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Ongoing saga of the Yamaha CR-n40s

EDITED:
Post #167 through to #227 are all between the gentleman CHAZIX and my good self. Summarised for your benefit, click here to skip this long conversation and see the result and rejoin this thread. :)


chazix said:
Tom B mentions CR-1040, but seems to be describing the CR-840 module set?

Also, installing IG02950 (CR-640 predriver) in place of IG02940 (CR-840 predriver) is risky. If we assume that they really were different modules, the IG02950 might not be able to withstand the full signal voltage swings that an IG02940 can. For receivers that aren't ever going to be pushed to near their maximum output, it probably doesn't matter if you make that substitution.

If anyone does need safe, drop-in replacements for CR-1040 or CR-840 predrivers, you can find my pitch for repro modules in BarterTown.

Cheers,

chazix
Click to expand...

I just picked up a CR1040 very cheap. Works, but the tuner face plate is a little rougher than i would like. Anyway, its in working order...other than no lights at all...light kit from ebay on its way...and the tuner knob is misaligned.

I would like to buy the parts now and shelve them. How do i find the ones you are listing?

Anything else i should buy to future proof this amp? The relay was making a bit of noise when i tried to run my cerwin vegas from it...are they easy enough to find.

Is there a servicing guide for them...i will open it and clean it when i do the lights...what else is normal maintenance for them? I can do anything mechanical like soldering and welding, but less so electrical.

Cheers

PS: anyone got any thoughts on perfect match speakers? I tried on jamo concert 7s and cerwin vega e312 and the relay clicks in and the overload light comes on when i go past 1 oclock on the volume - is the best best to use it as a phono stage? How do i play i loud?

PPS: i notice a sticker on the back saying it had been repaired when having no audio out...interesting.
 
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G'day JPete9,

You can find service info for the CR-1040 on hifiengine.com. You need to register, but it's no trouble, and very worthwhile.

The relay chatter is troublesome. There's virtually no chance that it's just the relay itself that's faulty. If you see the overload light, the receiver "thinks" that you're asking for an output level that will drive the power amps into clipping. Either that is in fact true (in which case the CR-1040 just doesn't have enough power for your needs), or there is an internal fault of some kind. The CR-1040 has level meters that are calibrated to read output power - how high do the meters go when you turn it above 1 o'clock?

By "tuner knob is misaligned", do you mean the knob itself is crooked, or that the frequency indicated on the tuning scale doesn't match what's really tuned in? If the former, it might just be that the tuning shaft bushing is loose - it will be obvious if you remove the front panel. If the latter, it's possible that it's just that the cursor is shifted, but it could also point to the need for a tuner alignment.

Cheers,

chazix
 
Thanks. I have 2 pair of speakers 1 is 300w the other 200 in the room...i dragged out some smaller 60w and tested with them. Its the left channel. The needle on the meter doesnt move much and that speaker doesnt get much volume. Previously they both cut out, now just that side. the right side i can max out and seemingly works fine.

Hit the mono switch and it works perfectly normal, back to stereo and the left is knackered.

Is this the typical output issue everyone else is having, is it resolvable?

Reading here, possibly an adjustment? http://www.audiokarma.org/forums/showpost.php?p=2128764&postcount=12

The knob shaft moves, i can push it back down into place, but i let go and it springs back.

EDIT: i spoke to the original owner today. He reckon its always done this and the fix is 'jiggle' the speaker AB selector and it comes good. Does this mean a good clean, deoxit is the next step?

He listens to classical and reckons he always ran it around 10 oclock on the volume and never really cranked, its been storage for years and he has been using a smaller NAD bookshelf system.
 
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I had similar issue on my 2040 when it arrived and i believe it was some dirty pots but i cant recall which resolved the issue
 
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Hi, JPete9,

Your picture shows that one of the power output packs has been replaced with a part labeled "STK0080", If the labelling is accurate, it's an incorrect part. It should be "STK 0080 II". The difference in name is a bit subtle, but the difference in the innards is not subtle - the II part has one more stage of current amplification.

The bolt head that appears in the photo also sets off loud alarm bells - it looks like it might be an "improvisation" to hold in the incorrect part.

At least one emitter resistor has also been replaced - the whitish components. There are two per channel, and should have been replaced in pairs, because it's highly probable that the same overcurrent that toasted one of them also flowed through the other.

One of your cross-referenced notes mentions the DC offset adjustment. It's important, and should be checked once everything else in the power amp stages is in good shape, but I think it's very unlikely to be the cause of the symptoms you're seeing.

