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Television Standards Converters, Modulators etc Standards converters, modulators anything else for providing signals to vintage televisions.

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Old 30th Sep 2018, 6:18 pm   #1
chriswood1900
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Default Identifying a System A modulator

On the Bring and buy at Harpenden I bought a die cast box with some sockets on. When opening it up this weekend I found it contained a well built System A modulator based on 2 MC1496 chips with Crystals for 41.5 and 45Mhz all on a single board. I have not seen one of these before can anyone help with the origin of this and possibly point me to a manual or other info.
Many thanks
Chris
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Old 30th Sep 2018, 8:33 pm   #2
Philips210
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Default Re: Identifying a System A modulator

Hi.

I don't know if the design could be similar to this one here https://www.thevalvepage.com/project...at/modulat.htm It certainly has many things in common.

Regards
Symon.
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Old 30th Sep 2018, 10:56 pm   #3
FERNSEH
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Default Re: Identifying a System A modulator

It's the David Looser circuit that appeared in a 1984 Practical Television magazine titled "A System A Modulator"
Uses two MC1496 modulator ICs and BFY90 transistors in the carrier oscillators.

DFWB
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Old 1st Oct 2018, 10:43 am   #4
Nuvistor
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Default Re: Identifying a System A modulator

Thanks go to David for the reference.
https://www.americanradiohistory.com...UK-1984-10.pdf
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Old 1st Oct 2018, 1:09 pm   #5
chriswood1900
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Default Re: Identifying a System A modulator

Thanks to those who responded.
I found the article and it looks to be virtually identical. It is a nicely made PCB so I assume at some stage someone must have designed and sold the PCB perhaps as a kit.
After some quick tests all seems to work so I and finished the case off and put some knobs on it. I now have another useful modulator for my 405 sets.
Chris
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