NBTV Scope Evolution

Forum for discussion of electronic television. Generally, stuff to do with CRTs and not using mechanical displays.

Re: NBTV Scope Evolution

Postby Harry Dalek » Mon Jul 20, 2015 11:53 pm

M3DVQ wrote:I have the Radioshack/Tandy Science Fair 75 in 1 where you (attempted to) trap wires in little springs, though that wasn't my first electronics set. Got that a few years later for very little in an auction.
Before that I had an "Electrics" set where you trapped wires under brass split pins stuffed through a board full of holes to connect bulbs and switches etc. then graduated onto "Electronics" with a set containing an amplifier of some sort where the wires fitted to several small pieces of solderless breadboard, just 1x6 or 5x6 etc. Lots of projects that made screechy howling noises in that one :D


The Thing that really got me started was at school making a relay from a bolt copper wire and a metal stip cut from a tin can and wire it up so the strip of tin would buzz away on the bolt as the electro magnet the bent tin strip to a nail the on switch it would turn on and off ..spring electro magnet idea ....lucky i didn't know at the time if i hooked it up to a transformer what it could do as i repeated the project at home . :shock:

The springs on those old kits were a good idea but the 75 science fair ones were a little tricky unique ...Wonder if Tandy is still going i think they shut the last stores here in Australia a few years ago like our dick smith they went from hobby electronics to consumer electronics very sad ...We just have one store Jaycar for parts now . :oops:

65 in one projects type thing with the easier springs for wiring that came after for me as i had to buy the thing my self so that cost more ..yes nice noise making circuits .i still have the schematic book,i got one similar for my boys if they get into it still a little young for this yet .
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il_570xN.465248876_qx68.jpg
this looks like my old one
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Re: NBTV Scope Evolution

Postby Steve Anderson » Tue Jul 21, 2015 2:31 pm

I had two electronics 'projects' (can't think of a better name) made by Philips. One was a reflex AM radio, complete with plastic case and looked quite good considering it was the 60s. But that was all it was, a radio and nothing else. I built it, tore it apart and rebuilt it many times.

The other was similar to those above but the components weren't in fixed positions. A breadbord type of arrangement was used with a split-pin pushed through from underside then a spring slid over formed the connection method. It was quite effective. Whatever happened to it - no idea.

Considering the lengths of wires used in these things it's a wonder they were stable and worked!

Suppliers in Melbourne - I remember McGraths (spelling?) in I think Little Bourke Street, an absolute haven! If you wanted to build/copy a project from 'Electronics Australia' magazine they always had the parts in stock, even the sometimes specially made custom ones. I think they must have had a deal with the publishers. But those were the days when I could drive up Swanston Street on my way to the RMIT - those were the days...

Steve A.

Amazingly I found some pictures of the Philips 'Electronics Engineer' kit thing on the 'net...such memories! Note the individually boxed transistors and diode in the inside view centre-top, all three of 'em. I think the were 1xAF116 and 1xAC126 as I recall, both PNP Germanium, the diode I can't remember what it was.
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Re: NBTV Scope Evolution

Postby Harry Dalek » Tue Jul 21, 2015 6:52 pm

Steve Anderson wrote:I had two electronics 'projects' (can't think of a better name) made by Philips. One was a reflex AM radio, complete with plastic case and looked quite good considering it was the 60s. But that was all it was, a radio and nothing else. I built it, tore it apart and rebuilt it many times.

The other was similar to those above but the components weren't in fixed positions. A breadbord type of arrangement was used with a split-pin pushed through from underside then a spring slid over formed the connection method. It was quite effective. Whatever happened to it - no idea.

Considering the lengths of wires used in these things it's a wonder they were stable and worked!

Suppliers in Melbourne - I remember McGraths (spelling?) in I think Little Bourke Street, an absolute haven! If you wanted to build/copy a project from 'Electronics Australia' magazine they always had the parts in stock, even the sometimes specially made custom ones. I think they must have had a deal with the publishers. But those were the days when I could drive up Swanston Street on my way to the RMIT - those were the days...

