Hi Tony if you take the cover off on the primary side where the AC side goes into the transformer, you will find a thermal fuse next to the primary windings many times it can be replaced and repair that problem
Thank you for letting me know! I didn't think there would be one on this small of transformer. I only do this as a hobby, but in my limited experience, I've only seen those thermal fuses on the big power transformers, usually the toroidal ones. I will certainly check that out. Thanks again!!
@@xraytonyb I have seen Paul Carlson of Mr Carlson's Lab open transformer's and sometimes it's just a break in the wire, I think that he used a signal generator to feed a signal in and a signal tracer to find where the signal stops to determine if it's repairable. In his case, the break was just under one or two layers of insulation and he was able to save it. Or unless there's a thermal fuse as the original poster has stated. I love older Kenwood equipment, their hi-fi side dropped of in quality after the 90's but their car audio kept going on, my son purchased a 5 channel Kenwood car amplifier and the construction and choice of components inside are amazing! It was nice to see after all these years even though aftermarket car audio is a dying breed that Kenwood is still there refusing to go cheap! It would be great to see this amplifier saved, hopefully it's transformer can be salvaged! I'm sure that there's someone out there who can rewind it although it's probably going to be more expensive and only worth it for someone trying to save their dad's pride and joy.... Which cost doesn't even come into the equation....
Hi Tony, Should the transformer be unfixable, replacing it with toroidal would be interesting. I did this with a old NAD1300 pré amp. Replacing the small size standard transformer, with the biggest toroidal i could fit. It went from a 20va unit, to a 120va unit. Also upgraded the rectifier to a 2a instead of 1a diode. Also placed fast recovery ones. Replaced the buffercaps with sturdy good ones, and recapped the unit. It now serves as a workhorse in my small audioshop. It sounds really, really. amazing. Huge soundstage depth, and open and very live sound. It never was this good when new! I did more upgrades, but these i mentioned are the most important ones. Off course all this work, and the costs involved exeeded the value of the préamp quite a bit, but i had a big urge to just try it out, and see how good i could make this amplifier play. Had a lot of fun during the process :) Good luck with this great channel, all the best from the Netherlands.
Hi Tony, I have 2 transformers that your welcome to have. I have restored 2 KA-9100's it only took 3 receivers to get enough parts lol. Just let me know where you want them shipped to. PS love your channel
I purchased a KA-8100 new in the mid 70s. I still use it and it sounds fantastic. As you noted, it is built like a tank. This was during the "golden age" of audio equipment.
Vintage equipment is worth salvaging just for the history of the era it was used in, these units brought much joy to the listener and still can with a little love a troubleshooting. Always happy to see these gems sing again.
I have several Kenwood amps in my collection. Not top quality like the big Sanyo's, Pioneers or Marantz, but quite reasonable. Give it a shot. It's a hobby.
Tony, do it. It's not for the money. It will be a special recovey project that all of us would like to see you doing it and the way it's gonna be done, like installing new toroids and new chips, and in the end, how it will sound, maybe better then original.
Fix it. I believe it's worth more than you think it is. I was in the middle of the receiver wars back in the 70's and I started collecting them after they fell out of vogue. In the last 10 years vintage equipment has become very desirable and I've sold many Marantz, Pioneer, Sherwood, Fisher and Kenwood units and for audiophiles the amps are especially attractive. I just sold a Phase Linear 400 for over 6 bills and am currently using another Phase Linear 700b that I have been offered into 4 figures for. With 110w/channel and all the features IMHO you won't loose any money, might make a few dollars and the content of your video would be great for the repair. I didn't even know there were company's that produced replacement parts like that, I'm always willing to learn.
I love these late 70's, early 80's amplifiers, they are so fun to work on because they were meant to repaired. Look at those test points, look at that schematics that even have the transistor pin outs. You can usually find the fault without taking anything out and when you do, you know what to take out. Beautiful!
I have an operating KA-9100 that has never been serviced though the switches and volume control could use some cleaning. I replaced the meter lamps with white LEDs. Purchased in 1978 new for $330.00. Great amp but will be a labor of love to repair. The design engineer of this amp went on to form the Accuphase company. Thanks for posting the wonderful video!!
I was excited when you mentioned it has two separate power supplies and being a Kenwood it must be good! My excitement vanished when I saw those integrated amplifier modules ;( I despise those ¬¬ EDIT: When I posted my original comment, I was still watching the video. After knowing that you found both options for replacing the amplifier modules and the transformer, my excitement came back immediately. I am invested! Looking forward to binge-watching this project, Tony. By the way, I also fix amplifiers as a hobby and I recently did something similar with a Denon PMA-320 with regard to the transformer. The original transformer had an open primary winding and it was potted. No viable fix. I found a nice replacememnt from Crinklewood Electronics (UK) and I had to design a mounting bracket and 3D print it in order to fit the transformer. The final result came out great! The amplifier sounds amazing and I even gained nearly 20 extra watts of clean power (1kHz at 8 Ohms)
This is for all the help I have gotten from your videos in the past (my favorite: the cheap frequency counter to generator mod I use all the time). Get some other folks to chip in on the parts, or at least have a beverage on me. Thanks!
