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Luxman R-117 distortion in the mid and upper range.

chazix said:
I think I risk being pedantic here, and I apologize if I am. But it is quite common for distortion problems to NOT be evident with headphones, due to their much lighter load on the power amps compared to almost any speaker.

Not saying that that is relevant in this particular case, but I think it could be.

As long as I'm kibittzing, I'd like to highlight that the symptom, as described, seems like something that is affecting both left and right channels. It's not a sure thing, but that tends to implicate problems in circuitry that is common to both channels, like power supplies.

Among the common power supplies that feed the R-117's power amps are + and - 16V supplies for the differential stages. The power amps might be able to limp along with one of those supplies being absent or low, so those are something that a tech might want to check.
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Or one of the transistors in the diff pair(s) or one nearby or a bad component in or near the diff amps causing them to become unequal. I agree with checking PS feeds. I don't think OP has a meter or other test gear though, and maybe not the effort or time to learn how to troubleshoot this. He may be too busy with other pursuits. He has not reposted now so I think we lost him possibly. and to RVT1K I think my post about headphones was #3. Your idea about trying different speakers was also valid though. I was just trying to cut to the chase faster with headphones which are easier to connect than speakers and could tell more I think about where issue lies in this amp depending on where headphones output is given in the amp. Maybe isolating it to the pre -section.
Mr. Bill
 
Mr Bill said:
Sounds like you have a bad component most likely a transistor or an electrolytic cap somewhere in the audio circuit. A good place to start would be to measure all the power supply voltages with a meter to make sure everything there looks to be in order. Then I would start with the freeze spray following the audio path through the various circuits.
Do you have an access to an oscilloscope and a meter and some type of source that would output an audio tones like a signal generator or a CD player with a test CD containing audio tones ? These 3 test items can be very useful for troubleshooting issues such as this. Remember I am only 20 to 30 minutes away should you need to bring it here to try finding your issue. Most good car parts stores sell freeze spray under $20 a can. Auto techs use it also for checking out suspected bad sensors in cars and trucks.
GOOD LUCK
Mr. Bill
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Hi Mr. Bill and all those who have contributed to this thread inquiry.
Been struggling these past few days with my phone photos and downloading images to my laptop. Still out of commission but I found this undercover image of the R117.
I popped the top on my unit and was tapping, wiggling wire harnesses and a general observation looking for anything unusual.
I spotted a burn mark transferred to the underside of the cover.
Burn mark coincides with the middle blue cap shown in the middle of the image.
I'm not sure if this is an amplification board or pre-amp board but the cap has leaked, possibly burst.
Assuming that there could be further damage to the greater board.
I haven't looked at the service manual schematic as yet but this is at least one failure point I discovered.
And you are correct on my resources and time. I have none of either to pursue this in depth by myself. My lot in life.
I have no equipment but for an ohm meter.
So yes, I would be needing assistance on this and would greatly appreciate your help if you have the time and interest. (I have the interest to learn more and participate., just not lots of free time).

R-117 Under the Hood.jpg
 
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I spent a few minutes this am looking at the schematic. Looks like C 751, 1000 Ufd @35V electro cap is the one in the middle that has self destructed on you. Does the picture you posted show the top or bottom cover removed ? I am just curious since I have never worked on one of these before. I would suggest NOT running the amp until we replace the bad cap and maybe also its' 2 mates C752 and C756 so they don't cause more trouble to you in a short period of time. We will also need to check the full wave bridge and the regulator transistor that is on the same line. You did a good job spotting this issue. I will try calling you soon at number posted in your PM to me.Repair manual posted below.
Mr. Bill


I see now after re-reading your last post that you removed the top cover. There is good reason why this capacitor failed as there are parts just below it / them that generate a lot of heat ! ( full wave bridge and voltage regulator transistor ) And a Large power transformer right next to it also which generates some heat. Over time this will bake out the electrolyte ( 99.9 % pure Glycol ) and cause the capacitor ( s ) to fail. Will audio design engineers EVER learn not to put electrolytic caps close by heat producing parts.
Mr. Bill
 
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Well dbtommy brought me his Luxman R-117 today and I took the PS apart to get to C 751, C 752, and C 756. That was sort of a task separating the 2 boards ! If they were not glued in at the factory then they are shot because of all of the residue left behind all over the caps and board. C 757 also was covered and had a leg break off while I was attempting to remove the dark brown residue from it. Also R 759 had its lead closest to this bank of caps turn green with oxidation. Not much but some. I cleaned it all off best as possible and also re-soldered that 1 leg on R 759 as it appeared to have a cracked solder joint around the soldered connection on the foil side of the board.

ANY SUGGESTIONS on what parts I should use for best life expectancy and where to get the 4 electrolytic caps. Is there a B.O.M. for these on AK with valid PN's for buying them now in 2025 ? NEED SAME Form Factor / mechanical sizes to fit them in here and at least the same tolerance and heat spec. I just cant understand why the designers did not realize this to be a ticking heat failure time bomb in these amps the way these components were placed. I can post photos later. Anyone that has not gone here yet with a Luxman R-117 had better take a look at this thread and do the same things I am doing. before they experience this same failure mode.
UUUUGGHHH Mr. Bill
 
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Mr Bill said:
ANY SUGGESTIONS on what parts I should use for best life expectancy and where to get the 4 electrolytic caps.
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Good luck with this!

