I found a Kenwood Super Eleven near my place a few months ago. The power cord was cut, and the wood case was in less than stellar condition. I had a good tech fix the cord. He resoldered a few things on the PCB. The receiver had a bad left channel with a lot of distortion, though. He didn't pin that problem down, and this went unrepaired.
I took the monster to another local shop in late March. The problem persisted, but it became intermittent.
I got the Eleven back from this shop with the tuner and lights in much better shape, at least. I cleaned the balance and control pots as best I could, several times. Still no joy.
In disgust, I opened up the case to visually check for bad caps or other easily identifiable problems. That's when I noticed the variable resistors on the main PCB. I figured: if I botch this, it cannot sound much worse than it already does.
I spent 20 minutes adjusting two of them. At one point, the Kenwood's protection circuit kicked in and stayed engaged. I unplugged the monster and put that resistor back to Last Known Good Configuration, and when I plugged it back into the AC and turned it back on, it worked again. Major improvement in the sound now, about 90% of the problem is gone. There is still a small amount of distortion in the bad channel at medium/high volume, say around 11:00 or 12:00 on the volume knob.
My question is... is the volume pot still dirty, or is something else causing that last bit of the problem?
I took the monster to another local shop in late March. The problem persisted, but it became intermittent.
I got the Eleven back from this shop with the tuner and lights in much better shape, at least. I cleaned the balance and control pots as best I could, several times. Still no joy.
In disgust, I opened up the case to visually check for bad caps or other easily identifiable problems. That's when I noticed the variable resistors on the main PCB. I figured: if I botch this, it cannot sound much worse than it already does.
I spent 20 minutes adjusting two of them. At one point, the Kenwood's protection circuit kicked in and stayed engaged. I unplugged the monster and put that resistor back to Last Known Good Configuration, and when I plugged it back into the AC and turned it back on, it worked again. Major improvement in the sound now, about 90% of the problem is gone. There is still a small amount of distortion in the bad channel at medium/high volume, say around 11:00 or 12:00 on the volume knob.
My question is... is the volume pot still dirty, or is something else causing that last bit of the problem?
Id say you still have bad caps, a dirty volume pot should not cause distortion. Just because they're not swol doesnt mean they're still good. Your pots are probably bias and transistor matching. So one pot sets how much current is going to run through the transistors, and the other makes sure equal current goes to each transistor in the pair.
An amp that old most likely has every electrolytic "on the edge" if not outright leaking. I posted the whole schema in "solid state pix". My 20 YO Nikko had the big caps leaked all over the board... The small HV supply caps bulging. If I was to fix it ( I gutted it instead - reused the trafo/heatsinks/case) I would of replaced ALL the caps. Caps are consumables , 10-15 years MAX. It is a nice 120W amp , worth restoring.
PS - looks like .22R resistors (big square ones near heatsinks) read 13-15mv across one of them. you might have a bad spot on the cheap bias control - that why it went into protect mode (opened up - too much current) replace them with 25 turn precision trimmers. Put heatsinks on them poor drivers , too. 😀
OS
PS - looks like .22R resistors (big square ones near heatsinks) read 13-15mv across one of them. you might have a bad spot on the cheap bias control - that why it went into protect mode (opened up - too much current) replace them with 25 turn precision trimmers. Put heatsinks on them poor drivers , too. 😀
OS
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Kenwood resistors
"PS - looks like .22R resistors (big square ones near heatsinks) read 13-15mv across one of them. you might have a bad spot on the cheap bias control - that why it went into protect mode (opened up - too much current) replace them with 25 turn precision trimmers."
I am a newb at working on audio equipment (I build computers, which is MUCH easier than this), so some of what you write zooms well over my head.
The two pair of vertical white squares should be replaced with precision trimmers.
Like these?
3296Z-1-253LF Bourns Trimmer Resistors - Multi Turn
Thanks for the help. This Eleven had me stumped.
