Thankfully the garage/estate sale season is over.
There are no thrift stores to speak of in the small city where I've lived for three years so my scrounging urges compelled me to attend garage/yard/estate sales in the area. I am also compelled to look for audio equipment and reorded music. Consequently those urges have caused me to bring home a few finds.
The last audio component I obtained in such a way was a Kenwood KR6030 receiver. I knew nothing of it's history other than the deceased owner bought it new and that fellow's next of kin were disposing of his belongings.
Once I had it home, I looked online for info on that model and saw that it had some respect. I also learned about the potential failure of it's power on / power off / speaker selector combo switch and it so happened that this receiver displayed a telltale sign of that failure. After reading that disassembling then cleaning the switch contacts plus installing a triac device was a recommended fix, I did that and it was successful.
There also seemed to be a need to spray contact cleaner inside the toggle switches. That was done and after which the switches were exercised 100 times. I performed that process twice and also included the rotary switches and potentiometers. Another chore I undertook was replacing all of the electrolytic capacitors on the power supply board but did not disturb the two large filter caps.
Afterwards, as far as I could tell, the receiver worked well. That is until I gave it an extended listen while playing LP's during which the volume periodicaly dropped slightly at random intervals. It was akin to turning a 10dB loudness switch off then engaging it again. The sound would recover, play normally for a short time then drop again. That cycle repeated over and over and it seemed to occur on both channels simultaineously. It also occurred with more than one input source.
Not kowing where to start looking, I first considered the input selector switch and took as good a look as I could with an illuminated magnifier. I could be mistaken but I was expecting the contact surfaces to be shiny metal but they are black.
The photo is of the switch in situ.
If someone would care to comment if the section of the switch that I was able to photograph looks normal or not, it would be appreciated. To my eye, it sort of looks like paint.
Is it supposed to be black?
There are no thrift stores to speak of in the small city where I've lived for three years so my scrounging urges compelled me to attend garage/yard/estate sales in the area. I am also compelled to look for audio equipment and reorded music. Consequently those urges have caused me to bring home a few finds.
The last audio component I obtained in such a way was a Kenwood KR6030 receiver. I knew nothing of it's history other than the deceased owner bought it new and that fellow's next of kin were disposing of his belongings.
Once I had it home, I looked online for info on that model and saw that it had some respect. I also learned about the potential failure of it's power on / power off / speaker selector combo switch and it so happened that this receiver displayed a telltale sign of that failure. After reading that disassembling then cleaning the switch contacts plus installing a triac device was a recommended fix, I did that and it was successful.
There also seemed to be a need to spray contact cleaner inside the toggle switches. That was done and after which the switches were exercised 100 times. I performed that process twice and also included the rotary switches and potentiometers. Another chore I undertook was replacing all of the electrolytic capacitors on the power supply board but did not disturb the two large filter caps.
Afterwards, as far as I could tell, the receiver worked well. That is until I gave it an extended listen while playing LP's during which the volume periodicaly dropped slightly at random intervals. It was akin to turning a 10dB loudness switch off then engaging it again. The sound would recover, play normally for a short time then drop again. That cycle repeated over and over and it seemed to occur on both channels simultaineously. It also occurred with more than one input source.
Not kowing where to start looking, I first considered the input selector switch and took as good a look as I could with an illuminated magnifier. I could be mistaken but I was expecting the contact surfaces to be shiny metal but they are black.
The photo is of the switch in situ.
If someone would care to comment if the section of the switch that I was able to photograph looks normal or not, it would be appreciated. To my eye, it sort of looks like paint.
Is it supposed to be black?
The two large filters caps are normally the first that are replaced as these have "suffered" the most normally.
Looks to me like a solder crack near the loudness switch circuit or the contact cleaner did not do a proper job.
This power supply has actually two separate rectifier bridges supplying the power output stage - I would refresh their soldering and also the inter-board connecting power cables joints.
