Retro SSTV Anyone? II

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.

Re: Retro SSTV Anyone? II

Postby Harry Dalek » Sat Dec 02, 2017 6:38 pm

Steve Anderson wrote:
Harry Dalek wrote:...makes me want to make Steve's when we can get around to it .

...should be a matter of days when I can resume work on the NBTV/SSTV-to-625 up-converter. First I have to sort out my office/workshop, clear out all the 'stuff' (read junk) cluttering the place up, get rid of all the rubbish and transport the office/workshop to the new location (earlier than thought) and get on with it.

Generator installed, works fine but only under manual control at the moment.

Steve A.


Good luck with the move Steve and no rush when ever you are is fine sure Klass Andrew and Chris would think the same .
This is some thing i would like to make so i will get stuck into it when we can .
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.
User avatar
Harry Dalek
"Fester! Don't do that to 'Thing'"
 
Posts: 3826
Joined: Fri Sep 26, 2008 4:58 pm
Location: Australia

Re: Retro SSTV Anyone? II

Postby Steve Anderson » Sun Dec 03, 2017 11:38 am

Thanks Harry. We've got a truck arriving Monday with a couple of guys to help load/unload. But even with the office/workshop downtime I'll still be popping in here each day.

You never realise how much stuff you have until you have to move it. I've discovered things I had completely forgotten about, Prototypes I built for clients perhaps two decades ago, useless to me now - in the bin.

Steve A.
User avatar
Steve Anderson
"Fester! Don't do that to 'Thing'"
 
Posts: 3741
Joined: Fri Mar 30, 2007 10:54 pm
Location: Bangkok, Thailand

Re: Retro SSTV Anyone? II

Postby Klaas Robers » Fri Jun 29, 2018 7:05 pm

This week I got for free a copy of my 7BP7 SSTV-monitor. Someone close to Eindhoven built it in .... say 1974 and is now emptying his shack. I will make a few pictrures of it and post them here. If anyone of you likes to have it, think about the transportation ...... Further you can have it for free.

Circuit details:
- Input-limiter TAA350 as 80 dB amplifier-limiter,
- audio input signal 0,3 mV - 30 V,
- couning detector (DTL one-shot) on both edges,
- passive LC (pot core) low pass filter 0 - 900 Hz, group delay compensated,
- sync detection by LC tuned circuit, 1000, 1100, 1200, 1300, 1400 Hz switchable,
- sawtooth generators - deflection amplifiers for H and V
- 5 kV generation by self oscillating inverter circuit
- 7BP7 picture tube (7 inch diameter) with 70 degrees TV-deflection yoke from 1955,
- power supply 220 V, can be recircuited for 110 V,
- printed circuits home built, not experimenters boards as I used,
- aluminium chassis for everyting,
- hard board cabinet, W = 30, D = 46, H = 26 centimeter.

I have to check the circuits / alignments, as it is not yet, or no more functioning comparable to my own, 'Heathkit-look' monitor. Read the thread "Retro SSTV anyone ?" number 1, now closed, to see my first experimental model on a wooden chassis (page 5) and the same circuits recently rebuilt in a Heathkit SB-500 cabinet.
User avatar
Klaas Robers
Frankenstein was my uncle.
 
Posts: 1397
Joined: Wed Jan 24, 2007 8:42 pm
Location: Valkenswaard, the Netherlands

Re: Retro SSTV Anyone? II

Postby Steve Anderson » Sat Jun 30, 2018 12:16 pm

Hmmm, if I were in Europe I'd be tempted. But this far away shipping would be simply be too much. I hope someone takes up the offer.

