Narrow-Bandwidth Television Association

Harry, I tend to forget people have junk-boxes full of stuff, so it does make sense to use what one has instead of buying.

The second stage varies a bit with a change from BC109Cs to either BC108s or BC107s, it's mainly in the biasing but it should still work OK, the AC (signal) gain is virtually unaffected. See below, Red=109Cs, Green=108s, Blue=107s.

Try turning to pot to minimum gain (maximum resistance) first and slowly wind it up...

A battery is a clead supply, true, but even 15cm of wire from it to circuit = inductance, significant at times. It also has internal resistance. Decouple/bypass my man!

Steve A.

Steve Anderson wrote:Harry, I tend to forget people have junk-boxes full of stuff, so it does make sense to use what one has instead of buying.

Yes i scrap stuff all the time ,i tend to just buy solder PCBs ic's never buy resistors or capacitors or wire ,i don't think i could do the hobby with the price of a project if i had to buy every part every time.

The second stage varies a bit with a change from BC109Cs to either BC108s or BC107s, it's mainly in the biasing but it should still work OK, the AC (signal) gain is virtually unaffected. See below, Red=109Cs, Green=108s, Blue=107s.

Oh thats good it still should work i can tell from the stages that do work in my own low tech way the tranys should of been ok but better hearing it from you !

Try turning to pot to minimum gain (maximum resistance) first and slowly wind it up...

I'll give that a go might have time tomorrow to have another look at it .

A battery is a clead supply, true, but even 15cm of wire from it to circuit = inductance, significant at times. It also has internal resistance. Decouple/bypass my man!

Steve A.

OH that could be why the first solar cell didn't work the length of the cells wires are long i forgot about that
one of the wires end insulation was off a bit had a bit of length and when i folded it over by mistake and touch the same connection it was soldered to, the circuit it seemed to work must of been just the right inductance to get the thing to work but it didn't click till now me dumb dumb.
I will add those caps that will teach me for being lazy.

i looked at it again today had made no mistakes so i had a look to see if i could make all the stages work.

I found the 1 meg resistor between the base and collector of trany 3 seems to do nothing changing the value also did little.

I found with my resistor wheel connecting trany 2 and 3s collectors the gain increases as the resistance is lowered but you are just bypassing the transistor 3 right to trany 4s base ,you could put a pot in here but the pot on trany 3s emitter does still control the gain it might be better with a higher value trimmer pot you have a lot of control with the 2.5k i had been using but 0 to full gain you need a higher value variable resistor perhaps 10k as perhaps 10 k no gain 0 full gain .

Still Trany 3 seems to me a bit pointless as it is as i could remove it and still have a gain control.

The original circuit at the out put of transistor 3 the sound level just drops some thing like a quarter of whats coming out of transistor 2 ,i know transistor 4s stage works again no3 there must be a mistake in this stage .

May be this might be a better idea ? the circuit reminds me a bit of the old 70s tandy electronics ampifier kits.

Tried a a few different ways to hook up a gain control to the last transistor this final version of this go seems best .

I am not sure with the amount of light i will get how much gain a head amp for a reflecting mirror camera would need ,i was a bit worried with the other one i have as it does have more gain than this one but it might be to much .
This one seems more well behaved at different light levels.

So may as well try this one see how it gos .

Back to the main camera i am thinking i will need a mask a thin slit so the light line from the polygon isn't to thick this is if i stay using a solar cell or i will need another lens .

A light sensitive trany i am thinking is a much easier solution and has been done before i will see what i have handy .

I have this photo transistor the MEL12 i must of had this many years.
Its a Darlington or Super-alpha pair of photo- transistors. It is typically ten times more sensitive than a normal photo-transistor.
Well it was way back when.

I am not sure yet what its sensitive to i hope its bandwidth to colour is wide .

I have been playing around with Leds as a light sensitive device and they are not to bad, the colour ones of cause are sensitive to its colour white light clear types have the range you want for a B/w camera ...

I would love to do it one day as i have never played with colour but the leds that do more than one colour and have their own output could be very useful for a colour camera idea.

The problem with Darlingtons is 1) a lack of speed, but for NBTV it should be OK, 2) saturation voltage is somewhat higher at 1.2-1.8V, but that also can be negated. 3). They can also be noisy. It IS worth trying though.

Steve A.

Steve Anderson wrote:The problem with Darlingtons is 1) a lack of speed, but for NBTV it should be OK, 2) saturation voltage is somewhat higher at 1.2-1.8V, but that also can be negated. 3). They can also be noisy. It IS worth trying though.

Steve A.

Yes i was thinking just because its more sensitive might not mean its appropriate ,i will give it a go if i get the thing going i will test a few ideas just to know what works best .

