Vintage Amp Restoration- Kenwood KA-8100

Fixing up an old Kenwood amplifier.

[@craigm.9070]

A top shelf technician showing his craft. I revisit this Kenwood restoration periodically to refresh on how things are SUPPOSED to be done. I hope to see you active again!

[@apolinarmartinez5723]

I miss your videos, I hope at some point you will return, one of the best channels of learning, repair and restoration.

[@taijkon]

Thanks. Today I am going to by one KA 8100. Had one 30+ years ago but it was stolen so this is some nice info.

[@arfer]

I wish this guy was in my part of the world to fix my electronics.....The thoroughness is very impressive.

[@sbx500a]

wow, this is the finest amplifier repair video i've ever seen on youtube. very precise and detailed.

[@lajson]

Maxxarcade, thank you that you showing and explaining how to calculate the amp load with an oscilloscope and multimeter in a simple way, you'r my real mentor when it comes to repair amps and I learned so much just watching your vids! Thank you sir and I hope you'r going to continue upping YT vids like this in the future too! Best regards from Sweden !

[@skyblinked]

I am always amazed in these videos that you actually manage putting everything back in, but it must come with experience

[@DR.ELEKTRIK]

Yea thats a bueatiful amplifier. The quality of the engineering really stands out. State of the art and top of the line back in those days.

[@Maxxarcade]

That's one of the cool things about older amps like this with adjustable bias. You can usually install newer transistors and compensate to a degree. And I agree, the controls are pretty well made on these.

[@cristobalsilva6288]

nice job! i've bought an old kenwood ka-3004 and it has some issues. you really gave me an idea of what it needs to be do.

[@leoj.nesuahecner1242]

By the way that was probably the best video on refurbishing and repair I've watched. Explanations were easy to understand. Easy to follow. I have taken all my amps apart to clean and depoxit. Some like yours on the 8100 I did not know how to enter so they are still scratchy. I'm not schooled in electronics so I'm trying to teach myself. I can read a schematic but that's about all. So I did understand your video and it was very in depth. Thanks.

[@krist0sh]

Nice repair! Love the sound your camera reproduces in my speakers, also that amplifier sure does sound very good.

[@johnallenrichter]

Another great video... Thanks for sharing. You have taught me a great deal about 70's equipment....

[@dirtydon8661]

Excellent video. Just what I was looking for to inspire me to replace caps on my fathers 1984 rotel system. It's currently working but I know it needs attention. Thanks again

[@MikeStolarchuk]

You do a great job thanks so much for making these videos!

[@sargetech]

May I say something with total respect and admiration!!!! SIR, YOU ARE THE REAL DEAL!!!!!!!! My mentor who taught me, used the same troubleshooting techniques! SUPERB! :) PS - My mind was also blown when I saw WINAMP!! such memories! Sorry but I don't use windows anymore. Total linux man these days....

[@whiskeyify]

beautiful amp, not too easy to service, but well made. my old pioneer looked a lot like this one, I really like the controls they seem like high quality. I'm sure your customer was happy with it.

[@nckeller]

Very thorough, another well done. I always learn something.

[@lordkillspree]

Nicely done. I learned a lot from the video. Also, kudos for having a good enough microphone that we could tell the quality of the amp instead of just hearing distortion. Oh, and fuck yeah, WinAmp!

[@biffnaked5363]

The overall quality of lower midrange stuff like this was just better than today.

[@dontcare563]

I had a KA-6100 that I bough new many years ago and it was a great amp!

[@Maxxarcade]

It sounds great, I'm just used to much larger amps nowadays. The camera also makes it sound a bit boomier than what it does in person.

[@Synthematix]

kenwood were TRIO here in the uk, very good quality amps these i love em. look a bit like the TEAC amps

[@danielchernev9319]

we in bulgaria just use those amps found beside swiss trashboxes .this guy is a god of .technician i admire the wish to want to hear sound with better quality.thanks bout the video

[@mspysu79]

Nice work, thats a really nice amp.

