If it is arching in power switch, how i can fix that? Deoxit? There is one cap soldered to contact pins.
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Ongoing saga of the Yamaha CR-n40s
- Thread starter merrylander
- Start date
If it is arching in power switch, how i can fix that? Deoxit? There is one cap soldered to contact pins.
clinic-audio
all on YAMAHA untill 1990
Hello ONEe
If it is arching in power switch, how i can fix that? by replacement of the defect switch NO OTHER WAY
I watch your movie (well made) but I don't see any flashing lamp and no krriii sound
I remember when I was refixed CRXXX40 in my lab 25 years ago , this noise was create by bad driver IC .
After replacement everything go back to normal function !
Are we talking about the same noise ? I don't know ...
If it is arching in power switch, how i can fix that? by replacement of the defect switch NO OTHER WAY
I watch your movie (well made) but I don't see any flashing lamp and no krriii sound
I remember when I was refixed CRXXX40 in my lab 25 years ago , this noise was create by bad driver IC .
After replacement everything go back to normal function !
Are we talking about the same noise ? I don't know ...
clinic-audio
all on YAMAHA untill 1990
Hello !
Here are the "official voltages" coming from original SM
I hope that my picture will be big enough to read !
Attachments
All i can say that meter lamps are flashing, it is not like on/off but its just small brightness change. In video, fm signal quality is low and when flashing stops and krrii sound stops its goes up. Time it takes to stop that sound is not same always, sometimes no krriii and sometimes few seconds.
EDIT: I think its bad power switch, listened very carefully close to power switch. What kind of power switch would be good?
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clinic-audio
all on YAMAHA untill 1990
Hello ONEe
Try these !
http://www.cpcares.com/pdf/1300.pdf
the L type would fit in place with no modification I think :thmbsp:
Try these !
http://www.cpcares.com/pdf/1300.pdf
the L type would fit in place with no modification I think :thmbsp:
Attachments
My local electronics shop does't have those and mouser doesn't have either.
Found this http://www.digikey.fi/product-detail/en/P227EE2B20A/EG1018-ND/149360, but don't know if it can handle 230VAC.
EDIT: I have one push button taken from scrapped amplifier. And it's SPST switch so can i use this? Also rating says 5A/80A250V
EDIT: I took that original switch off and it says 5A/80A250V, also original is DPST switch but uses only one of top switches so i can replace it with SPST switch. Only visual thing is that power button doesn't come out so much as in original and when powered on the button is same level with faceplate, so its flat when on.
Pictures from original switch and new one.
EDIT: I have one push button taken from scrapped amplifier. And it's SPST switch so can i use this? Also rating says 5A/80A250V
EDIT: I took that original switch off and it says 5A/80A250V, also original is DPST switch but uses only one of top switches so i can replace it with SPST switch. Only visual thing is that power button doesn't come out so much as in original and when powered on the button is same level with faceplate, so its flat when on.
Pictures from original switch and new one.
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One thing you may want to do if the problem is pretty frequent or easy to reproduce is to just temporarily bypass the switch with a jumper across the two wires or just solder the two wires together. If the sound/light problem goes away, then at least you are sure it's the switch. You can use a power strip as a temporary switch.
Well, that didn't come to my mind, but now i have new switch soldered.
EDIT: Thanks to clinic-audio and chazix for help me. No more krriii sound. Now I have to get new lamps, I measured lamp board voltages and there is coming 32v. Can those 14V lamps handle over voltage about 2v a lamp.
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Nice to see that you get your receiver in working condition. Where did you ordered those parts?
How hot those predrivers get? Heat sink mod here http://www.audiokarma.org/forums/showpost.php?p=6128467&postcount=60
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clinic-audio
all on YAMAHA untill 1990
Hello Kenwood61
I checked the "burnt" resistor and it is fine.
Your resistor is good because somebody replace it before (when this channel died) but they don't clean the PCB before to put this new resistor , that's what make me think that this unit has been refixed (or touched) before !
Good thing that you found this bad diode !
With both IC's out in the bad channel, the receiver now powers up out of protection mode as it should.
this is exactly what I suggested you to do ! now you can go ahead and refix this "bad" channel !
keep us updated ! :thmbsp:
I checked the "burnt" resistor and it is fine.
Your resistor is good because somebody replace it before (when this channel died) but they don't clean the PCB before to put this new resistor , that's what make me think that this unit has been refixed (or touched) before !
Good thing that you found this bad diode !
With both IC's out in the bad channel, the receiver now powers up out of protection mode as it should.
this is exactly what I suggested you to do ! now you can go ahead and refix this "bad" channel !
keep us updated ! :thmbsp:
I'm afraid I quit on my CR-840 and sold it cheap. Never got the breadboard predriver working. The Yamaha didn't have any tubes in it so it was too low in priority. Consequently I don't have much to offer about the predriver. If I remember, I powered mine up without the power IC installed to check the function of the predriver. I don't think it hurts anything. Sorry for the lack of help.
