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-   Television Standards Converters, Modulators etc (https://www.vintage-radio.net/forum/forumdisplay.php?f=95)
-   -   System A Ch1 modulator using MC1374. (https://www.vintage-radio.net/forum/showthread.php?t=173814)

murphyv310 2nd Dec 2020 8:39 pm

System A Ch1 modulator using MC1374.
 
Hi.

I have four MC1374 IC's that were used in a Channel 1 405 line modulator some years ago.
I need to build one up but have no info at all on it.
Does anyone remember these and if perhaps a PCB was or is available with a circuit.

Mods I'm not sure if this should be posted here or in the info wanted section, please move if necessary, thanks.

Cobaltblue 2nd Dec 2020 8:52 pm

Re: System A Ch1 modulator using MC1374.
 
One that I built a long time ago was in 405 Alive

Perhaps it was that one?

Now Here

https://www.bvws.org.uk/405alive/tech/modulator.html

Cheers

Mike T

Restoration73 2nd Dec 2020 10:21 pm

Re: System A Ch1 modulator using MC1374.
 
pages 59-61

https://worldradiohistory.com/Archiv...cs-1982-02.pdf

FRANK.C 2nd Dec 2020 10:41 pm

Re: System A Ch1 modulator using MC1374.
 
Hi Trevor
Circuit and PCB + some other parts are available here from ETF


Frank

murphyv310 2nd Dec 2020 11:56 pm

Re: System A Ch1 modulator using MC1374.
 
Thanks chaps.
The ETF one is it.
I made a couple many years ago, someone here gave me a couple of boards, both went to other collectors. I've one to make up and try at a lower frequency for a project.
All will be revealed in due course.

I've all the bits but no board unfortunately.

Ed_Dinning 3rd Dec 2020 8:20 pm

Re: System A Ch1 modulator using MC1374.
 
Hi Trevor, was this one used in the David Loser cct in Television?

Ed

FERNSEH 4th Dec 2020 12:34 pm

Re: System A Ch1 modulator using MC1374.
 
2 Attachment(s)
The attachments show an early ETF modulator. The example I have here required considerable modification before it would work.
The MC1374 was designed for negative modulation systems, that being the case a separate sync tip clamp is used to so that the sync tips can reference to zero modulation. An emitter follower is introduced between the input amplifier and the input pin of the MC1374. Seems that the IC demands a low impedance drive.
The carrier oscillators can be modified to crystal resonators.
Modulator will work on channel B4 frequencies.

Information about the MC1374.

https://www.circuitspecialists.com/c...27/mc1374p.pdf

DFWB

rambo1152 8th Dec 2020 11:59 pm

Re: System A Ch1 modulator using MC1374.
 
3 Attachment(s)
I built the ETF modulator on a breadboard three years ago to use with a PC graphics card project. It works so well it's still in the state you see it here.
Attachment 222147 Attachment 222148
I have started to build a slightly more presentable one on perforated project board, I must get round to finishing it.
Attachment 222149
Anyway, my point is the absence of a custom PCB shouldn't put anyone off.

Mine is tuned to B2, the free-running oscillators are no problem, set and forget. I didn't bother with the output filter, I don't think David did either.


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