Hi, I have just finished repair of the cassette recorder part of a Panasonic 5410. However I find that the cassette volume in playback is much lower than the radio. This means that I have to adjust the volume between playback of either source. If I forget, the radio playback is extremely loud. Questions: 1) Was this type of (significant) volume difference also present in the original units when they were new? 2) If not, what causes the low volume? I have cleaned the heads thoroughly. 3) Can I change the cassette playback amp section with higher gain / amplification such that it better matches the radio volume? I assume by changing transistors and R-values. I think my question is: has anyone done this? 4) I could create a small (opamp) booster circuit to go between the tape amp and the power amp but modifying the existing circuit seems more attractive. Keen to get your personal experiences and advice!
Those are really rare around here, we also had a JC Penny's Version (National Department Store Chain). Anytime I have volume issues I start with the function selector switch, usually it's left in the same position, probably radio in your case, and the other positions get corrosion and less signal. Over here we use DeOxit or FaderLube (from the same company). Over there you may have other electronic contact cleaners which work just as well, even car parts stores will have something like CRC Cleaner which has worked fine for me. The "recording bar" can also cause issues, I fixed my last one by pushing it a bunch of times but the correct way would be to clean it up good if the unit is open, Cassette2go has some photos floating around here on cleaning that part. https://audiokarma.org/forums/index.php?threads/the-idiots-guide-to-using-deoxit-revisited.207005/ https://caig.com/ https://stereo2go.com/forums/threads/sharp-gf-7850-hiss-problems.2803/ It sounds like you know your stuff so this may already have been done. Good luck with your repairs.
First of all, if you are comparing cassette playback to FM radio, then yes, the FM radio will always be twice the volume of cassette because of how the FM stations have their output volume at the maximum. Just a hair below distortion levels. What does the VU meter say? On FM it "slams" way up loud, right? But on Cassette is is down around 0 decibels on the meter? That's normal on my old Mono Boxes too. Because FM is transmitted so dang "loud". ("Loudness Wars" and all that is part of it. Google the term.) DeOxit thoroughly all the contacts and volume pots. And the other thing is to replace all of the electrolytic capacitors. Volume level overall increased in both Sony CF-1990 and CF-480 that I recently re-capped. And clarity and sparkle in higher frequency ranges in my opinion (maybe just my ears). The Panasonic 5410 was / is one of the other awesome Mono Boxes that I really like the look of Pictures! We wanna see pictures of the iconic 5410 !!