John
John
First off, let me just say: bummer!!
I can't speak for anyone but myself, but it might be that even CR-x40 mavens are a bit daunted by your situation. You've replaced every part that I've ever seen to fail in the amplifier section, you've double-checked your work, you got a legit-looking predriver, and as for the power pack... well, I'll just say it would be unusual for one to fail immediately, even if it's a counterfeit. So, it's a head-scratcher.
If I were in the situation, the first thing I'd check (though it's a long shot) is the voltage on pin 1 of the predriver. You can check that with all the parts still installed. The idea is to eliminate the possibility that a leaky coupling capacitor is feeding DC to the input of the amp section. The pin 1 voltage should be nearly zero. With a meter set to read millivolts, you'll see a positive DC voltage of perhaps tens of millivolts, due to a little bit of current coming out of the predriver itself. If you see more than, say 100mV, it could be a leaky coupling cap. (If so, the next step would be to remove the cap and see if things get better, but let's cross that bridge if/when we come to it.)
Now, what you actually asked about: the prospects for testing with one of the modules removed. It's not a terribly definitive test by itself, but it's safe to do (with either module), in the sense that nothing will be damaged. If you pick the power module as the one to remove, the protection relay should definitely close. If you remove the predriver, I'm not sure.
Let's say you remove the power module, and the relay closes. About all you can do at that point is to make sure that pin 14 of the predriver is at +40-ish volts DC. Pin 13 will probably be at -40-ish, but I don't think that's 100% certain. To really get an idea of whether the predriver is working, you have to have something acting as kind of a surrogate for the power module. Would you be comfortable tacking a couple of resistors onto the circuit board to act as the surrogate? If so, either let me know here, or you can find the procedure I'm aiming at earlier in this thread, with some helpful pictures courtesy of 4SeatPilot.
Back to my day job for now...
chazix
I can't speak for anyone but myself, but it might be that even CR-x40 mavens are a bit daunted by your situation. You've replaced every part that I've ever seen to fail in the amplifier section, you've double-checked your work, you got a legit-looking predriver, and as for the power pack... well, I'll just say it would be unusual for one to fail immediately, even if it's a counterfeit. So, it's a head-scratcher.
If I were in the situation, the first thing I'd check (though it's a long shot) is the voltage on pin 1 of the predriver. You can check that with all the parts still installed. The idea is to eliminate the possibility that a leaky coupling capacitor is feeding DC to the input of the amp section. The pin 1 voltage should be nearly zero. With a meter set to read millivolts, you'll see a positive DC voltage of perhaps tens of millivolts, due to a little bit of current coming out of the predriver itself. If you see more than, say 100mV, it could be a leaky coupling cap. (If so, the next step would be to remove the cap and see if things get better, but let's cross that bridge if/when we come to it.)
Now, what you actually asked about: the prospects for testing with one of the modules removed. It's not a terribly definitive test by itself, but it's safe to do (with either module), in the sense that nothing will be damaged. If you pick the power module as the one to remove, the protection relay should definitely close. If you remove the predriver, I'm not sure.
Let's say you remove the power module, and the relay closes. About all you can do at that point is to make sure that pin 14 of the predriver is at +40-ish volts DC. Pin 13 will probably be at -40-ish, but I don't think that's 100% certain. To really get an idea of whether the predriver is working, you have to have something acting as kind of a surrogate for the power module. Would you be comfortable tacking a couple of resistors onto the circuit board to act as the surrogate? If so, either let me know here, or you can find the procedure I'm aiming at earlier in this thread, with some helpful pictures courtesy of 4SeatPilot.
Back to my day job for now...
chazix
I think that rules out the leaky cap hypothesis. That voltage at pin 1 is definitely suspicious, but shouldn't be enough to drive the output to 40V.
We'd better make sure the predriver is getting its negative power supply. (Usually power supply problems would affect both channels, but anything is possible, and we're well into the grasping-at-straws stage.) What is the voltage on pin 6 of the non-working-side predriver? It should be negative DC, around -40V.
chazix
We'd better make sure the predriver is getting its negative power supply. (Usually power supply problems would affect both channels, but anything is possible, and we're well into the grasping-at-straws stage.) What is the voltage on pin 6 of the non-working-side predriver? It should be negative DC, around -40V.
chazix
jamesbrennan
Semiconductor Guru
I am suggesting shorting of pin 3 input to pin 1 input of predriver. This should break the feedback loop, allowing subsequent measurements of predriver IC and output IC voltages. Is output stuck at +41v? Let's find out.
I can't make sense out of those voltage readings. Even the ones for the good channel are inconsistent with good health. (In particular, both pins 4 and 5 should be fairly near to the negative supply voltage on pin 6.) I have to assume that some readings are incorrect, which makes me hesitant to do any reasoning with them.
