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 » Fri Jul 17, 2015 10:51 am

No worries steve...i have a little be of time this morning i will test your advice see what i get . Logical to leave he changes so far as in the 500 k trimmer 15k swipper resistor and 33nf cap see for a start .....and do your new test and check before going back to the original parts .

update

i just noticed a mistake when i replaced the trimmer ...i will repair this and report back on this posting...

Well i know the reason the 4011 was effecting the sync sep transistor ,it was a wireing mistake ...

I fixed that now ,what i am seeing out of pin 3 of the 4011 with the diode removed from the next stage is an inverted pulses ...on real signal out the diode.

The trimmer pot now adjusting it the led will go off and back on ...have not checked yet with the in4148 diode soldered back yet .

So the sync sep is working still a little messy mainly 400 hz pulses odd glitch here and there .but only with the 4011 removed with the ic plugged in the pulses look random.
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Re: NBTV Scope Evolution

Postby Steve Anderson » Fri Jul 17, 2015 4:06 pm

Check for any additional errors first then replace the 4011, who knows what those previous mistakes could have done to it...and you do get a very small percentage which are defective straight from the factory - it is a very small percentage though.

What is the source of your NBTV video?

Steve A.
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Re: NBTV Scope Evolution

Postby Harry Dalek » Fri Jul 17, 2015 8:11 pm

OK steve i will swap other 4011 see how that looks .

What i did was i connected 2 of the NAND gates together so the sync sep pnp transistors collector was going right to the input of the second NAND gate ..bit of a loop happening !

Heres what it looks like out the pnp with out the 4011 ........sync sep looks good but with the ic in pulses look random....

Yes will double check for mistakes .

Heres the video i have been using simple NBTV letter test card ..
Attachments
nbtv1.wav
(160.05 KiB) Downloaded 732 times
IMG_1419.JPG
out the collector of the pnp sync seperator with the 4011 removed
IMG_1419.JPG (104.32 KiB) Viewed 15455 times
Last edited by Harry Dalek on Sat Jul 18, 2015 10:10 am, edited 1 time in total.
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Re: NBTV Scope Evolution

Postby M3DVQ » Sat Jul 18, 2015 9:00 am

I have one of those drill bits with a plastic handle, but making all the cuts and then locating the inevitable barely visible short drives me round the bend.

I started using "tri pad" board for most prototyping now, though occasionally use the individual pad board too. It allows you to solder lots of DIL components at a good high density without having to cut hundreds of strip-board tracks, I'd never go back to stripboard now :)
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Re: NBTV Scope Evolution

Postby Harry Dalek » Sat Jul 18, 2015 10:28 am

M3DVQ wrote:I have one of those drill bits with a plastic handle, but making all the cuts and then locating the inevitable barely visible short drives me round the bend.

I started using "tri pad" board for most prototyping now, though occasionally use the individual pad board too. It allows you to solder lots of DIL components at a good high density without having to cut hundreds of strip-board tracks, I'd never go back to stripboard now :)


I just had it handy ,it is easy to make a mistake with strip board ,i suppose you could cut the tracks of strip board to make a tripad board with a ruler and something sharp that would be one way to use one .

I like matrix board and connect the tracks with bent copper wire strand from power cables thick enough to bend ,i was saying to Steve that if we asked every one how they made their circuits i bet every one would have their own sytle likes and dislikes .

Some types of PCB waste a lot of space ...i would never buy a strip board again if i didn't have to .
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Re: NBTV Scope Evolution

Postby Steve Anderson » Sat Jul 18, 2015 12:57 pm

As Harry effectively says, "To each their own." I'm so used to stripboard it's no hassle at all to me. Sure, barely visible shorts are a pain so I inspect each break I make with a high-powered magnifying glass. Solder splashes can be a another source of grief, but that's true of almost any board construction technique.