[@johnwelcker2831]

I picked a old fischer receiver from around 1970 and it was rated at about 20 watts per channel,but what head room and the bass blew my new at the time ka7100 out of the water for deep powerful bass.

[@PigsCanFly99]

kwik tip .. with access to the backplane ... solder-suck the solder from just one leg of suspect capacitors. Bend the cap lead so it's not touching the board. The cap is now effectively out-of-circuit and can be readily and reliably tested with an ESR meter.

[@electronicshelpcare]

Really nice work, Really beautiful

[@dxhighendamplifiers]

Very good.....my favorites...you are favorite

[@RonRivet]

That`s a pretty sweet amp! They don`t make them like they use to. That`s for sure.

[@sellsubz]

The filter are almost never bad. I would keep them in place. If they are no good the aligning process will normally reveal it. Otherwise this guy is very good.

[@frankscarano4708]

Great Video.... very thorough.. seldom find these caps go bad even after 30 years.. though its a good idea to do what you did anyways.. interesting to note that in all the years I have repaired these units I have never had the main filters ever go bad but I am sure they could potentially affect performance down the road 10-20 years from now so why not do it now. I have put several of these old caps on my sencore meter that does ESR and they all test perfectly.. they were built to last and they do!

[@Maxxarcade]

I agree, the caps in these were really good quality. I just didn't want to chance any of them shorting out from age.

[@agfamatic91]

thats a nice amplifier. kenwood seen to have made some very nice amplifiers back in the day i have never owned a kenwood amp though.

[@accordinglyryan]

Man I love your videos...

[@kd1s]

Nice restore. I've helped out coworkers with HDTV sets - those eat caps for lunch.

[@edjackson4389]

Thanks for your VERY helpful video! Made my day to find this. People like you make youtube great for us info hungry people. Thanks again!

[@TwinMillMC]

Man, I wish you would do other repairs besides your friends equipment. My vintage 1980's Harman Kardon stuff could use some going through. Someone like you would be one of a few people here on KZbin I would trust with it. My 1986 HK Tuner is sounding slightly distorted lately.

[@naterade21]

WOW thats a really nice amp id love to have one of them in my room

[@tedzomplin4810]

Excellent work !

[@slimjim119]

nice clean sounding amp nice job

[@SinnerSince1962]

It's interesting to explore different manufacturer's means and methods of design, layout of components, and serviceability. Through my years of working on them, I've found That McIntosh and Pioneer were the best. The worst was Marantz and Yamaha. Now that doesn't amount to any correlation in sound quality, but when I think about working one one of those, I shutter. Sansui was pretty hard also.

[@Tron1731]

keep those big ass caps could get you out of a pinch nice restore i bet the guy is so happy !

[@LarryDoolittle]

Thank you. I had the KA-9100 and loved it but it could have used your magic touch after years of use.

[@jesusgarcia2203]

HI Very intersting and nice restauration let me say this video inspired my for make same work in one pioneer amplifier model sa9500II find in junk in very good conditions and only need recap ,a deep clean and change the termic past of the transistor´s b618a and d588a just this and work at 100% very clear treble and kick bass thanks Maxx

[@theedrstrangelove]

There is some weird satisfying sound and feel of those older style toggle switches. My old Marantz tuner/amp has them as well. The combination of incandescent lights and brushed steel, not to mention the sound quality..............make this era of hifi so choice!

[@Maxxarcade]

I agree, I wish I could find a good source for audio signal grade caps that didn't cost a fortune. I only replace them all because I've had several cases where things would come back with the remaining caps being bad a couple years later. True on the resistors as well. The worst offenders were the carbon composition ones in the older equipment. Not only do they drift, but they can get very noisy at times.

[@e-hifipl]

Great works dude

[@revolvingtoto007]

cool vintage amp bro

[@NeCarbon]

Great Restauration Job, very well documented how and why are you doing it so My A/V Kenwood Receiver from the late 90s also has ELNA Caps on the mainboard and the filter caps so im pretty happy to know that their surely good

[@chairuser4]

great work

[@Maxxarcade]

I use an old Canon Powershot SX1 IS. One of the reasons I haven't upgraded it is because I like the sound. I did adjust the bias a bit, but it was pretty darn close to spec.