I think I can say this: if pin 5 really, truly has a higher positive voltage than pin 3, the predriver is not only bad, it isn't an accurate rendition of an IG02940. I can't think of any failure mode that could result in that condition. (I'm assuming here that the predriver is properly connected to the rest of the receiver's circuitry, that is, there aren't any solder bridges or the like.)
Oh dear, that makes me think - is there any chance that the predriver is installed backwards? It's physically possible. The two predrivers should be oriented in the same way.
Hi, jamesbrennan, I don't understand where you're going with your suggestion. With the diff amp inputs shorted together, I would expect the output to drive to either the + or - rail. I would expect the output could go either way depending on which way the diff amp offset falls. What am I missing?
chazix
I think I can say this: if pin 5 really, truly has a higher positive voltage than pin 3, the predriver is not only bad, it isn't an accurate rendition of an IG02940. I can't think of any failure mode that could result in that condition. (I'm assuming here that the predriver is properly connected to the rest of the receiver's circuitry, that is, there aren't any solder bridges or the like.)
Oh dear, that makes me think - is there any chance that the predriver is installed backwards? It's physically possible. The two predrivers should be oriented in the same way.
Hi, jamesbrennan, I don't understand where you're going with your suggestion. With the diff amp inputs shorted together, I would expect the output to drive to either the + or - rail. I would expect the output could go either way depending on which way the diff amp offset falls. What am I missing?
chazix
clinic-audio
all on YAMAHA untill 1990
Hello Kenwood61
I forget to come back on this thread and I did it now and realize that this story has no end so ....
When you have your receiver with protection activated because of one defectuous channel let me explain you this :
1) there is something very easy to do : make a mark (little drop of red paint) on the "working IC's " (the ones on working channel in fact)
2) delete all the IC's (bad and good one on both channels
3) siwtch the power on
4) make a mesurement test of voltages on each empty contact of IC's on the PCB
During this test with no IC's the relay should work and you will not damage anything ! confirm that speaker relay is working (no more in protection position )
5) once you have a model of voltages table , you will know then , what voltages values you should get on the bad channel at ech contact place of the IC's .
6) switch off the unit
7) discharge all the electrolytic capacitors of the power supply .
8) re connect the both "good" IC at their place .
9) switch the power on , the relay should work again
10) mesure voltages on this bad channel and make comparaison with "your voltages table" to see if there is anything wrong between the left and the right channels (when the 4 ic's were of the pcb )
come back to me with report , I will give you instructions to follow
I forget to come back on this thread and I did it now and realize that this story has no end so ....
When you have your receiver with protection activated because of one defectuous channel let me explain you this :
1) there is something very easy to do : make a mark (little drop of red paint) on the "working IC's " (the ones on working channel in fact)
2) delete all the IC's (bad and good one on both channels
3) siwtch the power on
4) make a mesurement test of voltages on each empty contact of IC's on the PCB
During this test with no IC's the relay should work and you will not damage anything ! confirm that speaker relay is working (no more in protection position )
5) once you have a model of voltages table , you will know then , what voltages values you should get on the bad channel at ech contact place of the IC's .
6) switch off the unit
7) discharge all the electrolytic capacitors of the power supply .
8) re connect the both "good" IC at their place .
9) switch the power on , the relay should work again
10) mesure voltages on this bad channel and make comparaison with "your voltages table" to see if there is anything wrong between the left and the right channels (when the 4 ic's were of the pcb )
come back to me with report , I will give you instructions to follow
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jamesbrennan
Semiconductor Guru
Hi Chazix,
I agree, some voltage readings are impossible.
With pin 1 shorted to pin 3, both pins were then at 0.5v and none of the other measurements changed. I am now suggesting shorting pins 1, 2 and 3 together. Forcing 0.00 v on both inputs. This should force preamp pins 4 and 5 near the negative supply.
Jim
I agree, some voltage readings are impossible.
With pin 1 shorted to pin 3, both pins were then at 0.5v and none of the other measurements changed. I am now suggesting shorting pins 1, 2 and 3 together. Forcing 0.00 v on both inputs. This should force preamp pins 4 and 5 near the negative supply.
Jim
I think the closest I can come to encouragement is to say that I'm sure this receiver can be fixed. But if the combination of your time and the community's collective knowledge isn't sufficient to get there, then it makes sense to go with a plan B.
If it comes to that, you might consider selling the whole unit "as is" instead of parting it out. It should take less of your time, and I think it's an attractive offering. (That's just my own bias, though. I'd make an offer myself, if I weren't impractically far away.)
chazix
If it comes to that, you might consider selling the whole unit "as is" instead of parting it out. It should take less of your time, and I think it's an attractive offering. (That's just my own bias, though. I'd make an offer myself, if I weren't impractically far away.)
chazix
To my eye the smoking gun is still the pin 3 & 5 voltages on the bad-side predriver. Those readings could not occur with a properly working predriver.
I don't see anything in the resistance or voltage readings that indicates that the power module is bad.
chazix
I don't see anything in the resistance or voltage readings that indicates that the power module is bad.
chazix