Vintage SSTV transmit converter

Forum for discussion of SSTV topics. Slow Scan television (SSTV) is a picture transmission method used mainly by amateur radio operators, to transmit and receive static pictures via radio in monochrome or colour.

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Re: Vintage SSTV transmit converter

Postby Harry Dalek » Sat Feb 10, 2024 12:03 am

:oops:
acl wrote:Harold,

You will only get outputs from U7 whilst the 'snatch' pushbutton is depressed.


It seems to be Start and snatch button when getting the address to work on the Ram some times it gets locked up i noticed when taking readings with the scope probe i think when touching noise is the cause .
So a switch off the power and back on reboot and again start snatch gets the pulses working again .

Looks like pins 12 and 7 from U7 are working correctly albeit some noise on the input signals.


Yes i think so too but i took those readings before i saw i had wired the address coming out of U11 to U12 was wired wrong so could of effected those scope readings may be ? i will double check tomorrow !

As you have shown U12 address lines starting at A0 should half the frequency as you move up the address numbers A0 to A6 appears good. For A7 to A13 we need an output from U7 pin 9. This is active only when 'snatch' is pressed , U7 pin 11 is high 'or' pin 10 (from U14) .


OH OK i will check this too in the morning i did seem to get pulses here stopped sort of at pins 9 and 10 or they are so long and slow i didn't wait long enough to see the switching so once again need to be sure .

The output from U7 pin 4 feeding pin 27 on the RAM chip is active only when the 'Snatch button is depressed and positive edged clock pulse appears on pin 2 from U6 pin 6
[/quote]

I think i noticed this had to hold it in for it to work ,i feel more confident this is coming together ! i don't know how some one would of made this back then with out a scope may be easier on a printed circuit board least you would know your wiring is correct on most of it .
Your Hints are very helpful to me ! reading the TTL circuit works in this project pages are confusing since i don't deal with them much apart from multivibrators .

Looking over circuit 3 not sure its working correctly problems with the Opamp 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: Vintage SSTV transmit converter

Postby acl » Sat Feb 10, 2024 8:39 pm

My philosophy with these type of circuits is to quickly go over digital outputs to check for any type of switching activity carefully checking for correct switching levels then, if it doesn't work after that home in and check in more detail each individual circuit element.

Good luck.

Chris
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Re: Vintage SSTV transmit converter

Postby Harry Dalek » Sat Feb 10, 2024 9:49 pm

acl wrote:My philosophy with these type of circuits is to quickly go over digital outputs to check for any type of switching activity carefully checking for correct switching levels then, if it doesn't work after that home in and check in more detail each individual circuit element.

Good luck.

Chris


Yes agree there i have been looking at where the problem is ,had me beat for a while today why my 555 stopped also noticed the 566 had also i found the C and N connection was causing it it seemed U14 74Ls02 had failed i can see it would cause the 555 to stop but it did effect the 566 also .

I had trouble with the LM324 at first passing any thing but does now to pins 4.8 but seems very low signal on the last stage u17C i might start looking at the 4066 see if its that could have another faulty IC

I will keep at it
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: Vintage SSTV transmit converter

Postby Steve Anderson » Sun Feb 11, 2024 2:51 pm

A suggestion...I can't recall if EA published erratas, but it may be worth checking subsequent issues of the magazine for any related to this project, and any other updates. Mistakes happen. Either with the authors original submission or in typesetting the article, including the diagrams. That respected publication, Wireless World, were virtually always apologizing for some mistake or another! Though often they were minor, silly or obvious.

I suggest this as this item is proving to be quite a headache! More than I would expect.

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Re: Vintage SSTV transmit converter

Postby Harry Dalek » Sun Feb 11, 2024 4:12 pm

Steve Anderson wrote:A suggestion...I can't recall if EA posted erratas, but it may be worth checking subsequent issues of the magazine for any related to this project, and any other updates. Mistakes happen. Either with the authors original submission or in typesetting the article, including the diagrams. That respected publication, Wireless World, were virtually always apologizing for some mistake or another!

Steve A.


Hi Steve

Yes thats a good idea i can go looking most are posted up on line all for that year so yep i will have a look .

If a mistake got though gone to far to stop this one ! but for sure will be great find out .