My best guess is that for starters, you should replace the suspect power pack with an "STK 0080 II", and replace (or at least test) the emitter reistors that are connected with it. The resistors should be 0.47 ohms.

There is s risk of getting counterfeit power packs. I believe most AKers have been satisfied with B&D Enterprises as a supplier. (I have been.) There are some who advise getting the next higher-power-handling part in the series, STK 0100 II. (I don't, but I don't think there's any harm in it.)

Cheers,

chazix
 
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Thanks for the diagnoses. I am no electronic expert, i understand capacitors, diodes, resistors and i can test and replace these...but thats about it. I can do most things mechanical. Is this job likely to require a high skill level?

Is the following the way to approach this?
1. Buy a STK 0080 II (this is a different part to the circuit board discussed in this thread?)
a) this one? http://www.bdent.com/stk0080ii-sanyo-audio-10-pin-integrated-circuit.html
Sadly, they are $50 in shipping to Oz. Would one of these be the same
http://www.ebay.com.au/itm/new-IC-SANYO-POWER-AMPLIFIER-STK0080-II-STK0080II-/280556420564
http://www.ebay.com.au/itm/1pcs-SAN...ics_Wholesale_Electronics&hash=item4633605c2a
http://www.ebay.com/itm/5X-SANYO-STK0080-II-Darlington-Amplifier-Power-m-/321332828343

b) safer to buy 2 and have one spare or will this be in production for ever?

2. Buy 2 resistors .47ohms
3. remove and refit above
4. install new lights (on order. not one works in this thing)
4. Set/check the DC offset

Is this a very good chance of restoring this to working order? If so i will go ahead, if not i might find something more likely to work - keen to spend more time listening than soldering.

Do i need to consider that something caused this to fail originally and is a good chance of reoccurring or is this just wear and tear/age etc? I already have a vintage turntable that doesnt work properly either :) http://www.audiokarma.org/forums/showthread.php?t=606867

Cheers and thanks for the help!
 
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Your approach looks fine, Jpete9.

The STK 0080 II is the power output pack. It is one of two modules that contain many of the components of the power amplifier sections of the receiver. The other module is the predriver, which is the harder-to-find item that's much discussed in this thread. In a nutshell, the predriver provides voltage amplification, and the power pack provides current amplification.

The ebay listings you found for STK 0080 II all LOOK like they are offering the correct part. Whether or not they are truly proper replacements, your guess is as good as mine. Since there is some risk of counterfeiting, I surely would not buy two at once. Rather, I'd buy one, and test that it works to my satisfaction at the highest volume I'd care to hear. Only then would I consider buying a spare, which might indeed make sense - the only market for these parts is vintage repairers, as far as I know.

I think the chances of this repair being successful are pretty good. Not sure what to say about chance of recurrence of the problem. I've always imagined that power pack failures are the result of some sort of abuse, like short-circuited speaker wiring, but I have no way to be sure of that.

I should probably say that there are many who avoid the CR-x40 line, even if they like Yamaha in general, precisely because it uses these modularized parts that are no longer produced by the original manufacturer (Sanyo). (Obviously, I don't belong to that school of thought, because the parts problem is not much of an issue for me, and I think there is a lot to be admired about the series, especially the tuner sections.)

Chatty chatty chazix
 
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Thanks for your patience. I am going to have a go. I did buy 2, they are were $10. I bought 2 with different markings from 2 different sellers. If any are no good i will have discovered it and can contribute something to this forum :)

After i looked a bit more carefully, i notice the other side isnt labelled STK0080II either, in the manual they are labelled 2960 IC Drive. One of mine is, the back one. Further down in the manual they are labelled 2970 (PDF page 31)

eg this is the one at the back http://1drv.ms/1DcLefF

Is this one correct, am i on the right track just replacing the one?

Sorry the endless questions, this is a bit confusing.
 
IG02960 is the correct part number for the original Yamaha-labelled power pack. As far as I know, the original Sanyo STK 0080 II is the same as IG02960.

The service manual does seem to have mis-named parts on the "Outlines" page, but the outlines are correct.

All looks well in your picture. Looks don't guarantee function, of course!

When you complete the repair, it would be a good idea to first power up the receiver with a "dim bulb" rig. You can find info on that all over AK. It just refers to having a light bulb in series with the AC power. For a CR-1040, probably a 100W bulb would be appropriate.

Good luck,

chazix
 
I removed the old power pack and added the china replacement. I cant see where a second resistor is missing (mentioned above). The single .47k measures .001 on the 2k scale, which seems out of spec, would it cause these types of issues mentioned below? this is the board with the powerpack out http://oi59.tinypic.com/2wh00w5.jpg

Powered on and red overload flashes and then goes off - no audio output. I attached a single speaker, no audio. I notice the audio muting (0-20db) is pressed in, when i release it overload instantly. I dont hear any relay clicking at any point.

