to post progress with this board and any work in progress files. In fact I'll probably whack it all up in github. Already I'm regretting some decisions - i'm having to do a _lot_ of wire stripping - so there would probably be a beneficial v2.0 in the pipe..