NBTV/SSTV-625 Up Converter MkIV

Where it all started as far as most are concerned and saw heavy use from the 60s through to the 80s. Colour and Hi-res modes have unfortunately pushed this system into the backwaters of SSTV. Time to resurrect interest in this simple analogue system.

NBTV/SSTV-625 Up Converter MkIV

Postby acl » Thu Jan 14, 2021 5:00 am

Steve,

Just finished the board and I am starting to check connections. I am using a logic probe which I find excellent for verifying wiring. 5 volts logic one red and logic zero green. If you touch the probe it makes them both light. So with all chips removed place the probe in the turned pin you wish to verify the route. Then rub your fingers down all sockets on board until the probe detects capacitance from your finger. To locate the actual continuity stick a wire in the pin you wish to verify continuity and touch with your finger an you know then thre is a circuit between the logic probe and the pin you have connected to. This is a very quick method of verifying shorts between adjacent tracks and uncut veroboard tracks.

Chris Lewis
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NBTV/SSTV-625 Up Converter MkIV

Postby acl » Thu Jan 14, 2021 8:34 am

IMG_3166.JPG
Just a few more disc ceramics to fit
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NBTV/SSTV-625 Up Converter MkIV

Postby acl » Thu Jan 14, 2021 8:39 am

Finished board
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Finished board component side
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Re: NBTV/SSTV-625 Up Converter MkIV

Postby Harry Dalek » Thu Jan 14, 2021 3:39 pm

acl wrote:Finished board


Good Work Chris looks like just have to slot those Ic's in place .
I have a case left over from last time we were about to start so looks like it will be used this time around .
Will have to start the power supply soon now i see the full circuit .
ON testing I have a few monitors to use and even a large plasma in my work area but way behind you your done.
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/SSTV-625 Up Converter MkIV

Postby Steve Anderson » Thu Jan 14, 2021 4:39 pm

Harry, yes those D-As you sent a few of to me should be fine, the specs read OK so no reason not to use them, I'll try a few this end too...

In a blinding flash of pure inspiration or perhaps a case of crass error-prone stupidity, I yesterday concluded this could all be done with just one processor!

Basically omit IC102! Though I'm not 100% convinced - yet. So I may go quiet as I dwell on this, there's a lot of 'hand-waving' and 'fag-packet sketching' to do yet. The rest of it should be much the same as already posted. But there are bound to be a few changes, hopefully minor. This may be like teaching a dog to walk on its hind legs, time will tell.

My saving grace may be that I'm running the read processor at twice the speed of the previous versions.

The biggest hurdle is interleaving the read output, which cannot be interrupted, with the non-synchronous SSTV input, More to come.

Steve A.

The pitfalls of designing as-you-go! If I'd presented this as a fete accompli none of this would have happened, but hey! It wouldn't be as much fun!

Anything like this in the future will use PIC24 (16-bit) devices, it's time to move on from 8-bit. This basically results in four times the throughput, minimum.

e.g. A 16-bit x 16-bit signed multiplication with a 32-bit result on a PIC18 takes 40 cycles, (2.5us), whereas a PIC24 takes maybe four, (250ns or 0.25us).

Who would have thought back in the '50s we'd be talking about these sorts of speeds for SSTV?
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Re: NBTV/SSTV-625 Up Converter MkIV

Postby Harry Dalek » Thu Jan 14, 2021 7:10 pm

Steve Anderson wrote:Harry, yes those D-As you sent a few of to me should be fine, the specs read OK so no reason not to use them, I'll try a few this end too...


That's good i still have a few left ,i didn't look to closely as far as drop in replacement but looked identical . SA...with the caveat of mine below in mind I hope they're all OK..

I
n a blinding flash of pure inspiration or perhaps a case of crass error-prone stupidity, I yesterday concluded this could all be done with just one processor!


Well that's a lot of wiring no longer needed if so a big positive .

Basically omit IC102! Though I'm not 100% convinced - yet. So I may go quiet as I dwell on this, there's a lot of 'hand-waving' and 'fag-packet sketching' to do yet. The rest of it should be much the same as already posted. But there are bound to be a few changes, hopefully minor. This may be like teaching a dog to walk on its hind legs, time will tell.


Arrrr well its getting smaller if so i will hang back and wait i still plan on ordering the 2 smaller ics and crystal .

My saving grace may be that I'm running the read processor at twice the speed of the previous versions.