One of the issues was the extremely crap soldering on the dodgy replacement part. (seriously chook **** blobs of massive solder).

I clean it with the wick as best i could, put the replacement in with a small amount of solder to test...

Here is a pick - the 2nd and 3rd pins from the right have pins above them and there is connectivity between those pins and the pins above them (does that make sense?), looking at the other side of the board and the service manual, looks ok, but i am not 100% http://oi58.tinypic.com/amqw7b.jpg

I removed the powerpack and the amp functions perfectly normal, on the right channel only. Is there a way of testing this powerpack to see if its a good reproduction?

Whats the next step to troubleshoot? I did buy another powerpack with slightly different numbering from a different ebay vendor - but i wouldnt mind a more graceful way of testing than installing my amp :)

Appreciate any help - i am limited in electronic skills, but I'm optimistic! :)
 
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Hi, Jpete9

I'm not sure what you mean about a resistor being missing. Your first pic shows two white ceramic resistors. They are different, so one (the larger) has been replaced in the past. The two should have been replaced together, because if one suffered an over-current, the other almost certainly did, too. They should both be 0.47 OHMS (not Kohms).

The symptoms you mention don't point in any particular direction, at least for me.

It's very unexpected that the audio muting switch would make any difference (unless perhaps the volume was turned way up to begin with), so that seems like a red herring, or possibly an independent problem.

You can't really test that a power pack is good except by putting it into service. You can make some checks that can tell you if it's definitely bad, though. If you know how to make "diode tests" on a transistor with your ohmeter, you can check some of the transistors in the power pack. See the outline in the service manual for what pins are connected to what transistor.

There is a procedure, discussed starting at post #40 or so in this thread, for testing whether the rest of the power amp circuit is OK after removing the power pack. It involves tacking in a couple of resistors, so it's not the simplest thing, but it might be a good next step if you can manage it.

Cheers,

chazix
 
Thanks, further testing on those resistors. The original measures 1.6ohm and the odd one is closed...i will replace these next...i am trying to work out the exact spec of a replacement. looks like a metal plate resistor, .47ohm, how many watt?

Once i have these parts in i will follow your guide earlier in the thread.

The audio muting issue is not consistant...i cant reproduce it now.

thanks for your patience.
 
I'm not sure what they were trying to say with "metal plate resistor". Perhaps what I'd call metal film. Any type of resistor that you can find with 0.47 (or 0.5) ohms and a 5 watt power rating will do. If you have a choice, avoid wire-wound resistors, but I wouldn't worry about it if that's all you can find.

Are you using a dim bulb rig when you power up? I think it's well worth the trouble.

chazix
 
Sorry i took the metal plate name from the service manual. I did some reading on measuring resistance! The replacement resistor is closed, the other has no resistance - same as the 2 on the other channel. i bought a couple of replacements - put new powerpack in, same issue. removed and replaced with the wrong stk0080 that the amp came with and it works, but not well.

Thanks for the advice on dim bulb. Did some reading, ahve a plan and off to buy the stuff for dim bulb.

I will shelf this for now until a new power pack arrives...

the one i used was this http://www.ebay.com.au/itm/181170157339?_trksid=p2057872.m2749.l2648&ssPageName=STRK:MEBIDX:IT - BUT the markings on the one they sent me are a little different :( http://oi59.tinypic.com/j0cuph.jpg

I have been reading the threads and posts you pointed me to and i was wondering if its possible some one adjusted something (DC offset) to allow for the wrong powerpack stk0080 and then when i put the stk0080ii in the setting is wrong causing it to overload?

PS: i recieved my globe kit today, i replaced one on the 4 globe bar for the tuner and knock off the lead, powered on and it sparked and blew the 1.6a fuse. Replaced the lead and the fuse and put old globe back then every time i switch on it blew the fuse, replaced the diode and globes and now i have a fully lit up unit!!!
 
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Nope, no way a DC offset adjustment can make up for the difference between STK0080 and STK0080II. The powerpacks make almost no difference to DC offset. What they do is boost the CURRENT-driving capability of the overall amplifier circuit. Less boost - a lot less - is provided by the STK0080 compared to the STK0080II.

I'm glad the sparks-flying episode didn't end badly, Jpete9. It reminds me to remind you that the voltages in the "dim bulb" circuit are lethal. Please take care!

