This is a rather complicated set - not the best for your first alignment, particularly the FM band. If it's not too bad, you might leave it alone until you've gained more experience with simpler sets?
Doug

:I have an RCA 612V3 with "tuner" problems of sorts. I need to know how to spread out the tuning distance to match with the indicator dial on the FM broadcast. The schematics I have don't say anything about how to adjust the tuning cap travel to dial travel. Or am I just missing out on what its called???
:Any ideas on any or all three questions?
:Regards
:Steve
:

You did not get specific with the tuning error, and there are two things to consider, firstly that the AM as well as Short Wave shares that same dial pointer…doesn’t it ?... and if any great tuning error is present on those bands also ?

Also, this units whole FM dial scale logging points is just 6 spread out numerical references. Take a look at the dial scale logging that they provided in the service literature below.

Getting back to just the FM tuning error aspect, …..does it seem to be equally displaced across the band…e.g…. is a station that you know to be on 90 Mhz, coming in at 95 on the dial …while you also find one that is known as being 100 coming in on 105 on the dial scale. ( Or that tuning error could be shifted to be erred lower in frequency /vs / dial scale logging in its calibration error.)
The other aspect being a nonlinearity of the dial scale accuracy, with a station in the middle of the band being right on its dial scale logging, while stations either extremes of that center station could either be compressed up or spread out on their readings presentations.

Give us some feedback of the tuning error readings that you found:

Do that by taking readings at the very lowest end of the band where you are receiving a station, then about 1/3 up the band on another station, and then at the center of the dial, and then at about 2/3 across the dial and finally towards the very highest end of the dial. That would fill us in on what correction needs to be initiated …within the realm of exactly what degree of correction that the chassis parts and design will let one make.

The primary aspect of the provided compensation of tracking of the dial scale is dependent upon the FM local oscillator frequency…. the high end of the dial scale is mainly dependent upon the capacitive setting of adjustable trimming capacitor C20 in the markup below …while its companion L9 is associated with the low end of the dial.

Now if you want to attempt a trial at closer calibration, take a blue micro Sharpie marker and take note of the slots in the cap adjustment screw and the slot in the slug and make coincident marks on a stationary reference right to the side of each slot…or on the coils form . That way you can find your way back to from whence you did begin initially.

PLUS…. the adjustment is not going to be like taking lug nuts off…I am expecting ~ 1/4 turn max in either direction from the initial setting.
The adjustments ideally need to be made with an hard insulated " slotted screwdriver" type of alignment tool, to preclude metallic interaction and a tuning error after removing a tool...a hard phenolic or plastic shaft can be filed to such shaping on one end. I have used large plastic knitting needles, plastic shafts of artist brushes, etc, etc.

The C20 capacitor adjustment tweaks the accuracy at the 88 end of the dial, while the slug in the L9 inductor affects the 108 end of the dial scale.


Electro mechanical referencing:

[ I’m not even going into the convoluted aspect of a set value of L in conjunction with a set value of C gives a set frequency…OR that C value can be decreased with an adjunct increase of L’s value to get that same set frequency or like wise, the addition of an additional padded value of C across the initial C value lowers the set frequency…but also decreased the available minimal value of C attainable with the tuning condenser at its 88 or lowest frequency which is acquired with the tuning condenser set at its maximum
closed position, therefore requiring a trim in of raising the L value to get the same set frequency. BUT the over all range of the tuning condensers maximum capacitive range…open to closed….has been altered by that additional shunt capacitance. Therefore, you can get a compression of the stations toward the lower end of the dial. The same is true while altering the L value of the tuning . Effectively, there are 4 possibilities by the tuning interaction. BUT…and heavy on the BUT..it is all dependent upon the tuning parameter aspects initially designed into the set by the manufacturer….so that is the end bench mark to shoot against, with the sets inherent limitations.]

73's de Edd

:I have an RCA 612V3 with "tuner" problems of sorts. I need to know how to spread out the tuning distance to match with the indicator dial on the FM broadcast. The schematics I have don't say anything about how to adjust the tuning cap travel to dial travel. Or am I just missing out on what its called???
:Any ideas on any or all three questions?
:Regards
:Steve
: