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Old 24th Feb 2019, 1:15 am   #5
Argus25
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Join Date: Oct 2016
Location: Maroochydore, Queensland, Australia.
Posts: 2,679
Default Re: Output of uhf modulators

Quote:
Originally Posted by Pieter H View Post
Two remarks to Graham's inputs:

The same was essentially true for the VCR UHF modulators, see e.g. https://www.maximus-randd.com/tv-tun...tml#vcrmodules. Otherwise a modulator module should contain two UHF oscillators.

Pieter
The balanced modulator IC's used, cited as the part number N343-OM are very interesting. For example it says here that they are the same as the TCA240, or that this IC is a development of them (which is an error)

https://www.radiomuseum.org/forum/n1...t_n343_om.html

The N343-OM is the TCA820 I think (not a TCA240), if you check the data sheet for these , pin outs etc you will see its the same part. These are spectacularly good balanced modulator IC's that work well into the UHF spectrum.

The TCA820's were also used inside the modulator unit of Philip's PM5519 Televsion pattern generator. The TCA820 went out of production during the course of that unit, so Philips had to replace them with the TDA0820T with different pin outs and as a result Philips had to change the pcb inside the modulator unit, and a customer had to buy an entire unit for repairs. Due to this I collected some of these IC's so I could make sure to be able to repair my PM5519's if required.
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