Technics SA-500 FM Stereo 'clicks off' ?!

Ramie

New Member
Hello! Just received a vintage Technics SA-500 and it got a little jarred in shipping coming from the east coast. In fact the plastic fuse box cover got cracked in transit so don't know if that's related to the problem (i.e. being jarred/smacked) but...

Connected speaker wire to the two FM terminals in back, spitting the top 3-feet into a tee for a dipole affect. It picks up stations fine... BUT...

In FM/stereo mode the red LED stereo light comes on and the meters register a great signal... and I hear a great signal... for only a few seconds then it goes dead, (not like loss of reception or crackle but dead) and stays dead. If I flip the switch to go FM/mono it plays fine.

So I turn off the unit.... flip the switch back to FM/stereo... turn the unit back on... and again it plays a few seconds wonderfully before cutting out dead again.

Now since it takes a second or two for the speakers to start playing, once or twice it went dead before I actually heard anything come out of the speakers (but the red stereo light was on so I knew it was GOING to work if it had lasted long enough) and in those instances I hear what sounds like a soft click from inside the receiver. I'm sure it happens every time it goes dead, but when music is playing I can't hear it. And when the signal cuts out the red stereo light goes out of course. Meanwhile the meters that measure signal strength are strong as ever.

So that leads me to believe it's a fuse tripping or something... but when it goes dead I can still flip the switch to go mono, and both speakers still work.

Anyone have any idea what would cause this behavior? CD player and mono FM/AM plays normally. It's only FM stereo with the problem.

Thanks for any guidance. Like "Shultz" on Hogans Heroes, I know nothing! :D
 
Agreed, looks like the muting/mono switch could use a deoxit cleaning. These switches are notorious for acting flakey.

It seems that (1) listening to FM stereo all is good then suddenly (2) no output at all? It isn't simply switching back over to mono? then... (3) manually flipping the switch over to mono gives you music again, then (4) switching back to muting on/mono off gives you stereo again?

There is an adjustment you can make using VR301 that you can play with if the tuner is not putting out MPX stereo (when in stereo mode). The service manual is at hi-fi engine, check figure 5. I would probably try adjusting it anyway, my SA-700 was not stuck in FM mono and adjusting this fixed it. But this may not be your problem. But it's easy to try.
 
@loopstick: Thanks and I will def trying deoxiting the switches. Have to pick some of that up...! The 550 is a cool receiver, you can't beat the vintage stuff!

Agreed, looks like the muting/mono switch could use a deoxit cleaning. These switches are notorious for acting flakey.

Good to know...

It seems that (1) listening to FM stereo all is good then suddenly (2) no output at all? It isn't simply switching back over to mono?

Right. No sound. Dead. Not switching back to mono.

then... (3) manually flipping the switch over to mono gives you music again,

Correct.

then (4) switching back to muting on/mono off gives you stereo again?

Usually not. I usually have to turn the unit off... wait a few seconds or longer... flip the switch back to FM/AUTO, then turn the unit on. And I will usually get FM stereo for anywhere from 2-40 seconds before it cuts out again. But sometimes the stereo LED just flashes a sec and goes out and no sound at all.

If I leave the unit on after the sound cuits out, flip to FM/MONO and hear music (it ALWAYS plays in mono)... then simply flip the switch back to FM/AUTO the stereo LED light will flash a second but rarely will it stay on and play music even for a second or two. For some reason the unit has to be turned off. Maybe turning it off re-sets a switch or something.

There is an adjustment you can make using VR301 that you can play with if the tuner is not putting out MPX stereo (when in stereo mode). The service manual is at hi-fi engine, check figure 5. I would probably try adjusting it anyway, my SA-700 was not stuck in FM mono and adjusting this fixed it. But this may not be your problem. But it's easy to try.

This is a great tip to try! I downloaded the service manual before the unit arrived. :D I will try adjusting the VR301 and also cleaning with deoxit and report back when I've done those things.

I really appreciate the help guys, thanks!
 
