Your Spectrum
Issue 2, March 1984 - Spectrolysis
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How do you get the best possible picture on your television from the Spectrum's video output or even more tricky, on a monitor? Ian Beardsmore completes the picture, and at the same time introduces a forum for readers to knock around ideas.
One of the idiosyncrasies of our beloved Spectrum, at least of the Issue 1 and 2 models, lies in the flexibility of the display. So far as the vast majority of Spectrum owners are concerned, their computer is not compatible with a monitor. Indeed, the machine will not even be compatible with some home televisions! Only the smug owners of Issue 3s are unaffected by these problems (although they may instead have trouble running some early software).
It's quite common to see Spectrum owners walking around Microfairs looking mystified at the sight of their computers doing the impossible: Spectrums on display being used with Toshiba televisions, and some even linked to the usually unusable Hitachi 14-inch colour portable. In the worst case of impossibility, a Spectrum may even be seen connected to a monitor. The more clued-up amongst us will be able to guess correctly that computers in this latter category have had the same modification as those Spectrums that entered schools under the 'Micros in Education' scheme. Fine for those in the know, but how about Joe User? "What the heck" you may think, "the Spectrum is a good enough bargain as it is". But if so, why the Issue 3?
Probably the most frustrating aspect of all this is that published solutions are not readily forthcoming even though the 'experts' seem to make the necessary modifications with consummate ease, thus leading to even greater feelings of alienation. But relief is at hand because, in point of fact, the necessary changes are actually quite straightforward, and certainly within the capabilities of any careful Spectrum owner. Of course there is a catch. Anyone taking the lid off their Spectrum will void the guarantee! So, what you decide to do at this point is up to you. But let us assume a reckless streak has suddenly
Circuit board
plunged into the otherwise calm breast of a dedicated user.
What would happen? How would our hero (or heroine) progress? First, of course, the top will have to be unscrewed, then lifted off. (This, in fact, is connected to the printed circuit board by two ribbon cables that are not long enough to allow the top to be kept completely clear of the rest of the computer. This just makes things more difficult, so take care.) Having thrown caution to the wind and voided the guarantee, the user in search of fine tuning must now locate two variable capacitors and two variable resistors. Not surprisingly (because we are dealing with the display) the area to search is around the modulator.

There are several components worth knowing about in our quest to re-tune the machine to a particular television. And also to be found in this general area is the 'VID' strap, something that will need dealing with if the computer
is to be used with a monitor. But more on that later because currently we are interested in the trimming capacitors, TC1 and TC2, and the variable resistors, VR1 and VR2. Working from top to bottom (see photo) this is what they do.

TC1 Controls the shimmer.
TC2 Tunes the colour in/out.
VR1 Adjusts the blue/yellow colours.
VR2 Adjusts the red/green colours.

First of all, beware ... when adjusting the trimming capacitors, it's best to use something non-metallic to adjust them with. A matchstick cut to shape is quite suitable. And, of course, added care should be taken anyway because all adjustments have to be made while the computer is turned on so that the results of 'tweaking' can be seen on the screen.
To begin with, adjust the screw in TC2 carefully in both directions until you find the point of strongest colour even if this is still too weak. That done, try bringing up the blue/yellow

end of the colour range by adjusting VR1. Once you've found the best colour here, bring in VR2 and tune in the red/green end of the colour spectrum. Essentially, what you need to do is balance those three components for the best picture. Again, the watchword is care and, as a precaution, it might be wise to take note of the pre-adjustment settings of the three variable components.
TC1 is the capacitor which controls the shimmer on the screen. Once the colour is as you want it, then this ought to be the final adjustment you make. One thing, however, is that sometimes shimmer can interfere with a viewer's perception of the other colours. It may be that further tiny adjustments of the first three will be needed, once changes have been made to TC1. Complete this juggling act and you should have your Spectrum finely tuned to a particular television.

So far so good for the person who is only interested in re-trimming the computer to another television. However, those thinking of greater things will first need to lash out on a monitor that accepts a composite video input, and then be prepared to do a simple soldering job.
Below the modulator, and just to the left of the gap between TC1 and TC2, there is a small white line marked 'VID'. At one end of this is a small solder point, and at the other, the hole of a through-the-board connection point. In fact, it's not quite as easy as it may seem to access this line because of the line of resistors that stretch out below the modulator.
'VID', in fact, marks a break in the video line between the modulator and the expansion port. Obviously, as there is a break in the line, the signal cannot reach the port; therefore, all you need to do is bridge this gap. How you accomplish this feat is up to you. The simplest (and nastiest) way is to stretch a blob of solder between the solder point and the hole. A short piece of wire is better, but for more ease a longer piece can be used. Whichever way, once done you will have a composite video signal available at the port.
Only two lines are involved at the port, the video line and the 0 volt line. These are placed next to each other, on the middle underside of the port. At the input end, where it enters the monitor, the video line goes to the central pin while the 0 volt line goes to the case. If you want you can adapt the UHF line supplied for use with a normal television. Otherwise, any electrical shop should have what's
needed. All that remains now is to decide how to take the video line from the port. The most flexible way would be to use a connector and motherboard. On the other hand, it's also possible to take the lines from another port for example, if you have the printer always connected, this could be used instead. However, be careful here because with some programs, if the printer is left connected, you get a screen dump. Those going as far as a monitor are, on balance, recommended to invest in a connector especially for it.

Despite this issue's content, don't run away with the idea that Spectrolysis has necessarily to be a hardware section. In fact, the intention really is to create a forum for information exchange about the Spectrum. Anyone with a particular problem (software or hardware) or those who have discovered some interesting application, or perhaps a routine without an obvious application, or maybe just the solution to someone else's problem whatever are all welcome to write in.
Just drop a line to me, Ian Beardsmore, c/o Your Spectrum, 14 Rathbone Place, London W1P IDE.
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