Modulation Tests

Moderators: Steve Anderson, Dave Moll

Modulation Tests

Postby Harry Dalek » Tue Feb 28, 2017 8:27 pm

Hi Klaas i am happy to report your design is modulating my beam ...all the controls seem to work,
The curse of the wiggle in the raster line has returned unfortunately...more head scratching !
But apart from that so far this is a very nice step forward...i tried your test card Klass and a checker board today ..i am not sure if i am on frequency for the line frequency seems very blown up picture so more than likely not but least i got something today and i know the circuits work ...
Now have to work out why my raster line has gone funny again.
Below quick not so great video sorry bit rushed today .

youtu.be/WhWoRkIB8rs

youtu.be/DrwzHmeJpvw
Attachments
IMG_1106.JPG
IMG_1106.JPG (345.21 KiB) Viewed 3991 times
IMG_1116.JPG
IMG_1116.JPG (233.28 KiB) Viewed 3991 times
IMG_1121.JPG
IMG_1121.JPG (228.4 KiB) Viewed 3991 times
Last edited by Harry Dalek on Tue Feb 28, 2017 10:22 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: 4426
Joined: Fri Sep 26, 2008 4:58 pm
Location: Australia

Re: Modulation Tests

Postby Klaas Robers » Tue Feb 28, 2017 9:37 pm

Harry,
this is surely something in the power supply. I see 6 negative peaks on a line.
- The monitor line frequency is almost synchronized, otherwise I could not read "SSTV".
- The SSTV line frequency = 16.667 Hz,
- so the "peaks" frequency = 16.667 x 6 = 100 Hz.
This is absolutely hum from the mains (power grid).

Check again your stabilized +12 volt and - 12 volt. I doný know how stable your power grid is. It is possible that the 240 voltage came down by 10%, or even more. Then the "raw" input voltage of the stabilizers may become too low.

Scope the input voltage of the stabilizers and check that it becomes not lower than 15 volt (12 volt + 3 volt margin). And please measure me from the scope the peak-peak voltage of the ripple. That should not be more than 1 volt.

Realize yourself that now the FM-demodulator is also drawing current, so the power supply is loaded more. That can bring the input voltage to a lower level.

Good luck!
User avatar
Klaas Robers
"Gomez!", "Oh Morticia."
 
Posts: 1533
Joined: Wed Jan 24, 2007 8:42 pm
Location: Valkenswaard, the Netherlands

Re: Modulation Tests

Postby Klaas Robers » Tue Feb 28, 2017 10:03 pm

Something else strange.... I see the text "SSTV" is negative. It should be white characters on a black background. This would say that the video transistor (ex BD115) gets a negative input signal.

You see Harry, this is the advantage of using a well known test picture. I know that in the FM signal the polarity is correct, low tones for dark, high tones for bright. I will examine the circuit diagrams of your video chain.......

I see in the old long thread that your video processing gives a positive video signal: low voltage for low input frequencies, high voltage for high input frequencies. That should give white characters SSTV on a dark (black) background. So, Harry, are you sure that you haven't interchanged the wire to the cathode and the wire to G1 ? If so, that will explain the "negative video" result.
User avatar
Klaas Robers
"Gomez!", "Oh Morticia."
 
Posts: 1533
Joined: Wed Jan 24, 2007 8:42 pm
Location: Valkenswaard, the Netherlands

Re: Modulation Tests

Postby Harry Dalek » Tue Feb 28, 2017 10:59 pm

Klaas Robers wrote:Harry,
this is surely something in the power supply. I see 6 negative peaks on a line.


I did swap back to the bench power supply so may be some thing not right here ,i was bit rushed after work this afternoon to check every thing ,i will have more time tomorrow afternoon .

- The monitor line frequency is almost synchronized, otherwise I could not read "SSTV".


I was thinking half frequency or double might have the effect of changing the image size i didn't have my frequency meter in my shed to check the line oscillator so you may be right with the wiggle in the line hard to tell changing the shape of things.
- The SSTV line frequency = 16.667 Hz,
- so the "peaks" frequency = 16.667 x 6 = 100 Hz.
This is absolutely hum from the mains (power grid).


OH Ok i will get my scope on the power supply see what happening

Check again your stabilized +12 volt and - 12 volt. I doný know how stable your power grid is. It is possible that the 240 voltage came down by 10%, or even more. Then the "raw" input voltage of the stabilizers may become too low.


I will have a look when i last checked when working on the 3bp1 i checked the mains and it was swinging a fair bit ...it was a very hot day today mains might be lower due to every one using more electricity for cooling .

Scope the input voltage of the stabilizers and check that it becomes not lower than 15 volt (12 volt + 3 volt margin). And please measure me from the scope the peak-peak voltage of the ripple. That should not be more than 1 volt.



OK i want a clean stable DC i will check whats going into the regulators .



Realize yourself that now the FM-demodulator is also drawing current, so the power supply is loaded more. That can bring the input voltage to a lower level.

