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Robot Research Model 70 SSTV Slow Scan TV working

PostPosted: Sun Jan 05, 2020 2:35 pm
by Harry Dalek
Noticed this Robot unit working not many images of the old device in operation

Re: Robot Research Model 70 SSTV Slow Scan TV woroking

PostPosted: Sun Jan 05, 2020 3:10 pm
by Steve Anderson
I but there's not many around these days in that condition. Both still work and look untouched inside. I wonder how old the photos are?

It's interesting to see how 'quaint' and widely spaced out the PCB is.

Steve A.

Re: Robot Research Model 70 SSTV Slow Scan TV woroking

PostPosted: Sun Jan 05, 2020 3:18 pm
by Harry Dalek
Steve Anderson wrote:I but there's not many around these days in that condition I would say. Both still work and look untouched inside. I wonder how old the photos are?

It's interesting to see how 'quaint' and widely spaced out the PCB is.

Steve A.


its a ebay sell right now
https://www.ebay.com/itm/Robot-Research ... SwOzleCS9H

Re: Robot Research Model 70 SSTV Slow Scan TV woroking

PostPosted: Sun Jan 05, 2020 3:24 pm
by Steve Anderson
Hmmm, price not so bad considering what they cost new adjusted to today's money, but I'm going to resist. Note the shipping costs!!

If anyone does buy one or both, check the power setting (120/230V) before plugging it in. The Robot 70 does have an internal link you need to set correctly.

Steve A.

Re: Robot Research Model 70 SSTV Slow Scan TV woroking

PostPosted: Sun Jan 05, 2020 3:35 pm
by Harry Dalek
Steve Anderson wrote:Hmmm, price not so bad considering what they cost new adjusted to today's money, but I'm going to resist. Note the shipping costs!!

If anyone does buy one or both, check the power setting (120/230V) before plugging it in. The Robot 70 does have an internal link you need to set correctly.

Steve A.


Its a pain of over seas buying the prices not to bad but the shipping is the killer ! i like to put up the photos as once its sold you loose those in the links so its always better to just post of the the images for the future .

Re: Robot Research Model 70 SSTV Slow Scan TV woroking

PostPosted: Mon Jan 06, 2020 7:34 am
by Klaas Robers
The PCB looks to be very simple but I counted 11 opamps on it. These are housed in a TO5 metal can housing, that we know of low power transistors, but these have 8 wires in stead of the normal 3. I recently used such a TO5 opamp of the 741 type, that might have been the reason that I recognised them.

A problem might be that I saw that the shown documentation is the documentation of the Robot 400 digital scan converter, but it is not impossible that the documentation of the model 70 monitor is also part of the deal. But that will say that a model 400 scan converter will have to live on without its documentation.

Re: Robot Research Model 70 SSTV Slow Scan TV woroking

PostPosted: Mon Jan 06, 2020 3:21 pm
by Steve Anderson
There must be another PCB hidden away somewhere as I counted 19 op-amps on the circuits in total I have, a mixture of 709c and 741c types. Also hidden are some logic chips, all 14-pin, presumably DIL, four of them, 2x MC777, MC790 and MC725...all run on a 3.6V supply!

The other clue to a second PCB is one diagram starts at U1, U2... and the other diagram also starts at U1, U2... not good practice in my opinion.

I have some LF357 op-amps in the 8-lead T099 package (a de-compensated LF356) and some LM394 (dual matched super-beta transistors) in the same package.

Steve A.

It is possible that later production runs used the 747 which is a dual 741, they were available in T0100 packaging, exactly the same but with 10 leads.

Re: Robot Research Model 70 SSTV Slow Scan TV working

PostPosted: Tue Jan 07, 2020 12:44 am
by Klaas Robers
Then it looks that you have the circuit diagrams, or the complete documentation of the model 70 monitor? I searched for it on the web, but did not find it.

I don't know why there should be a second board. For a full analogue SSTV monitor this would be sufficient. However, there has been a successor, the 70C (or something like that) That one could also run at a 4x lower speed, to display SSTV with 256 lines x 256 dots. Then the persistence of the P7 phosfor was not sufficient, but in a really dark room, you still could have an impression of the picture. And it had a few more new features that required extra circuitry.

I see two voltage stabilisers, for +15 and for -15 volt, the large TO3 enclosures, I see the deflection amplifiers with red and green power transistors (?), I see two full wave rectifyer bridges for the 1500 and the 2300 Hz video detection, a few opamps for the video low pass filter and I see quite some small black transistors. What should I need more? I don't see how they made the 5kV, however may be the aluminium can with the plastic hat?

This is called "backwards engineering" isn't it?

Re: Robot Research Model 70 SSTV Slow Scan TV working

PostPosted: Tue Jan 07, 2020 1:31 pm
by Steve Anderson
I think I have already scanned the circuit diagrams of the Robot 70, if I have I'll post them - first I have to find where I've tucked the files away. If I haven't scanned them I'll do it soon.

But remember products often get changes during a production run, supposedly for 'improvement', but usually to make them cheaper to increase profit margins. Me? Cynical? Never!

The 5kV, (actually 12kV on the circuit) for the CRT is just shown as a block on the diagrams, I presume a bought-in sub assembly, so it could be that cylinder with the 'hat'.

I made an error yesterday, it is 11 op-amps, I must have been looking at the wrong diagram!

Steve A.

I've found the scanned circuit files along with the pages of relevant text pages, it'll be several pages here as some files are quite large.

Generally I've heard it called 'Reverse Engineering', but it means the same.

Re: Robot Research Model 70 SSTV Slow Scan TV working

PostPosted: Tue Jan 07, 2020 2:02 pm
by Steve Anderson
First page (1 of 2) of the circuit diagram. Note this is referred to as the 70A, presumably there may have been a 70B, 70C....

Update, The caption in one photo below is mention of a Robot 70, 70A and 70B, the last page with the waveform photo, page 192 of the book.

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.

Re: Robot Research Model 70 SSTV Slow Scan TV working

PostPosted: Tue Jan 07, 2020 2:04 pm
by Steve Anderson
Second page (2 of 2) of the circuit diagram.

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.

Re: Robot Research Model 70 SSTV Slow Scan TV working

PostPosted: Tue Jan 07, 2020 2:07 pm
by Steve Anderson
First page (1 of 4) of the text pages.

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.

Re: Robot Research Model 70 SSTV Slow Scan TV working

PostPosted: Tue Jan 07, 2020 2:08 pm
by Steve Anderson
Second page (2 of 4) of the text pages.

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.

Re: Robot Research Model 70 SSTV Slow Scan TV working

PostPosted: Tue Jan 07, 2020 2:09 pm
by Steve Anderson
Third page (3 of 4) of the text pages.

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.

Re: Robot Research Model 70 SSTV Slow Scan TV working

PostPosted: Tue Jan 07, 2020 2:11 pm
by Steve Anderson
Forth and last page (4 of 4) of the text pages.

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..".

Note the curved scan-lines in the photo below, pincushion distortion.

Steve A.