Can someone recommend a small screen with composite input ?

Discussions about Sinclair ZX80 and ZX81 Hardware
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1024MAK
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Re: Can someone recommend a small screen with composite input ?

Post by 1024MAK »

The following photos show the results using the 15” Mikomi LCD TV, model LCD15796BF TV:

ZX81 via composite via a back porch generator circuit
ZX81 via composite via a back porch generator circuit
ZX81 via composite via a back porch generator circuit

ZX81 (2C184E ULA) via composite with the TV brightness and contrast at maximum
ZX81 (2C184E ULA) via UHF with the TV brightness and contrast at maximum
ZX81 (2C184E ULA) via UHF with the TV brightness and contrast at maximum

ZX81 (2C184E ULA) via UHF with the TV brightness and contrast at maximum
ZX81 (2C184E ULA) via UHF with the TV brightness and contrast at maximum
ZX81 (2C184E ULA) via UHF with the TV brightness and contrast at maximum

Mark
ZX81 Variations
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ZX81 Video Transistor Buffer Amp

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Trevor_B
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Re: Can someone recommend a small screen with composite input ?

Post by Trevor_B »

Thanks for the recommendations folks.

My local charity shops don't sell electrical items so that option wasn't open to me unfortunately. They don't have anyone qualified to PAT(?) test them so can't sell them.

I've returned the screen I bought from Amazon and bought a 2nd hand TV with a scart socket and composite input from Ebay. I'll start with just the composite and if that doesn't work I'll be speaking to Lardo about a scart lead!


...just realised I should be able to use it for my speccie and orics too - why didn't I do this before...
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1024MAK
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Re: Can someone recommend a small screen with composite input ?

Post by 1024MAK »

PAT, meaning Portable Appliance Testing. An electrical safety test where any exposed metal parts are tested to make sure they are connected to the earth pin (class I appliances only) and various insulation tests are done (all appliances).

It is also supposed to include a visual inspection of flexes (flexible mains leads) and the appliance itself for any damage.

The test is supposed to be carried out by a suitably qualified electrician (although the quality of training of some of the people that do this work is open to debate).

Before selling mains electrical items, it’s generally good practice for a organisation to check an appliance.

By the way Trevor, do you know which version of the ULA that is in your ZX81?

As demonstrated above in the photos I posted, a lot of colour TVs and monitors don’t like the first two ULA versions that don’t generate the back porch part of the video signal (hence the brightness and contrast needing to be turned up to the maximum).

It’s not a problem for the 2C210E ULA, as that does produce the back porch part of the video signal.

Mark
ZX81 Variations
ZX81 Chip Pin-outs
ZX81 Video Transistor Buffer Amp

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Moggy
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Re: Can someone recommend a small screen with composite input ?

Post by Moggy »

Oddly enough amongst the many things I have been in life I was also a PAT tester (my training was excellent ;) ) as this was a requirement for the power tool and light plant company I ran.

If memory serves 1500v for class one insulated and 4000v for class 2 or double insulated though this may have changed since I last flash tested in anger more than 25 years ago. Field coils and armatures also individually tested at voltages varying from 1500 2500 4000 volts.

In the bad old days before PAT testing equipment became mandatory we used a flash tester which comprised of a large box full of equally large capacitors. You would dial the voltage required for whatever was being tested then place two probes on the object then pray!!

There were a slew of rogues I seem to recall back in the 80's going round factories and offices with scare stories of danger all around and for a small fee they would test and certify everything from the office kettle to the secretaries intercom!

They truly were untrained and armed with a cheap PAT gave everybody a bad name which was hurtful to those of us who were fully competent and included it as a service and not a revenue stream.
Trevor_B
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Re: Can someone recommend a small screen with composite input ?

Post by Trevor_B »

@Mark

I've got 2 Minstrel 3's (one in a zx81 case, the other with built in keyboard) - these are my "goto zeddies"
I've got another with a VLA81, 16/32k RAM internal mod (though I could only ever get 16 to work..) and composite mod
The last (currently) is my original machine from 1981 (series one - yellow board, dated 1980); 1k RAM, unmodified. That's an 8134 chip. I really don't mind this one not having a signal - I'd rather leave it as it is. I only realised today that other than the ram, the VLA, ROM and CPU chips are socketed. The processor is a NEC D780C.
Trevor_B
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Re: Can someone recommend a small screen with composite input ?

Post by Trevor_B »

Thanks for the screen info folks.
I bought a "Technika" screen (tesco own brand I believe) off Ebay. I needed the SCART adapter after all, but it's all together and works with the 3 main machines. It has antenna input so I may even be able to get my original 1k zeddie to display a screen too.

At some stage I'll try the other machines (Speccie x 3, Oric x2, Acorn Atom with duff keyboard plunger and BBC B with recapp'd power supply).
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