Can't get a display output with my ZX Spetrum 128k+2 (Grey) model

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1024MAK
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Re: Can't get a display output with my ZX Spetrum 128k+2 (Grey) model

Post by 1024MAK »

Maybe.

It depends on how your existing cable is wired, what (if any) parts are needed, and your own ability to solder.

The details of the make-up of the cable are here.

Does your TV have a composite video input (round yellow socket, normally with white and red sockets nearby for the audio left and right channels)?

Do you have a phono cable that you don't mind cutting up?

Mark
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Re: Can't get a display output with my ZX Spetrum 128k+2 (Grey) model

Post by EranStockdale »

Thanks, I’ll give that a look!

In answer to your questions: yes, and I do believe so yes (I’m pretty certain).

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Re: Can't get a display output with my ZX Spetrum 128k+2 (Grey) model

Post by EranStockdale »

Update: I do indeed have a phono cable available, why'd you ask?

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Re: Can't get a display output with my ZX Spetrum 128k+2 (Grey) model

Post by 1024MAK »

EranStockdale wrote: Mon Dec 25, 2023 6:55 pm Update: I do indeed have a phono cable available, why'd you ask?
Because, on the Monitor DIN plug on the Zx Spectrum +2 (grey), pin 1 is normally Composite Video (if LK4 if fitted in the Speccy, which should be the case for UK models) and pin 2 is 0V/ground.

So you can connect the outer/screen of a composite video cable to DIN plug pin 2, with the inner signal wire to pin 1 of the DIN.

Not as good as RGB SCART, but better than an UHF/TV aerial connection.

Mark
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Re: Can't get a display output with my ZX Spetrum 128k+2 (Grey) model

Post by EranStockdale »

Oooh brilliant! I just checked the actual cable (my Mum said we have one, I didn't see it myself) and it's actually to halves of a composite cable. I'm going to have to solder the wires together but that should be doable. I'll let you know how it goes?

Eran

PS: Do I need to be extra careful about accidentally touching the composite signal while it's running?
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Re: Can't get a display output with my ZX Spetrum 128k+2 (Grey) model

Post by 1024MAK »

If you mean is it dangerous, no, the Spectrum does not produce any high voltages.

Your TV may however give you a 'tingle' if you touch any metal part of any connector or circuit connected to it. This is not unsafe and won't harm you, but may surprise you. It's due to the interference suppression capacitor that is fitted in its internal power supply.

If you mean, will I damage the Speccy if pin 1 and pin 2 accidentally get shorted together, no, as long as it's not left like it.

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Re: Can't get a display output with my ZX Spetrum 128k+2 (Grey) model

Post by EranStockdale »

Brilliant, thank you Mark :)

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Re: Can't get a display output with my ZX Spetrum 128k+2 (Grey) model

Post by EranStockdale »

Right so, I've gotten the wire stripped, now how do I work out which is the ground connection? Inside the wire is another shielded wire (in yellow insulation, would this be the composite signal?) and one that's many smaller metal wires all together.

Also, how do I identify which pins are pin 1 and 2?

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Re: Can't get a display output with my ZX Spetrum 128k+2 (Grey) model

Post by 1024MAK »

EranStockdale wrote: Mon Dec 25, 2023 10:39 pm Also, how do I identify which pins are pin 1 and 2?
DIN plug/socket numbering

ZX Spectrum +2 grey DIN socket details on Fruitcake
EranStockdale wrote: Mon Dec 25, 2023 10:39 pm Right so, I've gotten the wire stripped, now how do I work out which is the ground connection? Inside the wire is another shielded wire (in yellow insulation, would this be the composite signal?) and one that's many smaller metal wires all together.
The inside wire in the centre of the cable is the signal wire, that is the composite video signal, so this goes to DIN plug pin 1.

The thin outer wires (screen/shield/braid) should be twisted together, then connected to DIN plug pin 2.

See also the picture of a Coaxial cable here. Although your cable may only be lap screened and not have a metal foil or full copper braid (called "Woven copper shield" on the Wikipedia page). Don't worry about all the technical stuff in this page.

Mark
ZX81 Variations
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ZX81 Video Transistor Buffer Amp

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Re: Can't get a display output with my ZX Spetrum 128k+2 (Grey) model

Post by EranStockdale »

Brilliant, thank you! Do I just slot them into the DIN or should I solder them directly into where the DIN is soldered onto the board?
1024MAK wrote: Tue Dec 26, 2023 4:11 pm ZX Spectrum +2 grey DIN socket details on Fruitcake
Is that pinout drawn in such a way that when I'm looking at the DIN plug it matches up or is it horizontally flipped (as if I'm looking at the DIN plug from behind)? And will damage be caused if I somehow manage to connect the wires to the wrong pins?
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