Dynaco FM-3 High Fidelity Tuner Repair

I recently got to work on a very interesting Dynaco FM tuner, the FM-3, which was in the shop for an overhaul. The owner reported it wasn’t working that well anymore, which isn’t a surprise given it’s age. These are good performing, great sounding tuners with a healthy following to this day although they are known for having a few design issues and being somewhat tricky to align.

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This is a high-end tuner with 11 tubes including the indicator, and FM-MPX decoding. However, given these were all kits, the workmanship varies a great deal. Fortunately, this one didn’t have very many bad solder joints as some do. The owner selected an upgrade kit for this model, and it received a new filter capacitor as well. The upgrade kit replaced several of the coupling capacitors, which were already film, with improved modern versions, and replaced the three ceramic couplets with specialized PCBs for improved performance and audio quality.

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These resistors run hot and needed to be replaced for reliability.

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Upsized output capacitors for better frequency response:

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Time for an alignment! This one cleaned up very nicely, meeting its distortion and dial accuracy specifications. The alignment was very significantly off, by about 2 MHz. Stereo reception seemed to be spot-on, though, which was surprising.

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Works and sounds great!

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This entry was posted in Audio, Electronics, Projects, Radio, Radios and Tubes, Stereo, Vintage and tagged , , , , . Bookmark the permalink.

6 Responses to Dynaco FM-3 High Fidelity Tuner Repair

  1. Alex Yong says:

    It’s smart of you to do a blog post every other day; keep up the good work. I left a message for you on https://retrovoltage.com/radio-repair-logs/ Do you do appraisals?

  2. Dave DeRosier says:

    Nice job!

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