There seems to have been several models of these over the years that all have about the same controls. Apparently the markers are crystal derived. Do they actually contain a built in sweep generator, or are they an add on post marker generator to be used in conjunction with another sweeper? Anyone have experience using one, good-bad?

http://www.ebay.com/itm/Heathkit-ig-5257-Sweep-Marker-Generator-Tested-/260927682803?_trksid=p4340.m185&_trkparms=algo%3DSIC.NPJS%26its%3DI%252BC%26itu%3D UA%26otn%3D5%26pmod%3D170714717996%26ps%3D63%26clk id%3D5493499567610390714

I got a rough one of those this summer, but have not had time to test it. From the manual I got with it I'm fairly sure it has an internal sweep generator. It was designed for both Color TVs and FM radios, though I'm not sure which TV IF frequency(s) it covers.

Hi Tom, thanks for the info. All of them I've seen have the newer 40Mhz IF standards, none of the early 20Mhz markers. As cheap as they go, it would fun to try to modify one for the older IF frequencies. I suppose finding the correct crystals would be tough. Anyone know of an online manual/schematic source for any of them?