One more weird thing... I was using a long length of speaker wire split at the top for dipole affect. Wondered if an actual FM 300ohm dipole antenna would work better, so robbed one off another system in the house. Now the signal went from 3.5 strength to just shy of 5... so VERY STRONG... yet the receiver won't play FM stereo AT ALL with the dipole! The second I turn on the unit, the stereo LED flashes on but immediately off ...and nothing. Unless I switch to mono of course.

So it's bizarre to me that the speaker wire which brings in a weaker signal than the dipole, actually gets the receiver to play at least SOME FM music in stereo for some period of time... while the dipole that brings in the strongest signal doesn't work at all! (except in mono)

That is perplexing!
 
Give vr301 a shot. It doesn't affect the alignment. Don't be tempted to adjust anything else though.
 
Give vr301 a shot. It doesn't affect the alignment. Don't be tempted to adjust anything else though.

Sorry for the late response, but family matters intervened and took all my time up since I wrote last. I finally got a second to check out the VR301 on the service manual, remove the top and try adjusting it. It was slightly to the right of dead-center but still well within the 'stereo' parameter (B-D)... tried gently moving it within that full range (B-D) to see if it would make a diff. No dice. Stereo light refused to come on and no sound (so I know the stereo LED light didn't suddenly go out). And still, the 300ohm dipole FM antenna gets a 4.98 signal on the meter (highest is 5) and the FM meter is dead center, but the stereo light doesn't even flash on for a second, and no FM stereo whatsoever.

Just to see, connected the speaker wire again which was getting SOME FM and that's not getting anything now either (and tried before AND after VR301).

So still have to get deoxit and clean the switches and hope that works.... again will report back. [...]

EDIT UPDATE: Deoxit is out of my price range after all the $ I have spent on re-foaming, replacing tweeter, getting receiver, etc. But found this YouTube vid where the guy points out a Radio Shack brand of corrosive electronic cleaner has Deoxit as an ingredient (along with mineral oil and a few other things). He said it was $4. Local RS had it for $7 here, but still cheaper than Deoxit. ( http://www.youtube.com/watch?v=njwi-GwJBzc for vid and here is the product that contains Deoxit http://www.radioshack.com/product/index.jsp?productId=3511774) So ran to store and picked up a new dipole FM antenna since mine was old. $17 and change later, no difference. Sprayed into the FM/AUTO - FM/MONO switch (and the others).... put on new antenna... and I am getting ZIP.

UPDATE #2: Later after a drink of Tequila (yes, this is a critical component of vintage receiver care), I decided to squirt the VR301 with the jazz I mentioned earlier, just for the hell of it, because that's how you roll after a Tequila in combination with having tried everything else. :D And I'll be darned but after I did that I actually had for STEREO FM for like 40 seconds!!!! The LED stereo light came on and everything! I was actually DANCING in the tool shed (my receiver laid open before me as if in ER) as I heard wondrous, glorious FM stereo... before it died again.

I feel like I'm sooooooooooo close!!! Yet so far!!

PS I am a woman just FTR in case dancing in the tool shed was too alarming for you he-man types to reply to anymore. :D I like to celebrate a success, no matter how short-lived!
 
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I'm guessing VR301 is some kind of pot. Apparently after drinking copious amounts of Tequila you proceeded to spray de-oxit on a pot. In these forums that's like crashing your car into a busload of orphans. :nono:

Was only one drink, not copious amounts, so as an excuse it doesn't fly. :D

Meanwhile I read on another thread here someone with my exact problem (circa 2008) who was given the advice to spray the 19hz trim pot, as that cured the problem in at least his case. Thus, the attempt.

But nevertheless we have a new data point (actually several, you like to drink and dance :thmbsp:).

Not too often, but the occasion seemed to call for it. :D

I've read on other threads where guys by just barely moving one of those screwdriver type trim pots scraped away some crud that was preventing good sliding contact. Assuming VR301 is not a steaming heap of dissolved wafer I'm wondering if another tweak might be worthwhile? I'll defer to 39cross.

Can't see any wafers/chips here... just a steel trimmer.

BTW - my earlier recommendation was for using "de-oxit" on metal-to-metal switch contacts, not metal-to-resistive-wafer-thingy sliding interfaces. So we're probably going to want to rinse VR301 with the correct stuff eventually.

