Kenwood KA9100 Integrateed Amplifier No Sound from 1 channel

[@grahamevans7642]

I have one of these amp’s and it also has an intermittent loss of the right channel. The problem on mine was down to dirty contacts of the filter buttons and/also the tone defeat switch. Basically, a good overhaul and clean up with switch cleaner cured the problem. Purchased in 1978, I’ve had my money’s worth but it is still going strong.

[@davidgriffin79]

46 years old and still going strong. I've got an old Denon PMA 250 mk1 which I think is circa 1988; an Ebay spares/repair it just needed a little love (dry solder joints) and is now singing happily in my bedroom system. Now, unfortunately, everything's built be landfill in a few short years.

[@Zimmy_1981]

@@davidgriffin79 strange how disposable new gear is but yet they complain abt pollution & not recycling.....

[@robharley9838]

Great to see you get this classic up and running Dave! I recently got a friends amp of the same type repaired and was impressed with its build quality myself. With all due respect, despite its integrated module outputs, it's one of the best amps I've ever seen on your bench. The client should have you re-cap it if they're serious, it's worth it. Thanks for all the great content over the years, your skill with complex mechanisms is nothing less than amazing! Really appreciate what you do! - jrh

[@Zimmy_1981]

the outside and inside conditions of that unit re superb

[@Biela2008]

This video is a very good example when it comes to fixing amplifiers. ALWAYS check the mechanical stuff first.

[@12voltvids]

Yup

[@waynewayne3709]

It's good to see more vidz from a very good experienced electronics engineer who shows each step on troubleshooting and repair.

[@crashbandicoot4everr]

I was ready to comment about blown meter light bulbs but I ate my words as soon as you switched the workshop lights off. LOL

[@12voltvids]

It's pretty bright in here.

[@marvinwatkins8179]

Good morning you are absolutely top notch I wish you were here in Houston Texas.

[@lox_501]

Another neat video Dave. Looking forward to your next.! 😊

[@QsTechService1]

Wow that's a really nice receiver Looks like it's built like the tank

[@locutiss100]

It is, I have one in good working condition, at 43 years old 😊

[@WayneRite758]

Not a receiver, but happens to be one of the best integrated amps of its era.

[@ashleycox432]

they might use ICs but still a very decent amp. nothing wrong with integrated power modules in principle.

[@tacofortgens3471]

I agree, and ita well build as well. 90 watts per channel in 8 ohms will drive any dificult speaker

[@12voltvids]

They work untill they don't and these days when they don't it's a death sentence because finding a real one is next to impossible.

[@pdx27]

​@@12voltvidsThere's a company called pyramid audio who produce drop-in replacements for these power modules. It's a small PCB with discrete components and supposedly works really well from what I've heard. For the larger units this might well be worth it.

[@tonec3663]

I don't know what power modules are in this amp but if you require the Sanyo output modules, there are replacement kits available for those.@@12voltvids

[@12voltvids]

@@tonec3663 the problem is nobody is willing to pay for that. They are not cheap and people throw them away first.

[@RolandV3922]

Thank you for another interesting video. In your experience, is using contact cleaner a long-term fix ?

[@12voltvids]

Usually it is unless the switch is totally trashed as in worn out.

[@liecharleandado3194]

sir gud am, i have def. kenwood integ. amp, it is safe to check dc biasing for my ka990d without connecting output transistor, thnk you so much for your reply...God bless

[@kjellnilsson1615]

Hi Dave ! Must say ,,You are a Wizzard whith all electronic stuff ! Noting can bite a long experience ! You are simply the Best 😊👍👍👍👍👍

[@jonroberts4422]

I've done the same hookup mistake on the "bench reach around" myself and then it's a face palm moment that makes me chuckle at myself. Of course there's a couple @##$$%^ in there for good measure about placement of speaker terminals vastly different on that unit to ANY other common machine placed in the bench prior. Makes you wonder if the engineers had a bit of humor in mind to place the terminals opposite of anything else. Great to know it essentially was dirty pots and switches remedied with the magic spray. One saved from the scrap heap for connoisseurs of vintage.

[@EastAngliaUK]

is this cheap fix for them unless wanting new caps very simple problem. good

[@RalphRacc00N]

IC amps are better for bias tracking, only problem is lack of parts. :( I've been thinking of putting LM3886 chips in a SX-780 that should have STK0050. Thats a sweet amp.

[@greenlanternseven]

Are upgrade s available for those ic chips ? Meaning a transistor upgrade board in place of those ic's ? I know Pioneer does for their lower end receivers

[@12voltvids]

No because the cost to produce would exceed what anyone in their right mind will pay to fix it. Despite what some may think 99.99% won't spend more than about 100 bucks to fix this old stuff. You will find the keyboard warriers that will talk big about how much they pay to fix stuff. I have yet to meet any. They want stuff fixed as cheap as possible and if it isn't a cheap repair they walk away. It's no different than it was 40 years ago. People did not want to spend much then either.