"PS - looks like .22R resistors (big square ones near heatsinks) read 13-15mv across one of them. you might have a bad spot on the cheap bias control - that why it went into protect mode (opened up - too much current) replace them with 25 turn precision trimmers."
I am a newb at working on audio equipment (I build computers, which is MUCH easier than this), so some of what you write zooms well over my head.
The two pair of vertical white squares should be replaced with precision trimmers.
Like these?
3296Z-1-253LF Bourns Trimmer Resistors - Multi Turn
Thanks for the help. This Eleven had me stumped.
Caps
I'll look around for some now caps. The big power filter ones will have to be replaced first, I think.
I'll look around for some now caps. The big power filter ones will have to be replaced first, I think.
white square things are the emitter resistors from the outputs to the speaker. When the large output transistors are biased correctly... 15mv- .015/.22 = 68ma per device. do not replace these with a trimmer. The trimmer should be the only control close to the big output transistor/ emitter resistors , it is 1/2w (small power) but critical to the thermal stability of the amp.
If you have it working now , be thankful. With it's advanced age , you are lucky it has a protection circuit .... between the bad caps and old trimmers , it could go up in smoke at any time. 😱 I build PC's, too. My PC knowledge compliments my amp knowledge. Actually , a switching power supply in a PC is 10 X more sophisticated than these kenwood amps. But if you just "swap" PS's , that's a different story. I only bother with repair of 700-1KW PC supplies ... all the rest - to the garbage. 😀
(Below 1) is a basic amp like the kenwood . "B" is the emitter resistor and should have 10-20mV across it. "A" is one of those precision trimmers , clockwise makes the mV go up , counter clockwise makes it go down.
OS
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I cleaned the PCB where the variable resistors are...
and changed the speaker wire from spade terminations to bare wire. So far, so good. The monster is running very warm though, much more so than it normally does. Hopefully, the protection circuit won't be needed (and nothing will burn up).
I'll leave the local classical FM station going for a while longer while I get some things done (they have been playing opera all afternoon now
).
Thanks for the download, ostripper.
and changed the speaker wire from spade terminations to bare wire. So far, so good. The monster is running very warm though, much more so than it normally does. Hopefully, the protection circuit won't be needed (and nothing will burn up).
I'll leave the local classical FM station going for a while longer while I get some things done (they have been playing opera all afternoon now
). Thanks for the download, ostripper.
Checking and setting idle and bias
Anyone know how to accomplish these tasks? I don't want the big Kenwood to end up resembling a certain Deep Purple song, sans the water.😱
Any help on this is appreciated.
Anyone know how to accomplish these tasks? I don't want the big Kenwood to end up resembling a certain Deep Purple song, sans the water.😱
Any help on this is appreciated.
Mucking about with trimmer pots for bias current may end up in dead output transistors, as in most cases extreme settings are really extreme - one is zero bias (lots of distortion), the other is WAY too much bias = too much heat and dead transistors.
STOP twiddling those pots without knowing exactly what you are doing or your curbside find may well end up on the curbside again, in even worse shape. Honestly, i really don't understand where people get ideas that if it can be adjusted, it should, without the faintest on what is adjusted and shy. Would you open up the engine bay of your car and randomly screw or unscrew bolts and screws just because you can obviously do that?!
STOP twiddling those pots without knowing exactly what you are doing or your curbside find may well end up on the curbside again, in even worse shape. Honestly, i really don't understand where people get ideas that if it can be adjusted, it should, without the faintest on what is adjusted and shy. Would you open up the engine bay of your car and randomly screw or unscrew bolts and screws just because you can obviously do that?!
Good luck.....I found a pair of Advent speakers in the trash on Mulholland drive one day and picked them up.
One woofer was gone.....the other destroyed. I replaced with some equivalent Vifa woofers and been using them for 29 years......great tweeter/midrange....wonderful speakers....very strong, solid boxes
One woofer was gone.....the other destroyed. I replaced with some equivalent Vifa woofers and been using them for 29 years......great tweeter/midrange....wonderful speakers....very strong, solid boxes
And I thought I had too much caffeine this morning.