Yes the 2 x 12000 uF suffer the most normally. Highest inrush current too. The 2 x 220 uF at the other rectifier bridge can be replaced for 2 x 470 uF.
All useless for now as there is an issue to solve.
Reflow of all solder joints and disassembly of all switches is almost mandatory at this age. Until that is done other advice seems redundant. Cheap hoarded old audio devices are real time eaters. And since they are never alone the time must be multiplied by the number of devices. A normal person does not have that time so the general pattern is then 30 devices with each at least one complaint.
If the device has a loudspeaker relay that one is also prone to failure as japanese brands excelled in choosing the wrong relay for the purpose.
All useless for now as there is an issue to solve.
Reflow of all solder joints and disassembly of all switches is almost mandatory at this age. Until that is done other advice seems redundant. Cheap hoarded old audio devices are real time eaters. And since they are never alone the time must be multiplied by the number of devices. A normal person does not have that time so the general pattern is then 30 devices with each at least one complaint.
If the device has a loudspeaker relay that one is also prone to failure as japanese brands excelled in choosing the wrong relay for the purpose.
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A thank you to all for the replys.
Thanks for that. I appreciate the answer.
Yes, I understand that those large caps see the harshest duty but I must take replacement cost into consideration. Being retired with a fixed income plus experiencing negative cash flow means I must carefully consider each expense. I have been led to think that the larger the capacitor, the more impervious they are to degradation assuming it has not been overly taxed.
Since I must dig into this receiver, I will measure those caps if I am able and make the call to replace should they be out of spec.
That is something I will look for when I begin what disassembly is required to access the boards.
The presence of two rectifiers is noted. I did not realize that. And a good point re the interboard connectors. I will pay attention to those.
I happen to have already seen a video by someone who disassembled and cleaned a speaker protection relay in one of these. Not much of a tutorial in how to access, just a remark that it was defective.
Once I understand the relay better after a close up inspection, my inclination would be to replace it with a brand new one.
Thanks for that. I appreciate the answer.
Yes, I understand that those large caps see the harshest duty but I must take replacement cost into consideration. Being retired with a fixed income plus experiencing negative cash flow means I must carefully consider each expense. I have been led to think that the larger the capacitor, the more impervious they are to degradation assuming it has not been overly taxed.
Since I must dig into this receiver, I will measure those caps if I am able and make the call to replace should they be out of spec.
That is something I will look for when I begin what disassembly is required to access the boards.
The presence of two rectifiers is noted. I did not realize that. And a good point re the interboard connectors. I will pay attention to those.
I happen to have already seen a video by someone who disassembled and cleaned a speaker protection relay in one of these. Not much of a tutorial in how to access, just a remark that it was defective.
Once I understand the relay better after a close up inspection, my inclination would be to replace it with a brand new one.
+1. Pick a minimum 8A rated sealed one with silver alloy contacts (preferably bifurcated).
Good western made relays, not Ebay/Aliexpress ones. If you do this often you’ll notice many japanese brands to use the same 24V (sometimes 48V) model. It pays off to buy a few if so.
Good western made relays, not Ebay/Aliexpress ones. If you do this often you’ll notice many japanese brands to use the same 24V (sometimes 48V) model. It pays off to buy a few if so.
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No...... They´re not.
From the beginning, these are silver plated.
Turning black is oxydation, whitch is pretty bad on this one.
The most annoying/difficult places are, if the oxydation affects the contact points, where the "rivets" go through the pertinax.
Can (maybe) be fixed by first cleaning them with a fiber glasss brush and carefully soldered together.
You can see a few rivets are not affected. All the metal parts in the switch function are supposed to have that same color.
They did, when the switch was new.
"From the beginning, these are silver plated.
Turning black is oxydation, whitch is pretty bad on this one.
The most annoying/difficult places are, if the oxydation affects the contact points, where the "rivets" go through the pertinax.
