Oh my, did you make a great find without having a clue! These are supposed to be really great tuners, highly sought after! I expect to be working on one for another AK member after the New Year.
Here's what the Tuner Information Center has to say about it:
Sony ST-5000F (ST-5000FW) (1968, $450) search eBay or search eBay
Intended to compete with the Marantz 10B, the Sony ST-5000 was the first audio component widely distributed by Sony in the U.S. Built like a tank, more like military gear (or McIntosh tuners) than later Japanese electronics, it has a strong following even though the styling was not great (very typical of '60s hifi gear). The two variations had different front panels (the one with “5000F” on the front panel is the “5000FW”, as it says on the back panel) and differences in the front end, IF filter, and MPX section as well. Both had 5-gang tuning capacitors, with the ST-5000's being silver-plated. Both had an 8-stage IF filter section, and an all discrete multiplex section. The 5000's filters are adjustable LC type, and the 5000F uses the 4-pin ceramic type, so don't buy an ST-5000 or 5000F expecting to swap 3-pin filters. The ST-5000 is the earlier version and is very rare. Our contributor Charles says that his ST-5000FW has a beautiful sound, and that “in the next room, it really seems like you have musicians in your house.” He also finds it “almost as good as my KT-7500 [for DXing]... in situations that try the adjacent channel selectivity of any tuner. That's amazing performance for a 30-year-old unit with all LC filters and only one IF bandwidth.” Mike Zuccaro comments as follows: “The ST-5000 had LC IF filters, a CdS Rf attenuator in the front end, fully bipolar front end (no FET's yet), CdS muting and switchable AFC. The ST-5000F (“F” for FET), introduced about one year later, had 4 FET's in the front end- 2 RF amps, mixer and oscillator. It did not need AFC. The 3 ceramic filter blocks used in the 5000F actually each contain 4 filters (!). It's not shown this way in the schematic (just a filter block), but is buried in the circuit description ('uses 3 4-section multi-unit ceramic filters'). The 5000F had standard transistor-driven muting (no CdS cell) and marginally better sensitivity specs. Both are very highly rated tuners - I'd consider them sleepers. Replaced by the AM/FM ST-5130, which I have worked on and is a nice unit, but the build quality was not the same as the 5000. The ST-5000 was Sony's first tuner, aimed at a heavyweight (the Marantz 10B), and like McIntosh's MR-55, Sony spared no expense. Later tuners may have had equal or better specs, but were certainly 'made to a price' whereas the 5000/5000F seem to have been built with more care.” The ST-5000/5000F shows up a few times a year on eBay and can sell for $150-350. The sale price usually depends on condition, but a supposedly “like new” ST-5000 sold for just $158 in 12/03. [BF]