Modify an old VCR TV modulator to channel 5

[wa2ise]

I modified a salvaged TV tuner and modulator from a VCR. I changed the TV modulator to move the channel from the usual ch3 or 4, to channel 5. The modulator chip is an AN3117SA, download the datasheet here http://www.digchip.com/datasheets/pa...umber=AN3117SA.

What I did was replace the saw crystal resonator (which has inside xtals for channel 3's video carrier, and channel 4's), with a 25MHz xtal salvaged from a computer board. Looks like this chip is oscillating on the 3rd overtone, which is approx 75Mhz, which is fairly close to channel 5's video carrier. Apparently close enough for a modern BPC TV set to pull it in on channel 5. Channel 5 is supposed to be on 77.25MHz.

I added a second crystal, 27MHz, to create a channel 6, on the 2nd xtal input of the chip. approx 81Mhz, apparently close enough to channel 6's 83.25Mhz.