I wonder too. The poor things seem like the lowliest of all components. Not real pretty & not much press time like the electrolytic rage going on now.
I don't see ads for esoteric audiophile ceramic discs. There must be some though........
No, I had to replace that cap because the PLL was in free running mode ( no lock )
It was an issue and I replaced it with an other ceramic cap .
No improvement , only a repair .
It is unbeliavabe to find a wrong ceramic cap , due to their long life span .
Regarding PL 4000 , after recapping, no difference in sound .
Instead for Dynaco PAT 4 , probably there was an improvement .
But consider also that PAT 4 power supply is a " strange " circuit .
Unregulated power supply with 2 diodes rectifier .
As with most analog tuners they tend to drift with age. Over the years, I had the opportunity to watch Dean perform his magic on many a 5000 and 5100. I haven't seen a 5000 yet that has met factory specs. Unless of course someone else has done a recent alignment (say within the last 10 years). They all need a complete FM alignment. I have a Sound Technology 1000A, 1100A and 120. I hope someday soon to start working on my own tuners.
One of the most common problems with the 5000 is with the 390pF ceramic disc capacitor C22 located next to R39. This capacitor will go down is value by about 30pf. That is enough such that there isn't always enough range of adjustment with R39 in order to bring the 19kHz clock within the factory spec of +/-100Hz. Typically, old 5000's are off by around 1000 Hz. Dean would usually just tack/solder a 30pF cap on top of the existing cap.
With a properly operating 5000 tuner, you should have the signal strength at its maximum, the center tuning should be centered and the (19kHz) stereo pilot light should be illuminated. You shouldn't have to tune any of these parameters off center in order to obtain a better condition of any of the others.
A.P. Van Meter designed the Phase Linear 5000 tuner. A.P. had previously worked at McIntosh just after he graduated from the University of Oklahoma. A.P. was on the ground floor of FM stereo in late '61, early '62. He has a bunch of interesting stories about those early days. I had a McIntosh MX110 tube tuner/preamp that A.P. had a hand in designing. His name is also on some of the schematics.
To be honest Dynaco FM 5 ( 1972 ) has a PLL called Dynatune !
I have this tuner and it works very well .
Probably LM 1800 is the first IC that performs both FM mpx demodulator and PLL in the same case .
Regarding AP Van Meter I don't understand why he did not use the Hi blend filter function .
It' only one cap circuit . Oh , question mark !