Thread: Spectrum advice
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Old 2nd Jan 2020, 4:55 am   #1
arjoll
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Join Date: May 2006
Location: Invercargill, New Zealand
Posts: 2,846
Default Spectrum advice

I've wanted a rubber key Spectrum since the mid 80s - unfortunately at the time my parents had only recently bought at ZX81 so wouldn't buy me /another/ computer - I had the ZX81, and I could use dad's Sord M23, what else could an almost-teenager want?

Unfortunately, as with many things I missed the opportunity to grab one when they were in the "old junk" phase, and for the last few years they've been going for way more than I want to pay on Tradme, but I kept looking - and it sort-of paid off. Last year I saw a rather sick looking example - obviously the case was just hanging on, metal keyboard cover half detached etc - from a landfill recycling shop. I put in a silly low bid, and a week later I had one for $20 plus shipping.

I expected - and got - a broken keyboard membrane, so thought the plan of attack would be to start it up, make sure I got the Sinclair copyright notice, then buy and install a membrane (and I may as well do my ZX81 at the same time).

That was about six months ago, and today I've finally had a chance to have a look at it. I powered it up - it's dragging just under 600 mA at 9 V from my bench supply which seams reasonable - but instead of a copyright notice I have a very noisy picture on an era-appropriate NEC TV.

So, there's two things I'm looking for pointers on.

Firstly, I was expecting a channel 2/3 switch on this, the same as ZX81s and most 1980s VCRs had here in NZ - we used VHF until the end of analogue broadcasting, and until the mid 80s it was relatively rare to have UHF tuners - when this came out we had two TV networks, with a third starting in 1989. The picture did seem to be right on channel 2 though - I had to tweak a little to get the sort-of colour that's here, but the TV was last used with the output of a late 80s VCR switched to channel 2 (55.25 MHz vision).

Would I be correct to assume that this is actually on channel 2, or is it possible it's a UK model with UHF modulator and I am getting some kind of fluke harmonic? All of the other TVs I have here are auto scanning, and I'm not sure what they'll make of the Spectrum.

Secondly, where is the best place to start when diagnosing what's wrong with this Spectrum? Does the image give any clues at all, or is it just too much mush to tell?
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