Robot Research model 400 Ham slow scan tv converter

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Robot Research model 400 Ham slow scan tv converter

Postby Harry Dalek » Sun Jan 05, 2020 2:27 pm

https://www.ebay.com/itm/153779748164

cheap but i bet the postage is the killer
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Re: Robot Research model 400 Ham slow scan tv converter

Postby Steve Anderson » Sun Jan 05, 2020 3:32 pm

Another good find! But as you say, shipping could be the killer, just look at the Robot 70 you posted earlier...so I'm going to resist this too!

I repeat my warning on setting the power voltage correctly before plugging it in.

Steve A.
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Re: Robot Research model 400 Ham slow scan tv converter

Postby Klaas Robers » Mon Jan 06, 2020 4:12 am

This is the model that I have.! The red push button in about the center is not original and the two small switches on top are also not original.

And I had problems with the memory chips, but could find replacement chips. I am not really enthousiastic, as it shows very well visible contouring with its number of grey levels of no more than 16 (4 bits). That is black, white and 14 levels of grey.
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Re: Robot Research model 400 Ham slow scan tv converter

Postby Klaas Robers » Mon Jan 06, 2020 4:23 am

This is the model that I have.! The red push button in about the center of the front is not original and the two small switches above are also not original.

And I had problems with the memory chips, but could find replacement chips in Ukraine (!). I am not really enthousiastic, as it shows very well visible contouring with its number of grey levels of no more than 16 (4 bits). That is black, white and 14 levels of grey.

I see at the back that it has a hole for a "spare" connector. In my converter there is a socket mounted, identical to the other sockets. This converter should have a mains transformer for both 115 and 230 volt. I have all circuit information for you.
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Re: Robot Research model 400 Ham slow scan tv converter

Postby Steve Anderson » Mon Jan 06, 2020 5:30 pm

Klaas Robers wrote:This is the model that I have.! The red push button in about the center of the front is not original and the two small switches above are also not original.


And I had problems with the memory chips, but could find replacement chips in Ukraine (!). I am not really enthousiastic, as it shows very well visible contouring with its number of grey levels of no more than 16 (4 bits). That is black, white and 14 levels of grey.

I see at the back that it has a hole for a "spare" connector. In my converter there is a socket mounted, identical to the other sockets. This converter should have a mains transformer for both 115 and 230 volt. I have all circuit information for you.[/quote]
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Re: Robot Research model 400 Ham slow scan tv converter

Postby Steve Anderson » Mon Jan 06, 2020 5:31 pm

Klaas Robers wrote:...I am not really enthousiastic, as it shows very well visible contouring with its number of grey levels of no more than 16 (4 bits).

Yes, that really isn't enough, but in those days RAM was expensive. 6-bit would have been a great improvement (64 levels), but a bit awkward in allocating memory usage.

Now you can get serial static RAM of 128k x 8-bit for less that 2 Euros. So that's why I'm using 8-bit as it's easy, good enough, fast enough and cheap enough.

Steve A.

...and when you consider it, the Robot 400 had not a micro in sight! Though the Intel 4040 4-bit nibble processor was launched around the same time, 1975 - but it was probably not fast enough...
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Re: Robot Research model 400 Ham slow scan tv converter

Postby Klaas Robers » Tue Jan 07, 2020 12:19 am

Well Steve, developping such a circuit is rather time consuming, So they have been starting well before 1975. And then, when a micro processor appears, you don't know what to do with it in the beginning.

So it is very sensible why they designed the model 400 in the way it was designed.
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Re: Robot Research model 400 Ham slow scan tv converter

Postby Steve Anderson » Tue Jan 07, 2020 2:38 pm

Klaas Robers wrote:..So it is very sensible why they designed the model 400 in the way it was designed.

Indeed, having got the thing into early production, or very close, why undo all that work? Maybe if it had a longer production run and they waited for a more suitable micro they may have considered it. (A Robot 400B?)

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Re: Robot Research model 400 Ham slow scan tv converter

Postby Klaas Robers » Tue Jan 07, 2020 8:12 pm

Steve, there WAS a model 400B and also a model 400C. Besides that, the model 400 had a few revisions on the circuitry, A, B, C, D that repaired a few flaws. The real model 400C had some colour receiving possibilties.

Much later therw came a Robot model 1200C, which was microprocessor orientated. It could receive all modes in black and white and colour. But for today it would be more sensible to send .jpg pictures. I even have read about a Japaneese radio ham that suggested to send only a web-address, where the pictures then can be found. In that case you can also send a youtube address and you will have minutes of moving video, but to my opinion it has nothing more to do with SSTV.
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Re: Robot Research model 400 Ham slow scan tv converter

Postby Klaas Robers » Tue Jan 07, 2020 8:19 pm

Wow, it was not sold. Now the price went down to $ 35,- See:

https://www.ebay.com/itm/153786770461?ViewItem=&item=153786770461

But I fear that the shipping costs did not go down.
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Re: Robot Research model 400 Ham slow scan tv converter

Postby Steve Anderson » Tue Jan 07, 2020 8:57 pm

Klaas Robers wrote:Now the price went down to $ 35, But I fear that the shipping costs did not go down.

It seems someone urgently needs the cash, but as you say, it's still expensive with the shipping costs, and you really don't know what you're going to get...but that's always the case. Note the earth pin broken out of the power lead...common here as most older households only have US 2-pin outlets. This house are all three-pin US outlets with a proper earth-rod...even though used on 220V.

With what I'm hoping to achieve, SSTV-625 why bother? Unless you're hoping for plug-and-play...good luck with that! In the converse direction, 625-SSTV I have a few ideas brewing, but let's get this bit out of the way first!

So unless you're a historical SSTV hardware collector, I'll give it a miss thank you...

Steve A.
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