How to find what the specs are on a Ceramic Disc Capacitor?

[CodyRepairShop]

Hi so I have this board from a AV receiver Sansui 5050 and it has all kinds of these Ceramic Disc Capacitors like type of stuff and I have lot's of trouble trying to find the specs of these and can't find a online place to buy them at this is not just 1 kind I have all of the numbers of what they have on them just a model number I think you can see the picture I have on here for it check it out and tell me what kind is this the orange things that say .047uf KCK I wasn't sure if those are Ceramic Disc Capacitors or not?

[Jay_Diddy_B]

Hi,

KCK is the manufacturer and 0.047uF is the value. These are probably Y5U or Y5V, this is type of dielectric. It is not particularly good. These were used for coupling and decoupling where the value and the temperature coefficient is not important.

If I had to replace them I would use any 0.047 epoxy dipped ceramic capacitor. Vishay K473K10X7RF5UH5, available from Digikey would be way better than the original parts.

Why do you think you need to change them?

Regards,

Jay_Diddy_B

[CodyRepairShop]

Hi,

KCK is the manufacturer and 0.047uF is the value. These are probably Y5U or Y5V, this is type of dielectric. It is not particularly good. These were used for coupling and decoupling where the value and the temperature coefficient is not important.

If I had to replace them I would use any 0.047 epoxy dipped ceramic capacitor. Vishay K473K10X7RF5UH5, available from Digikey would be way better than the original parts.

Why do you think you need to change them?

Regards,

Jay_Diddy_B

Why do I think I need to change them because i'm getting ready soon to get this Sansui restored to be working again. And yes I know what i'm doing this is my first time I will have all the test stuff and everything later this year.

[Monkeh]

Why do I think I need to change them because i'm getting ready soon to get this Sansui restored to be working again.

Why do you think those caps will need changing?

[CodyRepairShop]

Why do I think I need to change them because i'm getting ready soon to get this Sansui restored to be working again.

Why do you think those caps will need changing?

Well you never seen the whole thing but this is a sansui 5050 and it's from 1976 mine was one of the first models made this receiver is pushing over 40 years it has problems too static in both channels but one channel is worse than the other not loud static but you can hear it and it will trip out before half the volume is there it needs to be fully restored it's very old capacitors only last 10 years and then after that the rating they were once at is out of wack and its not at that same rating.

[Monkeh]

Why do I think I need to change them because i'm getting ready soon to get this Sansui restored to be working again.

Why do you think those caps will need changing?

Well you never seen the whole thing but this is a sansui 5050 and it's from 1976 mine was one of the first models made this receiver is pushing over 40 years it has problems too static in both channels but one channel is worse than the other not loud static but you can hear it and it will trip out before half the volume is there it needs to be fully restored it's very old capacitors only last 10 years and then after that the rating they were once at is out of wack and its not at that same rating.

Who told you capacitors only last 10 years?

Not only is their lifetime infinitely more complex than such a simple rule, but ceramic capacitors are fairly stable and extremely resilient. I doubt sincerely that any of those capacitors are contributing to any problems in the device.

[CodyRepairShop]

Why do I think I need to change them because i'm getting ready soon to get this Sansui restored to be working again.

Why do you think those caps will need changing?

Well you never seen the whole thing but this is a sansui 5050 and it's from 1976 mine was one of the first models made this receiver is pushing over 40 years it has problems too static in both channels but one channel is worse than the other not loud static but you can hear it and it will trip out before half the volume is there it needs to be fully restored it's very old capacitors only last 10 years and then after that the rating they were once at is out of wack and its not at that same rating.

Who told you capacitors only last 10 years?

Not only is their lifetime infinitely more complex than such a simple rule, but ceramic capacitors are fairly stable and extremely resilient. I doubt sincerely that any of those capacitors are contributing to any problems in the device.

Now I don't want to get into a fight or anything but I have many people I know but it's hard to explain over the phone or text that they said that capacitors only have a 10 year lifespan and I know but go look it up on youtube theres near almost 20,000 results on restoring and repairing av receiver units and they always replace the caps and other parts ok then if your so smart then what is my problem with my unit it shuts down before reaching half way on the volume and it should not do that I could use different kinds on dummy loads or speakers and it does it every time it's at 8 ohms that's what it's rated for into 8 ohms.

[Monkeh]

Now I don't want to get into a fight or anything

You say that..

they always replace the caps and other parts ok

If they go around blindly replacing parts, that's their problem. Wet capacitors is one thing, ceramics is another. It's like replacing a tile because it has dust on it.

then if your so smart then what is my problem with my unit it shuts down before reaching half way on the volume and it should not do that I could use different kinds on dummy loads or speakers and it does it every time it's at 8 ohms that's what it's rated for into 8 ohms.

And here's the other side of 'you don't want a fight'..

Yes, I'm so smart I'll just pull the answer out my arse having not looked at the unit or its schematic. Having not looked at it, at all, I don't even know where to begin. But I know where not to: With ceramic disc capacitors!

Deal with the likely problems first, perhaps actually troubleshoot, before you risk further damage by shotgun replacement tactics.