Steve A.

Amazingly I found some pictures of the Philips 'Electronics Engineer' kit thing on the 'net...such memories! Note the individually boxed transistors and diode in the inside view centre-top, all three of 'em. I think the were 1xAF116 and 1xAC126 as I recall, both PNP Germanium, the diode I can't remember what it was.


The philips kit is new to me ,the spring idea is similar but not how you have to make it ,end result looks like the science fair radio shake ones .

I think you got the right kit as it really did turn you into kits name ! :P

Lot of fun those things and you just reuse the parts some thing never changes recycle i say .in those days those soild state parts would have been expensive sounded like you only got 3 ! 1970s i got 7 :wink:

I have never heard of McGrath Electronics but doing a google theres one in ireland but saw a forum they talk about the store mainly sydney but some melbourne replies
http://www.electronicspoint.com/threads ... ne.135600/

It sounded like the store to go to , nothing like wanting to make a project and the place does have every thing unheard of !

Times have changed and least we have online stores for parts as they are sure becoming rare to walk into !
The electromagnetic spectrum has no theoretical limit at either end. If all the mass/energy in the Universe is considered a 'limit', then that would be the only real theoretical limit to the maximum frequency attainable.
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Re: NBTV Scope Evolution

Postby Steve Anderson » Wed Jul 22, 2015 8:34 pm

Harry Dalek wrote:Times have changed and least we have online stores for parts as they are sure becoming rare to walk into !

1970s, no Internet, no mobile phones, no PCs or laptops, rotary-dial telephones, international calls cost a fortune and TV was monochrome (well, until 1975 in Oz). Not even a fax machine except for those with bucket-loads of money. Printers were ribbon and a security guard watched over the photocopier. Programs were run on the Uni's mainframe using punched cards and you waited a day or two to get the (usually) failed output. I was never any good at Fortran or Cobal.

Trams in Melbourne ran almost all the time with the doors open (no air-con), cars had no anti-pollution plumbing (and also no air-con) and petrol had added lead.

Kevin Dennis's New Faces was a TV program that was so chronically bad it was good. The live ads were usually a hoot with things going wrong 90% of the time. The weather girl had no idea where Alice Springs was.

Fond memories!

Steve A.
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Re: NBTV Scope Evolution

Postby Harry Dalek » Wed Jul 22, 2015 9:41 pm

Nothing like the 70s any more Steve those were interesting times ,watching colour tv for the first time took a while for the eyes to get use to that .

We were renting B/w tv at the time colour tv came to Australia and i recall asking my dad when we were going to get a colour tv and the answer was when the B/w set broke ....Well by then i knew what Transformers were and how they worked ..lets just say a screw driver brakes copper windings rather well and replacing the wax over the area none were ever the wiser ! and Yes i got to see colour tv that week ....

Bit of fun here in my photo on the jeremy circuit almost done one 555 to go ,getting a bit harder on the strip board have to pay attention whats connected where in 2 direstions easy to get caught out shorting something together that shouldn't .

Hope to finish it off tomorrow .
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Re: NBTV Scope Evolution

Postby Steve Anderson » Thu Jul 23, 2015 4:51 pm

I know we've drifted a bit off-topic, but I recall many an article or letter in 'Electronics Australia' regarding the introduction of colour. For about a year, perhaps 18 months prior to the big 'Switch-On' almost everything was transmitted in colour but the colour burst was suppressed so the colour TV at home thought it was a B/W transmission and displayed it as such - but the colour information was actually there.

Many an article or letter was written about how to locally reinsert the burst to recover the colour information. But of course it was fruitless. You simply need the TV stations reference which in this context is the colour burst, without it you're sunk.

As a footnote, for about a month in the run-up to the 'Colour Switch-On' the TV stations switched on the burst, then off a little later. Funny thing is this only seemed to happen during commercial breaks and not the main program! Sneaky.