Steve A.
User avatar
Steve Anderson
"Fester! Don't do that to 'Thing'"
 
Posts: 3741
Joined: Fri Mar 30, 2007 10:54 pm
Location: Bangkok, Thailand

Re: Retro SSTV Anyone? II

Postby Harry Dalek » Sat Jun 30, 2018 5:32 pm

May be if your willing to wait Steve the shipping via a ship might not be to bad airmail would cost a penny these days ,puts me off selling on ebay over seas ,i recall 2 old vintage telegraph books would of cost me 100 dollars hate to think what a SSTV with a Transformer would cost ...mmm may be if Klass takes that out might be better ?
Last edited by Harry Dalek on Sat Jun 30, 2018 8:22 pm, edited 1 time in total.
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.
User avatar
Harry Dalek
"Fester! Don't do that to 'Thing'"
 
Posts: 3826
Joined: Fri Sep 26, 2008 4:58 pm
Location: Australia

Re: Retro SSTV Anyone? II

Postby Klaas Robers » Sat Jun 30, 2018 8:03 pm

Not too fast....

In the mean time I have seen that the passive video low pass filter is working in a wrong way. I fear that Jacko mixed up the pot core inductors, so I am going to demount the filter and measure everything. I know how nice it could work, so it should do that.

Secondly I found out that the high voltage invertor is instable. The inverter has a feed back over the 5kV high voltage, to keep it constant on white (yellow) as well on black. But on black it shows a slow variation. Don't know what the cause is, but I will find it and solve it.

And then it needs an allignment of the horizontal + vertical deflection generator to display a true square picture. This is now not correct.

Before these things are corrected the monitor is not leaving my home.
User avatar
Klaas Robers
Frankenstein was my uncle.
 
Posts: 1397
Joined: Wed Jan 24, 2007 8:42 pm
Location: Valkenswaard, the Netherlands

Re: Retro SSTV Anyone? II

Postby Klaas Robers » Tue Jul 03, 2018 9:58 pm

This is the monitor, made by Jacco, PA0BOJ. Here are some photographs:

The front with the cabinet:
BOJ-front1.jpg
BOJ-front1.jpg (58.55 KiB) Viewed 980 times
Photo made in my shack, we had a clear sky, but in the shade then everything is blueish. In reality the cabinet is white, the front is aluminium. Jacco reused the majority of the knobs for another project.

The front with the cabinet (hood) taken off:
BOJ-front2.jpg
BOJ-front2.jpg (68.64 KiB) Viewed 980 times

The left side of the monitor:
BOJ-left.jpg
BOJ-left.jpg (72.32 KiB) Viewed 980 times
You see the picture tube 7BP7 with the deflection yoke. The yoke holds two magnetic rings for (magnetic) focussing.
Behind the picture tube is the transformer. I doubt if this is the optimal position. In the space below the picture tube is the high voltage (5 kV) inverter positioned.

The right side of the monitor:
BOJ-right.jpg
BOJ-right.jpg (71.95 KiB) Viewed 980 times
The printed circuit boards are, from left to right:
- input amplifier + counting detector,
- passive low pass filter (900 Hz) and group delay correction,
- sync pulse extraction circuit, switcheable for 1000 Hz, 1100 Hz, 1200 Hz, 1300 Hz, 1400 Hz,
- horizontal deflection generator (15 or 16.66 Hz) and driver amp for the deflection yoke,
- vertical deflection generator (8 or 7.2 sec) and driver amp for the deflection yoke,
- video amplifier for the picture tube,
- rectifiers and stabilisators for the power supply.
User avatar
Klaas Robers
Frankenstein was my uncle.
 
Posts: 1397
Joined: Wed Jan 24, 2007 8:42 pm
Location: Valkenswaard, the Netherlands

Re: Retro SSTV Anyone? II

Postby Harry Dalek » Wed Jul 04, 2018 7:59 am

That's a little transformer least it does not look to heavy once you have to mail it to someone ,,,did he have any shielding ?
Its good you saved it watching with interest .
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.
User avatar
Harry Dalek
"Fester! Don't do that to 'Thing'"
 
Posts: 3826
Joined: Fri Sep 26, 2008 4:58 pm
Location: Australia

Re: Retro SSTV Anyone? II

Postby Klaas Robers » Wed Jul 04, 2018 8:31 pm

Well, the transformer is not really small, but the monitor draws not so much current, from the 230 volt mains: 0,1A, that is 23 watts. So a larger transformer is not needed. However the monitor is quite large, see above, so the transformer may look smaller than it is.

