I have been a member of this forum for several years, but I have not been very active on it. So I am not aware if this topic has been discussed here before. I own two variations of the H.H. Scott 312D FM tuner. The earlier version uses conventional interstage transformers in the IF strip. This model dates from about 1968 and uses FETs in the front end and four of the typical uA703 opamps in the IF strip. It's a shame that this tuner wasn't more popular in its day (which makes them hard to find today) because it is a fabulously good performer with excellent sensitivity AND selectivity, especially since it if an early design with a single bandwidth IF. It is demonstrably better than ANY of the earlier (or later) Scott tuners - in my estimation it is the BEST tuner that Scott ever made. And it is absolutely competitive with any other analog tuners that I have used.
Scott later made a change to this tuner and fitted it with a different IF strip that contains early crystal (or ceramic) filter blocks. This IF strip appears to use some different opamps. The first amp may be a 703 as it has six leads. But the other two amps are 8-pin packages and carry the Fairchild ID logo. But I can't read the type number on them. Part of the problem is that Scott never changed the model designation for this tuner. They should have noted the different IF with a model number something like 312D-2 or some such. The two versions look identical on the outside. So you can't tell the difference between these variations without opening them up and inspecting the IF strips. Does anybody have a schematic for this later version of the 312D? Or does anybody know what opamps were used in this later version? It's hard enough to find tech info on the earlier version (I do have the service manual for it), bui I have been unable to find ANY tech info on this later version.
Greg Bogantz
Scott later made a change to this tuner and fitted it with a different IF strip that contains early crystal (or ceramic) filter blocks. This IF strip appears to use some different opamps. The first amp may be a 703 as it has six leads. But the other two amps are 8-pin packages and carry the Fairchild ID logo. But I can't read the type number on them. Part of the problem is that Scott never changed the model designation for this tuner. They should have noted the different IF with a model number something like 312D-2 or some such. The two versions look identical on the outside. So you can't tell the difference between these variations without opening them up and inspecting the IF strips. Does anybody have a schematic for this later version of the 312D? Or does anybody know what opamps were used in this later version? It's hard enough to find tech info on the earlier version (I do have the service manual for it), bui I have been unable to find ANY tech info on this later version.
Greg Bogantz