[@RalphRacc00N]

@@12voltvids Value of this equipment has shot up during covid. It may be a bubble like beanie babies, but nerveless while the amps are high valued you can charge a greater percentage of their worth for repair. Ask for more money Dave. I can't believe people aren't fighting over your services.

[@12voltvids]

@@RalphRacc00N actually they haven't really shot up here. I have a few pieces up for sale and i am just getting any offers on them.

[@KirksAudioSanctum]

These amps have a really good write up. Go for a nice price also! £500+

[@chetbaker6432]

What brand of contact cleaner do you use? Seems to do a great job. Doesn't look like DeOxit.

[@UHF43]

Nu-trol?

[@12voltvids]

Nutrol

[@chetbaker6432]

Thanks!@@12voltvids

[@dphauto6863]

Hi Dave; What brand of cleaner are you using, Thanks...Dave

[@12voltvids]

Nutrol

[@pdx27]

Great unit I guess. Dave, I'd like to ask you for an opinion... I have the KA-8300 which is supposedly the predecessor of this one and has a similar design. I like the unit a lot for its sound, but it has a problem: extremely annoying and rather loud distortion/interference from the powerline network adaptors that I'm running in my flat. That noise is even there when the volume is set to zero. When I connect the pre-outputs to another amp I get a clean signal, i.e. the noise goes straight from the power supply to the power amp. I've asked two professional electronics guys about that problem and was told this is probably a design flaw and not a defect. I'm not really willing to believe that.. I have a couple of other vintage amps in my small collection, and no other unit exhibits this. What do you think? BTW, thanks for all your videos, some of them were extremely helpful to me.

[@12voltvids]

Power line network adapters cause much interference. We get interference on moca adapters which causes disconnects and dropped packets. They create tons of harmonics. These units have pretty basic filtering. Try putting some torroidial chokes on the power cord and speaker wires.

[@SDsailor7]

@@12voltvids What year did those come out? so they are not recommended then? Thank you

[@12voltvids]

@@SDsailor7 my first akai stereo in 1979 had them.

[@pdx27]

​@@12voltvids Thanks, will try. I had already tried a few simple ferrit chokes on the power cord, but not on the speaker wires. I know using these powerline adaptors is less than ideal. They turn your entire electrical installation into a forest of antennas... Why I am not really satisfied with the conclusion that these units just don't have any decent filtering: I am currently running an early 70s KA-8004 as my main system, a KA-5500 (the KA-8300's little brother) in the kitchen, and I also have a Marantz 2270, a Sansui G-6700, and several Kenwood receivers from the mid 70s. None of the other units is affected at all by the powerline adaptors, though I wouldn't expect them to have any more advanced filtering than the 8300. But from your reply I conclude there's nothing that immediately comes to your mind in regards to the power supply filtering that could be broken or should be checked. So thanks again, I guess I have to live with that... cheers!

[@mcgjohn22]

I remember when these amps were first released. They were sure eye candy. Way out of my budget at the time. They did have an excellent bottom end on the bas response. Not 100% sure but think the next model down (8100 or 8300?) from the 9100 used discrete outputs in addition to the dual transformers.

[@pdx27]

The 8300 was the previous TOTL model and also used (the same?) IC outputs. The 8100 was the next model down from the 9100 and has discrete outputs. I don't understand Kenwood's naming conventions if they had any at all..

[@mcgjohn22]

@@pdx27 Thank you for adding the clarification on the model numbers.

[@kjellnilsson1615]

Kenwood make good amplifier !! I have myselfe a Technics integrated amplifier mod : SU - VX 700 ! That i have been service for cold solder joint ! Speciell the solder joints on the Power ic modules ,, that is common to fail ! It's have a greath sound , and i really like it ,, the switch es and volume control get a bit of cleaning / contakt spray every year ! Keep's it running !!!

[@kjellnilsson1615]

I have a good solder station Weller TCP from 1977 that is Amazing good ! Have change the heating element once , but have work great since thath ! The are very reliable solder stations,, and all spare parts and solder tipps are available still ,!!

[@worroSfOretsevraH]

Quality should be better on IC amplifiers compared to discrete transistor amps. Parts are much better matched inside an integrated package.

[@12voltvids]

They do, untill they don't and by don't I mean they blow up.

[@tacofortgens3471]

Except once the ouputs pop you are screwed and left with dead weight

[@kelleyhagan960]

Great Video.😊

[@zx8401ztv]

Odd how the inside looks dust free, the owner had a look and vacuumed the dust maybe. Pots and switches always get mucky. Slider switches with multi contacts always end up taken apart to clean. A better result, or i just like torture :-D

[@smartphonecomputerundmehr]

Nice video!