Can (maybe) be fixed by first cleaning them with a fiber glasss brush and carefully soldered together.
You can see a few rivets are not affected. All the metal parts in the switch function are supposed to have that same color.
They did, when the switch was new."
They are silver plated, correct. They are also self cleaning. Look closely at the clean portion where the wiper wipes the contact.
Silver, like silver cuttlery, tarnishes but even the tarnish is a good conductor of electricity. (Ask anyone who knows about Germanium transistors and BGA soldering with lead free solder).
If they are loose, they will be intermittent. If not I expect a dry joint or relay issue.
Turning black is oxydation, whitch is pretty bad on this one.
The most annoying/difficult places are, if the oxydation affects the contact points, where the "rivets" go through the pertinax.
Can (maybe) be fixed by first cleaning them with a fiber glasss brush and carefully soldered together.
You can see a few rivets are not affected. All the metal parts in the switch function are supposed to have that same color.
They did, when the switch was new."
They are silver plated, correct. They are also self cleaning. Look closely at the clean portion where the wiper wipes the contact.
Silver, like silver cuttlery, tarnishes but even the tarnish is a good conductor of electricity. (Ask anyone who knows about Germanium transistors and BGA soldering with lead free solder).
If they are loose, they will be intermittent. If not I expect a dry joint or relay issue.
Sorry, but with all due respect this argument does not sell. The "clean portion" is existing only due to mechanical wear caused by the wiper.
And that wear does not happen under the rivets.
Been there, done that...
The Kenwood receiver has been poised for me to do some disassembly but time has not been permitting. It has become that I only have an hour or so before I go to sleep at night where I can do any tinkering. There is a turntable in the way that I hope to button up today so then my next task would be this receiver.
My first objective would be to replace that aformentioned relay. In the coarse of disassembly to access it, I hope to more fully expose or potentially remove that input source selector switch for closer inspection.
By that point, I hope to have a better view of that board's solder joins and look for bad ones.
By that point too, I will likely replace what electrolytic capacitors I encounter and perhaps be able to obtain the physical dimensions of the large filter caps. Knowing that would allow me to determine replacements and likewise their cost.
I will add more photos of the source selector switch once I can view it from all sides.
My first objective would be to replace that aformentioned relay. In the coarse of disassembly to access it, I hope to more fully expose or potentially remove that input source selector switch for closer inspection.
By that point, I hope to have a better view of that board's solder joins and look for bad ones.
By that point too, I will likely replace what electrolytic capacitors I encounter and perhaps be able to obtain the physical dimensions of the large filter caps. Knowing that would allow me to determine replacements and likewise their cost.
I will add more photos of the source selector switch once I can view it from all sides.
Two days ago I was able to spend time and disassemble this KR6030 so as to access the power amp section. I've removed the relay and ordered an Omron MY4-02-DC24 to replace it. ETA is tomorrow.
I was unable to take off the origianl Fujitsu relay's cover off (I stripped the screw head) so cannot get a good look at the contacts, What I could see suggests that there is no discoloration so that orignal relay may actually be in good shape.
With the power amp board accessible, I replaced nearly all of the electrolytic capacitors. Those which have not yet been replaced are orange jacketed Elna capacitors which I understand are distinctive for being low loss / low leakage. I have on hand some brand new, small form factor 50V 3.3uF Rubycon capacitors
I removed one of the 25V 3.3uF Elnas, and tested it with a device that provides some data on capacitors. I did likewise with a 50V 3.3uF Rubicon:
Original orange 25V 3.3uF Elna - 3170nF - ESR 2.5 ohms - Vloss 2.4%
Rubicon 50V 3.3uF - 3240nF - ESR 6.7 ohms - Vloss 2.6%
Does the higher 6.7 ohm ESR of the Rubycon disqualify it as a replacement for the 2.5 ohm ESR of the Elna? Since the Elna is 47 years old, should it be reinstalled?
