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For HiFi, the resistors I use most often are the Vishay/Dale RN60D, but in terms of FM tuners, I was wondering if they can generally be used for repairs without their inductance at RF becoming a problem.
Specifically, I'm dealing with an older (~1970) Sony receiver that has a problem in the FM section that I've narrowed down to the end of the IF signal path. The problem is likely a transistor, but it could also be an intermittent resistor. The service manual says that the resistors are "carbon type," but it doesn't say composition or film. They look like carbon film to me (thinner in the middle), but I'm not an expert on Japanese parts.
Follow Ups:
The below posts are absolutely correct but, as the OP stated, the location in question is at the end of the IF strip, which most would agree does not exhibit the the level of inductance induced anomalies seen at true RF levels. almost non-existant.
Respectfully,
HA
As I posted below, I don't know enough about the reaction of alternative materials in RF circuit parts substitutions. Therefor I keep it conservative when working with my tuners.
"You won't come back from Fletcher-Munson curve"-Jan and Dean
I have an article here somewhere which goes into this subject in some detail. It refers to all RF circuits, not just FM tuners. My take-away point from reading it was to replace carbon or carbon film resistors with similar replacements. The circuits were designed to work with those types, and there is a difference in the way resistors perform at radio frequencies.
In the power supply and audio section, metal films are OK, of course.
I'll try and find the article and I'll post it if I can locate it.
"You won't come back from Fletcher-Munson curve"-Jan and Dean
Here's the pertinent portion of the article, mainly the second and third paragraphs, which pertain to replacing resistors in radio frequency circuits.
I included the cover and author to show that both the article and magazine were geared toward guys who made a living repairing VCRs, CB radios, etc, not toward magic crystal tweakers.
After reading this article in 1996, I've always substituted like for like in tuners. If it had a carbon, I replace it with a carbon. If it had a carbon film, I replace it with a carbon film. I don't know enough about RF circuits to know when it would be acceptable to deviate from this path.
"You won't come back from Fletcher-Munson curve"-Jan and Dean
Specifically, carbon composition parts are both non-metallic and non-inductive. Carbon film parts are spiral trimmed, which introduces inductance. Small amounts of inductance MATTER at RF.
There is 1st hand experience of metal oxide parts, which can sound like guano, working well at RF. See the AVA article on FM-3 tuner care.
Eli D.
No problem at all, they are my go-to choice for replacements, and yes I do a lot of tuner work.
HA
I don't do any work on components. But I had a friend who did and designed gear. And I recall when he modified my Dynaco FM3 that there were certain resistors that had to be carbon and definitely not changed to metal film. Sorry I don't recall any details. But be careful when replacing resistors in a tuner.
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