System A Ch1 modulator using MC1374. - UK Vintage Radio Repair and Restoration Discussion Forum

murphyv310 · 2nd Dec 2020, 8:39 pm

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

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

pages 59-61

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

FRANK.C · 2nd Dec 2020, 10:41 pm

Hi Trevor
Circuit and PCB + some other parts are available here from ETF

Frank

murphyv310 · 2nd Dec 2020, 11:56 pm

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

Hi Trevor, was this one used in the David Loser cct in Television?

Ed

FERNSEH · 4th Dec 2020, 12:34 pm

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

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.

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I have started to build a slightly more presentable one on perforated project board, I must get round to finishing it.

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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.

2nd Dec 2020, 8:39 pm	#1
murphyv310 Dekatron Join Date: Sep 2006 Location: Kilmarnock, Ayrshire, UK. Posts: 4,416	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. __________________ Cheers, Trevor. 2M0GZQ BVWS, GQRP KLARC. Member

2nd Dec 2020, 8:52 pm	#2
Cobaltblue Moderator Join Date: Dec 2010 Location: Exeter and Poole, UK. Posts: 4,659	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 __________________ Don't care if it was a bargain why's it in my kitchen Mike T BVWS member. www.cossor.co.uk

2nd Dec 2020, 10:21 pm	#3
Restoration73 Nonode Join Date: Jun 2013 Location: Surbiton, SW London, UK. Posts: 2,158	Re: System A Ch1 modulator using MC1374. pages 59-61 https://worldradiohistory.com/Archiv...cs-1982-02.pdf

2nd Dec 2020, 10:41 pm	#4
FRANK.C Heptode Join Date: Feb 2006 Location: Roscommon, Ireland Posts: 646	Re: System A Ch1 modulator using MC1374. Hi Trevor Circuit and PCB + some other parts are available here from ETF Frank __________________ www.electronics.frankcuffe.ovh

2nd Dec 2020, 11:56 pm	#5
murphyv310 Dekatron Join Date: Sep 2006 Location: Kilmarnock, Ayrshire, UK. Posts: 4,416	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. __________________ Cheers, Trevor. 2M0GZQ BVWS, GQRP KLARC. Member

3rd Dec 2020, 8:20 pm	#6
Ed_Dinning Dekatron Join Date: Jan 2004 Location: Newcastle upon Tyne, Tyne & Wear, UK. Posts: 6,716	Re: System A Ch1 modulator using MC1374. Hi Trevor, was this one used in the David Loser cct in Television? Ed

4th Dec 2020, 12:34 pm	#7
FERNSEH Dekatron Join Date: Mar 2005 Location: Gateshead, Tyne and Wear, UK. Posts: 6,481	Re: System A Ch1 modulator using MC1374. 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 Attached Thumbnails Last edited by FERNSEH; 4th Dec 2020 at 12:40 pm.

8th Dec 2020, 11:59 pm	#8
rambo1152 Nonode Join Date: May 2010 Location: Manchester, UK. Posts: 2,623	Re: System A Ch1 modulator using MC1374. 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. I have started to build a slightly more presentable one on perforated project board, I must get round to finishing it. 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. __________________ -- Graham. G3ZVT Last edited by rambo1152; 9th Dec 2020 at 12:10 am.