TS1000 Diagnostic Help

[msknight]

To be fair Michelle I've never known the original ULAs to just give up or even fail due to the much vaunted yet unproven myth of "heat damage" , rather they bite the bullet due to human intervention such as plug/unplugging an interface when the Zeddy is powered up, shorting them out whilst working on a powered up board etc or an already faulty interface innocently plugged in taking them out.

Of the six zeddies, two were no video output and swapping ULA solved it, so I presume they'd failed. At least one of which worked for a short time and then failed shortly after starting to use it.

Two were not capable of WRX, so I swapped them.

The other two, well, by this time I thought it would only be a matter of time, so I replaced them also.

I'm all too happy to bow to someone who has more experience than a beginner like me

It's a shame Andy Rea is no longer making his versions which at £15 a pop were good value, next time I see him I might just give him a prod.

Ha! Now you tell me!!!

[Moggy]

I'd lose the beginner tag if I were you Michelle, you have done more with the nuts and bolts than most of us in such a short time and very well too plus having visited your site possibly amongst the most well documented so most certainly a Zeddy-phile.

As for Andy's ULA's personal circumstance is against him at present which I won't elaborate on and brought his latest ULA design to a halt,but more germane is that I believe the chip he used on the old one is now defunct so I'm glad I have five of the buggers!

[1024MAK]

Yes, a problem with the market in programmable logic chips is that most 5V or 5V tolerant devices have been discontinued.

The main market is now 3.3V devices. To use with 5V TTL (such as the ZX81) means using level shifter chips or finding and adapting the design for one of the 5V or 5V tolerant devices that are still available.

Mark

[mrtinb]

Yes, a problem with the market in programmable logic chips is that most 5V or 5V tolerant devices have been discontinued.

I have bought some SLG46826G CPLDs. They have 15 I/O pin which might not be enough.

However they can have 2 input voltages. One is 2.5V to 5V and the other is 1.8V to 5V. So half the I/O pins have one voltage and the other half the other voltage. So it has built in 5V to 3.3V if you want.

On top of that it doesn't need a programmer, as you just program it with I2C.

I'm looking forward to play with it. I found 5 ICs for $15 on eBay.

[msknight]

I'd lose the beginner tag if I were you Michelle, you have done more with the nuts and bolts than most of us in such a short time and very well too plus having visited your site possibly amongst the most well documented so most certainly a Zeddy-phile.

(blush)

[DeLorean_4]

Thanks for the input everyone.
My new vLA81 arrived in the mail today and the computer is now up and running again!

[msknight]

Yay! Result!

[1024MAK]

Good news

Now you can have fun

Mark

[DeLorean_4]

I spoke too soon :'(

I put in the new vLA81, the computer ran fine. I hooked up the 16k RAM pack, still ran fine. Hooked up the printer being SUPER careful that it wasn't powered on, it worked fine. Powered the printer, it still worked fine.

I tried entering an LPRINT command and noticed the right-most column of keys didn't work.
I re-opened the computer, cut off a section of keyboard membrane ribbon that looked sub par, and re-assembled.

I think it worked for a little while, and now I'm back to exactly where I was before with the white screen.

I tried my spare vLA81 with nothing else connected to the computer. Still the white screen. Tried my spare Z80. Still just a white screen.
Like before, my LCD TV won't acknowledge that there's a signal. I only know I have a white screen from hooking up the computer to a CRT.

I think I can still order a new RAM chip for the TS1000, but I can't seem to find ROM chips anywhere. How would I go about getting one?

[1024MAK]

The next step is to connect the 16K RAM pack and try powering up. The RAM pack disables the internal RAM chip.

Actual ROM chips are only available from existing machines. They are fairly reliable and don’t fail very often. However, that doesn’t mean that they never fail. A 2764, 27128 or 27C128 EPROM can replace the ROM with a small bit of modification wiring. However, a chip programmer is needed to program the data into the EPROM.

If you only need one, you may be better off asking on here if someone can sell or give you one. Don’t forget to say where in the world you are, so someone in the same locality can help.

Mark