jd3rdcoast
Super Member
I obviously got this confused with another model. Probably the 2265 I worked on recently. My bad.
Marantz 2275 - no stereo FM
- Thread starter ssouci
- Start date
ssouci
Well-Known Member
some history...
- 10 years ago: full recap/restoration of this receiver (including radio boards), FM played fine, fully in stereo, used receiver exclusively for about 4 years, all good
- 5 years ago: FM still OK, but I stopped using this receiver regularly
- 2 years ago: tried receiver for a bit, FM seemed a bit weak (not pulling in stations too strongly, still passable?)... so I cleaned the variable cap on P100 board, but made no difference (but I had cleaned the AM cap by mistake! duh)
- 3 months ago: tried receiver (and did some switch cleaning maintenance), noticed FM was even weaker and could barely pull in any stations, with minimal SS meter movement (vs. my 2230 which has pretty good FM)... so FM was basically useless and "broken"
- 2 months ago: decided to bring to a local tech to get it checked and fixed by a pro... I picked up the unit, but at home immediately noticed that stations were now coming in again and meter(s) were moving more normally, however NOT in stereo, with stereo lamp not lighting... also, seems like there is more noise in general while tuning across the band, with more "weird noises" randomly across the tuning band (buzzes, hums, motorboating, etc.)... however when tuned to a strong station, it's fairly quiet and stable (but in mono)
when I had picked up the unit, the tech casually mentioned something about "not getting the stereo lamp" (barely), which was odd, but I assumed all was actually OK since I knew he was just using a small piece of wire for antenna... I did not test unit at the shop since he was busy
a couple of weeks ago, when I removed the top cover of the FM FRONT END (P100 board), I was disappointed to discover that the tech had broken one of those weird little yellow ceramic tubes, both part of the thin sidewall of the tube, plus an edge of the black "flat blade slot" inner adjuster (damage can be seen in my photos, on L103 located in very middle of board)... so he definitely made some adjustments on that board, but I'm not sure about any others (eg. P300, P200)
I had first asked the tech if he was familiar with FM alignments, etc. and he said he "yes was able to work on it" (he does mostly TVs, but also seems to do any audio stuff, and I saw a couple of Marantz receivers in his shop which was jam packed with units needing work)... I cannot say definitively how good/bad a tech he is, however, I was not thrilled that he returned the unit without the FM being in full stereo all the time -- especially considering I brought it in specifically for the FM!.. mono FM is obviously useless
so here I am, and obviously not keen on bringing it back to that tech, and fully realizing that techs with FM/RF expertise are not easy to find, and I have zero or limited choices in that regard, sigh..... :-(
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Thanks for that thorough history. I will say that TV techs are pretty sharp that can work on the old CRT types before they started doing nutso power supply stuff and using the large ICs. So it depends on what level he's a TV tech, these days they are board swappers due to the specialized test equipment needed for each brand being expensive and probably not productive at that. I used to work on TVs in the 80-'s on the side and can tell you stereo gear is much simpler. Well, except for the RF part!
Those tubes are very fragile and in general are not affecting the RF. The slugs are but if he was able to peak them after chipping them, that would be fine. Too much missing and it may not be adjustable any more and for sure if the slot got busted out. Front ends slide out of peak operation over the years so I wouldn't automatically think a component, chiefly the front end first stage FET, was failing. But it should hold steady on the sensitivity for quite awhile now. I have the hex slotted cores but not the flat rectangle ones and I think the outer diameter may be off.
It is a bit disturbing that he didn't inform you that he couldn't get it to operate in stereo. You shouldn't have had to mention that to him! Yes, you're correct that capable FM knowledgeable techs are getting rarer all the time. I recall your locale is Vancouver Island (you lucky dog!). You could try to contact AKer Arthur 'tarior' as he's in Washington but I don't recall where. He may be able to help.
ssouci
Well-Known Member
rBuckner: thanks very much for the info!... this guy has been doing it for 25 years, but that means mostly modern stuff when you think of it, plus, no doubt does a lot of board swapping on the TVs... I didn't get a sense he was an audio (and especially RF) expert, but I didn't really have another choice
also, it's great to get the moral support while my poor 2275 sits opened up on a bench with no fix in sight!... and it's too bad that shipping a massive/delicate thing like this to & from an elusive expert is way too expensive (and risky)
still hoping to find out: how & where do I coarsely adjust the 19kHz signal?... or is that not even possible?
I suspect that's why my R311 fine-tuning does nothing, and perhaps also lies at the root of my entire problem??? (but I could be dead wrong, since I don't understand this well enough)
also, it's great to get the moral support while my poor 2275 sits opened up on a bench with no fix in sight!... and it's too bad that shipping a massive/delicate thing like this to & from an elusive expert is way too expensive (and risky)
still hoping to find out: how & where do I coarsely adjust the 19kHz signal?... or is that not even possible?
I suspect that's why my R311 fine-tuning does nothing, and perhaps also lies at the root of my entire problem??? (but I could be dead wrong, since I don't understand this well enough)
You need a scope ideally and I know you don't have one. Possibly it can be measured with a multimeter that has frequency capability. It's done best with a signal gen with the pilot signal turned off and no audio on the high frequency carrier. Given that it doesn't lock now I bet a strong station would work. When the bench is clear of the behemoth Pioneer SX-1010 that is sitting there I'll get the 2275 and see what the range is that the pot can tune.