So you could run it at 8 MHZ but it would be slower could you run it double the 16 MHZ at 32 or it would need programming saying this is what you are using ...must have a range it works at curious !

The biggest hurdle is interleaving the read output, which cannot be interrupted, with the non-synchronous SSTV input, More to come.

Steve A.

The pitfalls of designing as-you-go! If I'd presented this as a fete accompli none of this would have happened, but hey! It wouldn't be as much fun!

Anything like this in the future will use PIC24 (16-bit) devices, it's time to move on from 8-bit. This basically results in four times the throughput, minimum.

e.g. A 16-bit x 16-bit signed multiplication with a 32-bit result on a PIC18 takes 40 cycles, (2.5us), whereas a PIC24 takes maybe four, (250ns or 0.25us).


This is over my head i am so glad you know what you are doing i am hopeless

Who would have thought back in the '50s we'd be talking about these sorts of speeds for SSTV?


Some would never think of going back to Analog it should not be forgotten its not a matter a worse system its the birth of every other system to come ..
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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NBTV/SSTV-625 Up Converter MkIV

Postby acl » Thu Jan 14, 2021 10:56 pm

Yes Harry I tend to agree with you there. I worked on nuclear sites where the last thing they wanted in their critical control systems was microprocessors that could latch up at any time . Many that did had analogue back up systems. Anyway I have filled in a PTGI form (permission to give in) with the crystals I purchased on Ebay. Tried loading O/P and checking for open collector outputs, Taking the unused pin to zero and still not luck. I have ordered some more with the makers data sheet attached.


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Re: NBTV/SSTV-625 Up Converter MkIV

Postby Steve Anderson » Thu Jan 14, 2021 11:42 pm

Hmmm, this is one of the reasons I'm somewhat reluctant in sourcing components from E-bay and the like. So many fakes, substandard parts and duds around. This subject matter surfaced somewhere here on this forum maybe a year or two ago. They may be cheaper, but is it worth the hassle? For me it's a big definite NO!

Even more so when, as here, we're pushing right at the limits of their speed ratings. But no over-clocking, I've done it and got away with it, but never on an item to be published.

If a component is a fraction of the price than that from a reputable supplier then there's something wrong - walk away with your wallet still firmly closed. It's the old adage, "If it seems too good to be true, then it probably is."

Steve A.

"Over-clocking", running a component beyond its designed maximum speed/power/whatever. You pays your money, you take the chance. In this case, failure is the only option...but maybe eventually...just when you really want to demonstrate your wonderful creation..."But it worked yesterday!' Not good enough. I've walked out on professional presentations that went just like that.
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Re: NBTV/SSTV-625 Up Converter MkIV

Postby Harry Dalek » Fri Jan 15, 2021 10:46 am

acl wrote:Yes Harry I tend to agree with you there. I worked on nuclear sites where the last thing they wanted in their critical control systems was microprocessors that could latch up at any time . Many that did had analogue back up systems. Anyway I have filled in a PTGI form (permission to give in) with the crystals I purchased on Ebay. Tried loading O/P and checking for open collector outputs, Taking the unused pin to zero and still not luck. I have ordered some more with the makers data sheet attached.


Regards Chris Lewis


Hi Chris you have Crystal module problems ! may be i will build an oscillator with a crystal ,that was the whole point with the module they are prebuilt should be easier ,i think i do have a 16 mhz crystal handy which i might knock an oscillator together and see if it works first before putting it in the project .

Steve mentioning the fake or poorly made parts ,it is pretty much hit or miss on ebay or aliexpress but you tend to see in there reviews if the parts work or not they will soon lose their sales if parts are fake .

I got a bag of faulty regulars mentioned months back but i gave them hell and got another bag this time worked fine free of cause ... replacements

Be good here if we had a List of good sellers ...some times its the other way when its over priced the poor hobbyist can't win .

I have been looking at the 2 little 1024 ics they all seem to be the same price range different sellers but if they are good or bad i have no idea again just try and check reviews and hope ...i am yet to buy them still looking .

I have started the build starting with the power supply and get that out of the way
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/SSTV-625 Up Converter MkIV

Postby Steve Anderson » Fri Jan 15, 2021 12:19 pm

Harry Dalek wrote:..may be i will build an oscillator with a crystal.

If, and it's still a big if, this becomes a single-processor device the remaining micro has an in-built oscillator. Just add a standard 16MHz crystal and two 22p caps - done!