Steve A.
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Re: NBTV Scope Evolution

Postby Steve Anderson » Thu Jul 23, 2015 7:24 pm

Harry Dalek wrote:..getting a bit harder on the strip board have to pay attention whats connected where in 2 directions easy to get caught out shorting something together that shouldn't. Hope to finish it off tomorrow .

If you're used to everything being isolated from the start, yes, I can understand that situation. I take the opposite sort of approach, that everything is connected together until I choose it not to be so. But if stripboard doesn't 'fit', don't use it. Each to their own - again. There's nothing wrong with any system of construction as long as the final outcome is the fact it works - and hopefully it's repeatable by others.

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Re: NBTV Scope Evolution

Postby Harry Dalek » Thu Jul 23, 2015 9:22 pm

No worries Steve ...i could very well have that issue of electronics Australia in my collection, its a bit scattered for the 70s so never know, would be 1975 one of the issues i suppose ,i missed the start of colour so didn't know about these tests very frustrating seeing the indents in B/w for colour tv ! :roll:

I recall seeing a colour tv in the 60s in a store window up in wollongong of all places must of been NTSC model ...they did do tests in the 60s closed circuit stuff like this
https://www.youtube.com/watch?v=NjiAprY1JuU

ON the project i am almost done 3 1k resistors to go .

Testing the frame sawtooth this works the line on the slope of the waveform looks a little jagged not sure why i will double check on the shed scopes,if the line saw tooth works i can see what i have got right and hope not to much wrong .
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The electromagnetic spectrum has no theoretical limit at either end. If all the mass/energy in the Universe is considered a 'limit', then that would be the only real theoretical limit to the maximum frequency attainable.
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Re: NBTV Scope Evolution

Postby Steve Anderson » Thu Jul 23, 2015 11:25 pm

Hmm, that is odd that jagged slope, it should be a nice straight sloping line. I suggest you check the 12V supply for ripple, it really does need to be properly smoothed and preferably regulated. The 'scope trace indicates that the jaggedness is at about 10ms intervals, i.e. 100Hz supply ripple.

I'm not sure where you're measuring that waveform but if it's at the output of the final op-amp that then feeds the two 1k mixing resistors which then go to to 'Frame Scan Output' connector, try slapping a 100uF or similar cap from the +ve input of that op-amp to ground (across the lower 22k resistor). But check the supply for ripple first! As little as 100mV of ripple could cause this effect. Eliminate the problem first rather than trying to cover it up...and I mean that in the nicest possible way.

This is true of all supplies, using a 78xx/79xx regulator will reduce ripple by around a factor of 1000, 1V of ripple in from the smoothing capacitor in the raw supply will (should) result in 1mV of ripple out. Almost immeasurable amongst all the other rubbish on most supply lines. Supply lines are the road gutters of the electronics world, all sorts of junk ends up in them. Also true of Grounds, Earths and 0V - whatever you wish to call them. This is particularly true of the standard bipolar 555, this device has a nasty habit of drawing some 300mA as the output switches, it's only for a handful of nanoseconds, but it can sure upset other connected logic devices. The CMOS versions are better, but caution still needs to be exercised.

Note below how I decouple/bypass the 78/78 series to keep them stable and provide a low-Z supply. Ignore the currents, it's something I'm working on right now and they're just estimates anyway.

Steve A.
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Re: NBTV Scope Evolution

Postby Harry Dalek » Fri Jul 24, 2015 3:07 pm

HI steve been side tracked to day fixing my trailer brake lights .hate car electrics .

Steve Anderson wrote:Hmm, that is odd that jagged slope, it should be a nice straight sloping line. I suggest you check the 12V supply for ripple, it really does need to be properly smoothed and preferably regulated. The 'scope trace indicates that the jaggedness is at about 10ms intervals, i.e. 100Hz supply ripple.