[@DGTelevsionNetwork]

woah, that thing is sweet!

[@d4v3tm]

really nice video!

[@Maxxarcade]

Integrated means having a preamp, tone controls, etc. as opposed to just a power amp.

[@timcoker4685]

I bought one just like this for $20 at the flea market about three years ago. Played perfect, but it was no match for my mighty Sansui. I sold it last year for $250.

[@johnwelcker2831]

wow I wish I had your talent for electronics sweet

[@Nix_sound]

Superb work, nice coverage in the video. Do you think in another restoration you could show some detailed shots of removing the caps and installing new ones please?

[@albertonaveiro3499]

Fantástica pieza¡¡

[@Maxxarcade]

I ran out of time to check. Might try it next weekend when I have my ESR meter back.

[@whiskeyify]

Great job, i used to work in a repair shop. You must have charged the customer a pretty penny for that job, it looks like you put in a lot of hours on this project.

[@daytimerocker]

Very nice.

[@iwpnj1]

YOU DO GOOD WORK. SHOULD SEND YOU SOME OF MY GEAR.

[@FedUpLurker]

Nice aesthetics, very sexy actually. And in pristine condition and filmed nicely.

[@KENWOOD9109]

love that kenwood (h)

[@johnbateman4255]

Thanks.

[@RonnieTheFish]

In the start of the video you said it lacked low end .. so did you notice a change after all the new parts ?? Great Video again Bro

[@gordysmith7390]

There is a model that was above that one.The KA-9150. I owned that unit for about 30 years. I originally repaired it as the original owner started a speaker voice coil on fire with it. This destroyed the integrated output IC. Rated at 100 watts/channel RMS into 8 ohms. It had a ton of dynamic head room. The one I owned had dual power (watt) meters in the upper right hand corner. Sorry I trashed it in a way but it was dated and had several problems that because of the time involved, I decided it was no longer worth the labor to tear this "tank" apart.

[@josephgonzales1403]

I have the same receiver. every now and then the volume cuts out. Is it cause there's dust in the receiver?

[@SaderStel]

I used the same Panasonic capacitors to recap my Telefunken amp with a little mix of Rubycon, feeling quite happy with the result I got, will upload second part of my video where I do it. Also you have that tool for wires, does it also used to put/twist them back, my amp has most of the connections that way, would be nice to get such a tool just in case. And as always, great video.

[@1112223333111]

nice amp

[@karizmatic5]

You're so good! Would you have any advice on how to start in the stereo refurb profession?

[@silvaniodinizleandro8500]

Só aparelhagem boa

[@gregporter1527]

Very interesting and informative videos of restoring excellent audio equipment from the days when people actually cared about sound quality. Also, can you tell me the name of the song and artist in the 15:00-16:08 segment of your video when you were testing the amp? It's the instrumental piece with the drums and keyboards. Thanks, Greg

[@xtraflo]

I'm currently looking at the KENWOOD KA-8100 and AMPLIFIER & KT-8300 on Ebay for $300 for the set. Only $40 for shipping> Damn tempting . . .

[@Synthematix]

those speakers sound great for car speakers, whats their frequency response and wattage?

[@mrGoesto11]

You keep the caps only based on esr readings? Isn't bringing them up to full voltage rating the best way to see whether it has the ability to charge and discharge like the old Sprague cap testers would do? Would have been nice if you had mentioned how you polished the rca jacks.

[@aaa000777]

You forgot to clean the dried glue that held the old capacitors to the main amp board. You can see the dark brown residue in the center of the board in the outline of the capacitor that was removed. The glue becomes conductive and will corrode the parts it comes in contact with including the component leads themselves. This was a very big problem for all of the japanese manufacturers during this time period. If you don't remove it you run the risk of causing damage to the amp down the road.

[@stevenking2980]

yeah he's done vids on that. Look at the velodyne subwoofer repair maxx did. He talks all about that. :)

[@hycarl.1623]

May i know where do you order for capacitors specifically the panasonic brand or other good brands?

