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I just had MAJOR problems with my Marantz 2275 receiver's FM tuner that were attributed to contamination of the variable capacitor and the surrounding FM front end board... do not underestimate how sensitive this part of the FM circuitry is, and how it will throw everything off downstream and...

*** FIXED !!!!! *** I finally was able to find a decent tech who fixed this receiver... turns out that the FM Front End board was significantly contaminated, which due to the very sensitive nature of that board, threw everything out of whack and did crazy things, all of which was transmitted...

Stayjoy78: thanks for the suggestion... but that's not my issue, because I'm using an external antenna (basic T-dipole), my speaker wires are fine, plus my 2230 receiver works fine for FM stereo reception in the same physical location... thanks anyway!

I've been out of commission for a bit (COVID, etc.), trying to get back on this between tax returns! fwiw, I received this comment on YouTube from Dave Sanders, which I think is valuable info: "The MPX board (P300) has the Stereo Decoder IC (H321) which is equivalent to the Hitachi HA1156 IC...

Capacitor C305: I replaced with a new one... NO DIFFERENCE... also tried adjusting the R311 pot, but as usual this strangely had NO DISCERNIBLE EFFECT, and did not activate stereo, despite trying full rotation each way (note: the original cap I pulled seemed to measure OK, so it was probably OK)...

I'm just going to replace cap C305 with a new one (might as well if I have to de-solder regardless just to measure it) also, I'm not ruling out a defective C305, but my gut is starting to tell me that my problem might be stemming from an incorrect adjustment (somewhere on boards P100, P200...

rBuckner: in posts #38/39, you said: I guess you're left with testing the parts that are in the 19kHz circuit off of the IC. I think that would be the pot of course, R311, R312 (16K) and the cap C305 (470pF). The cap C305 appears to be a polystyrene. Great caps unless they get damaged. They...

which specific components should I be checking that will affect the 19kHz?... are they only on the P300 MPX board?

Dankik: - the hFE values on my 2SC1815s were all around 220-230 - I did NOT replace H304, H305, H306, H307 (I only replaced the 2SC2828S transistors: H302, H303, H308, H309, H310, H311, H313, H314, H315, H316, H317) - I do NOT have a scope, frequency counter, or multimeter with freq capability -...

DEMO VIDEO: the "flashlight fix" phenomenon...

WHOOPS? as described earlier, I replaced (all of) the original 2SC828S transistors on my P300 board... (yup, shotgun replacement, since I'd seen others do that with success) it was suggested to me that the transistors I used might not be suitable, since they don't have a high enough frequency...

your guess is likely better than mine! however, keep in mind that I'm essentially using the "complete" front end from another receiver (the 2230), and injecting that into the FM-MPX board on my 2275... so I don't understand how any of the pre-MPX board circuits in my 2275 could come into play...

OK, NOW THIS IS SUPER WEIRD... I was probing around the 2275 looking for abnormalities, and I suddenly got stereo! (sound itself + stereo lamp) then I accidentally discovered that it was the FLASHLIGHT I was using that triggered this "fix" whenever I brought the flashlight near the stereo...

UPDATE: - tried adjusting the R311 pot (on the 2275)... turned back & forth through full rotation, but made no difference, still no stereo FM... as before, turning this has surprisingly little/zero effect - tried reversing one of the power plugs on the power bar, made no difference - plugged the...

Dankik: I will check that (about the grounding and plug orientation)... but I just thought of something: perhaps I need to adjust my R311 pot??? (on the FM-MPX board of the 2275... that fine tunes the 19kHz signal) currently, R311 is sitting where I last had it set, which might not be correct...

I will look tomorrow... actually, on the 2275, I de-soldered the pin and pulled it out, so I could keep the wire-wrapped connection intact my jumper cable is about 6ft long... is that OK?... (should be, since it did work... at first anyway)

OK, I used my 2230 receiver to inject a "known good" FM signal into the FM-MPX board on my sick 2275 I used a patch cable between the two receivers made from shielded video cable... removed the RCA jacks, and soldered the wires in place, both the inner lead and outer shielding (temporarily)...

thanks!... I'll try this test as soon as I can, should be very interesting and hopefully revealing RE: "I do find it interesting that the meter reads so high when tuned all the way to the left. Is there an adjustment for meter level and if so, was it adjusted? If so, the high meter readings may...

DEMO VIDEO showing my problem...

I'm (reluctantly) considering bringing in my 2230 receiver into this... with this idea to feed the P300 MPX board on my 2275 with a "known good" signal from the 2230 (which does get stereo FM)... and if I still don't get stereo FM, then it must be something wrong with my P300 board, not further...

would that Aven set cover the "adjustable parts" on my 2275's FM boards?

alignment tools -- assuming I'm stupid/desperate enough to try some manual fiddling on my FM boards... would either one of these alignment tool sets handle what's needed on a Marantz 2275? Aven 13016 Philmore 63-910

rBuckner: thanks for your info... fyi. being in Canada, I would most likely get anything from Amazon.ca (or maybe Temu!)

wondering about multimeters... Q1: are these (cheap) multimeters even capable of measuring frequency (Hz) accurately enough to be of use in this application? Q2: I guess they must have a Hz range of over 19kHz (eg. those with max 9.99kHz would be useless) Q3: I see these new ones that are...

I was not able to measure the frequency, only voltage, since I don't have the equipment (only a basic multimeter without Hz capability)