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Re: Robot Research Model 70 SSTV Slow Scan TV working

PostPosted: Tue Jan 07, 2020 2:13 pm
by Steve Anderson
Associated photos (1 of 1).

Click the image to get the full-resolution version. That works with my browser, Chrome. Then right-click that image and click "Save Image As..".


Steve A.

That's all folks...

Re: Robot Research Model 70 SSTV Slow Scan TV working

PostPosted: Tue Jan 07, 2020 3:14 pm
by Steve Anderson
Note: I've posted 8 times here today, depending your browser/screen resolution/settings you may miss some...scroll backwards quite a way...basically all those dated the same as this posting...depending on your time-zone. Europe and the UK should be the same date the 7th Jan, but early in the morning, the US it will be the previous day, 6th Jan, late evening, Australia & NZ afternoon of the 7th.

I also have the same sort of information on the Robot 60 & 61 SSTV viewfinders and the Robot 80A SSTV camera, though not scanned as yet. Anyone interested in those?

Steve A.

Re: Robot Research Model 70 SSTV Slow Scan TV working

PostPosted: Tue Jan 07, 2020 7:44 pm
by Klaas Robers
Thank you Steve, I have looked through the circuits and read the texts. It is almost as I was expecting, only the PLL for horizontal synchronisation is new to me. I will look at that more carefully.

I have a booklet about SSTV by Grant Dixon, John Wood and Mike Wooding (anno 1987). I have known Grant Dixon very well and I have been in contact with him very frequently. Grant was also important in NBTV, Jim Wood too. So SSTV and NBTV are very closely related. In this booklet I have read that there were versions until 70D. I think: 70, 70A, 70B, 70C and 70D. The D-version had provisions for double resolution, and a few more, that will need some more circuitry and, as I have seen, a few extra switches on the front.

It more or less compares to my "Heathkit-like" SSTV-monitor, so no need to buy it. But still thanks for the insight.

Re: Robot Research Model 70 SSTV Slow Scan TV working

PostPosted: Tue Jan 07, 2020 9:10 pm
by Steve Anderson
No problem, if I have the info I'm willing to share it.

Quite honestly we can do a better job ourselves, but there is some 40 years of development since these devices first appeared, so the challenges aren't quite as daunting as they faced...and they had to make a profit, we don't...though it would be nice!

Steve A.

Re: Robot Research Model 70 SSTV Slow Scan TV working

PostPosted: Tue Jan 07, 2020 11:08 pm
by Harry Dalek

Re: Robot Research Model 70 SSTV Slow Scan TV working

PostPosted: Tue Jan 07, 2020 11:39 pm
by Harry Dalek
I also came across these photos the ic lay out is interesting i didn't think it was that complex ! i am not great at this type of circuit but it looks like a memory to me ? so it had a memory board for replay ? i can't see any where on the panel for this ..has me wondering if this is a scan converter if so i don't know why it came with the robot TV...
edit ... hang on i just noticed the model 400 on the last page he must of got the documents mixed up so that is a scan converter

Re: Robot Research Model 70 SSTV Slow Scan TV working

PostPosted: Wed Jan 08, 2020 2:42 am
by Klaas Robers
The last three photos are from the documentation of the ROBOT 400 digital scan converter. This IS a memory and a lot of surrounding circuitry. I think this man has put the documentation of the ROBOT 70 monitor and the ROBOT 400 digital scanconverter together in one binder and overlooked that the second part is not at all from the monitor.

Almost all that surrounding circuitry Steve is going to catch into two microcontrollers. That is the ongoing miniaturisation of modern integrated cicuits.

Re: Robot Research Model 70 SSTV Slow Scan TV working

PostPosted: Wed Jan 08, 2020 8:04 am
by Harry Dalek
Klaas Robers wrote:The last three photos are from the documentation of the ROBOT 400 digital scan converter. This IS a memory and a lot of surrounding circuitry. I think this man has put the documentation of the ROBOT 70 monitor and the ROBOT 400 digital scanconverter together in one binder and overlooked that the second part is not at all from the monitor.

Almost all that surrounding circuitry Steve is going to catch into two microcontrollers. That is the ongoing miniaturisation of modern integrated cicuits.



Robot 400 scan converter for sure so your dead right Klaas

I noticed that Richard Lab guy has 2 of these robot 70's but hes used one to convert to display for hes image tube project


youtu.be/HBPk6av2hCY


youtu.be/zcUuoyxSJLY

Re: Robot Research Model 70 SSTV Slow Scan TV working

PostPosted: Wed Jan 08, 2020 10:21 pm
by Klaas Robers
Have you seen how high the intgernal resistance is of the HV generator of this monitor? Let me explain:

When there is a lot of "white" in the picture, the beam current will be large and the voltage (12 kV) will get down. With a lower accelerator voltage the electrons hit the screen at a lower velocity, but what is more: they travel slower through the tube. And then they will be deflected more, wider. So the picture on the screen is larger.

When there is a dark picture, the beam current is low and the voltage will rise. The electrons in the beam travel faster and will hit the screen earlier, when they are not yet deflected enough. So the picture will be smaller.

When there is insufficient capacitor in the HV output, the high voltage will vary on the level of the video signal and the width of the picture will vary with the brighness of the video on that height of the picture. You can see that best on the left edge of the picture. The small black bar at the left varies in width with the brightness of the lines. A larger capacitor in the 12 kV (!) will smooth that but the breathing of the picture size will stay.

This was a common problem in CRT television, that was solved by well designed HV generator circuits, and by some "overscan". The edges of the real picture were hidden behind the mask of the picture tube. When the breathing is slow enough people do not observe it as a technical flaw.