These micros offer a range of oscillator options, crystal, RC, ceramic resonator, internal (multi frequency), external and even a 32kHz watch crystal...if you don't need speed. Each has plusses and minuses. Speed, accuracy, cost, power consumption and so on...

I used the external oscillator just to ensure the two previous micros were locked together in frequency, if not phase...which doesn't matter here.

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Re: NBTV/SSTV-625 Up Converter MkIV

Postby Steve Anderson » Fri Jan 15, 2021 1:26 pm

Harry Dalek wrote:I have been looking at the 2 little 1024 ics..

Make sure you get the correct devices, 23LC1024s (RAM), not 25LC1024s (EEPROMs), it's an easy mistake to make! And they're both made by the same company, Microchip. What doesn't help is they're both memory and 8-pin devices...but not interchangeable.

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Re: NBTV/SSTV-625 Up Converter MkIV

Postby Harry Dalek » Fri Jan 15, 2021 2:09 pm

Steve Anderson wrote:
Harry Dalek wrote:I have been looking at the 2 little 1024 ics..

Make sure you get the correct devices, 23LC1024s (RAM), not 25LC1024s (EEPROMs), it's an easy mistake to make! And they're both made by the same company, Microchip. What doesn't help is they're both memory and 8-pin devices...but not interchangeable.

Steve A.


So am i right in saying the 23lc1024's all come from the same place as i see different sellers .
I started the project today bit of multitasking with the other things i am up to but this is on a want to do list as well so spent today working on it finished the AC side of it getting 13.5 0 13.5 out of the Transformer should do the job and i can copy your power supply .
I think i have enough room on the board for every thing ,work on the DC side next .
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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/SSTV-625 Up Converter MkIV

Postby Steve Anderson » Fri Jan 15, 2021 2:22 pm

Harry Dalek wrote:So am i right in saying the 23lc1024's all come from the same place as i see different sellers.

Yep, they all come off the same production line, no matter who sells then on to the end-user. However, caution is advised as there are in some cases fake/copy devices out there. Make sure they're genuine manufacturers parts. Which is why I rarely use E-bay, if ever at all.

The difference in price is down to profit margins, the quantity they buy in, and any middle-men (Farnell, RS, Digikey etc.). If you want to buy in bulk, say 10,000 minimum you'd deal with Microchip directly...unsurprisingly the site is called Microchip Direct. No middle-men and vast discounts. And of course they're all genuine.

If any are found to be defective but genuine they'll often replace the defective items with twice the quantity of good ones at no charge. That's how sure they are of their product. Not just Microchip, but most other manufacturers have a similar arrangement for quantity buyers. Defective parts on a production line is a disaster! Not just electronics, but anything, cars - wrong/defective bearings deep inside the engine - oh dear!

Steve A.

Second-sourcing is commonplace, often the military insist on it. If Intel go bust they can still get AMD devices...Microchip now second-source Atmel devices, if they didn't neither would get any sales...it's often an uncomfortable relationship! Sharing your technology with a competitor. Still, it gives the legal guys, lawyers, a licence to print money.
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Re: NBTV/SSTV-625 Up Converter MkIV

Postby Harry Dalek » Fri Jan 15, 2021 4:01 pm

Steve i forgot must be a few years now we were going to make something like this and i came across some thing i ordered back then is this the same thing ? the 1616 number worries me ? i think from memory i ordered 4 but i can only find these 2 due to the size no wonder .

EDIT.....................

My memory is not as good as it use to be but looking back on MK3 i did order the same thing shown mentioned half way down the page
viewtopic.php?f=24&t=2351&start=45
So if they work all i need is really the programmed chips or chip depending on your rethink onit and work out the crystal oscillator

i am half way done on the DC power supply .....Now where did the other 2 23lc1024's go mmm...
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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/SSTV-625 Up Converter MkIV

Postby Steve Anderson » Sat Jan 16, 2021 12:22 am

Decoding that part number...23LC...OK so far, B=soic, 1024 device and package, which they plainly are, I=industrial temperature range, then SN-no idea!, then Pb-free (no lead symbol (e3)), then year code 16=2016, week code 16th week of that year, then an alphanumeric traceability code. So they are the correct items, including the Microchip logo. To decode all that you need to refer to the last few pages of the Microchip datasheet. That's true of most small package items these days, they can be quite cryptic at times...

Steve A.
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