Back to this one I was looking at this part of the circuit today so far good to U17b pin 1 and the 4066 pins 4 and 8 ( did BTW swap the 4066) this are the reading test points today .
CD4066-internal-structure.jpg
CD4066-internal-structure.jpg (16.97 KiB) Viewed 497 times
Screenshot 2024-02-11 151636.png


As mentioned before i wish they would use the old idea of small scope shots or drawings on what comes out where on schematics or projects would be make the testing so much easier knowing what you are looking are is close correct or wrong .

Having got this far in the circuit to work thought it was time to see if the panel controls are really controlling the video so that what i did today ..
With the snatch button pressed in i get this result below think i stopped and press the button again half way



Adjusting the panel contrast control below



Adjusting the brightness panel control



So this to me looks promising still some thing up around U17D last time i looked so U17c the lm566 and U17d next need checking
Attachments
DSCN9649_x264.mp4
(10.83 MiB) Downloaded 88 times
DSCN9650_x264.mp4
(7.98 MiB) Downloaded 90 times
DSCN9651_x264.mp4
(7.47 MiB) Downloaded 82 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: Vintage SSTV transmit converter

Postby acl » Sun Feb 11, 2024 6:17 pm

Harry,

Looks promising. Worth connecting a speaker on the output to see if it sounds like the normal SSTV 'chirping' with synch signal . Then it is down to meticulously following through Leons setting up instruction's.

Regards Chris
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Re: Vintage SSTV transmit converter

Postby Steve Anderson » Sun Feb 11, 2024 6:32 pm

Whatever this problem is, I hope it gets sorted soon. I'm of the mind to bring this up-to-date in the near future once I get clear of 'real work' bogging me down at the moment. The input side would be much as published recently here, plus an update to the MkI Down-Converter I did some years ago, though not published.

An estimate would be six or seven chips, not including power-supply, the largest being a 28-pin (maybe 20 or 18-pin) 0.3" DIL. Though first I need to find a source of 625 video!

As SSTV is really a string of stills it might be better and easier to convert jpgs, tiffs, gifs or whatever to SSTV. Much as I did for the first Up-Convertor. It should also result in a better quality result, the first one did...it also doesn't need such a hi-speed A-D...which could be 8-bit not just six, removing much of the visible 'contouring'.

The advantage of using stills rather than video is the abundance of material on the 'net in addition to your own...though it would need some simple preparation before use...follow-up to come...

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Re: Vintage SSTV transmit converter

Postby Harry Dalek » Sun Feb 11, 2024 7:39 pm

acl wrote:Harry,

Looks promising. Worth connecting a speaker on the output to see if it sounds like the normal SSTV 'chirping' with synch signal . Then it is down to meticulously following through Leons setting up instruction's.

Regards Chris


That's a problem i have at the moment Chris not being able to listen to the result so far signal to low to drive a speaker lucky to see it on the scope ! i can't say i have found any mistakes in the wiring so far checking them all a few times ,i just swapped the opamp again just incase but didn't look yet at that end if it fixed that problem or not .
I could try my old crystal ear phone ( i used this to check circuits years ago before i had a scope my only way to se if something worked)
I do have a USB sound card for this newer lap top so i have a mic input i have been viewing on MMSSTV in case i have a hint of a signal i do see an off an sync bar buried in the snow but not video information that i could say yes thats an image off sync .
I need to know the video is controlling the 566 VCO i don't or can tell yet it is .
I can say a lot of this seems to work so far with the TTL circuits little did i know what should be the easier part of this ( i thought the end ) is making me work for it .
But i will keep at it .
Yes i will do a another good set up on the trimmer frequency at the end
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: Vintage SSTV transmit converter

Postby Harry Dalek » Sun Feb 11, 2024 8:00 pm

Steve Anderson wrote:Whatever this problem is, I hope it gets sorted soon. I'm of the mind to bring this up-to-date in the near future once I get clear of 'real work' bogging me down at the moment. The input side would be much as published recently here, plus an update to the MkI Down-Converter I did some years ago, though not published.

An estimate would be six or seven chips, not including power-supply, the largest being a 28-pin (maybe 20 or 18-pin) 0.3" DIL. Though first I need to find a source of 625 video!

As SSTV is really a string of stills it might be better and easier to convert jpgs, tiffs, gifs or whatever to SSTV. Much as I did for the first Up-Convertor. It should also result in a better quality result, the first one did...it also doesn't need such a hi-speed A-D...which could be 8-bit not just six, removing much of the visible 'contouring'.

