UM1662 RF Modulator

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johnkenyon
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Joined: Wed Jul 20, 2011 3:21 pm
Location: Coventry
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UM1662 RF Modulator

Post by johnkenyon » Wed Mar 20, 2019 12:23 pm

Whilst rummaging around a box of spares I've found a UM1662 RF modulator - It modulates video+mono sound onto channel 36 with the sound on the former UK standard 6MHz subcarrier.

I can find a couple of photos of the first page of the datasheet, and absolutely nothing else.

I then thought of searching around for schematics for devices which used it - if I could only find such a device.

So my questions are:

Does anyone have a datasheet for this device?
Does anyone know which equipment this unit would have been fitted in? (Not Dragon 32/64: UM1287, Not any type of Spectrum: UM1233 the lot)

For the record, all I want to do is to spit out RF for in house distribution from a composite video CCTV camera signal.

Thanks in advance

Kazzie
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Re: UM1662 RF Modulator

Post by Kazzie » Wed Mar 20, 2019 1:33 pm

According to this page the Atari XL series used the UM1662. The Field Service Manual for the 800XL (here) lists the UM1652 (NTSC version) on its parts list.
BBC Model B 32K issue 7, Sidewise ROM board with 16K RAM
Archimedes 420/1 upgraded to 4MB RAM, ZIDEFS with 512MB CF card
RiscPC 600 under repair
Acorn System 1 home-made replica

johnkenyon
Posts: 246
Joined: Wed Jul 20, 2011 3:21 pm
Location: Coventry
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Re: UM1662 RF Modulator

Post by johnkenyon » Thu Mar 21, 2019 9:29 am

I've also found out that the A3010 used a UM1662.

Unfortunately the A3010 doesn't have a composite video output, so I can't see how the UM1662 video in differs from bog standard CVBS out.

I'm struggling to find a useful Atari circuit diagram.

I think I will just suck it and see.
My expected problems are that I'll need an amp to increase a line level signal to that required by the modulator, and that the modulator won't like 5v from a modern switched mode USB adapter...

/John

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