[@greenlanternseven]

New electrolytic s on 30+ year old gear always makes a huge difference in sound

[@12voltvids]

Not necessarily. I did a full recap about 12 years ago and had to change them back because the dramatic change in sound did not impress the owner. He said it sounded unnatural and wanted the old caps back in. So i charged him a second time to put the old ones back and he was happy. Yes it sounded brighter but as he put it, it sounded like the bass and treble was turned up even when flat. Many people once they are used to the sound they like to keep it that way. They don't buy a new one because they like the sound of the old. Change the caps and it sound like a new amp. One of the reasons is old caps were generally oil filled and the new ones water based. Different chemestey = different sound.

[@greenlanternseven]

The secret to recapping any vintage amp is to stay with same name brand capacitors like the Elna Selnec 2 which is comparison to the standard Elna s from past ..oh yes you are correct about electrolytic compounds however the Selnec 2 is a fantastic capacitor for overhauling vintage Elna capped amps , Elna hasn't really changed since their original days a fantastic cap maker , Nichicon s sound different to Elna as do the Panisonics , I find it amazing that all the top model amps in the past almost all used Elna , I recapped my Sansui Receiver model 7000 with Elna Selnec 2 s and Cerophyn s and it is absolutely outstanding

[@12voltvids]

@@greenlanternseven last one I did the client bought a kit of all original nichicon and rubycon. Same as original and he wasn't happy with the sound, so the originals went back in and I made another 150 to put it back.

[@greenlanternseven]

He wasn't happy ..that's funny , I bet his speakers are Bose lol

[@12voltvids]

@@greenlanternseven have no idea.

[@radio-ged4626]

Well, yes - it's never what I think - LOL. That's why I like fault finding - it's always the same in that it's never the same.... unless it is.

[@Tron1731]

I don't know if you can tell, but that amp sounds like mud like every single capacitor is just done 48 year old capacitors ....

[@12voltvids]

They might be old but there was 50 bucks in it to clean the controls. Owner wasn't prepared to spend hundreds to recap it. I keep hearing the internet keyboard heros say how much they pay or how much they make doing these old amplifiers however in my 40 years of servicing electronics I have yet to meet a single person that says rebuild it. Whatever it takes just do it. Every one is a penny pincher and wants it done literally for free. It was that way 20 years ago when i retired from the repair business and it hasn't changed. I did 1 recap for a guy about 10 years ago and he made me put the originals back because it didn't sound right to his ears. He was used to the sound and brigtning it up to him made it sound "harsh" so the old caps went back in. He took all the old parts and brought them back.

[@Tron1731]

@12voltvids yea, I'm the type that wants to have my equipment in top shape it's amazing how stupid and cheap people are. You do good work and keep making great videos. Thanks

[@12voltvids]

@@Tron1731 you are few and far between. 1 in 1000 so they say. Most want it running for next to nothing because there is a new one that is faster and better down at best buy. I fall into that category. If it's a simple fix great otherwise it's time for a new one. Especially cameras. If a camera let's me down once it's done.

[@markmarkofkane8167]

Bad IC? Just guessing. I'll watch and find out. Interesting. Edit: Wrong again. Well, you know I don't gamble. I lose most of the time.

[@dell177]

We are all subject to occasional cockpit error.

[@12voltvids]

Brain fart 😂

[@흑석김용호]

speaker terminal made me confused

[@12voltvids]

Me too. Didn't expect them to be laid out that way. Generally they are the other way. At least on every amp I have owned.

[@locutiss100]

I've made the same mistake on 9100 to. It's an unusual design for A , B speakers

[@Johnathan_Waters]

Does anybody else think that that music playing during the diagnosis was possibly the worst abortion they've ever heard? I had to turn off the video I thought I was going insane after about five minutes of it

[@12voltvids]

Ah poor baby. I have the same reaction to hip hop, cRAP, grunge, and any of that garbage they play on 90% of the radio stations but you don't see me getting all worked up over it. In order words it sucks to me you! 😋🍺

[@locutiss100]

Fans on of 12 volts are not here to listen to music. Also have to be careful about copyright issues.

[@Johnathan_Waters]

LOL. im not actually complaining because it's causing me some kind of "harm", im just pointing out something i noticed. Theres a difference. Its not by any means going to stop me watching your videos! Just god damn, that music is awful lol.@@12voltvids

[@12voltvids]

@@locutiss100 that's right. I am limited as to what i can play. Has to be licensed royalty free content. Now if you want me to use good music I can certainly do that but i won't be able to monetize my content as the rights holders would do that so then you would have to pay me direct. How does 1.00 per view sound. I know I would be happy getting a dollar a view. Shit I could even retire from my day job and live like a king. But considering that I tried that with patreon and that earns me about 100 bucks a month.

[@12voltvids]

@@Johnathan_Waters opinions are like assholes everyone has one. I happen to like jazz. Being a musician I wish i was talented enough to play it. Those that are musically minded tend to enjoy classical and jazz and the some folks like that pop crap and hip hop where you don't need any talent whatsoever.