Many electronic items go to the dump every day and most of them deserve it. However, a classic such as this one need to be preserved. Please restore it.
You can fix the bent corner of the face plate by using a couple of adjustable crescent wrenches and some cloth to keep from marring the metal. Put the wrenches on the bent area and tighten down with some cloth on both sides. Then you have a grip on it and you gently bend it back into shape.
If it were my KA-9100, I'd go for the parts, then repair and restore it. Functioning stock examples are in the $750-900 range, so it's definitely worth dumping $300+ worth of parts into. The KA-7100 and KA-9100 date from around the time that Kenwood's best engineers had a big blowup with the bean-counters who wanted to cheapen their designs, quit and then founded Accu-Phase. Accu-Phase is still in existence and specializes in really high-end audio equipment. It's possible these amps were designed by the Accu-Phase guys before they left. All I know is that pre-blowup, Kenwoods could be counted among the best of the mainstream audio gear. And I'm a sucker for the "Kenwood Sound" of the mid- to late-1970's and before.
I rebuilt one a few years ago. It is in near perfect cosmetic shape. It’s an absolute beast. Only bad part is it uses the power packs. As long as they are working it’s a great amp.
Please rebuild this Tony. This is one that can't get away. I have seen some of your most challenging videos, and this one you can beat. I know cost is a factor. But it is a classic dual supply amplifier. Unless you pay serious green for today's stuff, you ain't getting one. So $300.00 is not too out there. Besides love the adventures you have. Plus I learn so much from these challenging ones.
Crazy your working on one of these i have one on my bench as well .Im using the Pyramid modules as well mine is a 9150 pretty much the same unit . cant wait to see the solution you use for the XFMR replacement .
My Power amp will cost 4 figures for a full restoration, but its worth it to me as it was TOTL in 1977 and I have the matching preamp, tuner, speakers. That Kenwood is pretty, keep it alive.
Really like this! I have had Kenwood amps of this vintage for years. Can't wait to hear what you decide. Be sure to post a vid on your ultimate decision!
I have a KA-9100 still in the original box that a co-worker gave to me. He purchased it while he was in the Navy back in the late 1970's. He said it had been sitting in his closet for 35 years before he asked me if I wanted it. It has a few minor problems, but does work overall. The biggest problem is the speaker select switch. No amount of cleaning or Deoxit treatment seems to be able to get it to reliably work. So one day I will see if I can find a replacement. I did purchase 2 of those Pyramid Audio replacement chips in case they are needed in the future. But anyhow, I think that this would be a very interesting project. I personally would do it.
I would love to see you rebuild this. I have stayed away from this era of electronics so a successful rebuild may be the spark I (and others?) need. On the other hand, it's your money and time and if you decide not to, I fully understand.
Please forward a big thank you to Dave for getting these old audio components to you to restore! I really enjoy watching you work your magic on them. It’s always so much fun to see a master at work! Thanks Tony
I also have a KA7100 and after years I am still surprised how good this sounds. I have numerous vintage Marantz and Sansui and I would pit my Kenwood against any of them.
@@KillerKlipsch people forget that kenwood was one of the best brands at the time, even in the 80´s they had a lot of quality components compared with other supposed to be better brands
This was an interesting journey; I would think the population of these amplifiers has been reduced substantially over these many years by just this type failure or similar failures. Have you had any luck on a parts search through your AK contacts? Maybe a donor unit transformer and those module kits (to keep costs down) - that toroidal transformer path would make that amp some kind of performer! Again, thanks for your time - keep us posted, thanks!
I don't know Tony, tough call. These are fantastic amps and getting rarer. My own approach would probably be to re-wind the bad tranny, but I certainly appreciate the idea of hot rodding it. I repaired one of these for a friend a year or so ago, he had purchased it used back in the late 80's. I was extremely impressed by the build quality of the thing. It would be very interesting to see the modifications, I'm sure I'd learn a lot! Whatever you do, it'll be outstanding content as usual. Best of luck with it and I look forward to seeing the next appearance of it, no matter which way you go with the Beast.
The output modules are a bit of a letdown, as you are experiencing. Other than that the amp has good bones and promises to be a keeper if all tuned up. I'm also thinking a thermal fuse is at play here. Please take the time to open it up and have a look. I don't see smoke stains that are usually present from a cooked transformer. Good luck Tony
New to your channel, from the era of these beautiful pieces of old school gear. I thing you should do the mod fix. I may learn how to fix my Sylvania Receiver.
I would really like to watch this upgraded and restored. Doing this type of project would be cool and fill in some gaps in my knowledge. I've been watching mostly tube stuff. I need to learn also about older but newer. I've been spending money on test gear, but I'll really only be getting together an actual bench this month.
