NBTV Camera version 2

[Harry Dalek]

Having played around a bit with the flying spot type i am going to try the other harder type lens nipkow right to sensor .

I am reusing my test bed camera ...looks a little different now another redesign to house the encoder circuit and the sync and video mixer circuit a nice little metal flat case for them which sits right under the camera screwed on and then tripod.

Reading a past newsletter i forgot to write the number down its by Pedro a circuit redesign head amp...called daylight viewing camera preamp.

Pedro made a day light only needed viewing camera with cd about 12 years ago i think ..i have just made the preamp in a old tv video to RF modulator metal case and works so i will give that a go.

My only change to Pedros circuit is i am using a small solar cell instead of the dome sensor to do away with the optics as it will be very close to the nipkow and see all the scan where as a dome sensor or Light Dependent Resistor would need a lens to focus the scan area to the smaller size if that sensor .

I will take some pictures when i have some more time tomorrow .

[Harry Dalek]

Took a few pictures today looks a bit different been working out mounting the head amp.

[Harry Dalek]

Peros circuit i am using has some faults which has been pointed out in the other camera topic .

The circuit works but looking closer not well as it could .

I have been doing some testing the feed back resistors 2.2meg do not seem to be doing much at all...think i will scrap them.

Feed back works seems to work well via the second transistor collector to either its base or back to the first transistor..my resistor wheel only gos to 1 meg and that seems best back to the first trany so far .

The circuit is pretty fussy for the working voltage very different to the other head amps i have made just a touch over 5 volts it works best ,theres a drop off below and same above like a volt or 2 above nothing ..i am thinking its that 100k pot on the last trany causing that .

I have taken in your advice Steve and Klass so i will change a few things on it...looks like from a quick play it can be improved .

I should of just made the club suggestion circuit that will teach me for being inquisitive

[Harry Dalek]

Today had a go at the original circuit i was planing on using when i started the flying spot camera .

Making the last pedro head amp i wanted to see the difference between these two .

After many hours today partly working on it i finished it .

2 aims to make it small as + make it with the transistors i had handy .

I also liked that has been tested enough to be on the web site .

Now the transistors i used are

BC109....now BC458
BC 212.........BC558
2N3704........2N3904

I didn't have to change any of the resistors seems to work as is.

But am using the little solar cell again instead of the dome sensor

Differences between this and the last 3 head amps all the last were either 3 or 4 transistor BC108s ..this one seems better than my last best and lower noise...

[Steve Anderson]

Well, I guess I have to eat my own words as Perdo's design obviously does work but without building it I'm mystified as to how.

Harry, your transistor substitutions are fine.

Steve A.

Hang on a sec Harry, I'm confused as to which one you've actually built. Was it the one in the post above? (kit31_409.gif). Or the previous circuit (Screen 00005.jpg)?

[Harry Dalek]

Well, I guess I have to eat my own words as Perdo's design obviously does work but without building it I'm mystified as to how.

Harry, your transistor substitutions are fine.

Steve A.

Hang on a sec Harry, I'm confused as to which one you've actually built. Was it the one in the post above? (kit31_409.gif). Or the previous circuit (Screen 00005.jpg)?

Hi Steve

Glad i got the transistors right ! seemed the best i had handy to replace most that i didn't have .
i made both in fact i have 4 working ones ..i made pedros and the club circuit steve those are the last 2 i made .
Yes Pedros works its sensitive but the amplifying part not as good ,i found doing what some of the other had done i have seen in the newsletters using feed back from the collector to the base got it to work better ..still now having made this club version its best of the lot so i will work with this one .

I like making them reminds me of making radios and such way back when pulling low signals out of the void.

The Club circuit from the beginners camera section was the one i made yesterday ...seems to have the highest gain out of every thing i have made so far so looks to be worth a shot at using it to try the other type of camera.

[Steve Anderson]

I think it's only fair we conclude discussion on Pedro's circuit as he isn't a member here and has no way to defend his offering. But I will stick with what I have already said on the matter and go no further.

Steve A.