[@TheSoxmania]

you should see about a pair of mission 781 speakers, they crank a chunk of bass, last time i tested mine and they can rattle a whole house

[@Enigma758]

Are those some sort of rivets you inserted in the switch casings after melting the holes?

[@Zockopa]

Well,this is one fine amp. But not entirely "DC" like stated on the frontplate. There are coupling caps at the phono eq out and in the tone controls. Personaly i had not changed the main supply caps on a hunch,especially not on this particular amp which showed no signs of heavy use. For output stages not only the absolut value is important but also the contactsurface. So if renewed i had chosen 100V types to come close to the originals. But usualy if the amp was not used permanent on its limits the big cans are the last to go EOL. Similar for all other lytics i wouldve chosen higher voltage types. The few coupling caps i had changed with foil-types. Like WIMA MKS for example or Panansonic PPs. However,if every penny counts the green nichicon bipolars are also ok. Another little trick is to change the ceramics in the feedback loops of the power amps with silver mica`s. They are simply the best part for that particular spot. Some ceramic-c`s in compensation-limbs like miller compensation etc. i had changed with small foil-types like Panansonic EC-Q or the yellow Nichicon XY 100V types. And the resisitors surrounding the input differentials of the poweramp frontends i wouldve changed with 1% metalfilm resisors.... Well,you see changing simply all lytics with the watering can princinple is not the cheapest way to success and sometimes it even sounds kinda worse afterwards.

[@johnwelcker2831]

I had a KA- 7100 and when I bought it a had a pioneer receiver with about 35 watts per channel I think it was around 1977. I was to excited to get it home with it's 60 watts per channel, money I saved for a good while to get it, I was seventeen. I was so disappointed in it, no low end (bass) very flat response. I thought it was maybe my old bic venturi speakers, but they sounded better from my pioneer. Even when I got my Klipsch hereseys, the kenwood sucked, with I could have got my money back.

[@stevenking2980]

That's what kenwood heads don't understand about the other stuff like sansui and marantz and pioneer.

[@stevenking2980]

Yeah I had the same problems. Now I've got sansui and marantz and much much better sound. Kenwood seems to lack in the low end. I sold my kenwood stuff too.

[@SuperBoobaloo]

Which DeoxIT product do you use for this kind of work? Fantastic videos. Please keep up the good work.

[@robpaints100]

I have that same amp with very weak left channel output. Do you have a video how to trouble shoot what is wrong or do you know what causes that problem? Thank you.

[@m1engineer]

Great Job, could we talk about getting an amplifier of mine fixed?

[@Maxxarcade]

The caps were too big for my tester. But if you aren't getting any hum, they are probably fine for now.

[@johnbateman4255]

Do you come across Hitachi HA amplifiers ? I have 2 HA 7700 which I will be joining together as a pre amp and amp.

[@CovertCulvert]

I have a Kenwood KA-7100 that I want to recap. It has the original Elna caps in it. The caps are four different colors: Black (large filter caps) grey, light (or dull) orange and bright orange. I have the service manual with the listed values. I was intending to replace the caps with Nichicon. How do I match the original caps to the correct series of new caps? I assume the colors of the original are indicative of the Elna series used, but I can't find a cross-reference. Can you give me some advice? Thanks!

[@DavidBerquist334]

is ka7100 dual powerd it has 1 transformer but each chanel uses seperate windings of the transformer thanks

[@DavidBerquist334]

i have ka7100 it dosent have a line fuse in ac primay that i could see do you have a manual is fhere one

[@leoj.nesuahecner1242]

I have the entire line of KA models 3500, 5500, 6100, 7100, 8100, and 9100. My 6100 also lost the right channel but I think it's the input slelctor are, it had a bad noise when switched to aux I think and on one switching back and forth I lost the right ch.

[@smiegal00]

Had just begun to dissemble my KA-8100 when I found this video. Any chance you've got a list of the necessary caps, and maybe a good suggestion of a site to buy from?

[@bucsateflon]

The big caps can be replaced without any modification(holes) is just that they will end up offset from each other.