I had the 9100 recently for a few years. The build quality, design, and power is very impressive. I love the option in various tone controls. However It still had Kenwood parts, so the sound quality is good but not great. Sold it for a new better sounding amp, but damn the 9100 looked INSANE in my setup. Would love to see someone build one up 👍
Those power transformers have thermo fuses that are embedded in the windings, but are accessible and can be jumped. If the transformers supply fuse was good, the internal thermo fuse most likely failed on its own. Open the transformer, if it smells burnt the transformer is bad, if not the thermo fuse failed. I've never had a jumped thermo fuse create a problem
Amazing stuff here.. iteresting when beginning to learn details... This will be interesting. Is it worth it ?? depends on how much quality is built into the rest of the unit as a whole.. including the preamp, I guess.
Thanks for another great video! I think you've got a pretty good plan hatched out and yeah.. I'm one of the ones who would like to see you do a proof of concept on this. Especially replacing the amp modules with the improvised discrete replacements. It's sad sometimes we put more into something than it's worth, but the challenge is often worth the price I guess. Lastly? How about a rewind on the primary in the transformer? I have a place not too far away from me that builds and rewinds them, but it's quite a wait time. I'd love to see if you can figure out what popped it. I'd say your theory is on the mark. Somebody stuck like a 20 amp fuse in there and smoked it due to whatever was shorted out and pulling current.
I hope you restore this! I have a 9100 on the bench at the moment with the TA100-WA modules dead in each channel. Everything else works fine. I’d install the Pyramid modules but shipping to Australia is over $200! I’m trying to figure out another solution using Darlington transistors cos I can’t justify that cost!
Sometimes, a challenge by oneself to oneself needs to be accepted. It would be satisfying to replace the transformers with the drop ins and have a very special KA-9100.
I have the KA-3700 as the amp for the monitors connected to my audio interface on comp - perfect little quality amp for the application imo. This just looks liker a bigger better version with meters :)
I had the KA-3500 in about 1976 for a couple of days. I got it home and I couldn't get any bass out it. Took it back and it was the only one they had, so I got my money back.
Tony, hay sitios donde rebobinan los transformadores y los dejan exactamente igual como eran o si no, les das las características del transformador, voltaje del primario, voltajes de los secundarios si tiene dos devanados secundarios que es el caso, y la potencia del transformador (corriente de los secundarios) y con esas especificaciones te lo rebobinan y quedan bien, y sale mas económico que comprar uno nuevo. Me imagino que en EEUU hay sitios donde hacen eso. O en el mejor de los casos hay transformadores que traen un fusible interno, desármalo un poco y revisa, si lo tiene, haz corrido con suerte porque solo seria remplazar ese fusible interno.
I got the KA-3500, used it a lot during when I grew up, I got it in a broken state but I fixed it and the caps was bad in it along with very noisy pots, at this time it was the big Bulk caps that was completely dead. had it for years and had to fix it again after one output channel died with broken transistors, still have it but it is tired, if I wanna take it back into use I have to make a complete re-cap of it. but these amps are very nice so it may be a good thing to do actually
From a user stand point it checks all the boxes on features, bigger than usual power for this era of HiFi. Reliability you mentioned is a question, if you can't source replacement transistors, might turn some off. Those into vintage HiFi and Kenwood gear will be all over something like this. A top shelf unit of the time. Until Class D amplifiers where available, 90 watts per channel was huge in 1975. The typical home HiFi Receiver was more like 35 watts to 60 watts per channel in the 70's
I think you should go ahead Tony. I have one which played pretty nicely even though it needs a full service (it’s waiting for me to get on with it). Judging by the smell mine was clearly used as a cats toilet for a while which can’t be good for audio electronics! The sound definitely seemed to have some heft to it. Plus you can make some of your investment back since you’ll have a very valuable spare output pack and a transformer to sell on to someone who would love them I’m sure.
I’ve just been repairing a NAD amplifier that has a failed thermal fuse. I’ve had to unwind the secondary of the toroidal transformer to get to it and am in the process of rewinding. It’s not going to be pretty being manually rather than machine wound, but I thought I’d give it a go.
It is a good looking amp I would see if it can be made to look as new first so getting that front panel straight would help my decision. I'm not a big fan of those modules and can't even tell you why but if you got the money and the time then do it as a personal project with no expectations of getting your money back then yes, if it were me it's a resounding NO !...cheers EDIT:- would love the heatsinks ! RIP Calculon
I wouldn't dump too much money into it. I would look closer at the transformer to see if it is easily fixed or if someone has an extra laying around. Getting an STK replacement sounds like a good idea.
It would be interesting to see the amp restored with the aftermarket transformers and discrete modules; theoretically it would be a better product than when new, with the caveat that the rest of the amplifier had the design tolerance to accommodate any increased voltage/current.
A bent on the front this much damage also on the transformator. Should economically not good to invests so much money. Nice fault find and good vid. Thx
I know this is a long-shot, and I know you're very methodical... could the lead from the x-fmr have an open in it? As far as fixing it, I would consider keeping it on the shelf after fixing all of the board issues. If the x-fmr is in fact damaged, you may come across another one "bad" unit. My personal opinion on getting the toroidal x-fmrs is way too expensive. The discrete replacement for the IC is interesting and probably worth getting.
Hi, I’m very curious to know if you went on to try those replacement TA power packs. Please let us know if you ever complete this project and give us your thoughts.
