SSTV-625 up-converter MkII

[Steve Anderson]

Hmmm, I would be careful, what we call a schematic my not quite be quite the same in Italian. I would like to see even just a corner of the page(s) before I shelled out the cash. After all that's only what Klaas needs, he's already got one...unless he wishes to stockpile them!

The Robot 400 only had 16 levels of grey, 4-bit, which can work quite well. But aside from the history you may be purchasing, even though the price is OK, I think I would pass. However, I have to admit, if I were in the UK right now, I might be very tempted...

Every time I'm in the UK I end up shipping a load of stuff back to Thailand. I've just today had notification that what I shipped by sea from the UK in February is due to arrive soon. Of interest here may be two analogue open-reel tape recorders, both valve/tube, from the early 60s I guess. I have all the service data for them as well as a box load of tapes...which may or not be OK. Of greater concern is the condition of the heads, that we will have to wait and see...

I didn't buy them, a friend had them and wanted to get rid of then, so I swapped them for a Samsung dumb-phone that I didn't like...it seems he's quite happy with it...I now have a Vivo phone, made in India (Top quality sire) and has features that the Samsung didn't and is one third of the price...go figure!

Steve A.

[Harry Dalek]

Klass theres a bit on the Robot 400 scan converter in this link to a 1977 73 magazine issue you can download few pages onit .

I have not found it yet but theres a bit on Modifying the ROBOT-400 in the english CQ tv magazine .

Looking on the net had no luck on a manual or schematic but in the information from some selling it seems there is a schematic for it as Andrew has found some where else so it must come with one .

https://archive.org/search.php?query=ro ... 0converter



SSTV CONVERTER ROBOT MODEL 400
FOR SALE. USED TO CONVERSE A QSO WITH TONY ENGLAND, W0ORE, IN THE 80'S ABOARD THE CHALLENGER SPACE SHUTTLE.
HAS NEVER BEEN ABUSED AND CABINET LOOKS ALMOST NEW. VERY EASY TO HOOK -UP AND USE . INSTRUCTION MANUAL INCLUDED WITH SCHEMATIC . ONE OWNER USER AND NEVER EXPOSED TO SMOKE . TAKEN GOOD CARE OF SINCE BOUGHT IN 1982. I STILL HAVE THE SALES RECEIPT . MY COST WAS $679.95. I WILL LET IT GO FOR $150.00. CONTACT ME VIA E-MAIL ONLY PLEASE.
DAN ////////wa5cyr@gmail.com

Robot Research Inc. (619) 279-9430
5636 Ruffin Rd
San Diego, CA 92123
Robot manuals only.

[Harry Dalek]

Nice reel to reel tape recorder Steve they still turn up now and again i have a smallish one have always great memories of playing with it and dad doing mic recordings close to the tv ...being naughty not keeping quiet ~!

[acl]

Hi there Steve,

Just showing how construction progress is going with the Robot front end. I bought myself a capacitance meter from Maplins so I can check values of all capacitors and using Fluke resistor values before construction. This minimises errors when testing especially as active filters can appear to function abeit poor performance. Good luck with your software.

Regards Chris Lewis

Chris, I hope you don't mind, I re-sized the photos to fit most people's screens, but I left the originals in place. Steve A.

[Klaas Robers]

I have (a copy of) the original documentation. That starts with a contents list and that does not anounce a circuit diagram. There is a list of all components and a lay out of the large PCB. I fear Steve is right an there is never given free to the circuit diagram.

However, I see two wire links, on is marked 1, 2, 3 and the other 4, 5, 6. I can nowhere find what these wire links do and how they should be connected for which situation. Strange. but it is time to connect a monitor and power.

[Harry Dalek]

I have (a copy of) the original documentation. That starts with a contents list and that does not anounce a circuit diagram. There is a list of all components and a lay out of the large PCB. I fear Steve is right an there is never given free to the circuit diagram.

However, I see two wire links, on is marked 1, 2, 3 and the other 4, 5, 6. I can nowhere find what these wire links do and how they should be connected for which situation. Strange. but it is time to connect a monitor and power.