EDIT: Didn't hit the bench all day today!
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@ssouci
I just completed the test. I used my bench meter if Frequency mode. As expected, it read 19.000kHz with the stereo light on. Turning the pot counterclockwise, the point at which the stereo light went off it read 18.35kHz. all the way down CCW it was 17.67kHz. Going back clockwise, it turned off past the "stereo" zone and the reading was 19.70kHz. At full CW it read 22.41kHz. The sweet spot on this 2275 was at about one third clockwise from full CCW. The meter in AC volt mode read 1.463Vac and on DC it was 1.54Vdc.
I just completed the test. I used my bench meter if Frequency mode. As expected, it read 19.000kHz with the stereo light on. Turning the pot counterclockwise, the point at which the stereo light went off it read 18.35kHz. all the way down CCW it was 17.67kHz. Going back clockwise, it turned off past the "stereo" zone and the reading was 19.70kHz. At full CW it read 22.41kHz. The sweet spot on this 2275 was at about one third clockwise from full CCW. The meter in AC volt mode read 1.463Vac and on DC it was 1.54Vdc.
ssouci
Well-Known Member
a few PHOTOS of my P300 FM-MPX board... shows the new transistors just installed... the caps were installed 10 years ago (Panasonic FCs and films)
one shows how I held it up temporarily using masking tape... this allowed me to solder without having to remove this board (and disconnect all the wires!)... I had to bend over and solder "upside down", but it actually was possible
one shows how I held it up temporarily using masking tape... this allowed me to solder without having to remove this board (and disconnect all the wires!)... I had to bend over and solder "upside down", but it actually was possible
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As the SM states for adjustment, black/neg lead to ground and red/plus lead to J310 - it is right by the R311 adjustment pot and has no wires to it.
In general, Marantz gets a "D" for serviceability engineering. The 2500/2600 gets an "F-"!
Gee, if Marantz gets a D, some of the others need a different alphabet.
ssouci
Well-Known Member
OK, I took voltage readings on pin J310 (at my current position of pot R311) and got:
AC = 1.857 V
DC = 1.587 V
then I rotated R311 through full CW/CCW rotation, but the voltage reading(s) did NOT change
(note: I was not able to measure the frequency, only voltage, since I don't have the equipment)
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The frequency didn't change? If it didn't, what was it?
ssouci
Well-Known Member
I was not able to measure the frequency, only voltage, since I don't have the equipment (only a basic multimeter without Hz capability)
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See if your local big box home store has one, or Harbor Freight. I believe it is crucial to know. Looks like it's running though (the PLL oscillator) or you wouldn't have gotten that AC voltage reading. Here's one from HF:
https://www.harborfreight.com/dm300-pocket-sized-digital-multimeter-64018.html
ssouci
Well-Known Member
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 fairly cheap (~$100), yet are actually also oscilloscopes with a graphical screen!... would these be useless in helping me with my FM debugging?
Q4: my current multimeter has "transistor hfe" function, which I have used (with special E-C-B sockets)... I imagine any new meter I get should also have this, but it seems many do not
open to any more suggestions for meters to buy, however I don't want to go nuts $-wise, simply because I'm not trying to be a tech or anything
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 fairly cheap (~$100), yet are actually also oscilloscopes with a graphical screen!... would these be useless in helping me with my FM debugging?
Q4: my current multimeter has "transistor hfe" function, which I have used (with special E-C-B sockets)... I imagine any new meter I get should also have this, but it seems many do not
open to any more suggestions for meters to buy, however I don't want to go nuts $-wise, simply because I'm not trying to be a tech or anything
A1: Absolutely! Yours is likely not near 19kHz, that's what we need to find out.
A2: The one I listed says it will do 100kHz. But yes, 9.99kHz wouldn't be enough.
A3: I would bother with these, but I was a career electronics tech/engineer! The resolution wouldn't be enough to discern much I'd think.
A4: I'd say not necessary, you already have that function covered.
I just got a nice meter from Amazon, Kaiweets HT118A, at $33.29 with some kind of 15% coupon. I will see how it does on the 2275's 19kHz test point. If good, forget that other one I found!!
Well, it didn't measure it. Probably the audio riding on it messed it up. I used a signal generator and it read fine up to 19kHz. Dang!!
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).
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).
I thought I'd take a look at your board pics. The cap C305 appears to be a polystyrene. Great caps unless they get damaged. They don't take heat well. If you can't test it, I'd suggest trying to order one but may be hard to find new - I wouldn't trust old ones. You could get a C0G dielectric one or better. NPO is next best type.
One other observance, you used film caps for the 3 bipolars next to the IC. I have heard that sometimes this doesn't work but don't recall what the failure mode was. You might try putting the old caps back in. Two of them are to do with "19kHz loop filter" and the other is "Stereo switch filter". Hmmm... maybe this is the issue?
One other observance, you used film caps for the 3 bipolars next to the IC. I have heard that sometimes this doesn't work but don't recall what the failure mode was. You might try putting the old caps back in. Two of them are to do with "19kHz loop filter" and the other is "Stereo switch filter". Hmmm... maybe this is the issue?