Huummm, a "Pyramid" in the future. These 30 mins. or so were good trouble shooting, you decide; which you will do. I enjoy the learning. Thanks for your time as always.
You can likely get the transformer rewound for a reasonable price, I would search for places that do this for guitar amps. Heyboer Transformer is one such place that is popular on Audiokarma, might be worth getting an estimate. It's a great amp, and people love watching restoration videos, I say go for it, you'll sell it no problem.
I think this would be a really interesting project and the Amplifier is well worth it. Is it fininacially viable? No. It would just be for the love of quality amplifiers and the satisfaction of getting it to run very nicely again. If youre will to invest that much, i'd say go for it! I'd love to see this amplifier running againand the journey to it ^_^
In my opinion and that’s just my opinion it’s up to you what you want to do with it I would fix it personally just because even though his aunts are old you don’t run across that type of amp every day so it’s a rarity and I’m like some people who I like to see it up and running and then find out what you want for it which by the way where are you located like what state or are you in Canada?
Visual check. New fuse and operate on the DBT. Bulb will be bright. Disconnect the feeds and or components till the bulb dims. Obvious culprits on a PS would be the diodes and transistors.
gud am sir, i have def. kenwood integ. amp, it is safe to check dc voltage biasing without connecting output transistor for my ka990d, thnk you so much for your reply...
I would shelve this one and move onto the next one. Not that I wouldn't return to it, but if you have a long list of projects, this would put the brakes on them.
Another viewer mentioned this. I never thought of that, for this amp. I've only seen those thermal fuses in the larger amps with the huge transformers. I'm certainly going to check that out.
Kenwood has a rep for using cheap components. If you replace the transformer with the toroidal, it would be a lot of work and it could lead to something else failing. Another commenter mentioned getting the existing broken transformer rewound; that and new IC kits imho would be the way to go. And then there's still the bent faceplate.
Hi Patrick. Do you still have theses heatsink blanking plates. There are 4 of these I'm missing from my KA-9100. Do you have them? I take the chance to ask :)
It would be interesting to see the process of retrofitting the unit, but as a consumer, I would not buy the amp since it would not be (mostly) original (and possibly, the audio coloring will differ).
Well, B4 you spend big bucks on new transformers, remove that "bad" one, remove the bells, and see if it has a THERMAL FUSE embedded in it's PRIMARY. IF it's there I'll bet big bucks it's OPEN-and I'm not the betting type-LOL!!!! I've seen this MANY times in equipment older and newer. They fail if you look at the unit wrong so, either replace it or bypass it and you just might be back in business. Then scour the web for an original output pack. Yeah slim chance but you never know. If that's a no go then do the replacement modules and let er buck :)
Probably not worth it to replace the modules and transformers to that quality standard. I think it would be worth choosing some bog standard stereo amplifier chip, and just using the one remaining good transformer to power it. The result could comfortably give say 15 watts per channel just for the owner's use.
Hi Tony if you take the cover off on the primary side where the AC side goes into the transformer, you will find a thermal fuse next to the primary windings many times it can be replaced and repair that problem
Thank you for letting me know! I didn't think there would be one on this small of transformer. I only do this as a hobby, but in my limited experience, I've only seen those thermal fuses on the big power transformers, usually the toroidal ones. I will certainly check that out. Thanks again!!
@@xraytonyb You're welcome! When I had my business in the 80s and '90s and I would fix those transformers to save the customer's money
@@xraytonyb I have seen Paul Carlson of Mr Carlson's Lab open transformer's and sometimes it's just a break in the wire, I think that he used a signal generator to feed a signal in and a signal tracer to find where the signal stops to determine if it's repairable. In his case, the break was just under one or two layers of insulation and he was able to save it.
Or unless there's a thermal fuse as the original poster has stated.
I love older Kenwood equipment, their hi-fi side dropped of in quality after the 90's but their car audio kept going on, my son purchased a 5 channel Kenwood car amplifier and the construction and choice of components inside are amazing!
It was nice to see after all these years even though aftermarket car audio is a dying breed that Kenwood is still there refusing to go cheap!
It would be great to see this amplifier saved, hopefully it's transformer can be salvaged! I'm sure that there's someone out there who can rewind it although it's probably going to be more expensive and only worth it for someone trying to save their dad's pride and joy.... Which cost doesn't even come into the equation....
Hi Tony,
Should the transformer be unfixable, replacing it with toroidal would be interesting. I did this with a old NAD1300 pré amp. Replacing the small size standard transformer, with the biggest toroidal i could fit. It went from a 20va unit, to a 120va unit. Also upgraded the rectifier to a 2a instead of 1a diode. Also placed fast recovery ones. Replaced the buffercaps with sturdy good ones, and recapped the unit.
It now serves as a workhorse in my small audioshop. It sounds really, really. amazing. Huge soundstage depth, and open and very live sound. It never was this good when new! I did more upgrades, but these i mentioned are the most important ones. Off course all this work, and the costs involved exeeded the value of the préamp quite a bit, but i had a big urge to just try it out, and see how good i could make this amplifier play. Had a lot of fun during the process :)
Good luck with this great channel, all the best from the Netherlands.