I asked the question on this site because I don't know how to fix the problem. And your analogy doesn't really work, because the Super Eleven is not a car. No one will be harmed (except for the prior repair costs) in the event a high-speed receiver crash; the owner will walk away without a scratch, even if the old monster is totaled.
Advent find
I bought a pair of B&W DM10s in 2004 from a craigslist seller. Can't visualize Sunday afternoon jazz (local Pacifica station plays great stuff) without them and my old Luxman R-1050.😎
I bought a pair of B&W DM10s in 2004 from a craigslist seller. Can't visualize Sunday afternoon jazz (local Pacifica station plays great stuff) without them and my old Luxman R-1050.😎
Hoya Fan.....as in Georgetown?
Good story. We should start a thread on abandoned old gear!!! I have 2 Son of Ampzilla amps that I got from RECYCLER ads. One I had rebuilt by James Bonjornio himself.....nice guy. I am always hunting eBay for stuff.
Those Advents are amazing.....cabinets were cosmetically beyond saving so I did a "rat rod" redo. Flat black paint. I put a 3/4" in chipboard front panel over the existing one so I could fit the woofers which were fractionally smaller than the originals. The guys at Speaker City Burbank CA told me they were and odd size....maybe metric. I remounted the tweeters forward on the new front.....so I have a 1.5" front panel!!!
Not beautiful, but they sound great being drive by a grandson and a mini Chinese preamp with PGA2311 chip.....what a clean sound.
Fun to put these oddball but great sounding systems!!
Good story. We should start a thread on abandoned old gear!!! I have 2 Son of Ampzilla amps that I got from RECYCLER ads. One I had rebuilt by James Bonjornio himself.....nice guy. I am always hunting eBay for stuff.
Those Advents are amazing.....cabinets were cosmetically beyond saving so I did a "rat rod" redo. Flat black paint. I put a 3/4" in chipboard front panel over the existing one so I could fit the woofers which were fractionally smaller than the originals. The guys at Speaker City Burbank CA told me they were and odd size....maybe metric. I remounted the tweeters forward on the new front.....so I have a 1.5" front panel!!!
Not beautiful, but they sound great being drive by a grandson and a mini Chinese preamp with PGA2311 chip.....what a clean sound.
Fun to put these oddball but great sounding systems!!
Old gear
As in Georgetown, yes. When I graduated from GU, the following still obtained:
a well-built PC cost over $1000
Polk speakers were still made in Baltimore
Maxell XLII-S cassette tapes were a bit more than two dollars at Luskins
I bought my CD player, an ADC (with Monster Cable Interlink 500 running to my Kyocera R-451)
I was buying all of my audio gear new
I am not a tech. I don't even play one on TV. About a year and a half ago, my old Thorens turntable distortedly rumbled (a bad RCA plug) and took out the woofer of one of my DM10s. I got a replacement driver for about $40 from eBay. I installed it and hoped for the best; that was the first time I had opened up a speaker cabinet for any reason. It still sounds great today.
What I just described is easy as pie to almost everyone else on this board. I was actually wary of doing it, and only fixed it myself because B&W wanted more than the speakers were worth to perform the work.
As in Georgetown, yes. When I graduated from GU, the following still obtained:
a well-built PC cost over $1000
Polk speakers were still made in Baltimore
Maxell XLII-S cassette tapes were a bit more than two dollars at Luskins
I bought my CD player, an ADC (with Monster Cable Interlink 500 running to my Kyocera R-451)
I was buying all of my audio gear new
I am not a tech. I don't even play one on TV. About a year and a half ago, my old Thorens turntable distortedly rumbled (a bad RCA plug) and took out the woofer of one of my DM10s. I got a replacement driver for about $40 from eBay. I installed it and hoped for the best; that was the first time I had opened up a speaker cabinet for any reason. It still sounds great today.
What I just described is easy as pie to almost everyone else on this board. I was actually wary of doing it, and only fixed it myself because B&W wanted more than the speakers were worth to perform the work.
