Kenwood Stereo Repair Attempt - Replace Capacitors
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- Опубликовано: 18 окт 2024
- My old and trusty Kenwood KVR-A70R (55wpc) stopped working about 6 months ago and I thought I had figured out what was wrong. There were several of the large capacitors that had a slight bulge on top and some serious discoloration around the bottom on the board. I figured most likely these had gone bad and I hoped replacing them would fix the receiver...
Capacitors
What is a capacitor? It's a small component in electronics that can store potential electrical energy. Like a battery. Most have two metal surfaces separated by a non-metallic, non-conductive material. This separation causes the capacitor, when electrified, to build up a charge that can be saved for later.
What does a capacitor do? In stereos they are usually used in a couple of different ways:
1. To make the electricity coming out of a power supply smooth. The power supply changes Alternating Current (from the wall socket) into Direct Current (like a batter) for electronics to use. When it makes this change the Direct Current electricity can be jagged, uneven and bouncy. The Capacitor takes that bouncy electricity and makes it straight.
2. In the amplifier part of the stereo (this takes a very quiet sound and makes it much much louder), you need bigger Voltage to make bigger sound. These Capacitors like the one in my video take a voltage and save it up like a battery, then the speakers can take the voltage when they need it. It is very clean voltage to make clean sound, not wavy or bouncy voltage directly from the power supply.
They have many more uses, and they are all very complicated even for me to understand.
Also, yes I know you can use a braided copper desoldering wick to remove solder from components to make it easier to remove them from a circuit board. I just didn't have any.
So, if anyone has any other ideas or suggestions about what might be wrong with it, I'd be happy to hear.
In a power amplifier, there are numbers of audio source(input) to choose and yours is in CD source(displayed in your amplilfier screen). Which audio jacks did you connect? CD, tuner, turntable, cassette deck, aux...?
Never solder by putting solder on the iron tip and then adding that molten solder to the pad. If you do it that way you're going to end up with piss poor connections and cold solder joints. Apply the hot iron to the pad you're soldering, let it heat up, then add the solder to the heated pad, when the pad is covered and the lead of the component is submerged in solder, stop applying solder and leave the tip of the iron on the newly soldered pad for a couple of seconds and then remove the iron from the area. When you're finished your soldered connection should look like a volcano with the component lead coming up the middle of it and not like lump curdled milk or a bubbled blob. I understand that you may not solder much, I get it - I was there too once. But heed constructive criticism and practice. Cheers! :)
Thanks! I'm not sure why I did that there :D that's not how I would usually solder stuff. You're right, what you said is best
Hi the Omron speaker protection relay is not changing over hence no Audio, check the voltage on the common terminals of the relay switching contacts to see if either has high DC. If there is high DC on either, then the protection circuit is operating correctly and there is a fault with the respective channel. If no high DC is present then there's an issue with the protection circuit.
The reason your solder joints look bad is because you didn't remove the old solder and re-solder with new. You're re-using old solder that has no flux in it and that doesn't bond very well with the pad and leads. Use new solder with flux core and your joints will look more professional.
Parts changing with no diagnoses seldom works. Also that's some wishful soldering, keep practicing you,LL get there. Hope it works out.
That lamp had perfect timing. It might have made me and Gideon jump. :) Next video needs a short description of what a capacitor does.... please.
Thanks Luk! Yea, the lamp made me jump too! I thought my stereo was blowing up. I think my mind raced to the location of the nearest fire extinguisher.
I''ll update the description of the video with a basic explanation of a capacitor. And I'll try to remember in future videos to include that kind of info. I know I appreciate videos that keep it simple and explain those kinds of things, especially about technical things that I don't always know what they are or what they do.
You could have problems with smaller capacitors, as well. Check the fuse on that one board I can see. Check the output transistors, as well as other transistors. Also, fusible resistors have been know to drift, causing failures in some systems. You'll need a schematic & part list to find which resistors are fusible. Also, what are the components on the top side of the board, where the back side is slightly darker?