Merci for this video.
Hi Tony,
I have 2 transformers that your welcome to have. I have restored 2 KA-9100's it only took 3 receivers to get enough parts lol. Just let me know where you want them shipped to. PS love your channel
I purchased a KA-8100 new in the mid 70s. I still use it and it sounds fantastic. As you noted, it is built like a tank. This was during the "golden age" of audio equipment.
Vintage equipment is worth salvaging just for the history of the era it was used in, these units brought much joy to the listener and still can with a little love a troubleshooting. Always happy to see these gems sing again.
I have several Kenwood amps in my collection. Not top quality like the big Sanyo's, Pioneers or Marantz, but quite reasonable. Give it a shot. It's a hobby.
Tony, do it. It's not for the money. It will be a special recovey project that all of us would like to see you doing it and the way it's gonna be done, like installing new toroids and new chips, and in the end, how it will sound, maybe better then original.
Fix it. I believe it's worth more than you think it is. I was in the middle of the receiver wars back in the 70's and I started collecting them after they fell out of vogue. In the last 10 years vintage equipment has become very desirable and I've sold many Marantz, Pioneer, Sherwood, Fisher and Kenwood units and for audiophiles the amps are especially attractive. I just sold a Phase Linear 400 for over 6 bills and am currently using another Phase Linear 700b that I have been offered into 4 figures for. With 110w/channel and all the features IMHO you won't loose any money, might make a few dollars and the content of your video would be great for the repair. I didn't even know there were company's that produced replacement parts like that, I'm always willing to learn.
I love these late 70's, early 80's amplifiers, they are so fun to work on because they were meant to repaired. Look at those test points, look at that schematics that even have the transistor pin outs. You can usually find the fault without taking anything out and when you do, you know what to take out. Beautiful!
I have an operating KA-9100 that has never been serviced though the switches and volume control could use some cleaning. I replaced the meter lamps with white LEDs.
Purchased in 1978 new for $330.00.
Great amp but will be a labor of love to repair.
The design engineer of this amp went on to form the Accuphase company.
Thanks for posting the wonderful video!!
I was excited when you mentioned it has two separate power supplies and being a Kenwood it must be good! My excitement vanished when I saw those integrated amplifier modules ;( I despise those ¬¬
EDIT: When I posted my original comment, I was still watching the video. After knowing that you found both options for replacing the amplifier modules and the transformer, my excitement came back immediately. I am invested! Looking forward to binge-watching this project, Tony.
By the way, I also fix amplifiers as a hobby and I recently did something similar with a Denon PMA-320 with regard to the transformer. The original transformer had an open primary winding and it was potted. No viable fix. I found a nice replacememnt from Crinklewood Electronics (UK) and I had to design a mounting bracket and 3D print it in order to fit the transformer.
The final result came out great! The amplifier sounds amazing and I even gained nearly 20 extra watts of clean power (1kHz at 8 Ohms)
The repair would be a bit expensive, but seeing such an upgrade/repair would be very interesting.
It's refreshing to see the old honest specs where distortion is given at rated power.
This is for all the help I have gotten from your videos in the past (my favorite: the cheap frequency counter to generator mod I use all the time). Get some other folks to chip in on the parts, or at least have a beverage on me. Thanks!
Thank you!!
I would go for it Tony. The audio gear of that area are well build and deserves to be rescued!
Re build it Tony !
As PracticallyFixed says, your videos are an inspiration. Whether you decide on parts or a new schematic light we are here to watch :)
Thank you!!
Many electronic items go to the dump every day and most of them deserve it. However, a classic such as this one need to be preserved. Please restore it.
I think you should go for it. The amp when working has a good sound to it
Go for it, Tony. I really love your videos. Not just entertaining, but full of information too. Thanks for sharing.
You can fix the bent corner of the face plate by using a couple of adjustable crescent wrenches and some cloth to keep from marring the metal. Put the wrenches on the bent area and tighten down with some cloth on both sides. Then you have a grip on it and you gently bend it back into shape.
If it were my KA-9100, I'd go for the parts, then repair and restore it. Functioning stock examples are in the $750-900 range, so it's definitely worth dumping $300+ worth of parts into.
The KA-7100 and KA-9100 date from around the time that Kenwood's best engineers had a big blowup with the bean-counters who wanted to cheapen their designs, quit and then founded Accu-Phase. Accu-Phase is still in existence and specializes in really high-end audio equipment. It's possible these amps were designed by the Accu-Phase guys before they left. All I know is that pre-blowup, Kenwoods could be counted among the best of the mainstream audio gear. And I'm a sucker for the "Kenwood Sound" of the mid- to late-1970's and before.
Dumping parts ! How BLAZE.
I never knew any of that. Thanks for sharing!
I rebuilt one a few years ago. It is in near perfect cosmetic shape. It’s an absolute beast. Only bad part is it uses the power packs. As long as they are working it’s a great amp.
Looks like a nice amp. Shame about the bent front, I might try to bend that back and see how good i could get it cosmeticly beffore trying to rebuild.
