TV pattern generator, diy

[djrm]

I just received this TV pattern generator from ebay today. I think it may have been a kit or have been re-boxed at some point.

It kind of works a bit though the signal seems to be modulated with some mains hum, not surprising considering the age which was stated as 60's in the listing but it is probably a bit more recent. 

The whole thing is powered by a 9 volt mains supply with a derived 5 volt supply to the 74 series TTL logic. There is a TBA990Q device which a web lookup tells me is a colour demodulator, so perhaps this is being re-purposed somehow. Loads of presets to twiddle and a sub board for good measure. Output is from a UHF modulator with a variable capacitor to tune the channel. Switches on the front have labels R-Y off, B-Y off, Lum off, BARS

I'd be interested to hear if anybody has seen anything like it before. I'm going to have to remove the circuit boards to see if there is anything written on the reverse side, the front is completely bare.

Kind regards, David.

   

[Refugee]

It looks like it has been built from a magazine article.
I built an audio sweep generator once and it never worked with the faster opamps until I visited it many years later to sort out the power supply arrangement.
Have a look at the date codes on the parts and see if you can narrow the date down a bit and have a look at some TV mag back numbers.

[djrm]

Good tip to look at the date codes, thanks. The latest chip has date code '76 others range from '73 to '75.
Funny you mention a power supply problem, when I tried to remove the main smoothing cap I found the veroboard strip cracked and it looed like the cap had never been joined.
I've corrected it and the hum bar has all but vanished, power supply should be 12V regulated by zener - its still a bit low. I'll scope it and see when I take it to the workshop.

Underneath is says 'Colour Test Gen. CMN6 cManor Supplies 1976'
A big transistor dropped out as I removed the board from the case, it looks like the second regulator 5.6 zener feding an emitter follower perhaps.
It was working, colour bars and crosshatch.

Board connections are labled:
12v
5V
(gnd)
ld
fd
mb
(gnd)
out
in

The second, smaller board says 'Random Interlace S.P.G. CMN 4' The output from is the only signal feeding the UHF modulator.
This board has been hacked around a bit some connections have been rremoved.

Havn't seen anything from Manor for a while now, they used to advertize in magazines.

Major component counts:
2x 555
4x7400
1x7493
1xTBA990Q
14 transistors
12 pots!

David.

[ppppenguin]

Manor supplies is long gone. I remember them well. Not too far from me. I did a school holiday job there c1970. Discovered all sorts of dubious things they got up to.

[Alistair D]

I used to subscribe to Television magazine around 1976. I don't remember any articles about a Manor supplies pattern generator but that was 42 years ago and my what do you call it ... memory... is not as good as it once was. I think. Thank goodness for sites like American Radio History.

https://www.americanradiohistory.com/Pra...gazine.htm

If nothing else you might find an advert for it.

Al

[Amrad]

A friend of mine bought a Manor Supplies Pattern Generator kit and found when it was built, that the colour bars were in reverse order to normal! It could also provide R-Y and B-Y signals.

Regards,

Dave.

[djrm]

Hi Dave,
Do you mean like this ;-)
I was thinking it loked a bit odd, the line tear doesnt help either, it is very hard to tune accurateley.
I have seen a better picture but not photgraphed it, honest.
   

[Refugee]

Did you say earlier that it uses a de-modulator working backwards?
It might make sense of what we see on that flat screen set.

[Gryphon]

The TBA will have been there for its balanced modulators, which will encode as cheerfully as they will decode.  Probably cheaper (and possibly requiring a lower component count) than two MC1496s.

At a rough guess, the 7493 is the colour bars generator.  This is a ripple-counter, but it seems to be only capable of counting up, which would account for the reversed order of the colour bars.  Knowing how Manor Supplies used to work, they'll probably have bought a few thousand of them for coppers each at a disposal sale, and cast around for something they could use them in that would sell.  What is slightly surprising is that, having put some 7400s in the design, they didn't put another one in with the gates strapped as NOTs.

Some of their designs were... I think the polite word is probably "idiosyncratic", at best.  In their defence, however, I ought to point out that their test gear largely did what it was intended to, and was targeted at a market for whom "official" kit would be prohibitively expensive.  I wonder what the cost of, say, the Labgear colour bars generator was in 1976?

(One of their later colour bars generators was actually designed by a former colleague.  That one used a Ferranti SPG chip, and an Astec modulator, so you got proper syncs, and tone as well, I believe.  The subcarrier oscillator free-ran, so not math PAL, unfortunately).

[Amrad]

Hi Dave,
Do you mean like this ;-)
I was thinking it loked a bit odd, the line tear doesnt help either, it is very hard to tune accurateley.
I have seen a better picture but not photgraphed it, honest.

Yes, that's it! But you have an odd looking bar to the right of the yellow bar, It ought to be white and there should be a black bar to the left of the blue bar. In the normal sequence, the white bar would be on the left and the black on the right I can't remember if the one my friend bought had the black and white bars, though I can see no reason why it wouldn't. I will have to find out.

Regards,

Dave.