Interesting......my sister went to Georgetown, know a lot of people from there. I went to Holy Cross.
I too am not a tech.....at least not in electronics, I have made lots of speakers, and built some tube amp kits. Now I am just into some good vintage stuff and get a kick out of having it work well.
I am in the LA area.....you?
cheers,
Dick Lague
I too am not a tech.....at least not in electronics, I have made lots of speakers, and built some tube amp kits. Now I am just into some good vintage stuff and get a kick out of having it work well.
I am in the LA area.....you?
cheers,
Dick Lague
Nostalgia from 37th and O Streets
I'm still in the DC area. Where there is a definite dearth of good audio shops, I might add.
As for my undergrad time... I remember when Lauinger had not yet been renovated.
And when a late-April or May class in White-Gravenor meant a rather warm hour or two studying the Defenestration of Prague.
I remember Astronomy class in Reiss at 8:00 am.
Saxa Sundries in the basement of Healy. Sugar's on 36th Street.
It's been a while.
Some of my vintage stuff works well, like my Luxman components (four receivers and a tape deck, all in very good shape). Some of this old gear does not.
The Kenwood Super Eleven? Uh, no. Not yet, anyway.
The two Denon tape decks (the Luxman was a backup, originally) that need motors? Can't find a decent replacement motor that doesn't cost three figures.
The Arcam CD player? Needs a laser. Maybe even some capacitors replaced.
My Polk subwoofer that has a 50 watt amplifier and a 10 inch driver? Bottoms out fast, and gets boomy easily. So I have to baby it.
The 12 inch B&W sub with a 300 watt amp? I will check on that by Christmas. Life is too short to have anything but sterling low end. Bass that makes the 2005 version of King Kong (and the 2009 Star Trek remake) rattle the windows.
I'm still in the DC area. Where there is a definite dearth of good audio shops, I might add.
As for my undergrad time... I remember when Lauinger had not yet been renovated.
And when a late-April or May class in White-Gravenor meant a rather warm hour or two studying the Defenestration of Prague.
I remember Astronomy class in Reiss at 8:00 am.
Saxa Sundries in the basement of Healy. Sugar's on 36th Street.
It's been a while.
Some of my vintage stuff works well, like my Luxman components (four receivers and a tape deck, all in very good shape). Some of this old gear does not.
The Kenwood Super Eleven? Uh, no. Not yet, anyway.
The two Denon tape decks (the Luxman was a backup, originally) that need motors? Can't find a decent replacement motor that doesn't cost three figures.
The Arcam CD player? Needs a laser. Maybe even some capacitors replaced.
My Polk subwoofer that has a 50 watt amplifier and a 10 inch driver? Bottoms out fast, and gets boomy easily. So I have to baby it.
The 12 inch B&W sub with a 300 watt amp? I will check on that by Christmas. Life is too short to have anything but sterling low end. Bass that makes the 2005 version of King Kong (and the 2009 Star Trek remake) rattle the windows.
On the simples tlevel, let me ask you this: if you wiggle pots around and it ends up in smoke, what will you learn, assuming learning was the idea? Maybe, that it's not a good idea to mess around with pots, which is what i said. There is a chance you had to deal witha woefully incompetent tech so some adjustment may cure the problem, but if that person knows 50% of what they are doing, what makes you think going in blindly with meaybe 10% of that knowledge will result in you doing a better job? You asked about it, and i answered honestly - to be blunt, pots do not misadjust on their own (i.e. gnomes did not get in there over night and played with them, although an incompetent tech may well do it), unless they get damaged or corroded (in which case they are best replaced and then adjusted) - do you know how to recognise this?
I should also mention that often it is written on the PCB what the pots do. And, some settings are destructive (although not necesairly immediately so). Oh, and some CAN end up in your house burning down, and, obviously, poking around inside can cause electrocution, which is why it says on the back panel 'no user serviceable parts inside'. So, believe me, the analogy holds - I can tell you that from a lifetime of servicing and designing electronic equipment, including certifying it so ut may actually be sold to people. Some of this experience is way too many repairs of other people's 'repairs' or users fiddling around blindly with anything that fits a screwdriver. I will gladly admit that reading about it touches a nerve or two.