[@DAVIDGREGORYKERR]

Does it have a Class A Output stage if so re-caping might be the way to go but with Class A amps they are inclined to run very hot if people wanted cool running amps then you would see Class D amps in the shops.

[@williamdorrit3849]

Maxx, First my daughter loves your avatar. Thanks for putting out this type of tutorial, there is a mountain of excellent audio gear from the 70s and 80s that I fear is headed for the scrap heap because the cost of having a shop repair the equipment is more than the re-sale value. I noticed that you have a methodology you walk through when you bring the units in, it may seem repetitive, but could you walk us through each time from unpacking to test. At age 30+ agree it's time to replace all of the electrolytic caps, and if a certain component fails, all of the same model component failed. I know that on the audio path, people hate to replace working transistors for fear of changing the sound quality, so maybe this is the exception and just replace the bad ones. I am gearing up to recap a number of my units, and appreciate you sharing your knowledge. I have yet to buy my first video camera, so with no experience I wonder if yours has a macro function that would allow you to take closer shots of say failed solder joint. Again thanks for sharing.

[@Maxxarcade]

I generally don't replace transistors unless they are known to be failure prone or noisy. With caps, I usually just replace them, with the exception being certain large main filter caps. Sometimes they are still good, and can be very expensive to replace, so I only change those as needed. Also, not all caps are the same. Some are rated for lower DC leakage, some are for audio signal coupling, and some are for power supply circuits. So you need to know what you are replacing before picking a new type.

[@williamdorrit3849]

Again, thanks for sharing your knowledge. I am just beginning to be able to read the schematics, with a way to go. Actually, I am drawing a schematic of my unit from how I think it should work and will compare it to the actual for reference when I think it's done, I have a way to go. Most of my gear is working and working well, but at age 30 it's time to replace the electrolytics. The first amp that I am looking at is a Yamaha mx-600 which is fairly spacious inside. Starting from zero, (actually I had 20 years experience in prod. mgmt. and mktg. for telecom equip. manufacturing companies, so am familiar with many things but did not go hands on at the board level) I am just beginning to wrap my mind around the concept of the power path and the audio path and regulation and amplification. For the large electrolytic filter caps, I decided to go slightly overrated with the high temp caps for a little extra margin. I have a friend who is a digital engineer who is, or will be, helping me with my first project (s), and probably a few afterwards, so hopefully I won't smoke the amp or burn the house down. From my experience, your methodology is sound and I appreciate you sharing it with us. Perhaps a discussion of the signal path and issues and power distribution may be in order for you next amplifier or pre-amp project. From my discussions with engineers and techs.....is that the characteristics and quality of any modern quality electrolytic is better than any from 30 years ago, and the issue is optimizing aka how much better do you want it?

[@machannel8746]

Hi. Did the low end punch that you said was missing got fixed with the recap ? Great job, getting access to the boards is sometimes the toughest part isn't it ... By the way, the filter caps are now not being secured in place by anything won't that stress the main board a bit when the amp gets moved around ?

[@khmabk]

Maxxarcade I have a question for you. Did the bass/punch improved after changing caps?

[@Maxxarcade]

Not a whole lot, since the original caps were still in pretty good shape. It sounded pretty good after I tweaked the tone controls better though.

[@phamhuy3698]

Your amplifier looks like brand new. How did you clean it ? I have a KA 8700 and I also want to clean and recap it. Please advise. Thanks

[@kkoller8952]

After you replaced the filter caps did you check the old ones to see if they needed to be replaced? I'm just curious because I have both a KA-6100 and KA-8100 that I plan to restore and if possible retain the original filter caps. Actually my KA-8100 lacks bass also but my KA-6100 sounds like brand new (but doesn't look pretty)...plenty of bass, very clear midrange, and great sound stage! Great video....very informative. will save for future reference when I get into my 8100.

[@alexjensen80]

Nice work, but was it really nessesary to replicerer 4x 10000 uf? and finalen, do you have done problems with the subsonic filter on/off? My ka-8100 Will only diktering on left channel