It was suggested elsewhere that I replace with a film cap instead.
Those are substantially higher in cost compared to electrolytics and If it were just those on the power amp board, that wouldn't matter but there are considerably more orange jacketed capacitors on a circuit board I have not accessed yet.
That board is referred to in the service manual as "Tone Control"
If I were to extend capacitor replacement to the Tone Control board, the cost of film capacitors could make purchasing the quantity needed cost prohibitive,
Would going that route be considered a sideways move, somewhat recommended or highly recommended?
With regards to the input selector switch, it is located in such a spot where it looks like I would need to remove the dial string in order to get at it. I can say that I am not thrilled with that likelyhood.
I was unable to take off the origianl Fujitsu relay's cover off (I stripped the screw head) so cannot get a good look at the contacts, What I could see suggests that there is no discoloration so that orignal relay may actually be in good shape.
With the power amp board accessible, I replaced nearly all of the electrolytic capacitors. Those which have not yet been replaced are orange jacketed Elna capacitors which I understand are distinctive for being low loss / low leakage. I have on hand some brand new, small form factor 50V 3.3uF Rubycon capacitors
I removed one of the 25V 3.3uF Elnas, and tested it with a device that provides some data on capacitors. I did likewise with a 50V 3.3uF Rubicon:
Original orange 25V 3.3uF Elna - 3170nF - ESR 2.5 ohms - Vloss 2.4%
Rubicon 50V 3.3uF - 3240nF - ESR 6.7 ohms - Vloss 2.6%
Does the higher 6.7 ohm ESR of the Rubycon disqualify it as a replacement for the 2.5 ohm ESR of the Elna? Since the Elna is 47 years old, should it be reinstalled?
It was suggested elsewhere that I replace with a film cap instead.
Those are substantially higher in cost compared to electrolytics and If it were just those on the power amp board, that wouldn't matter but there are considerably more orange jacketed capacitors on a circuit board I have not accessed yet.
That board is referred to in the service manual as "Tone Control"
If I were to extend capacitor replacement to the Tone Control board, the cost of film capacitors could make purchasing the quantity needed cost prohibitive,
Would going that route be considered a sideways move, somewhat recommended or highly recommended?
With regards to the input selector switch, it is located in such a spot where it looks like I would need to remove the dial string in order to get at it. I can say that I am not thrilled with that likelyhood.
Geez, replace these for "anything". If film caps are too costly then any new capacitors (from respectable suppliers) will do.
Thanks. I appreciate the advice and will take it. But I would like to excercise some care in making my selections.
The tally of orange jacketed capacitors that I would replace is 14. I began costing out replacement film capacitors on Digikey's site and soon learned that their cost will excede what I am comfortable with. So new capacitors will be electrolytics. I would go one voltage step higher than the originals but keep capacitance values the same.
Since those orange jacketed Elna's are "low loss / low leakage", should I be trying for the lowest ESR values I can find? And what exactly constitutes low ESR? Is there a treshhold number that a low ESR capacitor must be below?
As mentioned in my first post, the ESR of the existing original Elna 3.3uF cap which I was able to measure is 2.5 ohms. And that the small Rubycon 3.3uF cap I have on hand is 6.7 ohms. Navigating the Digikey site using basic specs for 50V 3.3 ohm capacitors produced a selection of 8 candidates. Only one, the least expensive option, has an ESR value attached to it and the ESR number cited for that one is 80.381 Ohm @ 120Hz.
The other seven choices had no ESR values displayed.
How would I make an appropriate choice?
The 14 orange jacketed Elna's are comprised of 4 different values. Since ESR values are not disclosed on Digikey's site, are there certain brands or a series within a brand that I should focus on?
The tally of orange jacketed capacitors that I would replace is 14. I began costing out replacement film capacitors on Digikey's site and soon learned that their cost will excede what I am comfortable with. So new capacitors will be electrolytics. I would go one voltage step higher than the originals but keep capacitance values the same.
