Luxman L-85V – rebuilding amplifier boards

About a year or so ago I have purchased two Luxman L-85V amplifiers. Both not working. One was an easy fix as it only needed fuse. About $1.10 later, I had a nice working amplifier. The other amp had bigger problem. The amplifier boards had missing and mismatched transistors, burned out resistors and overall, they looked terrible. Swapping the boards from working amplifier brought the other amp to life so even with my limited electronics knowledge, I have decided to rebuild them. $55 later I had all the parts needed to do a complete rebuild. Honestly, the whole project took me about a year since I got distracted by family, other projects and bunch of other things. Just recently, I remembered that I have the boards in the closet. They were about 95% done. About an hour later all components were soldered in and the boards were ready for a test phase.

As always, I use DBT (dim bulb tester) to connect every project I am working on. In this case the DBT proved itself very useful. The moment I switched the power on, I got a bright light from the DBT. Back to the test bench checking every component. I have started with the obvious: transistors. I was almost sure that I got something wrong here. Well, I was right. I had two transistors incorrectly positioned on the board. After correcting the problem, I gave it another try. DBT still brightly lit. Since there was no smoke I have decided to check if I get any output. After connecting my iPod and cheap set of headphones, I got sound. Next I have tried to adjust BIAS and DC offset. That dimmed the light a bit but I was unable to get the BIAS down to 50mA as indicated in the service manual. The lowest setting on the trim pot got me down to about 190mA. That made the heatsinks very hot.

So again, I took the boards out and started checking the resistors values. To my surprise, I have put two resistors on the board according to the service manual and not the actual value of the resistor that was replaced. I am glad that I took a detailed picture of the boards before the disassembling them. I was able to read the resistor color codes of the old resistor. So I have replaced the parts with correct values and now I was able to adjust the BIAS down to 50mA. DBT was finally off.

Another test thru the headphones revealed what a great amplifier the Luxman is. It clearly tops all of my other gear that I own. On one hand there is no surprise as I own some low powered Marantz and Sansui models. But on the other hand this is a first amplifier that I can enjoy listening with all the tone controls disabled. The Luxman L-85V is very musical. Still a week after the rebuild was finished, I am listening to the Luxman amp with only loudness button on. All the other tone controls are defeated.

So now, few pictures from my rebuild. Here is a picture of the amplifier boards before rebuild. You can see mismatched transistors, burned out resistors and crappy service work that was performed in the past.

Luxman L-85V - rebuilding amplifier boards

Here are the same boards with some new components (NOTE: this picture was taken before the transistors and resistors were fixed).

Luxman L-85V - rebuilding amplifier boards

Here is the amplifier in my stereo rack next to the matching Luxman T-88V tuner.

Luxman L-85V - rebuilding amplifier boards

I already bought capacitors to do a recap of the power board so that’s going to be my next project. I also need to clean the switches and Deoxit all the pots. I did not want to bother with that before I was sure that I had a working amplifier.

Luxman L-85V - rebuilding amplifier boards

Thanks for reading.

18 thoughts on “Luxman L-85V – rebuilding amplifier boards

  1. Rafael R. Robles Reply

    Nice work on your L-85v… 😀

    I noticed that you’ve replaced the 2sd382/2sb537, what transistors did you put in?
    By the way I’m Raffy and after searching for a schematic and service manual for my Luxman L-505v it somehow led me to your site. Now you might be confused but the power amp boards of L-85v are similar (well not really) in configuration and placement of components although the only similar component that they both have is the 2sd382/2sb537.

    Mine got busted when I bought the unit. Had to find a suitable replacement for the output transistors and driver and right now it’s working albeit a bit problem on the right channel. The driver and output transistors are not matched (2sd424/MJ15004 & 2sd382/2sb546) which probably explains why the dc offset on this channel is always drifting (unstable) and heats too much.

    I hope you could me a little insight on how you made it your amp work.


  2. David Reply

    can you upload or send me the pic of the preamp stage PB-1033
    there are some diode missing when I take look at it so would like to compare with working set.
    I have purchased the same model and rebuilding amplifier stage but do not get any sound from the earphone when connect through the phone connector
    Any help will be appreciated

    • Alex Post authorReply

      Unfortunately, I did not take any pictures of the other boards when I recapped them. My Luxman is now out of rotation safely packed in storage. Looking at the schematic, there are 4 capacitors so I would replace those first. Then you have 14 diodes and 109-112 do not have values on the parts list in SM so I would assume that they were omitted on purpose.

  3. David Reply

    Also for the PB-1037 the two transistor Q10 and Q9 have there collector been cut-off in your picture is it normal? My initial board also did not have collector but by looking at the SM it does not make sense.

    I will first try to replace the 4 cap and try once more.

    By the way will the headphone work without the main amplifier stage(PB-1037)??
    To get the audio out to the headphone do I need to set the speaker to A or off??

    Thanks for your help

  4. Alex Post authorReply

    Yes, both transistors have the middle leg cut. It was like that in both of the L-85Vs I had. If I am not mistaken, headphones will not work without operational power board. When you look at the schematic, output for the headphones is taken directly from speaker output. They only added 680 Ohm resistors (R09 and R10) to limit the output.

  5. David Reply

    I have one more question. When I see your rebuilt amplifier you have one resistor that is not in the service manual(one close to left veractor). My original circuit had 4.7ohms is this close to what you had? also do you remeber which resistor value was different from the service manual??


  6. javi Reply

    Hello, casually, I´m trying to repeair the same board, the pb 1037…So I can read, there are two resistors that are not correct on the service manual…do you remember what number are and “the good” values? very thanks

  7. javi Reply

    well, I see again and again the manual service…there´s a difference on the part list: R 13 (5,6k) and R 16 (4,7K) and then, on the esquematic R 613 and R 616 that are 150 and 100 of value…is this the real trouble with the resistors?

  8. David Reply

    It will be great if you can tell me which resistor was different from the service manual.
    I got to the part where my two amplifier works but my operational power board is not working.(dead transistors)

    but would like to know which resistor it was that was different so that I could bias and set the dc offset



  9. javi Reply

    David, please….do you have the original board Pb1037 without any modification? (my boards are totally changed..) could you send me a photo of this board to my e-mail?

  10. Tony Reply

    Good afternoon Alex, I need to do exactly what you have done as the Luxman L-85V I have got is showing the same damage. I am having great difficulty sourcing a lot of the parts and was wondering if you still had a parts list of the replacements you used to assist in my rebuild. Any help would be appreciated as the code numbers for some of the transistors are proving impossible to find. Many thanks in advance for any help you could possibly offer.

  11. Alex Post authorReply

    Tony: When I ordered the parts, I went with the service manual values which were compared to the actual board (whenever possible). Unfortunately, I have all my documentation in storage now. I found an old Mouser order where some notes mention Luxman so this may be my parts list for the rebuild. You will still have to compare the values but you should be able to find out what replacements I have used for the out of production parts.

    Here is the link to the parts list:

  12. Bruno Louis Reply

    hi alex
    Nice work. Can you please tell me what pair of output transistor you used. the 2sd382 was replaced with MJE15030G. and for 2sb537 with what did you replaced it. thanks for replying

  13. Alex Post authorReply

    According to my notes from 2012, I have used MJ21193G for 2SA679 and MJ21194G for 2SC1079.

    • Bruno Louis Reply

      hi alex thanks for replying , one last question. Did you change the transistor on the output board

  14. Alex Post authorReply

    Bruno, if by output board, you mean the two amplifier boards that are pictured in the post, then yes. I did replace all parts on those boards.

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