Cheers,

chazix
 
Thanks. I guess i was asking if some one may have messed with this setting to try and compensate, causing further issues?

I got a new powerpack, i installed it and the amp now powers on very gracefully. Previous power pack gave large pop/bang in the speakers during power on.
I connected speakers, if connected in any combination to the left output, any speaker switch position except off, the left meter shows about 50% less than the right meter and the sound is crackling and poor.
Unplug the speaker and the meter returns to normal - with the wrong power pack the meter runs 50% less all of the time. << this is new.
Headphones work perfectly. Everything about the amp appears brand new - didnt occur to me to test this before now so i dont know if this is new. Does this mean i should stop troubleshooting the powerpack or the predriver?

Voltage at the speaker terminals seems to be 515mv on the right (working channel) and 260mv on the left not working one.

Any thoughts on what next?

I was going to measure these. http://www.audiokarma.org/forums/showpost.php?p=858813&postcount=6 Dumb question, but i want to be cautious, do i get the negative side from the chassis?
 
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Hi, Jpete9

First thing to rule out: Is there any chance you've got a partial short in one of your speaker wires? You could swap the speaker connections from left to right (at the receiver end) to check that.

But I'll assume we're still chasing an internal problem. So, it seems like the distortion only happens when there's a load. (Headphones present very little load.) That suggests that the power pack is either unable to do a good enough job at boosting current, or something else is limiting the power pack's ability.

I think my suggestion for the next step would be to check the voltages at pins 1 and 10 of the suspect power pack (the outermost). One should be about +3V, and the other about -3V. If you measure with respect to the chassis (that is the usual case when measuring voltages), the DC offset at the speaker terminal comes into play. So, in the case of the bad channel with about 1/4V offset, you'd expect 2 3/4V and 3 1/4V at the power pack pins.

The post that you referenced is merrylander's observation about what voltages to expect at the predriver when the power pack is removed. I believe it's correct, but it's another example of a test that can tell you more about whether something is bad than whether it is good. That is, it's not a very sensitive test of whether the predriver is completely healthy.

chazix
 
chazix said:
Hi, Jpete9

First thing to rule out: Is there any chance you've got a partial short in one of your speaker wires? You could swap the speaker connections from left to right (at the receiver end) to check that.
Click to expand...

Thoroughly changed out the wires and speakers with others i have here. Tested the Speaker switch position, speaker wire and speaker combos in every combination.

But I'll assume we're still chasing an internal problem. So, it seems like the distortion only happens when there's a load. (Headphones present very little load.) That suggests that the power pack is either unable to do a good enough job at boosting current, or something else is limiting the power pack's ability.

I think my suggestion for the next step would be to check the voltages at pins 1 and 10 of the suspect power pack (the outermost). One should be about +3V, and the other about -3V. If you measure with respect to the chassis (that is the usual case when measuring voltages), the DC offset at the speaker terminal comes into play. So, in the case of the bad channel with about 1/4V offset, you'd expect 2 3/4V and 3 1/4V at the power pack pins.

The post that you referenced is merrylander's observation about what voltages to expect at the predriver when the power pack is removed. I believe it's correct, but it's another example of a test that can tell you more about whether something is bad than whether it is good. That is, it's not a very sensitive test of whether the predriver is completely healthy.

chazix
Click to expand...

Tonight I will start testing each component from the speaker circuit back to the power pack and see how far i can get. I will test the power pack voltage you mentioned and go from there.

Both of these powerpack are from ebay china - different vendors and different markings. The first one is broken big time, when i power on the overload is on and cant do anything, this second one seems to let me power up and play music but original issue still exists, but i think its less pronounced (but i cant be sure) - maybe i should unsolder the working one and drop it into this side as a test? I did buy another power pack from utsource, but not arrived yet (i realise its not the most scientific approach).
 
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Recieved new powerpacks from utsource. No difference. :(

I did buy the predriver packs from them too-i am tempted to try those and if it doesnt work, part it out and buy something more working.

I tried testing the outer pins, on both power packs they seem like a closed circuit and i get nothing on the multi meter.

I did find that the 2 white resistors near the working right power pack have .000 resistance the 2 new ones i replaced on the not working left channel have .470 resistance. Is it possible i used the wrong ones.

Original on the left, new ones on the right
http://1drv.ms/1GFPoxI

I found another resistor seemingly out of spec. Near the 2 fuses on the little circuit board there is 2 180ohm resistors. one read .180 and the other .02.

Is it possible something has gone wrong on this thing in the past a number of components are now cactus - in which case unless you're an electronic expert this is going to be a long haul?
 
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