Oh, and if capacitors only have a 10 year lifespan, I dare you to explain the decades old devices which still work without any capacitors, ceramic, tantalum, or aluminium, being replaced.

I have ceramic caps which predate your unit - and they're under stress of kilovolts, not single digits or tens of volts. They're still good, and they likely still will be in another 45 years.

[CodyRepairShop]

Ok to make you happy I won't replace them and see how that goes. but how would I know if a Voltage Reference Diode is bad since the static I hear people do say those that are giving you static fuzzy sounds through the speakers only some would need replacing?

[gnif]

Ok to make you happy I won't replace them and see how that goes. but how would I know if a Voltage Reference Diode is bad since the static I hear people do say those that are giving you static fuzzy sounds through the speakers only some would need replacing?

I completely agree with Monkeh, I don't think I have ever seen a ceramic capacitor fail unless it was abused by a high voltage surge which blew it apart, or mechanically crushed. Those in the photo look physically fine, I doubt there is any need to go near them.

It makes me laugh at how stupid some people can be when they ask for help, and when the help provided conflicts with that they think they know, they attack the person that tried to be helpful.

Rule of thumb, don't blindly assume or replace things, check voltages first. If you suspect a component, pull it and test it, don't just replace it.

A quick google turned up both the service manual and schematic:

Service Manual
Schematic - Better schematic is in the service manual.

then if your so smart then what is my problem with my unit

If you're so smart then why are you looking at the area of the circuit that is clearly the AM/FM tuner for what seems to be a power amplifier fault.

There is also voltages marked on the schematic to test for, verify all these are correct, I would start by checking the power amplifier transistors and surrounding components located in the area designated F-2648. The service manual shows how to check and adjust the bias currents, etc. It sounds like the speaker protection circuit is kicking in due to a failed transistor or bad bias. According to the service manual the protection circuit will also kick in if there is DC offset of > 2.5V on the output.

[tautech]

I too am of the view that disc ceramics are probably the last thing to expect when fault finding, however any component can fail. What you do find is voltage headroom is minimised for all types of componentry mostly by manufacturers looking to cut costs in the BOM. This happens when "bean counters" take over manufacturing from the design engineers.

But one must look first at the componentry types that are most prone to failure.
#1 on any list is electrolytics, more so those used on power rails and while a shotgun approach will normally bring success there is little learned by doing so.
Appropriate equipment and the knowledge of its use along with a good dash of experience will find faulty and "not quite right" componentry.
Just where any component is used matters too, it maybe coupling or bypass, you shouldn't be using low ESR caps for coupling.
One must balance the cost of any test equipment against a good stock jellybean parts that get used as time goes by, nevermind those generic parts are unlikely to match those specified in the original design. There is always careful tradeoff to be made in replacements, more so if substitution need be made.

So to dive into an amp like the OP, old school signal tracing methods are the most appropriate in order to find the stage/s where any problem lies. Break a job into blocks, it's not that hard. 

/ramblings.

[T3sl4co1l]

Ceramic capacitors basically don't fail.

Type 2 dielectrics (which would be what they used here) do age over time, and you might measure them an average of 20-50% below rated value.  They would only be used for bypass capacitors, where the value is large enough not to matter, so this shouldn't be an issue.

The smallest (and most precise) capacitors, are usually type 1 (C0G/NP0), indicated with a black dot on top.  They do not age.

At worst, the capacitors can be annealed (hold soldering heat on the leads, 10 seconds per lead, one at a time), which will restore some capacitance.  I doubt it's worth it, unless you can identify some parts which are specifically out of tolerance.

Oh, tolerance: it was usually +/-10%, +/-20%, or +20/-80%, depending on type.  (Usually, the worst tolerance is indicated with the letter 'Z'.)

On the other hand, electrolytic capacitors are well known to age and degrade at a steady rate.  10 years is a typical time span for failures to show.  These are plastic-wrapped metal cylinders, not ceramic disks.

Tim

[CodyRepairShop]

Well ok I must have been confused on what I was thinking  But what about one of these voltage reference diodes how would I know if what one is bad because my both channels do some static fuzzy sounds when the unit is in use just being on it would be static fuzzy sounds not loud but just loud enough for me to here it about 1 foot away in a quiet room and the volume can be all the way down and still hear it is this a noisy diode?

[gnif]

1) Those are NOT diodes, they are transistors - 2SC1364 (NPN) & 2SA773 (PNP)
2) Again, don't just replace parts, MEASURE THEM.
3) Check the voltages! Check the voltages! Check the voltages!
4) Check the power amplifier output transistors, etc..
5) Read the service manual.

There is also voltages marked on the schematic to test for, verify all these are correct, I would start by checking the power amplifier transistors and surrounding components located in the area designated F-2648. The service manual shows how to check and adjust the bias currents, etc. It sounds like the speaker protection circuit is kicking in due to a failed transistor or bad bias. According to the service manual the protection circuit will also kick in if there is DC offset of > 2.5V on the output.

Edit: I can see this amplifier ending up dying a sad death... I hate to see vintage equipment hacked on.

You literally could not have asked for more detailed information with that service manual, it is a repairman's dream to come across such detailed information when repairing equipment these days.