I've serviced all the tuners mentioned in this thread at one point or another. Even though these days my main business is building tube amps and preamps, I kept all my tuner troubleshooting gear from the old days.
There are several points to keep in mind with all old tuners:
The tubes must be good
The filter caps must be in good condition
Coupling caps should be looked at (some Fishers have real trouble with this)
The tuner should be in good alignment, particularly the ratio discriminator.
If you experience excess noise when tuning the station, that is caused by corrosion in the bearing of the tuning capacitor, and can be sorted out with a shot of Deoxit.
I always like the Scott tuners as they could have very good performance for the dollar. Outside of the Marantz I think one of the Scotts was the only tuner other than the Marantz that had 4 tuning caps in the front end. They built one with cosmetics meant to match that of Marantz, to fill that market for Marantz owners before the model 10 came out. Their layout and construction is pretty spartan, but they are also done rather thoughtfully so they are easy to service.
The Macs were all good too, with much more grandiose chassis hardware. The Marantz 10 was the king of all tube tuners and took a bit more finesse to sort out, but are quite reliable once that is done. The scope was fun but an unneeded extravagance. They get good money for that CRT on ebay if yours is bad! Rebuilding them is a pain but worthwhile. The trick to them is get a good copy of the schematic- it is laid out exactly the same as the internals, and so also functions as a layout guide. They have some special circuits for muting and the like that use neon lamps and LDRs; if these fail they can be rebuilt easily enough.
I have a Dyna FM-3 myself. Its weakness is the glue that holds the IF transformers together is often failing so you sometimes have to perform surgery on them to get the tuner to really perform. They sound fine but don't have the sensitivity of the other tuners, and try finding that seeing eye tube if its bad (fortunately that is a rare issue).
In all cases and including MPX adapters, alignment is critical! If this is off, stereo separation suffers or may not even exist, and some may also generate beat tones depending on the design. So this is one area that is best left to someone who has an FM Stereo generator.
There are several points to keep in mind with all old tuners:
The tubes must be good
The filter caps must be in good condition
Coupling caps should be looked at (some Fishers have real trouble with this)
The tuner should be in good alignment, particularly the ratio discriminator.
If you experience excess noise when tuning the station, that is caused by corrosion in the bearing of the tuning capacitor, and can be sorted out with a shot of Deoxit.
I always like the Scott tuners as they could have very good performance for the dollar. Outside of the Marantz I think one of the Scotts was the only tuner other than the Marantz that had 4 tuning caps in the front end. They built one with cosmetics meant to match that of Marantz, to fill that market for Marantz owners before the model 10 came out. Their layout and construction is pretty spartan, but they are also done rather thoughtfully so they are easy to service.
The Macs were all good too, with much more grandiose chassis hardware. The Marantz 10 was the king of all tube tuners and took a bit more finesse to sort out, but are quite reliable once that is done. The scope was fun but an unneeded extravagance. They get good money for that CRT on ebay if yours is bad! Rebuilding them is a pain but worthwhile. The trick to them is get a good copy of the schematic- it is laid out exactly the same as the internals, and so also functions as a layout guide. They have some special circuits for muting and the like that use neon lamps and LDRs; if these fail they can be rebuilt easily enough.
I have a Dyna FM-3 myself. Its weakness is the glue that holds the IF transformers together is often failing so you sometimes have to perform surgery on them to get the tuner to really perform. They sound fine but don't have the sensitivity of the other tuners, and try finding that seeing eye tube if its bad (fortunately that is a rare issue).
In all cases and including MPX adapters, alignment is critical! If this is off, stereo separation suffers or may not even exist, and some may also generate beat tones depending on the design. So this is one area that is best left to someone who has an FM Stereo generator.