Thanks for the feedback Mike, when I have a chance to get this project back out I'll check on those things you were asking about. At the moment I've got my hands full with the Datsun in the background of the video :-)
did you have it on the right source? i heard you say you were hooking up your aux cord but it looked like the display on the unit said "cd"
Thanks, on this old unit the aux is the CD input.
hi ..i have kenwood vr507 no pwr on no standby...main fuse ok...i test the large transformer and i get 0vdc...any help would be appreciated
Clean de board!
What value caps in power supply would be used on 100 what per chanel and what would be the transformer secondary ac be
You know, I really honestly have no clue about those details. I was looking around a bit and found that the KVR-A90R actually goes up to a rated 80wpc. So that's a pretty big jump from the 70.
Hello Mathew. Did you ever get your receiver working and if so what was the issue? Thank you
Hey Cole, thanks for asking, I actually haven't had a chance to work on her anymore. She's been sitting on a shelf, so it's not working yet :(
Easy repair. Chk output trans and spkr relay voltage.
I have a question.
Is it possible to add base on my amplifier with a higher capacitor of more than 25v 4700uf?????
you cant go higher on capacitance you can only go up on the cap voltage
@@snipermanboss how can I do that???
Please what may happend with the sound,if the capactor is guilty ? Thanks Andy
Good Question! I have not figured that out. I have a one and a half year old and too many other projects (rust on that Datsun is one of them) so I have not had a chance to revisit this issue on this receiver to figure out what else might be wrong. I will post an update if I do though!
A hum mostly, especially if it’s there when all volume is down.
When the electrolytics have to be changed, the transformer emits an annoying humming, the capacitors can't handle the spikes, they overload the humming transformer. That hum is not heard in the speakers.
Awesome vids
Lol.
So...if there is a burnt up residue surrounding the bottom of the cap, and if the cap is slightly deformed....is that a safe assumption that the Cal is done for??
Hey Corey, I'm no professional just an amateur here. But that is a good sign the capacitor has been compromised. In general you want to look for the top of the cap BULGING, not just a slight deformation, but any deformation can be a sign of troule. Also I think the cap can go bad, even without any visual sign. Anything burnt up is also a good sign that there is a problem, but if possible, you want to identify and trace it as best possible to identify the correct part that may have malfunctioned.
The raspy sound of kenwood ka-36 ampli is what it used to be
Yes. When power is pushed and a second or two you should hear a click. If not, there is a problem in the protect circuit, relay, test. Get all that old brown glue off. It is corrosive and conductive.
Sorry to bother you, I'm poor and have a decent amp it has a remote control for power and the switch...when I click the switch I comes on then a second later it switches off...any ideas...you're my last hope Im in a 3rd world province🤣
Hey Matthew .
I do basic audio repairs for fun and to help out buddies.
Anyway I got a unit that belonged to a guy who had died and his brother now owns it.
Its a kenwood ked-891 and it won't power on.
Fuses are good.
I'm thinking its a capacitor 35/2200
Clearly it has leaked some and the glue is almost like rust now.
Should I replace all the capacitors on the power board or just that 1.
By the way...i don't hear any relays clicking either..
Hey Corey! I hope I can be of some help, but I'm just a hobbyist like you. I would start with just replacing anything that looks suspicious, I wouldn't touch any components that don't look like they have a problem. The only exception would be if you have capacitors that comes in pairs and you see one that needs to be replaced, then I'd replace both of them at the same time. Hope that helps! Let me know how it goes!
Why not use a solder sucker or de-soldering braid? Should clean the board with solvent and check the tracks for damage! Looks like loads of dry joints! Very bad soldering technique.
You can download the KENWOOD KVR-A70R Receiver Amplifier service manual from off the net.
The copper tracks and jumper wires are clearly corroded due to leakage of the dielectric. You need to check continuity and test the components. The speaker output will be driven through the large power transistors (with heat sinks) at 100W unless that amplifier has some protection it will fry the output transistors. I notice that you when you switched it on you did not load on the output - that's bad news.