I do a basic layout and move things around until I'm happy, the layout and photo of an example board are below. I don't draw every component or connection/wire, just the major parts. I colour-code main busses, red for +12V, blue -12V, orange for +5V and green for 0V/ground. Other colours are used for the occasional other voltage, yellow for +3.3V for example.

The tri-pad DIP-layout board is quite useful but the density can be a bit low and it's not so good if you're mixing DIP and discreet components, usually analogue circuits.

The single-pad matrix board I have never used - except the type where the pads are on a much wider spacing than 0.1". I use these only in high-voltage circuits, CRT power supplies for example where voltages can run to several kV.

Steve A.

Later..one downside of stripboard is it can have quite a bit of stray capacitance between tracks, especially if long. In most applications including NBTV it's usually of no real significance. In the example here the PIXEL ADDRESS buss is sensitive to capacitance as the pixel rate is over 7MHz. So the chips that are connected to it are close together and the tracks are as short as possible. In a production environment not using IC sockets would help too, they do add a couple of pF to each pin.
Attachments
SSTV-625 Board Layout 1-Model.gif
SSTV-625 Board Layout 1-Model.gif (29.08 KiB) Viewed 15442 times
SSTV-625 5.jpg
SSTV-625 5.jpg (97.06 KiB) Viewed 15442 times
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Re: NBTV Scope Evolution

Postby Steve Anderson » Sat Jul 18, 2015 1:34 pm

Harry, I've just had a look at the waveform of the nbtv1.wav file - the frame sync (missing sync) is wrong - or at least it's not to the NBTVA standard. You may still have some issues with the circuit but this signal will not help!

Steve A.

I also checked it on the 'scope to confirm...ignore the measurements down the side of the 'scope screen.
Attachments
NBTV 1.jpg
NBTV 1.jpg (42.13 KiB) Viewed 15440 times
TEK0050.gif
TEK0050.gif (4.76 KiB) Viewed 15440 times
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Re: NBTV Scope Evolution

Postby Harry Dalek » Sat Jul 18, 2015 2:14 pm

OK now on the sync sep and 4011 frame sync selector part of the circuit ....i have 400 hz at the sync sep and 12 hz at the output of the 4011 and its adjustable ..
Partly problem was a mistake in wiring and a solder touching another track and i changed the cap to .0027 and i have a 500k with 15k for fine tune control and in series a 1m and 150k on the other swipper this seems enough and this part is now working ...At last i can move on to the next part ...
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 Jul 18, 2015 2:20 pm

Hi steve i got the circuit to work what would be a good one to double check with a wave form ...of nbtv standard ...

I am pretty sure its doing the job now its behaving well .
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 M3DVQ » Sun Jul 19, 2015 6:04 am

Oh certainly everyone has their own favourite method of construction. I know someone who hates tri-pad board with a passion though I never quite understood his argument against it.

That and single pad matrix board are in a sense "additive" while stripboard is "subtractive". I just find it easier mentally to connect pads where I want a connection rather than cut tracks where I don't but can see benefits of both ways (though as I say the physical cutting, finding shorts, and cleaning the mess put me right off!)

Often for power buses etc. I will tack some stripped bell wire down on the tripad and run the iron along so it solders all the pads together. To be honest in my most recent few things I've built it makes no difference whether I use tripad or .1" pad board because I've been wiring everything point to point with enamelled wire on the solder side. You can get some absurdly dense circuits that way, almost like wire wrap. But just like a dense wire wrapped project it's an absolute nightmare if you have to debug it later on :shock:

Here's something I built on pad board back when I was young and naive before I'd discovered the wonders of enamelled wire and was still making a stinky mess with PVC sleeved bell wire:
kb.jpg
kb.jpg (766.18 KiB) Viewed 15414 times


Anyway, sorry to go so far off topic :D

Alistair.
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Re: NBTV Scope Evolution

Postby Harry Dalek » Sun Jul 19, 2015 12:53 pm

Hi Alistair

Well wiring is part of any project and helpful for others for sure so no worries ...