Yes it is i have never seen this effect on a saw tooth i will double check the wiring ,it could be i have not finished it off with that 1 k resistor on the output of last opamp where its mixed with the PWM from the other 1k resistor ....still i would think that would no matter .

I'm not sure where you're measuring that waveform but if it's at the output of the final op-amp that then feeds the two 1k mixing resistors which then go to to 'Frame Scan Output' connector, try slapping a 100uF or similar cap from the +ve input of that op-amp to ground (across the lower 22k resistor). But check the supply for ripple first! As little as 100mV of ripple could cause this effect. Eliminate the problem first rather than trying to cover it up...and I mean that in the nicest possible way.


PIn 8 of the 348 i have used the right side opamps for the frame sawtooth ,i will try that capacitor across the opamps supply easy fix if so .

Well i used the same power pack on the original circuit and that sawtooth slope was fine still this is a different circuit different problems i suppose .


This is true of all supplies, using a 78xx/79xx regulator will reduce ripple by around a factor of 1000, 1V of ripple in from the smoothing capacitor in the raw supply will (should) result in 1mV of ripple out. Almost immeasurable amongst all the other rubbish on most supply lines. Supply lines are the road gutters of the electronics world, all sorts of junk ends up in them. Also true of Grounds, Earths and 0V - whatever you wish to call them. This is particularly true of the standard bipolar 555, this device has a nasty habit of drawing some 300mA as the output switches, it's only for a handful of nanoseconds, but it can sure upset other connected logic devices. The CMOS versions are better, but caution still needs to be exercised.


So you think it might be the timer its self to blame sounds like another one of its other quirks...... BTW is there a ic timer like this that has replaced the 555 ?

But i will look into testing it with other supply which i know uses the 7812 .

Note below how I decouple/bypass the 78/78 series to keep them stable and provide a low-Z supply. Ignore the currents, it's something I'm working on right now and they're just estimates anyway.

Steve A.


I will put in some decoupling capacitors that might be the way to go if my problem is noise ...
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348 opamp
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Re: NBTV Scope Evolution

Postby Steve Anderson » Fri Jul 24, 2015 3:55 pm

There hasn't really been a replacement as such for the 555/556, they're still made by the millions each year but I suspect the CMOS versions form the majority of them. (Lower current consumption and without that nasty supply glitch - or at least much much less). Signetics developed the original 555 around 1971, it's now over 40 years old, not many devices have a lifespan as long. Signetics was eventually bought up by Philips in 1975.

Signetics introduced the worlds first and only WOM (Write Only Memory), the 25120 in 1972, I don't know if it was launched on April 1st. (pdf attached).

Your best bet is to actually have a look for noise/ripple on the supply with a 'scope. It should be a nice straight line at +12V. AC-couple the input and wind up the gain to 100mV/div, in a perfect world it should still be a nice straight line. But chances are you'll see all sorts of rubbish there.

Steve A.
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Re: NBTV Scope Evolution

Postby Harry Dalek » Sat Jul 25, 2015 9:29 pm

Steve Anderson wrote:There hasn't really been a replacement as such for the 555/556, they're still made by the millions each year but I suspect the CMOS versions form the majority of them. (Lower current consumption and without that nasty supply glitch - or at least much much less). Signetics developed the original 555 around 1971, it's now over 40 years old, not many devices have a lifespan as long. Signetics was eventually bought up by Philips in 1975.

Signetics introduced the worlds first and only WOM (Write Only Memory), the 25120 in 1972, I don't know if it was launched on April 1st. (pdf attached).

Your best bet is to actually have a look for noise/ripple on the supply with a 'scope. It should be a nice straight line at +12V. AC-couple the input and wind up the gain to 100mV/div, in a perfect world it should still be a nice straight line. But chances are you'll see all sorts of rubbish there.

Steve A.


Thats surprising to me ! a while back i got a few free surface mount 3 pin timer i think it only needs a resistor and cap to work being surface mount i of cause have misplaced it ! i think they were saying it was better than the 555 if i come across the packet i can google the part again at least ...