Good luck!


Yes thats true i will check all these things tomorrow and take down some readings .

Any case i was happy the modulator is working today .
Perhaps klass thats some thing else i will check ...i colour coded my wires i was sure the white was the cathode but i will doublel check.

I do see your point of using the test card !
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: 4426
Joined: Fri Sep 26, 2008 4:58 pm
Location: Australia

Re: Modulation Tests

Postby Andrew Davie » Tue Feb 28, 2017 11:04 pm

Well done Harry - following this with great interest! And great support/advice Klaas - it's like watching two masters at work. :)
User avatar
Andrew Davie
"Gomez!", "Oh Morticia."
 
Posts: 1552
Joined: Wed Jan 24, 2007 4:42 pm
Location: Queensland, Australia

Re: Modulation Tests

Postby Klaas Robers » Wed Mar 01, 2017 12:01 am

I realize that it is at least remarkable that we are doing these things at a distance of amost 20 000 km, the largest distance possible. Sometimes I have the feeling that I am looking into his circuits from here, the other side of the globe. Harry is learning a lot from these experiments.
User avatar
Klaas Robers
"Gomez!", "Oh Morticia."
 
Posts: 1533
Joined: Wed Jan 24, 2007 8:42 pm
Location: Valkenswaard, the Netherlands

Re: Modulation Tests

Postby Harry Dalek » Wed Mar 01, 2017 2:57 pm

Andrew Davie wrote:Well done Harry - following this with great interest! And great support/advice Klaas - it's like watching two masters at work. :)


Hi Andrew
OH Klass is the Master i am the grasshopper if you remember the old Kung Fu show :wink:
I am very happy Klass is helping me ,i sort of remember what to do making one of these but my first SSTV monitor was made over 30 years ago and that worked first time a good success but mistakes you make are more memorable for me any way ....why i left it behind when i moved to Melbourne was a doozy ! :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: 4426
Joined: Fri Sep 26, 2008 4:58 pm
Location: Australia

Re: Modulation Tests

Postby Harry Dalek » Wed Mar 01, 2017 3:55 pm

"e="Klaas Robers"]I realize that it is at least remarkable that we are doing these things at a distance of amost 20 000 km, the largest distance possible. Sometimes I have the feeling that I am looking into his circuits from here, the other side of the globe. Harry is learning a lot from these experiments.[/quote]

Yes Sir .. and very much so distance doesn't matter any more . :arrow: The forum is my favourite place to learn .

You were very much on the ball thinking the problem i reported on yesterdays test was some thing to do with the power supply .
Well i worked it out it was the bench power supply from your advice on testing the voltage side of things ,it was not up to the job ....ok for little circuit testing but the deflection circuits was a bit much for it ,i looked i only have a very small 500ma transformer in that by the looks of it !
I swapped to the Bench 3pb1 and also now also The Deep image Ac power supply it feeds via cable to the SSTV monitors rectifier regulator DC circuits ,it has a large Toroidal transformer that i am using on the dual 12 volt supply ...
So that stopped fault finding i just started to look at the Dc supply on the scope ...i saw 2 things i see sawtooth from the deflection board on the dc supply of about a fourth of a volt weak but there when the board was hooked up gone when not ..i also saw the inverter high frequency waveform half a volt but does not seem to effect any thing on the screen might be to high above the frequencies used here .
Those 2 things together again i am not seeing being a problem on the monitor screen
So Happy to report another step forward nice raster lines today ...modulation seen much better now .
I still have to look into the inverted video on your advice look into the cathode and control grid are swapped .
I took a photo the white wire i was thinking is the cathode but looks like i made a boo boo its pin 5 the control grid the light blue is pin 7 the cathode ...i should put this post in the control grid modulation :) whoops i will fix as soon as i can !


youtu.be/_u5sPaghDwg"

youtu.be/PulGRrBFD4E
Attachments
IMG_1170.JPG
IMG_1170.JPG (219.33 KiB) Viewed 3970 times
IMG_1172.JPG
IMG_1172.JPG (164.69 KiB) Viewed 3970 times
Screen 00001.jpg
Screen 00001.jpg (14.24 KiB) Viewed 3970 times
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: 4426
Joined: Fri Sep 26, 2008 4:58 pm
Location: Australia

Re: Modulation Tests

Postby Harry Dalek » Wed Mar 01, 2017 4:48 pm

Swapping the control grid and cathode was an easy fix so did so results as Klass expected .
I am now thinking time to think about syncing the monster !

youtu.be/B8n444XZrcg
Attachments
IMG_1182.JPG
IMG_1182.JPG (263.66 KiB) Viewed 3969 times
IMG_1180.JPG
IMG_1180.JPG (216.79 KiB) Viewed 3969 times
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: 4426
Joined: Fri Sep 26, 2008 4:58 pm
Location: Australia


Return to Harry Dalek's 5AHP7A Vintage SSTV The Deep image

Who is online

Users browsing this forum: No registered users and 1 guest

cron