Zx Spectrum 128k Toaster RGB pinout

Beaps · August 2014

Hi all

When I use my +2 scart cable on my 128k the picture looks terrible, so I have bought the din plug to make my own.

Most sites from what I can see say the 128k & +2/3 all use the same cable, is that correct.

If not has anyone got a pinout I can follow for the 128k

Ta
B

balford · August 2014

In short, yes there are differences.

Here's a link to Paul Farrow's pages on the subject.

Consider it the bible :)

B

Beaps · August 2014

I have seen that but it's a little confusing :(

I am looking for a pic of the back of the din (parts to solder to) and the pin number on the back of the scart I need to solder to.

balford · August 2014

Afraid I can't be of much use in that case. I've only ever done a composite adapter (which has the advantage of working with both 128 and grey +2 models, at the expense of a little picture quality)

Others with more relevant experience should be along shortly though :)

B

jimre · August 2014

Hi!

If you would like to make an RGB cable for the Toastrack 128K Spectrum the circuit shown on Paul's site is best solution. As it is shown on the schematics the "CVBS" signal is connected through a 15 ohm resistor, the R, G, B signal should be connected through 150ohm resistors. As long as the brightness is not included on Toastrack in the R, G, B signal, it should be connected through diodes. (If you leave this out, the BRIGHT 1 colours will be the same as the BRIGHT 0 colours.) Of course the ground is connected to every ground connections of the SCART.
Function switching is not necessary in most cases. If it is present, the TV could detect it and switches on and selects the SCART input. I didn't use that, so I have to select manually the SCART input of the TV.
The interesting point is the "BLANKING" signal! That input should be at the appropriate voltage level to command the TV to switch to RGB mode. Otherwise the picture quality will be much worse, since it will use the composite signal (probably that was the case with your +2 cable) There were many discussions on the forum from where one should get the appropriate voltage. Paul suggested the safest method using an external 12V power supply. I personally use the +5V from the USB connector of my LCD TV through a series resistor.

Beaps · August 2014

I picked up a 75 ohm for the cvbs, how come you recommend 15 ohm out of interest?

Also the other link doesn't mention putting 150 on the RGB inputs?

jimre · August 2014

Look at the schematics at the bottom of the page (the last one):
http://www.fruitcake.plus.com/Sinclair/Spectrum128/SCARTCable/Spectrum128SCARTCable4.htm
That's what you need if you would like to have RGB output.

Beaps · August 2014

Right I think that is the end of my tinkering lol

Just spent 3h doing, re-doing this bloody scart cable only to find the image is exactly the same as when I tried the +2. The only difference is this new scart doesn't show anything on my plasma but when I try it on my BVM with scart input I get this.

(Ignore the thick black bar, it not there in person)

If I turn the brightness/contrast up I get a ret warning light on my BVM saying CRT overload (I think its because I am setting the brightness to high)

Any ideas folks?

Asure · August 2014

Beaps wrote: »

Right I think that is the end of my tinkering lol

Just spent 3h doing, re-doing this bloody scart cable only to find the image is exactly the same as when I tried the +2. The only difference is this new scart doesn't show anything on my plasma but when I try it on my BVM with scart input I get this.

(Ignore the thick black bar, it not there in person)

If I turn the brightness/contrast up I get a ret warning light on my BVM saying CRT overload (I think its because I am setting the brightness to high)

Any ideas folks?

You need voltage to have RGB on the scart cable.
Otherwise it will use the composite video signal you are feeding to it.

Pin 8 needs 12V DC to switch to AV mode, but can usually be skipped.
TV Won't switch to AV when you power on the Spectrum then.
Use remote control to switch to AV1 input :)

Pin 16 on the scart connector forces the rgb mode. Required, or pic will be same crappy quality as the +2 cable.

0-0.4V DC = Use composite video input, on pin 20
1-3V DC = Use R/G/B inputs

1024MAK · August 2014

Maybe, but my brain is rather tired at the moment :-x

Tell me what connections you made, that is how you wired up you lead.
Also do both the 128k+ "toast-rack" and the grey +2 work okay on composite or UHF?

Do you have a 1.5V, 3V or 9V battery?

And finally, do your TVs have SCART input selection via the remote control / on screen menu?

Mark

Beaps · August 2014

I am pretty scared when it comes to using voltages & scart :(

Can someone sell me a scart cable that will do the jobs please. :grin: or can I send this scart cable to you guys in the hope you can fix it (for a fee I understand)

On the Plasma I select the channel at the moment, on the BVM I just whack it in the scart socket

1024MAK · August 2014

Try wiring in a 1.5V AA size battery (using a holder, or for now just holding the wires on with small magnets/tape/your hands) as per this picture (remove any existing connection to pin 16):

Mark

1024MAK · August 2014

Beaps wrote: »

I am pretty scared when it comes to using voltages & scart :(

Can someone sell me a scart cable that will do the jobs please. :grin: or can I send this scart cable to you guys in the hope you can fix it (for a fee I understand)

On the Plasma I select the channel at the moment, on the BVM I just whack it in the scart socket

I don't have my own working toast-rack 128k+ to test it. I do have a grey +2 though.

Mark

Beaps · August 2014

So twist wires 8 & 16 together, is that what your saying? :confused:

1024MAK · August 2014

Beaps wrote: »

So twist wires 8 & 16 together, is that what your saying? :confused:

Err, NO!

There are two different control inputs on a RGB SCART socket. They do different things and use different voltages.

In the picture diagram I posted above, the diagram shows the symbol for a 1.5V AA size cell (battery). Connect the positive end (+) via a wire (shown in red on the diagram) to SCART plug pin 16 after you have removed and insulated any existing wire. Then connect the negative (-) end of the cell via a wire (shown grey on the diagram) to SCART plug pin 18.
Now try the modified SCART lead and report back.

Mark

Beaps · August 2014

Oh gotcha, I don't have a holder can I solder the wires directly to the battery or will it blow up lol

1024MAK · August 2014

Beaps wrote: »

Oh gotcha, I don't have a holder can I solder the wires directly to the battery or will it blow up lol

If you have a suitable soldering iron (read high power) and are very quick maybe, but I don't recommend it.
If you have two small magnets, sometimes these can be used. Or use sticky or insulation tape.

Mark

Beaps · August 2014

Ok hooked up the battery and not much difference if I'm honest

1024MAK · August 2014

Next, I need to understand how the lead is actually wired.
Can you please post pictures showing the SCART plug end showing the wiring from at least two angles. Also do the same for the Spectrum DIN plug end.

If you made up the lead, can you list the resistor values that you used please.

Mark

Beaps · August 2014

I gave up mate, bought one off eBay. Although I will check it with my one to see where I went wrong.

Zx Spectrum 128k Toaster RGB pinout

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