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Old 3rd Aug 2022, 5:20 pm   #3
murphyv310
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Join Date: Sep 2006
Location: Kilmarnock, Ayrshire, UK.
Posts: 5,422
Default Re: Band 1 Rod Pentode modulator (Part 2)

Hi.
More work done today and some changes to the circuitry.
The 45Mhz crystal is low and doesn't always start and the 41.5Mhz crystal is as dead as a dodo. So I have found a 44.3Mhz crystal for Vision and a 40.815Mhz crystal for sound, both a bit low for channel 1 and of course not exactly a 3.5Mhz spacing but it works extremely well.
It has been pointed out to me on post 1 I have quoted the wrong valves they are 1ZH37B NOT 1ZH42B (there is no such valve as a 42B anyway its a 1ZH42A) Just to clear up any confusion.
I have contacted Vincent Jakomin re 45 & 41.5Mhz crystals.
I have also tidied up the bias arrangements.
I'll upload a revised diagram in due course.
Two further Videos here: https://youtu.be/CiT2tFXA-4M
https://youtu.be/7rQrSisX10E
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Trevor.
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