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Old 29th Mar 2019, 7:54 pm   #14
Argus25
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Join Date: Oct 2016
Location: Maroochydore, Queensland, Australia.
Posts: 2,679
Default Re: Assistance with modulator design

Quote:
Originally Posted by Autozavod View Post
Hi everyone,

I rebuilt an old Soviet KVN-49 tv from the 50’s, and whilst I can run it by directly injecting a PAL signal into the video amplifier, my preference is to run it as intended.

One option is to feed a PAL signal into a pair of MC1374 chips using the design found here http://www.earlytelevision.org/405_modulator.html
THese could be modified and as noted the IC is up to the task, but there may be better IC's. I'm not 100% sure but as I recall the supplied PCB for this modulator does not have a ground plane. When I was testing one on the scope I found the measurements were difficult because of the residual RF at different points on the tracks that were ground or common. But the PCB may have been modified since it was first introduced by the ETF and despite not having a ground plane the PCB worked well and as far as I know many people have used these without difficulty. As noted you would just need the one and modify for the addition of FM sound according to the IC's data sheet.Since its L/C and not Xtal tuned you could just adjust it to suit the existing set tuning.
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