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Old 09-09-2016, 01:05 PM
Zenith6S321's Avatar
Zenith6S321 Zenith6S321 is offline
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Join Date: Aug 2010
Location: Charleston, West Virginia
Posts: 303
Version 2 of the EPROM modification uses a 2732 4K Byte EPROM which provides room for more modification code. My goal for version 2 was to make the VA62/A be able to:
1. Not disable any original VA62/A functionality.
2. Allow you to enter four digits for the video carrier frequency to support all IF frequencies (assuming the PLL oscillator will lock).
3. Make the VA62/A provide the same functionality for the early low band IF TVs as it does for the 45.75 MHz IF TVs.
4. Be easy to use (no need to use the frequency offset stuff)

This is how to use the V2 EPROM to generate the same 25.75 MHz IF signal as the version 1 does:

1. At VA62A power on and set for no modulation, IF output, 35-50MHz you should see this normal VA62A functionality.


2. Now enter 2575 (25.75 MHz).


3. To modulate this 25.75 IF signal with the video and audio test patterns rotate the RF-IF SIGNAL switch to the PROG CABLE CH2-99 position. Then select the audio and video test patterns you want. That's it.



4. A Teletone TV-149 video carrier is 37.30 MHz so


5. Want to set the TV-149 sound trap? Rotate the RF-IF SIGNAL switch to the 41.25 (sound trap for a 45.75 MHz IF) and the mod calculates the sound trap frequency and sets it for you.


The RF-IF switch positions for the 45.75 MHz IF traps are all set to the proper frequencies that correspond to the video carrier frequency you entered. So the V2 EPROM modification provides all of the functionality for early TV low band IFs as the 45.75 MHz sets.
Attached Images
File Type: jpg V2-3500.jpg (142.4 KB, 186 views)
File Type: jpg V2-2575.jpg (142.4 KB, 181 views)
File Type: jpg TT-3730.jpg (56.6 KB, 174 views)
File Type: jpg TT-3280.jpg (144.6 KB, 176 views)
File Type: jpg 630TS-2575Modu.jpg (56.4 KB, 174 views)

Last edited by Zenith6S321; 09-09-2016 at 02:11 PM.
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