The 555 has its flaws i am fond of it and the 741 op amp have been around a long time ,it is good btw they still make parts as large as they do or the hobby would be very different i don't think many of us have watch maker eyes for surface mount parts .

I have finished the circuit but i have some problems with the circuit as is.......

As is the line circuit does not make a saw tooth with the parts in the schematic its a square wave still ,the hight control i get a bit of amplitude adjustment but i think its still needs different value trimmer

I tried to get a sawtooth by changing the .022 to a 10 uf Titanium (sorry about the blury photo) the sawtooth has a bit of a curve to the sawtooths line slope ...

I mention in the photos what is what .

I am wondering if the line circuit should be a square wave or sawtooth i am confused i would think sawtooth ....using a bc559 after the line 555 the trimmer is around 600k can't think of any thing else is different to the schematic /
Attachments
IMG_1480.JPG
took this picture...... circuit is as in the schematic, but i did short the 10k after the diode from the line 555 out to get a larger amplitude pulse when trying for the sawtooth in the next picture
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IMG_1479.JPG
Ok heres the sawtooth i got placing a 10uf cap over the .022 amplitude of the waveform is helped by shorting that 10k resistor i mentioned in the last picture
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IMG_1473.JPG
THis was a mistake i made i connected the positve input of the line opamp to the positive rail instead of ground,this was infact the first result i saw when i finished the circuit and go me looking for mistakes
IMG_1473.JPG (95.57 KiB) Viewed 17251 times
The electromagnetic spectrum has no theoretical limit at either end. If all the mass/energy in the Universe is considered a 'limit', then that would be the only real theoretical limit to the maximum frequency attainable.
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Re: NBTV Scope Evolution

Postby Harry Dalek » Sat Aug 08, 2015 3:06 pm

Back from hoildays and spent some time this morning looking into the line sawtooth problem ....it was my mistake again i had a strip board track with the positive rail connected to the collector of the line PNP trany once i removed this problem the circuit is as in jeremys schematic ,i had the sawtooth as with the parts in the circuit.

I had already replaced the 10k fixed resistor with a 10k trimmer at the base of the PNP line trany thats the blue trimmer top right hand side as it helped before i fixed my mistake any case i can see the reason for a 10k resistor any thing lower the line square wave pulse shows up between the sawtooth.

BTW was testing it free running ...

I'll next hook it up to the scope and see what happens .
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The electromagnetic spectrum has no theoretical limit at either end. If all the mass/energy in the Universe is considered a 'limit', then that would be the only real theoretical limit to the maximum frequency attainable.
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Re: NBTV Scope Evolution

Postby Steve Anderson » Sat Aug 08, 2015 7:56 pm

Harry Dalek wrote:Back from holidays....it was my mistake again.

It's amazing what a fresh clear mind can unravel that which seemed impossible the day before.

Steve A,
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Re: NBTV Scope Evolution

Postby Harry Dalek » Sat Aug 08, 2015 9:24 pm

Steve Anderson wrote:
Harry Dalek wrote:Back from holidays....it was my mistake again.

It's amazing what a fresh clear mind can unravel that which seemed impossible the day before.

Steve A,


Yes sir its easy to make a mistake and blame some one or something else ,a strip board connection i forgot to disconnect ...another one for the long line of construction mistakes .

I took the circuit out to connect to my best crt scope, i was getting a raster of sorts but no video could be seen pretty much blank .

i checked every thing before doing the test so i had to do some more fault finding and it ended up this time being a poor soldering connection to the positive supply of the 4093 pin 14 ... :roll:now rechecking i can see the pwm on the frame sawtooth ramp hope its still there next test.

I will give it another go tomorrow....
The electromagnetic spectrum has no theoretical limit at either end. If all the mass/energy in the Universe is considered a 'limit', then that would be the only real theoretical limit to the maximum frequency attainable.
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