FM alignment resources

invalidbuffa

invalidbuffa

Super Member
I've been doing repairs for a while and I'm at the point where I'd like to learn how to perform my own FM tuner alignments, especially in situations when instructions are unavailable. I can do AM alignment just fine, but FM and MPX adjustment is a new territory to me. I'm looking for any books, literature, or videos to help me get started on the right foot.

I believe I posses the necessary equipment (Panasonic VP-8132A AM/FM/Stereo frequency synthesizer, HP 3324A function/sweep generator, Keithley 2015 THD meter, and various oscilloscopes). Am I missing anything?

Thank you all!

Here's a couple I've found so far:
https://worldradiohistory.com/Archi...49/Radio-TV-Training-School-Lesson-75-opt.pdf
https://www.fmtunerinfo.com/
 
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Frequency counter..

Good set of alignment tools

Experience

You get it and can apply to your alignment technic on other tuners.

Learning theory and understanding the circuits and having experience how that was aligned on other similar tuners also helps.

Another thing experience will teach you. Sometimes the measurement is really good and experience tells you don't touch it, you will make it worse and have a devil of a time getting to back to that point.

Recommend getting some tuners and following the manuals as practice. Pioneers usually have a very verbose theory of operation with is a good place to learn also. Kenwood manuals aren't bad either. Sansui, may be the worse.
 
You might study the manual for the Sencore SG-165, which believe is readily findable online. It's not a great instrument, but its manual has a pretty good section on tuner circuit operation.
 
When i tooled up I had to get lots of “accessories” like adapters to convert been BNC and RCA and F/ coax. Also depending you might need 50 ohms or 75 ohms and 300 ohms and between these.
Besides the instruments mentioned already, A spectrum analyzer makes it easy to
Adjust the 19khz pilot filters. You can “see” the pilot and adjust to minimize it. And they start at 50$ these days. A probe with a built in RF log-amp combined with your scope might be a great way to work on IF section of your units.

But as Mike said, experience will teach that there are many ways to do the same adjustments depending on tools on hand. Beginners follow service manual instructions to the letter and can’t spot the mistakes or the omissions or try to use exactly the instruments mentioned. 60s tuner manual will talk about VTVM but you are in 2022. I’ve seen several manuals with zero information on the RF section for example. Today we have access to tools and software simply impossible for a tech to own even the 90s.

you can also get some old books on “fm servicing” as it was called way back.
 
Take a look at the AKAI AT-2600 manual its one of the better manuals with some theory.
Old FM radios were more involved, having adjustable IF strips and ST decoders using tuned circuits
Models with PLL based ST decders, which you have to set the VCO free running freq (76kHz) and sometimes separation adjustments for different IF filter settings.
Sanyo LA34xx used ceramic resonators so no VCO adjustments
 
I am in the same scenairio, restore lots of tube amps, preamps etc...but never really worked on any tuner repair or alignment. I only have a scope and signal generator . I have a Scott 340B, which I have restored with new caps, tubes etc and sounds amazing. The FM section works, gets the stereo light to come on for max 10 minutes and then stereo cuts out. I have swapped out all the tubes, replaced some older caps. One local strong station seems to hold stereo. The literature I have found requires a sweep gen. at least a 100MHZ scope. Not sure if I want to invest into these is I only do FM work rarely. I have downloaded the FM training .pdf listed above, will read. Any other suggestions on using just the tools I have?
 
invalidbuffa said:
I've been doing repairs for a while and I'm at the point where I'd like to learn how to perform my own FM tuner alignments, especially in situations when instructions are unavailable. I can do AM alignment just fine, but FM and MPX adjustment is a new territory to me. I'm looking for any books, literature, or videos to help me get started on the right foot.

I believe I posses the necessary equipment (Panasonic VP-8132A AM/FM/Stereo frequency synthesizer, HP 3324A function/sweep generator, Keithley 2015 THD meter, and various oscilloscopes). Am I missing anything?

Thank you all!

Here's a couple I've found so far:
https://worldradiohistory.com/Archi...49/Radio-TV-Training-School-Lesson-75-opt.pdf
https://www.fmtunerinfo.com/
Click to expand...
xrraytonyb on youtube has great videos on tuner alignment.
 
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