Yesterday I found a problem in the video low pass filter. This morning I repaired it. It was not in the low pass filter itself, that was passing straight from 0 to 1000 Hz and then cutting off sharply, but is was in the all pass filter. Jacco used a wrong type of ferrite potcore. I think that he was not aware that there should be used two different types, mostly a type with an air gap, but occasionally one without an air gap. He made all with an air gap. Luckily I had still a few of the correct type, without the air gap, so I changed the cores.

Now the most visible problem is a very instable sync, noise on the line sync. But I noticed already that in the sync separation circuit there is as well a potcore of the wrong type, so I am going to change that as well.

I will add the picture of the right side of the monitor with a red circle on both potcore inductors.
BOJ-right2.JPG
BOJ-right2.JPG (45.91 KiB) Viewed 968 times
User avatar
Klaas Robers
Frankenstein was my uncle.
 
Posts: 1397
Joined: Wed Jan 24, 2007 8:42 pm
Location: Valkenswaard, the Netherlands

Re: Retro SSTV Anyone? II

Postby Harry Dalek » Wed Jul 04, 2018 10:06 pm

Klaas Robers wrote:Well, the transformer is not really small, but the monitor draws not so much current, from the 230 volt mains: 0,1A, that is 23 watts. So a larger transformer is not needed. However the monitor is quite large, see above, so the transformer may look smaller than it is.


Yes a lot of space in the tube part of the cabinet ,is the case home made ? must of been even harder back then to find a case to but for some thing like this .
BTW the little circuit boards look like yours must of been the norm around when you and your friend made the monitors ?

Yesterday I found a problem in the video low pass filter. This morning I repaired it. It was not in the low pass filter itself, that was passing straight from 0 to 1000 Hz and then cutting off sharply, but is was in the all pass filter. Jacco used a wrong type of ferrite potcore. I think that he was not aware that there should be used two different types, mostly a type with an air gap, but occasionally one without an air gap. He made all with an air gap. Luckily I had still a few of the correct type, without the air gap, so I changed the cores.

If my memory is right i recall my original SSTV the passive filter used 33mH round core i didn't make them but a friend did ,had no way back then on test inductance i was lucky my friend knew how to wind the 2 needed worked well .
Did he say he had any problems with the SSTV as it sounds like it would of effected the viewing results which must of looked very washed out /

Now the most visible problem is a very instable sync, noise on the line sync. But I noticed already that in the sync separation circuit there is as well a potcore of the wrong type, so I am going to change that as well.


This must of also been a big problem trying to to receive any thing but harder as its all on the on the HF band and i suppose in Europe CB band too .

This tube is magnetic focus yes ? it looks to me like a permanent magnet on the yoke ? my first one tended to loose focus as the coil heated up with use.

I think this monitor has a good repairman after all these years :wink:
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.
User avatar
Harry Dalek
"Fester! Don't do that to 'Thing'"
 
Posts: 3826
Joined: Fri Sep 26, 2008 4:58 pm
Location: Australia

Re: Retro SSTV Anyone? II

Postby Harry Dalek » Thu Jul 05, 2018 10:41 pm

Here's some information i found ,the magazine list 15 and 16 i have not seen or heard of but the information is good for any one interested in the old system or new to it if you have translate seems to on my chrome web browser.

http://www.robkalmeijer.nl/techniek/ele ... index.html
http://www.rfcafe.com/references/popula ... t-1973.htm

Heres some nice vintage sstv shack photos 1972
https://www.flickr.com/photos/tift/4297 ... otostream/

Literature list
QST, aug.sept. 1958, A new narrow band image transmission system, Part I / II, W4ZII / 2.
QST, Apr. 1960, Slow scan Image transmission, a process report.
QST, Jan / Feb. 1961, SCFM, An improved system for SS Image transmission, Part I / II, WA2BCW.
QST, mar. 1964, A compact SSTV monitor, WA2BCW.
QST, jun / jul / aug. 1965, Slow Scan Vidicon Camera, Part I / II / III, WA3BTK.
QST, dec. 1968, Slow Scan with regular vidicons, WA2EMC / 8.
QST, jun. 1970, Slow Scan TV viewing adapter for oscilloscopes.
QST, mar. 1971, A solid state SSTV monitor, W9LUO.
QST, Aug. 1971, Feedback (correction on monitor from 08) p. 41.
QST, Nov. 1971, Recent Equipment Robot Research model 70 SSTV monitor and model 80 camera.
QST, Jan. 1972, What you all wanted to know about SSTV ... W1VRK.
QST, Jul. 1972, A storage tube monitor for SSTV.
QST, Jan. 1973, SSTV video inversion and short scans, p.42, W4TB.
QST, mar. 1973, A solid state SSTV monitor, Mark II, W9LUO.
ELECTRON, 5-1973, Solid state Slow scan Television monitor, PA0DTL.
Radioamatööri 3-1973, SSTV testikuvageneraattori, OH2KT.
The Shortwave Magazine, May 1973, Knowing about SSTV, p. 152.
EJR Hubach, PA0FIN.
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.
User avatar
Harry Dalek
"Fester! Don't do that to 'Thing'"
 
Posts: 3826
Joined: Fri Sep 26, 2008 4:58 pm
Location: Australia

Re: Retro SSTV Anyone? II

Postby Klaas Robers » Tue Jul 10, 2018 7:40 pm

Yes Harry, the case is home made. Jacco used aluminium L-profile, aluminium sheet material and pop-nails. The "hood" is made of white finished hard board. The support of the deflection coil and of the CRT-screen is something original, that I haven't ever seen before.
The small etched PCBs are made by Jacco himself, this was not uncommon in the 70s. Etching with ferrichloride on the kitchen table. In my monitor on the wooden chassis I built everything on experimenters board. The same boards are reused in the Heathkit-cabinet monitor.

The inductors were made on Philips pot-cores. They had different values, the number of turns and the wire diametre were published after I calculated them. The problem was that two different types of pot-cores were used, most of them had an air gap and could be adjusted, but for two of them a pot-core without airgap were needed, because of the high inductance. This was overseen by Jacco, so those inductors had a value far too low. That gave a different behaviour, but it still worked more or less. If you don't check the wave forms with an oscilloscope you might not discover this, but the monitor worked sub-optimal. May be that Jacco haven't discovered that in the 70s, if you don't know what to expect, you might think that it isn't better, especially on the noisy HF bands.

The tube has magnetic focus and this is done by two permanent ferrite magnetic rings. The distance between the two can be varied, which optimizes the focus.
User avatar
Klaas Robers
Frankenstein was my uncle.
 
Posts: 1397
Joined: Wed Jan 24, 2007 8:42 pm
Location: Valkenswaard, the Netherlands

Re: Retro SSTV Anyone? II

Postby Harry Dalek » Tue Jul 10, 2018 9:32 pm

May be he didn't have a scope to test ? ..very well done if so that makes it so much harder ,sad but he was more than likely forced to move onto new SSTV systems making the monitor redundant .
Not to us few :wink:
Doing the focus with permanent ferrite magnetic rings is a great idea a powered coil was a pain as i recall :roll:
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.
User avatar
Harry Dalek
"Fester! Don't do that to 'Thing'"
 
Posts: 3826
Joined: Fri Sep 26, 2008 4:58 pm
Location: Australia

Previous

Return to Cop McDonald's FM SSTV System

Who is online

Users browsing this forum: No registered users and 1 guest

cron