Please rebuild this Tony. This is one that can't get away. I have seen some of your most challenging videos, and this one you can beat. I know cost is a factor. But it is a classic dual supply amplifier. Unless you pay serious green for today's stuff, you ain't getting one. So $300.00 is not too out there. Besides love the adventures you have. Plus I learn so much from these challenging ones.
Crazy your working on one of these i have one on my bench as well .Im using the Pyramid modules as well mine is a 9150 pretty much the same unit . cant wait to see the solution you use for the XFMR replacement .
My Power amp will cost 4 figures for a full restoration, but its worth it to me as it was TOTL in 1977 and I have the matching preamp, tuner, speakers. That Kenwood is pretty, keep it alive.
Really like this! I have had Kenwood amps of this vintage for years. Can't wait to hear what you decide. Be sure to post a vid on your ultimate decision!
Very interesting approach, I vote yes, this will be a total rebuild that will prove educational, (a great learning curve).
I have a KA-9100 still in the original box that a co-worker gave to me. He purchased it while he was in the Navy back in the late 1970's. He said it had been sitting in his closet for 35 years before he asked me if I wanted it. It has a few minor problems, but does work overall. The biggest problem is the speaker select switch. No amount of cleaning or Deoxit treatment seems to be able to get it to reliably work. So one day I will see if I can find a replacement. I did purchase 2 of those Pyramid Audio replacement chips in case they are needed in the future.
But anyhow, I think that this would be a very interesting project. I personally would do it.
Do it love to see it
Why not rewind that broken transformer? There are specialists who can do that. Perhaps cheaper than two new ones.
I would love to see you rebuild this. I have stayed away from this era of electronics so a successful rebuild may be the spark I (and others?) need. On the other hand, it's your money and time and if you decide not to, I fully understand.
Please forward a big thank you to Dave for getting these old audio components to you to restore! I really enjoy watching you work your magic on them. It’s always so much fun to see a master at work! Thanks Tony
Will do!
Would love to see you rebuild this amplifier…. Kenwood’s are highly underrated… I don’t think you will be disappointed..
cool idea may be a neat 1 off those descrete boards are sweet way better then oem
I have a KA7100 amp, excellent specs, clean & powerful. I can only imagine what the KA9100 is capable of after a xrayT restoration 😊
I also have a KA7100 and after years I am still surprised how good this sounds. I have numerous vintage Marantz and Sansui and I would pit my Kenwood against any of them.
@@KillerKlipsch people forget that kenwood was one of the best brands at the time, even in the 80´s they had a lot of quality components compared with other supposed to be better brands
@@RUfromthe40s Amen
Tony, as always...great video.
Will be awesome if you decided to rebuild the whole Amp.
This was an interesting journey; I would think the population of these amplifiers has been reduced substantially over these many years by just this type failure or similar failures. Have you had any luck on a parts search through your AK contacts? Maybe a donor unit transformer and those module kits (to keep costs down) - that toroidal transformer path would make that amp some kind of performer! Again, thanks for your time - keep us posted, thanks!
I don't know Tony, tough call. These are fantastic amps and getting rarer. My own approach would probably be to re-wind the bad tranny, but I certainly appreciate the idea of hot rodding it. I repaired one of these for a friend a year or so ago, he had purchased it used back in the late 80's. I was extremely impressed by the build quality of the thing. It would be very interesting to see the modifications, I'm sure I'd learn a lot! Whatever you do, it'll be outstanding content as usual. Best of luck with it and I look forward to seeing the next appearance of it, no matter which way you go with the Beast.
Very interesting video Tony, no matter what you decide to do with this amp. 👍🏻
The output modules are a bit of a letdown, as you are experiencing. Other than that the amp has good bones and promises to be a keeper if all tuned up.
I'm also thinking a thermal fuse is at play here. Please take the time to open it up and have a look. I don't see smoke stains that are usually present from a cooked transformer.
Good luck Tony
New to your channel, from the era of these beautiful pieces of old school gear. I thing you should do the mod fix. I may learn how to fix my Sylvania Receiver.
I would really like to watch this upgraded and restored. Doing this type of project would be cool and fill in some gaps in my knowledge. I've been watching mostly tube stuff. I need to learn also about older but newer. I've been spending money on test gear, but I'll really only be getting together an actual bench this month.
We can rebuild it, faster.... stronger....
Cheerz!!
Go for it, as it will be quite enjoyable to watch. I say it would level up Tony to badass status.
I had the 9100 recently for a few years. The build quality, design, and power is very impressive. I love the option in various tone controls. However It still had Kenwood parts, so the sound quality is good but not great. Sold it for a new better sounding amp, but damn the 9100 looked INSANE in my setup. Would love to see someone build one up 👍
Tony you're crazy and I can't wait to watch you do the modification-repair !! :)
As a current owner of one of these units, i hope you might continue with the rehab of this beast. I'd be very curious to see it resurrected.
I’d love to see a rebuild of this amp in the way you described, it would be much more interesting than just a normal service! Andrew 🇬🇧
I had the 40w version of this. I loved the hell out of it.