Since those orange jacketed Elna's are "low loss / low leakage", should I be trying for the lowest ESR values I can find? And what exactly constitutes low ESR? Is there a treshhold number that a low ESR capacitor must be below?
As mentioned in my first post, the ESR of the existing original Elna 3.3uF cap which I was able to measure is 2.5 ohms. And that the small Rubycon 3.3uF cap I have on hand is 6.7 ohms. Navigating the Digikey site using basic specs for 50V 3.3 ohm capacitors produced a selection of 8 candidates. Only one, the least expensive option, has an ESR value attached to it and the ESR number cited for that one is 80.381 Ohm @ 120Hz.
The other seven choices had no ESR values displayed.
How would I make an appropriate choice?
The 14 orange jacketed Elna's are comprised of 4 different values. Since ESR values are not disclosed on Digikey's site, are there certain brands or a series within a brand that I should focus on?
My request for recommending capacitor brand / series can be ignored. I ordered Nichicon UKL series for all but the 3.3uF.
For that value, I ordered UPX series as there were no UKL series on the Digikey site. I will either install those or maybe those Rubycon's that I have on hand.
For that value, I ordered UPX series as there were no UKL series on the Digikey site. I will either install those or maybe those Rubycon's that I have on hand.
My capacitor order arrived from Digikey earlier today and the first ones I intended to install were the 3.3uF Nichicon UPX series I received. As previously mentioned, I ordered UPX series in lieu of UKL series because Digikey had no stock of 3.3uF UKL. Digikey's site had UPX categorized as Audio Grade so I thought that would do.
They were my choice to replace the orange 3.3uF low loss / low leakage Elnas in the earlier photo which produced an ESR reading of 2.5 ohms on the device I have.
What I first noticed was a big difference in diameter. Although it will fit on the board, the new, brown 35V 3.3uF UPX is much wider than the 25V 3.3uF orange Elna. Plus the device I have displayed an ESR for the UPX of 0.36k ohms which my math says is 360 ohms.
If ESR is important, it would seem that I should not use this 35V 3.3 ohm UPX but rather use that small black 50V 3.3 ohm Rubycon depicted earlier. It's ESR of 6.7 ohms is a heck of a lot closer to the Elna's 2.5 ohms than the 360 ohms displayed by the just received Nichicon UPX.
It seems than that the designation "Audio Grade" when it comes to capacitors, does not mean an automatic low ESR.
Am I on a ghost chase? Should I be concerned about ESR? That specification is all but ignored on Digikey's capacitor descriptions.
Should the V-loss figure command more attention? Is that the "loss" attributed to those low loss orange Elnas?
The V-loss figure of that Nichicon UPX I just received is considerably less than the orange Elna.
They were my choice to replace the orange 3.3uF low loss / low leakage Elnas in the earlier photo which produced an ESR reading of 2.5 ohms on the device I have.
What I first noticed was a big difference in diameter. Although it will fit on the board, the new, brown 35V 3.3uF UPX is much wider than the 25V 3.3uF orange Elna. Plus the device I have displayed an ESR for the UPX of 0.36k ohms which my math says is 360 ohms.
If ESR is important, it would seem that I should not use this 35V 3.3 ohm UPX but rather use that small black 50V 3.3 ohm Rubycon depicted earlier. It's ESR of 6.7 ohms is a heck of a lot closer to the Elna's 2.5 ohms than the 360 ohms displayed by the just received Nichicon UPX.
It seems than that the designation "Audio Grade" when it comes to capacitors, does not mean an automatic low ESR.
Am I on a ghost chase? Should I be concerned about ESR? That specification is all but ignored on Digikey's capacitor descriptions.
Should the V-loss figure command more attention? Is that the "loss" attributed to those low loss orange Elnas?
The V-loss figure of that Nichicon UPX I just received is considerably less than the orange Elna.