This stuff did have Deoxit in it, which is why I got it. I cannot buy Dexoit... it's against my religion to buy any product that is overpriced to that degree regardless of how well it works. If they want to overprice it so much, they should sell little mini-spray cans like an inhaler size for a few bucks... enough to clean up one or two pieces of equipment. I'd spend $20 on it (CA tax is now 9.75%) then end up having to take it to a recycle center 5yrs down the road when I'm cleaning all the hazardous cr-p out of the shed. It's a waste. I'll listen to FM in mono if it comes to that.

Meanwhile I took the receiver apart more completely.... took the face plate off, (bottom and sides too)... cleaned the tuner up... sprayed all the switches again from the front this time, and NOW they click like they should instead of feeling mushy.

Put everything back together and turned it on and ... FM STEREO.... WONDERFUL FM STEREO.... for about 40 seconds. This time though it cut out at 2 different points for a fraction of a second then came back... so it IS that damn MUTE function tied into FM/MONO.

I fooled with ALL the FM trimmers (scold me, I'm ready) that were potentially relevant according to the service manual. Eyed where they were before messing... messed... put them back where they were. It's just being stubborn.
 
Sorry to hear your success is limited. You do need to take the thing apart to get deoxit into the switches. Make sure you also spray the selector switch. This may be the problem.

Even though it is frustrating, don't be tempted to play with any of the other adjustments, it will only make things harder for someone else to fix it.

On my system, tweaking that Vr301 pot brought stable FM mono reception into stereo and kept it there. Why it was out of adjustment I don't know, maybe there was bit of corrosion there and adjusting it cleaned it. That's the only adjustment you can (successfully) make without specialized tools.

At this point I would give the selector pot some more attention, this could still be culprit. it can take multiple attempts to clean these. If they were as crusty as it seems, they could all (including the FM mode switch) use some more cleaning. If that doesn't work, you'll need to bring it into a professional to fix it, if you want to. It's possible an alignment would clean it up. I will mention that I had an older Sony receiver that had odd FM stereo issues, and they turned out to be caused by cold solder joints. I am not suggesting this is the case here, just that when something is wonky it can be caused by a variety of possible problems.
 
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Sorry to hear your success is limited. You do need to take the thing apart to get deoxit into the switches. Make sure you also spray the selector pot. This may be the problem.

Funny you should mention that as it is the one thing I did not spray as it's two plastic gears that look pristine. I only now went and re-checked and the arms from these gears DO enter a closed metal rectangular housing (pot?). I will look to see where might be best to give this a shot of cleaner.

Even though it is frustrating, don't be tempted to play with any of the other adjustments, it will only make things harder for someone else to fix it.

OK. I won't be taking it to anyone else for such a minor problem as it would be too expensive and not worth it to me, but sounds like it won't help the problem anyway, so I won't.

On my system, tweaking that Vr301 pot brought stable FM mono reception into stereo and kept it there.

By putting it in FM stereo mode, then trimming the pot until it came in, right?

Why it was out of adjustment I don't know, maybe there was bit of corrosion there and adjusting it cleaned it. That's the only adjustment you can (successfully) make without specialized tools.

Yeah, unfortunately.

At this point I would give the selector pot some more attention, this could still be culprit.

By selector pot you mean the switch that chooses the output function, right? Like AM FM PHONO AUX ... or are you still referring to the selector switch that is FM/AUTO FM/MONO/MUTE ?

it can take multiple attempts to clean these. If they were as crusty as it seems, they could all (including the FM mode switch) use some more cleaning.

OK. I just read over and over not to go crazy with the cleaner... just spray little amounts and work the switch/pot.... so I guess what you're saying is do that... then let it sit and do it again like the next day... and maybe it takes multiple times.

I will mention that I had an older Sony receiver that had odd FM stereo issues, and they turned out to be caused by cold solder joints. I am not suggesting this is the case here, just that when something is wonky it can be caused by a variety of possible problems.

I understand.

This morning after letting it sit all night, I got FM stereo radio... then after 30 secs or so it started cutting out, but coming back on immediately, then cutting out, coming back on, then went out for good. (stereo light going off and on accordingly) So it's trying. Before once it cut out, that was it. Since cleaning it's made a little progress.