Those power transformers have thermo fuses that are embedded in the windings, but are accessible and can be jumped. If the transformers supply fuse was good, the internal thermo fuse most likely failed on its own. Open the transformer, if it smells burnt the transformer is bad, if not the thermo fuse failed. I've never had a jumped thermo fuse create a problem
I've used AnTek toroids on my "home-brew" power amp projects. Very Good product.
Go for it,,, if in doubt replace,, I'd like to see the whole rework
Looking forward to your decision
I'd be very interested in seeing this project continue with the new toroidals and the discrete STK replacements, and believe that the amp is worth it
Amazing stuff here.. iteresting when beginning to learn details... This will be interesting. Is it worth it ?? depends on how much quality is built into the rest of the unit as a whole.. including the preamp, I guess.
Thanks for another great video! I think you've got a pretty good plan hatched out and yeah.. I'm one of the ones who would like to see you do a proof of concept on this. Especially replacing the amp modules with the improvised discrete replacements. It's sad sometimes we put more into something than it's worth, but the challenge is often worth the price I guess. Lastly? How about a rewind on the primary in the transformer? I have a place not too far away from me that builds and rewinds them, but it's quite a wait time. I'd love to see if you can figure out what popped it. I'd say your theory is on the mark. Somebody stuck like a 20 amp fuse in there and smoked it due to whatever was shorted out and pulling current.
I hope you restore this! I have a 9100 on the bench at the moment with the TA100-WA modules dead in each channel. Everything else works fine. I’d install the Pyramid modules but shipping to Australia is over $200! I’m trying to figure out another solution using Darlington transistors cos I can’t justify that cost!
Sometimes, a challenge by oneself to oneself needs to be accepted. It would be satisfying to replace the transformers with the drop ins and have a very special KA-9100.
Love to see it fixed
I have the KA-3700 as the amp for the monitors connected to my audio interface on comp - perfect little quality amp for the application imo. This just looks liker a bigger better version with meters :)
ive put tons of money and time into realistic equipment but i like them i have a childhood love for them i remember sitting at the window like Ralphy
Just don't shoot your eye out ;)
I had the KA-3500 in about 1976 for a couple of days. I got it home and I couldn't get any bass out it. Took it back and it was the only one they had, so I got my money back.
Tony, hay sitios donde rebobinan los transformadores y los dejan exactamente igual como eran o si no, les das las características del transformador, voltaje del primario, voltajes de los secundarios si tiene dos devanados secundarios que es el caso, y la potencia del transformador (corriente de los secundarios) y con esas especificaciones te lo rebobinan y quedan bien, y sale mas económico que comprar uno nuevo. Me imagino que en EEUU hay sitios donde hacen eso. O en el mejor de los casos hay transformadores que traen un fusible interno, desármalo un poco y revisa, si lo tiene, haz corrido con suerte porque solo seria remplazar ese fusible interno.
Nice one. Thanks for sharing.
You can't save every neglected audio gear out there - that said, Kenwood makes first-class equipment that will last forever after you're done with it
Sometimes you just have to let things die. SCRAP it for parts is the correct move. Thanks for your great videos.
I got the KA-3500, used it a lot during when I grew up, I got it in a broken state but I fixed it and the caps was bad in it along with very noisy pots, at this time it was the big Bulk caps that was completely dead. had it for years and had to fix it again after one output channel died with broken transistors, still have it but it is tired, if I wanna take it back into use I have to make a complete re-cap of it. but these amps are very nice so it may be a good thing to do actually
This old equipment just sounds good to me
@@elonmust7470 yes these amps can sound really good when they are in good condition
From a user stand point it checks all the boxes on features, bigger than usual power for this era of HiFi. Reliability you mentioned is a question, if you can't source replacement transistors, might turn some off. Those into vintage HiFi and Kenwood gear will be all over something like this. A top shelf unit of the time. Until Class D amplifiers where available, 90 watts per channel was huge in 1975. The typical home HiFi Receiver was more like 35 watts to 60 watts per channel in the 70's
With easy to drive speakers 35 watts was and is plenty.
I think you should go ahead Tony. I have one which played pretty nicely even though it needs a full service (it’s waiting for me to get on with it). Judging by the smell mine was clearly used as a cats toilet for a while which can’t be good for audio electronics! The sound definitely seemed to have some heft to it.
Plus you can make some of your investment back since you’ll have a very valuable spare output pack and a transformer to sell on to someone who would love them I’m sure.
I’ve just been repairing a NAD amplifier that has a failed thermal fuse. I’ve had to unwind the secondary of the toroidal transformer to get to it and am in the process of rewinding. It’s not going to be pretty being manually rather than machine wound, but I thought I’d give it a go.
Please let us know here if it works out
How about remove the bad amplifier and power supply sections and replace them with a TPA3255 board and a Mean Well module?
as long as it fixs it design changes are ok.cost vs 100 watts ah depends i guess on cost.darn nice looking amp 400 dollars max may be
It is a good looking amp I would see if it can be made to look as new first so getting that front panel straight would help my decision. I'm not a big fan of those modules and can't even tell you why but if you got the money and the time then do it as a personal project with no expectations of getting your money back then yes, if it were me it's a resounding NO !...cheers EDIT:- would love the heatsinks ! RIP Calculon
I wouldn't dump too much money into it. I would look closer at the transformer to see if it is easily fixed or if someone has an extra laying around. Getting an STK replacement sounds like a good idea.