Heres my style of soldering a board ,,,,,,,it was reused so a little messy with old solder from the last project .

I use copper wire( strand of copper wire from a power cable) for the circuit tracks on the matrix board so i don't waste to much solder ,i only cross matrix tracks with solder if is a short distance .

My thinking is try and remove as much plastic coated wire from the project as possible (the rats nest look) ...i like matrix board as its the most efficient PCB for placing maximum parts for the space ,i suppose double sided matrix is the ultimate but they are a pain to scrap if you make a mistake or pointless to try and reuse and the bane of my existence if i want a part off a circuit board i want to scrap parts from.

So really i try and do a printed circuit board idea with wire .

Below is the last scope tv project to finish top and bottom the wireing idea ...
Attachments
IMG_1174.JPG
i use the stands from power cable
IMG_1174.JPG (150.87 KiB) Viewed 15410 times
IMG_1424.JPG
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IMG_1423.JPG
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IMG_1422.JPG
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Last edited by Harry Dalek on Sun Jul 19, 2015 11:41 pm, edited 4 times in total.
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 » Sun Jul 19, 2015 3:24 pm

I have finished the next part of the circuit i tackled the shift oscillator and pulse width modulator which uses a 4093 and one Nand gate from the 4011 ,seems to work ...i am getting 36.8khz out the oscillator i can see the triangle wave and a pulse width signal out the last stage of the 4093.e
Attachments
IMG_1436.JPG
out the sync sep
IMG_1436.JPG (94.4 KiB) Viewed 15406 times
IMG_1428.JPG
out the frame sync selector
IMG_1428.JPG (92.82 KiB) Viewed 15406 times
IMG_1447.JPG
where i am up to at the moment which is the worst of it over ....i think !
IMG_1447.JPG (111.4 KiB) Viewed 15406 times
IMG_1451.JPG
out the frame 555 where i am up to this afternoon on construction
IMG_1451.JPG (104.83 KiB) Viewed 15403 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 M3DVQ » Sun Jul 19, 2015 11:26 pm

Harry Dalek wrote:I use copper wire( strand of copper wire from a power cable) for the circuit tracks on the matrix board so i don't waste to much solder ,i only cross matrix tracks with solder if is a short distance .


Yep, that's pretty much what I do now. That photo was again back before I realised that building bridges of solder was a messy waste of time and solder :)
I now just put a very small bit of solder along a bit of wire just to hold it down, or sometimes just at regular intervals. Same idea though, building a "pcb" by joining the copper back together in lines :D
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Re: NBTV Scope Evolution

Postby Harry Dalek » Mon Jul 20, 2015 6:33 pm

I started out on those circuit boards where you use a PCB but has nothing to solder just twisting the parts wire together mainly the Tandy electronics or Radio Shack, Science Fair kits this short wave one was my favourite,notice the germanium transistors ...i broke a few of those over the years .
http://my.core.com/~sparktron/pbox.html

On the solder bridges its a easy fix for short distances but yep not a good idea for all the board ,I use a battery soldering iron pen thing these days so can't get to carried away soldering or my batteries die.

I am glad to hear you use the wire idea as well ! i suppose using the same boards every one works it out in time .

Results on the jeremy scope tv circuit made so far the black level adjustment seems critical to get an out put of the 4093 , the sawtooth seems low to me in the high mV range ,the output which i hope is PWM is a little over 3 volts ...
i will work on the sawtooth part of the circuits later in the week .
Attachments
110P1.JPG
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110P6.JPG
110P6.JPG (123.51 KiB) Viewed 15383 times
$_12 (1).JPG
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$_57 (4).JPG
(312.64 KiB) Not downloaded yet
Last edited by Harry Dalek on Mon Jan 23, 2017 9:49 pm, edited 3 times in total.
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 M3DVQ » Mon Jul 20, 2015 8:32 pm

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
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