I am starting to wonder if the tuners in these Technics receivers from 1977 are just too greedy (i.e. not all that well designed) when it comes to needing a big fat stereo signal for stereo reception. Because I seem to remember my original SA 404 (can't remember if it was a 404 or 500, but one or the other) doing this too, even when it was new... to the point where it was too irritating to listen to FM stereo because it was always cutting out. I didn't care that much b/c I rarely listen to radio, but maybe there is just too much interference here in the South Bay section of LA, 22 miles or so away from the main radio broadcast stations up on Mt Wilson. (I think that's where they are.) But you'd THINK if the meter is registering a signal near 4.7 it should be strong enough!

Thanks for all your help. I will try spraying the pots again!
 
Took off bottom, sides, faceplate and sprayed again.... waited a bit... put all back together. Same result. The switches feel clean though, clicky and nice. I think this is just as good as it gets. I don't feel like more attempts will make a diff. Tried adjusting VR301 again too, but it's where it originally was, which seems to get the best result, as brief as it is.

Since it's not the end of the world, I am moving on... but if I come across something that fixes this in the future (by chance or otherwise), short of professional help (which I won't be seeking), I will come back and report it in this thread.

Happily it plays everything but FM stereo fantastically, so I am ready to enjoy it!

Thanks again for the help, I learned a lot which is always valuable!!
 
Once again sorry to hear it hasn't gotten any better, just teased you. You have to spray the cleaner inside the metal housing of the selector switch(am/fm/phono/aux), and work the knob back and forth a whole buncha times. Same thing for the selector switch. If they are really crusty it does take multiple attempts.

It seems that the signal is strong enough for stereo, so that's not the problem. And it has tantalized you with sporadic success, so it's not like it's completely broken. Well, maybe you should just listen to it for a while and hope for a spontaneous remission ;-) If it is something more complex it will have to be diagnosed by a pro. in any case, I do hope you enjoy it, I am assuming you are getting stereo out of the aux (and phono if you use it).
 
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Once again sorry to hear it hasn't gotten any better, just teased you. You have to spray the cleaner inside the metal housing of the selector pot (am/fm/phono/aux), and work the knob back and forth a whole buncha times. Same thing for the selector switch. If they are really crusty it does take multiple attempts.

I am already considering opening it up again. :D Most of the round pots have an access port/hole, about the size of the straw on the cleaner. So it is easy to spray those, and I have done that, maybe 3x (at least). Meaning once or twice, on three separate consecutive occasions.

The rectangular selector pot housing does NOT have such a hole or port (that I could see), so it's tricky knowing how to get the cleaner in there. I sprayed the plastic gears then tipped the entire receiver back to allow the cleaner to seep into the housing. That's all I could come up with.

It seems that the signal is strong enough for stereo, so that's not the problem.

That is a very good point, as when it DOES play there is not one iota of interference or static .. it sounds absolutely WONDERFUL. Almost better than a CD.

And it has tantalized you with sporadic success,

Yes, dammit! It's absolutely torturing me! 50 Shades of Almost Working!

so it's not like it's completely broken.

Amen!

Well, maybe you should just listen to it for a while and hope for a spontaneous remission ;-)

I think the stress of holding on to that thin expectation might require too much Tequila. :D

If it is something more complex it will have to be diagnosed by a pro. in any case, I do hope you enjoy it, I am assuming you are getting stereo out of the aux (and phono if you use it).

Hell to the yes I use phono! Love that vinyl! My extensive collection of records is very dear to me. And yes, the AUX and everything else works as if new.

What I hear from you is that spraying the cleaner even more times might, or might not make a difference. But it is significant than spraying it made SOME difference already, so that would lead me to think maybe I should try doing that a few more times. I have to wait for a re-foaming kit for one of my speakers anyway, so.... I have the time and maybe I WILL do that.

Thanks once again for your continued help!
 
Looking closer I did see a hole in the right, back, top corner of the rectangular housing for the selector pot. So sprayed into that, and into the gears and tipped it, and worked the selector switch and saw the cleaner rise and fall in the port hole, so it was working in there... (also ran on to the main circuit board but just used a soft cotton cloth to clean that up).