Why not type 'Kenwood super eleven service manual schematic' into google and see what it comes up with? Also, some patience may pay off - ask first (here?) then tweak pots. At that point you may actually know what they do.
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Kenwood Pots
I put the question on this site, with some of the background information, hoping that some Kenwood aficionado would be able to hazard an educated guess as to what is wrong. And possibly the extent of the problem(s). So far, no luck on that.
You mention the service manual schematic. I have the PDF, and I can barely make heads or tails of it. As I mentioned earlier to another diyAudio guy, I am a NEWB.
And no, there will be no re-enactments of the Chicago Fire. Basic precautions must be taken, and I do take them. When I am not home, the Kenwood is left switched off and unplugged. You mentioned that some people do electrocute themselves. In all my life, I have had one non-static electricity shock. From a bad light switch in a 100 year old house. And I have not just been lucky for over 20 years, I am actually careful. So I must not be as heedless as you seem to think I am.
I put the question on this site, with some of the background information, hoping that some Kenwood aficionado would be able to hazard an educated guess as to what is wrong. And possibly the extent of the problem(s). So far, no luck on that.
You mention the service manual schematic. I have the PDF, and I can barely make heads or tails of it. As I mentioned earlier to another diyAudio guy, I am a NEWB.
And no, there will be no re-enactments of the Chicago Fire. Basic precautions must be taken, and I do take them. When I am not home, the Kenwood is left switched off and unplugged. You mentioned that some people do electrocute themselves. In all my life, I have had one non-static electricity shock. From a bad light switch in a 100 year old house. And I have not just been lucky for over 20 years, I am actually careful. So I must not be as heedless as you seem to think I am.
Kenwood still problematic
I got the Kenwood back from the tech on Saturday.
A while back, I posted my Kenwood's issue, the bad left channel. Guys here mentioned the problem could be the trimmers, and I should replace them with multiturn resistors. I'll order them (3299W-1-502LF Bourns Trimmer Resistors - Through Hole) tomorrow, things got delayed as I haven't had the old Kenwood in my hands for a while. The tech has had it, and he told me last week that he'd fixed it. This is his second try in so doing. He replaced some of the caps, and all four output transistors. These are now On-Semi MJ21193 and 94.
The fix did not last. The distortion came back in less than two hours of use. What has caused me confusion (more than usual, anyway) is that the distortion is now in the right channel.
Time for my Wild Assed Guess. Could the balance potentiometer be the problem?
Thanks for any help you can render.
I got the Kenwood back from the tech on Saturday.
A while back, I posted my Kenwood's issue, the bad left channel. Guys here mentioned the problem could be the trimmers, and I should replace them with multiturn resistors. I'll order them (3299W-1-502LF Bourns Trimmer Resistors - Through Hole) tomorrow, things got delayed as I haven't had the old Kenwood in my hands for a while. The tech has had it, and he told me last week that he'd fixed it. This is his second try in so doing. He replaced some of the caps, and all four output transistors. These are now On-Semi MJ21193 and 94.
The fix did not last. The distortion came back in less than two hours of use. What has caused me confusion (more than usual, anyway) is that the distortion is now in the right channel.
Time for my Wild Assed Guess. Could the balance potentiometer be the problem?
Thanks for any help you can render.
This site promises that you can download the service manual for free after registering, but I haven't taken then up on the offer. 😉
Kenwood Super Eleven | Owners Manual, Service Manual, Schematics, Free Download | HiFi Engine
From the looks of it, there is quite a lot that can go wrong underneath the hood.
Kenwood Super Eleven | Owners Manual, Service Manual, Schematics, Free Download | HiFi Engine
From the looks of it, there is quite a lot that can go wrong underneath the hood.
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