Recently, when you have tight fits, I will mic the dimensions. BUT, suppliers have sent the wrong parts. So, I end up buying the same parts from several suppliers in the hope of finding the correct ones.

This all makes the fix take longer and longer... :(

For the last few amps like this, I've actually bought donor units (shh, don't tell the other techs) to experiment with the spare boards. And not to be forced to save the only one.

Personally, I've stopped fixing these smooshed, high-density, complicated units.
 
Found in my stash a 47 ufd rated at 50 V and 105 degrees C. I need to pop it on my old Tektronix curve tracer and see if it is resistive yet as it is a used one that will fit in the space for the old 35 volt part. Now I just need the 3 1000 ufd at 35 volt caps. Anyone have 3 I can purchase or trade for ? The originals have a Luxman PN which does not mean much I think 35 years later. They were made by ELY ? never heard of them before..... THANKS Mr. Bill

PS update: These caps are 1/2" diameter by about 1" in height OK if they are shorter in height but can't change diameter as they are right next to each other. These caps all still work but are slightly leaky and low in value ( measured 924 ufd, 944 ufd and 937 ufd. I believe now that the brown crap all over them was glue from the manufacturing process, not leakage. This glue was also all over closely spaced components including 1 lead of the resistor R 759 which was just starting to turn green at the junction with the component side of the circuit board. Solder side of this same connection had a micro crack ring all around that solder joint. Cleaned it all up and am measuring values of all parts in the area. I have read and therefore know use of these glues by some manufacturers has caused similar issues on also other brands of equipment.
 
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Mr Boochie said:
Good luck with this!

Recently, when you have tight fits, I will mic the dimensions. BUT, suppliers have sent the wrong parts. So, I end up buying the same parts from several suppliers in the hope of finding the correct ones.

This all makes the fix take longer and longer... :(

For the last few amps like this, I've actually bought donor units (shh, don't tell the other techs) to experiment with the spare boards. And not to be forced to save the only one.

Personally, I've stopped fixing these smooshed, high-density, complicated units.
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Mr. Boochie I totally understand.... but this amp is a worthy old unit in nice original condition. I am just hoping that this is all that is wrong with it right now.
Mr. Bill
 
OK I replaced caps in PS and re-soldered 2 bad power resistor leads. Now amp plays OK except no center imaging. I play a CD and vocals disappear when balance centered.
turn balance off center either left or right and vocals reappear either to left or right depending on which way balance control is turned. ANY ideas out there before I waste a lot of time trying to troubleshoot this issue ? I could use some help this is my first repair on Luxman R-117. A very complicated system.
Mr. Bill
 
Mr Bill said:
OK I replaced caps in PS and re-soldered 2 bad power resistor leads. Now amp plays OK except no center imaging. I play a CD and vocals disappear when balance centered.
turn balance off center either left or right and vocals reappear either to left or right depending on which way balance control is turned. ANY ideas out there before I waste a lot of time trying to troubleshoot this issue ? I could use some help this is my first repair on Luxman R-117. A very complicated system.
Mr. Bill
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Wow! My wild-@ss guess would be centered around that balance section (and perhaps, also, the tone stack-sections). You are getting some oddball positive-negative-canceling interactions going on.

Those can be a beech to nail down. Perhaps start with a thorough inspection of all solder points and any damaged components in those areas. Check the boards for tracer damage and lifted pads.

Good luck! I like using this and a good lamp to inspect.
 
Thanks Mr. Boochie: Yes I have an optivisor and always use it which is how I spotted the 2 bad solder joints on the 2 PS power resistor leads. I call them 4 eyes 1 more than a minion. n n Maybe I should change my handle on AK to 4 eyed Minion ! I am not sure where this fault lies there are also analog IC switches in the audio chain....
Mr. Bill still for now !
 
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Your new avatar!
 
Trying to help out a fellow AK-er any Luxman R-117 owners or Luxman repair techs seen this before ? when balance on center no vocals from either FM or CD either with CD Direct button in or out. Switch on back of unit for OFF ON Signal Processior Unit IS IN OFF position. traced signal on schematic. appears could be balance controls. I do not want to clean it as I have read warnings that they use thin carbon traces in these controls. Signal passes through many other boards looks like including analog switch chips and a few Op amp circuits. HELP NEEDED PLEASE Mr. Bill Still I am doing this for free to try to help a fellow AK'er.
 
Mr Bill said:
appears could be balance controls.
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If the block diagram in the SM that I have is to be believed (hardly a guarantee), the balance control is not enabled when using the CD input with "CD Direct" selected. Does that seem to be true?

It's not clear to me whether anyone has used the preamp in/out connections to localize the fault to either the preamp or power amp. Especially with a very odd symptom, I would think this would be high on the priority list.
 
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