Interesting to see the results Klass.
The cq issue i tracked it down is below but i don't think you will want to fiddle with yours just yet .

[Steve Anderson]

Just showing how construction progress is going with the Robot front end...

Very neat, I can never achieve that level of neatness however hard I try. Probably because I cram as much as possible into a small space.

Now when it comes to the logic/processor part you're going to have to forget making it neat, lead-length and stray capacitance are your enemies. Ground and supply impedances are to be minimised. Decoupling/bypassing all over the place is essential. Internally these processors PLL the 16MHz crystal to 64MHz...there's quite a bit of number-crunching required!

Photo of how the MkI version ended up is below...note the dust on the chips...hasn't been powered for at least six months...

I'm about half-way through the logic/processor board build for the MkII version. Interesting to note that I use the same process during a build. I print the circuit and as I fit each component or wire I too highlight it with a yellow marker.

Steve A.

[Steve Anderson]

Quick photo of MkII board as it currently stands. Last item to add is add the top-side wiring - that's when it gets messy - then a buzz-check (continuity test) to find any shorts, opens or errors.

If you don't intend to program your own devices then the two 6-pin headers and the two reset buttons at the top are not required.

Note the similarity of the right-hand side to the MkI version...

Steve A.

[acl]

Steve,

No problem with the photographs. With regard to the neatness I am envious of your design and software skills so each person has their own specialities. With regard to the processor board I intend to solder wire wrap cables underneath the board and keep the wires as short as possible. The only thing I don't understand is why two reset pushbuttons? are these used during programming?

Regards Chris Lewis

[acl]

Sorry I didn't read your last post about pushbuttons

Regards Chris Lewis

[Steve Anderson]

Some of the wiring will be on the underside in my version, but most top-side.

Using the programmer I do, a PicKit 3, you can hold a processor in reset from the PC, but as there are two I thought I'd add the switches just in case. More on this later.

Well, as for my design skills we'll have to wait and see on that! I'm going down a road not traveled before so I'm wary about others building this until I'm sure it is possible. The SQI RAM chips are a recent introduction and as yet there's no dedicated SQI interface peripheral on PIC micros for it. So I'm going to have to bit-bang it. Hence the requirement for the speed. The MkI read processor loafed along at only 8MHz.

But I have used ordinary SDI RAM chips at this speed before but you would need one chip per bit. In the application they were used only three bits were required, 8 colours, akin to teletext. The primaries (RGB), their compliments (CMY) and black/white.

Steve A.

NOTE TO SELF...Remember to change 5V supply to 3.3V! DONE, 22/04/17

[Klaas Robers]

I got a circuit diagram of the Robot 400 !! Rommert Zonneveld, a Dutch member of the NBTVA, sent it me by e-mail. He has read on this forum that I bought the 400 and lacked the circuit Diagram.

The diagram came in 3 .jpg parts. In the mean time I "glued' them together, but I need at least an A3 printer to print it. On A4 it is too small to read. I need some time to go through it, I don't see yet the logic in it.

They "programmed" in a few chips the differences for 50 Hz countries or 60 Hz countries. That is done by clipping off certain IC pins before they were soldered in the PCB. So that was programming in 1979. One of them is a 7430 8-input NAND. I think this is a reset pulse for the line divider, to get 312 or 262 lines per scan. The line frequency will be constant I think, 63.5 us or 64 us is too close to adapt the circuitry for it.

[acl]

Images show complete decoder section built on strip board. Outstanding work is to add more decoupling on twelve volt rails and to check against circuit diagram. Please note any unused track will need to be isolated with spot face cutter in order to reduce additional inter track capacitance effecting filter performance and cross talk between circuits. One tip with strip board. If you score both sides of the board where you want to cut the board you can snap a clean line over a straight edge.

[acl]

Copper side

[Steve Anderson]

I got a circuit diagram of the Robot 400 !! Rommert Zonneveld, a Dutch member of the NBTVA...

What a stroke of luck! Right on your doorstep! I honestly thought you had very little chance...but there you are...amazing!

Steve A.