[Zenith6S321]

As an avid reader of these forums I came across Bob's post about wanting a wider frequency range on the VA62. A few months ago I did my first restoration on a 721TS and found out how touchy analog RF generators are to use for a marker generator. I happened to have a VA62 and its schematics which I used to fix its 1MHz reference to the PLL. Back in the day I did some digital design work. So, like Jeremy Clarkson of Top Gear (love that show) I figured "how hard could it be?". I read the EPROM, used Google to find a dissasembler, and spent a few evenings looking through the schematics and the 28 pages of assembly code. I found the code that limits the keypad frequency input to 35.00 - 50.00 MHz and changed the limits to be 3.00 - 99.00 MHz. As Bob's cool video shows, the VA62 is designed for the 35-50 range, but will work outside that range to some extent. My Run 18 VA62 can reliably be programmed for 15.00 - 99.00 MHz. Below 15 is hit or miss. My VA62 uses a 2716 2K Byte EPROM, but the schematic shows a jumper to accomodate the 2732 4K Byte EPROM that Bob's has. The 8035 microcontroller can address two 2K Byte program memory banks. It would be useful to know if there are different firmware revisions or if they all use the same version. If you want to mod your VA62 PM me. I can supply the .HEX file if you have an EPROM burner or I can burn your EPROM if you send it to me along with a prepaid box to ship it back to you. As Bob's video shows the mod requires opening the VA62, removing the old EPROM and inserting the mod EPROM. This static sensitive electronics, so you do this at your own risk.