You should use an oscillascope to trace the signal path and see where the signal disappears
I suggest that you stick to your day job.
The transistor ( or other component) beside the caps, with the small heat sink, looks fried by the looks of the back of the board. Anybody know what it is?
It'd be cool if the model # was in description.
Good point! I added it
How many watts per chanel is this unit
Looks like it's (under)rated at 55wpc. Really I always thought it put out a healty 100-200wpc based on how well it would push big floorstanding speakers like my JBL S312 speakers.
Is the standby LED incorrectly indicated?
I have a Kenwood 1090VR which just stopped outputting audio for any input Tuner/phono/cd etc. Did you ever figure it out?
No I'm sorry :( I never was able to fix it
Capacitors expansive is better for audio if i replace my, i be got better sound?
Bro, why are you using the Race's logo
ruclips.net/user/WeAreTheRaceabout
Kapasitörleri değiştirdikten sonra lehimleme işleminiz biraz daha özenli olabilirdi lehim telini kapasitörlerin ayaklarına tutarak lehimleseniz dahada güzel olabilirdi yinede güzel bir çalışma emeğinize sağlık👍
"After changing the capacitors, your soldering process could have been a little more careful if you soldered by holding the solder wire to the feet of the capacitors, it would be even better, but still a nice work, thank you 👍" THANKS!!!
The original ones had 3 legs up put in ones with 2 legs consult with a autherized service center
I’ve got a noisy pioneer avr. Problem is, hifi insider etc says it’s their most powerful one... im nervous about fucking it up. Every tech I call sounds too bothered to help me, so wish me luck lol. Thanks for the great video, I hope mine aren’t glued in and I’m buying solder wick!
Good luck man! Yes maybe the comments on my video have helped give you more tips on what to do and what not to do :)
What model is your avr?
Matthew Brazle it’s a VSX-D1S, and I’ve unearthed the caps and order replacements. It’s gonna take forever though! The ones in question that I figured were the issue from listening were in fact the only that were off spec, and they were bulged. Gonna get those switched, now onto the nikko power amp that’s stuck in protection mode.
Matthew Brazle I replaced them, and the noise is still there! I’m gonna shotgun the rest of the electrolytics some time down the road.
@@graxjpg hmmm, that's definitely tricky. Hope you get it figured out. Is the noise steady or does it change with different inputs or settings?
Matthew Brazle the noise is there even if the volume is all the way down on every input and output. It has several amps inside, and each have that noise. That leaves me to believe that it’s their common power supply that is supplying the noise.
Why not use a solder wick or solder pump
I didn't have those and didn't know what they were. I do now
In my dvd home theater system Phillips htd3510/98, rear left channel sound is very low compared to the other channels and I tried to increase the db -6/ 0 /+6 but too low volume Gain From O to +6 no difference its like low frequency . Now I've set SL to maximum +6 gain and the other channels set to _"O"+ .why? Any solution 🙏
Sounds like there is a problem with a component, not the settings. Might be a problem with the speaker or the wire or the Phillips home theater receiver. Change the wire first, then change the speaker, then test the receiver as best you can
Remember though, the rear channels usually don't have much sound coming out, it might only be a special effect that happens on occasion, not constant noise or sound.
Thank You!🙏
Use desolder tools u make it to hot and make chance to distroi the print or components
Thank you for the tip, I need to get those tools
Check out the adapter inputs in the back..
One connection is missing (White).
How did you get on with this amp?
Thanks for checking in on it. Sadly I never got back into it to try more trouble shooting or repairs.
Lol just get a solder vacuum pump, wiggling and heating constantly is gonna damage the board or heat other components unnecessarily
Amplifier model
Output transistor and also chk spkr relay voltage
Thanks! I'll check those like you and AAS recommended.
There is an L in soldering, you pronounce the L.
Cool beans bro, did you even Google that before you commented??
@@Brazzzzzle The word solder originates in Middle English. The Latin origin is the word solidaire, meaning to “to make solid,” which is where the -l- in solder comes from. Solidaire (v.) - to join, be united, standing together, or interdependent.