Hello from Fort Worth, TX

Introduce yourself to your fellow forum members - what was your journey into the Sinclair world?
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GTS1000TX
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Hello from Fort Worth, TX

Post by GTS1000TX » Sat Apr 13, 2019 8:00 pm

Hello Everyone. My name is Glenn. I got my start in computers with an Atari 800. Back then, I did have access to all the information I have now. I knew about the Apple 2, Commodore and Tandy computers. I wasn’t aware ok what the UK was using. But I’ve been learning about the early home computers. And the Sinclair line has piqued my interest. I’ve listened to a few podcasts. Watched some documentaries on Youtube. Even watched the BBC film Micro Men. From those sources, the home computer market appears to have been stronger in the UK than it was here in the States.

So i decided to take the plunge. If I understand correctly, the Timex/Sinclair 1000 was the Sinclair entry into the American computer market. I recently acquired a boxed unit which appeared to be unused. i hope to see what it can do.

My Timex/Sinclair 1000 arrived yesterday.The seller said it was untested. But it appeared to have never been used. First I tested the 9VDC power supply with an analog and digital meter. It was reading about 11 - 12VDC on the analog meter. Higher on the digital. About 14V. But they both read higher than rated on some other DC adapters I have. So I plugged it into the PC without connecting to the TV. Well, there was no sound, smoke or heat right away. So I hooked it to the LCD TV. Turned it on. First wasn't sure it was working. A lot of interference on the TV. Even in the sound. So I muted that. The K appears in the lower left. I tried typing some keys. But what I pressed did not translate to the screen. So I thought maybe keyboard. But then I pressed P, which should automatically display the PRINT keyword. It didn't print PRINT. And each time it was different variation of a 5 character word. So is this a bad keyboard or something at the board level?

Thanks,
Glenn

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RetroTechie
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Re: Hello from Fort Worth, TX

Post by RetroTechie » Sat Apr 13, 2019 10:42 pm

Welcome here, Glenn! :)
First I tested the 9VDC power supply (..)
Toss that! Well, not in the bin, but back into the box where it came from. It's giving out a fairly high voltage with light load (with just a TS1000 hooked up, around 12V is not unusual), its capacitors will be in poor shape by now, and I have even seen the transformer itself go bad in one of these. Even though I don't own that many original Sinclair psu's - 4 or so. The voltage regulator inside the machine turns that extra voltage into heat, and that helps to shorten what little life may be left in this machine's components. :cry:

Instead, use a regulated supply that puts out as little as possible above 7V DC. For example a regulated 8V, 1A unit would be perfect. But check polarity on the plug before using! There's no reverse polarity protection inside this machine.
It was reading about 11 - 12VDC on the analog meter. Higher on the digital. About 14V.
Check which of your meters is working, and which isn't. 11-12V vs. 14V is waaayyy outside normal tolerances (and in this case, not due to a meter's input impedance).
The K appears in the lower left.
For a ZX81 / TS1000, that alone reads as "almost there!". There's very little inside this machine that can fail, and still have that "K" appear. 8-)

For the words showing up, do the characters itself appear okay? Like, normal readable A-Z? And: if you go over the keyboard, and press each key one or more times, do you see any response? (on screen). This type of keyboard was flaky even when new, and time is not gentle on them. If you find some keys are 'dead', please make a note of which keys do something, on which ones do nothing.

I suspect you may have a bad RAM chip. But that's just a hunch. See if you can post a (few?) screenshots? Also you may want to check the first few chapters of the EXCELLENT manual for this machine - it's online somewhere.

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1024MAK
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Re: Hello from Fort Worth, TX

Post by 1024MAK » Sun Apr 14, 2019 7:38 pm

Welcome on board Glenn!

:D :D :D

Hello Glenn. A warm welcome to Sinclair ZX World.

The 9V PSU supplied with these TS1000 / ZX81 computers is an unregulated type. So without the computer connected (‘no load’), the output voltage will be in the 12V to 16V range. This is normal. The computer will work fine with it (assuming there are no defects or faults).

When connected to the computer, the nominal 9V PSU output voltage should be in the range 9V to 12V approximately.

Having said that, as RetroTechie indicates, the voltage regulator circuit inside the computer converts the input voltage down to a regulated steady +5V for the computer logic to run from. The minimum that this circuit needs is 7.5V from a regulated DC PSU. The required voltage from an unregulated PSU has to be higher due to the limitations of this design of PSU.

So you can reduce the amount of heat generated inside the computer by using a regulated PSU that has an output voltage of between 7.5V and 9V DC. Always test and double check the polarity before connecting to the computer for the first time.

Note that different PSU arrangements may be needed with some makes of external RAM packs.

These computers don’t have a sound output and there is no provision to do anything with the sound channel on the RF output to the TV. So just turn the volume down to minimum on the TV.

If you get a inverted K in the bottom left corner of the picture, the computer has managed to do a lot of things to get to this stage, which is a very good sign.

As RetroTechie says, try all the keys. And attach a couple of photos here so we can see what you are seeing.

One online version of the ZX81 manual is here. The ZX81 and TS1000 are very similar, the BASIC being exactly the same.

Mark

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