Afterward, tried it and FM stereo played longer than ever before, before cutting out. Maybe a full minute. So sprayed it again and am letting it sit, and will repeat this over the next couple days and report back!
 
Yes, dammit! It's absolutely torturing me! 50 Shades of Almost Working!

I think the stress of holding on to that thin expectation might require too much Tequila. :D
LOL x2!

Put a Jane Fonda deoxit workout tape in the vcr and then go and exercise those switches ;-)

Even if this does not fix the FM stereo problem, cleaning the selector pot will help it work better overall, so it's not a waste of time. And in that vein, since you have it open, while you are merrily de-oxit-ing you should hit the other pots as well.

What's the history behind this receiver? Seems like it may not have been used for quite some time.
 
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It's possible that if you repeated all the same steps - powered down, worked the switch (the function selector is not a pot-entiometer), powered it back up - you might see the same results. IOW go through this cycle of mechanical activity without any spraying and see what happens.

Oh, ok! I will do that.

The intermittent mechanical connection may not be firmly in contact - be it a switch contact, cold solder joint, etc. If it does go into stereo for a short while even without any spraying then there is hope that one of these times it will go into stereo and stay there. Meanwhile it's at least as good as a broken clock, it's right at least twice a day. :D

Unfortunately we are all OC about our vintage gear, so being right twice a day is a little bit of a mind-screw. :D If it does in fact remain as it is, I will simply wipe the idea that it even has an FM stereo function from my mind so I don't have to feel it is lacking. :D

LOL x2!

Put a Jane Fonda deoxit workout tape in the vcr and then go and exercise those switches ;-)

LOL! Maybe Led Zeppelin or Allman Bros. (Whippin' Post sounds about right!)

Even if this does not fix the FM stereo problem, cleaning the selector pot will help it work better overall, so it's not a waste of time. And in that vein, since you have it open, while you are merrily de-oxit-ing you should hit the other pots as well.

Will do!

What's the history behind this receiver? Seems like it may not have been used for quite some time.

That's possible. I got it on eBay from a seller with 100% rating who's done a lot of business selling cool vintage gear like receivers, Fender amps, etc.

I'll tell you one thing, it's immaculate. There was ZERO dust inside on the circuit board or anywhere else. The seller said he sprayed the pots and while they felt a little mushy when I got it, they made no static or noise. Now they feel clicky, as mentioned before.

I think there is a very good chance it was stored and covered, as I don't see how the seller could have removed dust from the circuit board so completely and cleanly, even using a compressor. You normally would still see little dust particles stuck under wires or snagged on to edges when something's been cleaned up. (I am relating it to cleaning motherboards anyway.) This receiver virtually looks new.

As luck would have it my last foam kit arrived today for the last Cerwin Vega that needed re-foaming... but haven't had time to work on anything as I've been otherwise predisposed. I am headed out to the shed now, so will do another round of spraying while I re-foam the last woofer, then as loopstick suggested, continue to work the switches for the next week or so, even after spraying is done and it's all setup in its new location.

Will check back in, and as always, MANY THANKS!:beerchug:
 
I have a confession. I can't bring myself to spray the receiver anymore because what I've already done has left oily residue on the (formerly immaculate) circuit board where it's run from the pots, even though I've tried to clean it, and that really bugs me. (So I have been working the switches as loopstick suggested, without spraying.)

I know... it's my own fault for using RS Corrosive Contact Cleaner [which contains oils and Deoxit], instead of a non-residue product (like pure De-oxit). So now I want to spray the circuit board there with a different product to clean up that oily residue so it doesn't attract dirt and dust. You guys know what I can use to do that? If I have something to keep the circuit board clean, then I can spray the pots again.

Meanwhile the record for FM stereo playing is now 2 min. But not every time... but one time it got there!
 
Isopropyl alcohol and some swabs might do the trick. If you can get 100% that would be best. I've seen it in computer stores in a spray bottle.

You should read this if you haven't already: http://www.audiokarma.org/forums/showthread.php?t=207005

It is tempting to us a sub for deoxit but it's recommended for a good reason. Maybe you would be up to 4 minutes of stereo!
 
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Isopropyl alcohol and some swabs might do the trick. If you can get 100% that would be best. I've seen it in computer stores in a spray bottle.