It would be interesting to see the amp restored with the aftermarket transformers and discrete modules; theoretically it would be a better product than when new, with the caveat that the rest of the amplifier had the design tolerance to accommodate any increased voltage/current.
ya thats older classic amp alright, collectors already. looks build solid too,, but you know this era solid units. hard find parts though IC chips.
Its a shame to end up a parts unit because a friend has this amp and its one of the best sounding classic models I have heard.
A bent on the front this much damage also on the transformator. Should economically not good to invests so much money. Nice fault find and good vid. Thx
I know this is a long-shot, and I know you're very methodical... could the lead from the x-fmr have an open in it? As far as fixing it, I would consider keeping it on the shelf after fixing all of the board issues. If the x-fmr is in fact damaged, you may come across another one "bad" unit. My personal opinion on getting the toroidal x-fmrs is way too expensive. The discrete replacement for the IC is interesting and probably worth getting.
Tony , is there a thermal fuse in the open transformer that has blown ??
+1
Hi, I’m very curious to know if you went on to try those replacement TA power packs. Please let us know if you ever complete this project and give us your thoughts.
Huummm, a "Pyramid" in the future. These 30 mins. or so were good trouble shooting, you decide; which you will do. I enjoy the learning. Thanks for your time as always.
You can likely get the transformer rewound for a reasonable price, I would search for places that do this for guitar amps. Heyboer Transformer is one such place that is popular on Audiokarma, might be worth getting an estimate. It's a great amp, and people love watching restoration videos, I say go for it, you'll sell it no problem.
I think this would be a really interesting project and the Amplifier is well worth it. Is it fininacially viable? No. It would just be for the love of quality amplifiers and the satisfaction of getting it to run very nicely again. If youre will to invest that much, i'd say go for it! I'd love to see this amplifier running againand the journey to it ^_^
I am also looking for the 2 top covers if you decide to part it out. I have another one I kept from my stereo store, but the covers went missing
In my opinion and that’s just my opinion it’s up to you what you want to do with it I would fix it personally just because even though his aunts are old you don’t run across that type of amp every day so it’s a rarity and I’m like some people who I like to see it up and running and then find out what you want for it which by the way where are you located like what state or are you in Canada?
I just saw the thumbnail! I have one. Let’s go through it and any tips and techniques would be appreciated
Definitelly, it's worth this investment (moeny and time).
Visual check.
New fuse and operate on the DBT. Bulb will be bright. Disconnect the feeds and or components till the bulb dims. Obvious culprits on a PS would be the diodes and transistors.
gud am sir, i have def. kenwood integ. amp, it is safe to check dc voltage biasing without connecting output transistor for my ka990d, thnk you so much for your reply...
Good to see an educated brain working
You have to fix it for us Tony. Please.
WOW nice ❤
Check if the transformers have an internal thermal cutout or fuse.
I would shelve this one and move onto the next one. Not that I wouldn't return to it, but if you have a long list of projects, this would put the brakes on them.
Does the transformer have a thermal fuse that may have gone open?
Another viewer mentioned this. I never thought of that, for this amp. I've only seen those thermal fuses in the larger amps with the huge transformers. I'm certainly going to check that out.
I would suspect this also. They can typically be bypassed.
Kenwood has a rep for using cheap components. If you replace the transformer with the toroidal, it would be a lot of work and it could lead to something else failing. Another commenter mentioned getting the existing broken transformer rewound; that and new IC kits imho would be the way to go. And then there's still the bent faceplate.
Yes, but since this will be a "special" edition, I'm sure a jig can be setup to bend the other 3 to match!
I have one of these parted out, with 2 good transformers. Thats about all thats left. It was in rough shape, one output chip blown as well.. Want 'em?
Hi Patrick. Do you still have theses heatsink blanking plates. There are 4 of these I'm missing from my KA-9100. Do you have them? I take the chance to ask :)
It would be interesting to see the process of retrofitting the unit, but as a consumer, I would not buy the amp since it would not be (mostly) original (and possibly, the audio coloring will differ).
The transformer is on the AC power side and would in no way affect the audio coloring.
Yes but original parts aren't available, you can't see the difference when the case is closed up and toroidal types are very good.
Well, B4 you spend big bucks on new transformers, remove that "bad" one, remove the bells, and see if it has a THERMAL FUSE embedded in it's PRIMARY. IF it's there I'll bet big bucks it's OPEN-and I'm not the betting type-LOL!!!! I've seen this MANY times in equipment older and newer. They fail if you look at the unit wrong so, either replace it or bypass it and you just might be back in business. Then scour the web for an original output pack. Yeah slim chance but you never know. If that's a no go then do the replacement modules and let er buck :)
Probably not worth it to replace the modules and transformers to that quality standard.
I think it would be worth choosing some bog standard stereo amplifier chip, and just using the one remaining good transformer to power it.
The result could comfortably give say 15 watts per channel just for the owner's use.