The advantage of using stills rather than video is the abundance of material on the 'net in addition to your own...though it would need some simple preparation before use...follow-up to come...

Steve A.


It is one of those things Steve there are of cause better ways to do the same thing endless if we think about it better and worse ways ,you just have to pick some thing like this and it is what it is and take it as that and see if it can be made to work .
It is like a simple systems converter which is sort interesting
Because there were no result images i would really like to see a result ! so far i have seen many wave forms but wouldn't it be great to see what this thing should do .
I love this out dated and useless ! reminds me of me :lol:
I will of cause give yours a go as well when your right for it to be built i don't mind trying other ideas .
An update of this one would be great to see .
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Re: Vintage SSTV transmit converter

Postby Steve Anderson » Sun Feb 11, 2024 8:35 pm

I probably won't bother with the video-to-SSTV version, the resultant SSTV images were inferior to 'still-to-SSTV', which came as no suprise.

The lack of screen-shots in both articles does make one wonder. I would have thought the author would have been proud of them.

I haven't dug into the circuit to any extent, that many chips and transistors when it can now be done with less than a third of them? Yep, it sure is 'Retro'!

But it was late 80s/early 90s, so credit where credit is due.

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Re: Vintage SSTV transmit converter

Postby Steve Anderson » Mon Feb 12, 2024 3:18 pm

Earlier this morning I came across software for PCs to convert images (jpgs and the like) to a SSTV wave file. Conceptually removing the need for this type of hardware completely, i.e. it's simply not required. Those I did look at, but didn't try, don't include the original Cop McDonald square 8-second monochrome mode. However, obviously it could be done if someone wanted to.

It's deflated my interest in doing it in external hardware somewhat, that is, why bother? I understand the 'retro' appeal of what Harry is in the middle of, it was almost the only way of doing it at the time. But an updated hardware version in 2024?

A similar situation exists with NBTV. Why use Nipkow discs when we now have huge multi-megapixel flat-panel displays in colour?

I guess it's a case of, "We can, we want to, so we will"....There, I feel better already!

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Re: Vintage SSTV transmit converter

Postby Harry Dalek » Mon Feb 12, 2024 5:58 pm

Steve Anderson wrote:The lack of screen-shots in both articles does make one wonder. I would have thought the author would have been proud of them.
Steve A.

I did have a look in the following EA mags but nothing was mentioned about this project so its is a head scratcher why their were no shots, 1990 i think the monitor side could of been a PC but as i recall XT around then ( i never had one of those i started with a 286 ) and the graphics cards monitors were not at the photographic displaying stage. forgot how primitive the computer era was then .
So i guess he would of used a CRT display . also i recall in the later end of 1990s digital cameras first came out so i would think not some thing he had yet .
May be the film camera idea on a P7 monitor was not easy ? We know they did it for FSC colour .
I know he's a Ham and i do have contact with Chris Long may be i will ask him if he knows the fellow or a way to ask for he's email .Sounds like hes still alive and kicking
https://vklookup.info/#%20VK2DOB%20
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: Vintage SSTV transmit converter

Postby Steve Anderson » Mon Feb 12, 2024 7:23 pm

The author does mention on page 129 (Aug.1990), "Assuming you have a receive scanconverter...". We can only assume he did. And it would be logical to have a receive device before a transmit one. That should have been a usable arrangement.

Also, a lot of 'medium quality' film cameras used to have a 'B' shutter setting that held the shutter open for as long as the shutter was pressed, if the display were P7. Several sweeps of the CRT would do it.

Anyway, it's academic now, if the author is still with us it's unlikely he'll still have the screen-shots today, if he took any, it was some 34 years ago.

Steve A.
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Re: Vintage SSTV transmit converter

Postby acl » Mon Feb 12, 2024 8:34 pm

Harry,

I have emailed you with a postal for Leon in NSW.

Regards Chris
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Vintage SSTV transmit converter

Postby acl » Tue Feb 13, 2024 7:35 am

Well I have made a start Harry. I always find it is easier to build and test on a piece of plywood before committing to a case



IMG_4642.JPG
Video processing board


IMG_4644.JPG
Power supply


IMG_4645.JPG
Breadboard
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