Hi everyone.
Just getting back into 80's computers and trying to put together a collection of the machines I wanted at the time.
Had one of the first zx81's back in the day but gave it away many years ago. I then ended up working in a nuclear power station, writing reactor control software in CUTLASS and maintaining Honeywell DPS 6 supermini's and 8086/80286 target control computers. The amazing thing is, they are all still there and working !
Have a issue 1 zx81 needing repair, so may ask for some help. ULA is giving a clock signal and a blank video signal, but the processor isn't running
Also got
BBC B (fully working)
Spectrum (now fixed)
Apple ii eruoplus with z80 second processor (in need of tlc)
TRS80 series 4 (currently on shelf at work where it's been for 35 years, in process of being liberated)
3032 commodore PET (fully working, case needs a spray job)
Wanted
RM-380Z (pipe dream ?)
Memotech MTX-512
Hello
Re: Hello
Hello Gary C,
welcome to our crazy club... bear in mind some of us are crazy also anyway you've come to the right place for some help with the hunble 81.
you say the ULA is giving a clock signal but is it getting to the cpu? check pin 6 at the cpu, it is an inverted signal from the ula , been inverted by tr2.
regards Andy
welcome to our crazy club... bear in mind some of us are crazy also anyway you've come to the right place for some help with the hunble 81.
you say the ULA is giving a clock signal but is it getting to the cpu? check pin 6 at the cpu, it is an inverted signal from the ula , been inverted by tr2.
regards Andy
what's that Smell.... smells like fresh flux and solder fumes...
- RetroTechie
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Re: Hello
Welcome, Garry!
For fixing your ZX81, what tools you have available? Scope or even a simple logic probe would be very helpful. Any other ZX81's in your possession that you could swap parts with?
Usually ZX81's are easy to fix, with 2 exceptions:
For fixing your ZX81, what tools you have available? Scope or even a simple logic probe would be very helpful. Any other ZX81's in your possession that you could swap parts with?
Usually ZX81's are easy to fix, with 2 exceptions:
- ULA itself. If that's dead (or its video output blown), there isn't much you can do. Some modern ULA replacements are out there, though.
- Keyboard. But you can buy replacement keyboard foils. And some die-hards like on here have built their own keyboard for the Zeddy.
- 1024MAK
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Re: Hello
Hello Gary
Welcome to our forum
Please take a look around. There are gems of information everywhere. And if you have a question, please ask.
Mark
Welcome to our forum
Please take a look around. There are gems of information everywhere. And if you have a question, please ask.
Mark
ZX81 Variations
ZX81 Chip Pin-outs
ZX81 Video Transistor Buffer Amp
Standby alert
There are four lights!
Step up to red alert. Sir, are you absolutely sure? It does mean changing the bulb
Looking forward to summer later in the year.
ZX81 Chip Pin-outs
ZX81 Video Transistor Buffer Amp
Standby alert
There are four lights!
Step up to red alert. Sir, are you absolutely sure? It does mean changing the bulb
Looking forward to summer later in the year.