So i am going to connect this to the front end of the just made head amp so i going to do a james bond Never say never and change the front of it for this

I feel reviewing old newsletters of past experiments mainly by Alan short that the photo transistor or something of that size is the way to go on a mirror camera the solar cell is a little large for this without adding a lens or mask as that thinking about it more sort of defeats the purpose.

I now have the Mel 12 photo transistor in the head amp circuit .

Now either of the gain controls work the 10k pot on the photo trany seems to give better low to high level control so the pot and 1k resistors on trany 3 could be just removed also full gain if need be the 10 k pot on the mel 12 could be removed and just use the 2.2k resistor and have full gain all the time ,i will just see how it gos i know its best to have as few pots as needed .

I will work out now how to mount it for testing .

Started to see if i can put it all together ,the placement of the head amp i will have to experiment with .

I expect there might be noise from the motor suppose i will see when the relay and motor are working if it causes noise in the head amp .

Back onto the electronics side whats left is to connect the sync and head amp video up to the video sync mixer rest depends on promising results out put plugs battery operation and such a big fingers crossed

I started today finishing off hooking up the head amp and and sync up to the mixer i ended up trying pin 7 of the monostable which i think is correct .
Inputting this to the lap tops audio input well this latest one ,i had forgotten to set the audio mic settings to 16 bit 44100 and cd 2 channel quality this let me use the lap tops sound input as line input.
https://www.youtube.com/watch?v=c7i6LJs3b6E

i keep forgetting to check this but its working now .

Before i did the adjustment the record level is a bit high ,i recorded the sync out of the monostable in the file below this was a quick one ,The clock is very supply voltage sensitive very like a 555 Astable if i have any success with this i will change the 4060 to crystal version.

Now i checked to see best case scenario with a nbtv wav from my iphone (a working replacement for a camera)to lap top to check the now line input settings as i need to know all this works or i will have no hope with this camera idea ,tried garys Big picture and i had trouble i ended up checking with Garys nbtv viewer the tiny one as it has a video invert and it worked then so i think this lap top inverts the sound as i didn't have that problem on the last computer so least i know NBTV viewer is the way to go to check camera testing with.

Harry TBP has an invert audio feature as well (under settings/soundcard).

TBP also has a scope function so you can actually see the audio and therefore determine whether levels etc. are ok.

TBP also has the advantage of allowing you to turn off sync processing which is often the main cause of picture breakup.

Harry I have had a good look at your wave file - I don't know how you can say it is inverted as it is more or less symmetrical around zero - in other words you have a positive going pulse and a negative going pulse - either one could be the sync pulse.

Here are videos taken by TBP V2 alpha - one with sync processing (this gives a good indication of how close to speed to are, and the other with sync - these videos are exactly what I would expect your picture to look like.

gary wrote:Harry TBP has an invert audio feature as well (under settings/soundcard).

TBP also has a scope function so you can actually see the audio and therefore determine whether levels etc. are ok.

TBP also has the advantage of allowing you to turn off sync processing which is often the main cause of picture breakup.

Oh i will have a look at that invert i didn't see it boy i need my glasses !

I do use your scope a bit but i forgot at first i needed to change this laptops sound card settings as it has line input but i needed to change some settings

I will use it again tonight i haven't had time today to try any thing else . Still i like the little nbtv viewer its good .

gary wrote:Harry I have had a good look at your wave file - I don't know how you can say it is inverted as it is more or less symmetrical around zero - in other words you have a positive going pulse and a negative going pulse - either one could be the sync pulse.

Well i wasn't to sure which to use out of that monostable the one out of pin 7 looked correct ,didn't know it didn't matter .
My other go at a video sync mixer had a sync level control this one doesn't it seems a bit loud to me when mixing it i might stick a pot trimmer in.

Here are videos taken by TBP V2 alpha - one with sync processing (this gives a good indication of how close to speed to are, and the other with sync - these videos are exactly what I would expect your picture to look like.

When i did that quick sync recording i hooked up all my circuits and forgot i have a voltage adjustment on the motor apart from that frequency adjustment on the 4060 it did need tweaking /
thanks for the work there on there on the sync thats interesting before i tweaked the motor supply voltage it was close but i could see a slight shake to the sync back and forth i was thinking with video it might look a bit like that ,the sync is spaced the same much better than my encoder cut out .
That good to see your work on the syc to see what its going to be like .
Thanks gary

Today was a step forward step back bit of a waste ..i converted the 4060 to a crystal operation with the circuit below but i lost my 12 hz clock due to the crystal used .
So just remade the old circuit i'll put up with a little inaccuracy

I ended up buying a few CA3140 ics to replace the what i have been using i more than likely just need one but good to check.

I will get back to it tomorrow