Thanks.


I happened to come upon that last night in my research, but posted to a different thread here, where a long debate ensued about how Dexoit 5 can actually ruin some pots by dissolving something or other.... that one of the additives in D5 is responsible... so to use the Dexoit 100% formula was safer (D100-something) but not to confuse it with another Dexoit called D100-something else)! And back and forth it went... with some insisting to be totally safe only to use Faderlube. By the time I was done reading all that I had a headache. (ref: http://www.audiokarma.org/forums/showthread.php?t=173470 )

And a guy who had a bad experience with his particular receiver using Deoxit: http://www.audiokarma.org/forums/showthread.php?t=279187

Now I am too ignorant to know what kind of volume thingy I have or if it is packed with grease or what. I also have no idea what my pots look like inside... if they are all metal or have other parts....

It is tempting to us a sub for deoxit but it's recommended for a good reason. Maybe you would be up to 4 minutes of stereo!

LOL. I wondered. And I also discovered they DO make little inhaler size cans for $6 or so, but can really only be found online where shipping makes it ridiculous. So then next best deal I found (through these forums) was Sweetwater ... $14.99 free shipping for larger can: http://www.sweetwater.com/store/detail/DeoxIT/

And apparently Guitar Center carried these...

But which formula now, is the question. And I would have to re-read the entire debate referenced above to get it straight, which one is safest for someone like me who knows nothing about the insides of my pots. (And I won't be spraying the volume anymore anyway, as it doesn't need it... or the tuner.) Only the FM/Auto switch and the selector (AM/FM/PHONE/AUX). But that long debate really made my head spin.

In the meantime I happened to have to go to BestBuy right now, so I will look for 100% Isopropyl in a spray bottle and let the rest go until I am clear on it.

EDIT UPDATE: Well five stores later, no 100% isoproply ... (or even close). Not at any pharmacy, or BestBuy, or even a MEDICAL SUPPLY STORE I went to last that I thought for SURE would have it. I called Signal Electronics when I got home and they have it by MG chemicals... [nothing is 100% but this is 97 or 99 or something], but it's $10/can.... and that's before the Deoxit rabbit hole even gets started (which they don't have, but "the non-residue MG equivalent"). My OC'ness is starting to irritate me more than the problem. I feel like I'm spending more money/time on cleaners than I did on finding/buying the receiver!
 
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It's OK to use 90%, I didn't intend to send you down the rabbit hole. I've seen the 100% at our local Microcenter, and yes it's not inexpensive. Also, if you have a Guitar Center nearby they should have Deoxit. Don't sweat it too much. Maybe just clean it up to your satisfaction and just use it for a while. You can always tackle it later. There's nothing wrong with mono FM, and as the other functions are working to your satisfaction, maybe just dial it back for now.
 
It's OK to use 90%, I didn't intend to send you down the rabbit hole.

You didn't. You have been very helpful. It was really the debate about all the different Deoxits that put me off my feed. :D

I've seen the 100% at our local Microcenter, and yes it's not inexpensive. Also, if you have a Guitar Center nearby they should have Deoxit.

I know, but :dammit: of all places! It's worse torture to walk through all those gorgeous instruments than Jack Bauer being taken by Russians. (been playin' all my life!) I avoid GC, Sam Ash... and donut shops.


Don't sweat it too much. Maybe just clean it up to your satisfaction and just use it for a while. You can always tackle it later. There's nothing wrong with mono FM, and as the other functions are working to your satisfaction, maybe just dial it back for now.

Yeah that's pretty much the conclusion I came to. Will forget about the FM stereo for now. Maybe down the road when I haven't just spent a ton of money re-foaming and buying tweeters, and receivers and such, dropping $50 for the chance it might fix the stereo FM will sound more appealing. :D Like you pointed out earlier, it could be cold solder joints or something else. I'd rather delay any potential disappointment, especially if it's going to cost me $50 more bucks. :D And I'll order from Sweetwater when the time comes... so I can't see all the guitars I can't buy. :D

Hope you have a great weekend and can't thank you enough for the feedback and advice. I really did learn a lot. (Thanks to loopstick too!)

:music: :yippy:
 
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