luxman schematic, and advice needed

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monkeyworks

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Joined 2010
#1
Hi,
I'm new here, thank you for making me feel welcome. I've acquired a Luxman lv 102 which I'm trying to rescue. I'm hoping somebody has a schematic to share with me; it would really help me effect this repair. Additionally, I mean to replace the BJTs and Fets (one of the large transistors blew during diagnostics) and cannot discover current replacements to the originals - hence another reason I need the spec docs. If anybody out there knows which BJTs and Fets I can use to replace or upgrade the originals with, please pass that along. I can forward the designations printed on each transistor if anybody wants a crack at this. Thank you in advance, vic.
 
#2
Hi I have manual for LV103 which might be closely related if you cant find the 102. Luxman always used the best parts available so I wouldnt change much on them except if they are damaged. I suspect the mosfets you are talking about is 2sj115 and 2sk405, these you can still buy off ebay, not cheap as its dicontinued parts but its better to stay with originals as you may have to change compensation and biasing scheme if you use other parts.
 
#3
Thank you for your quick response. I would love to see the lv 103 manual. Can you email me a copy, or send a copy in the mail? The fets in the 102 are j77 and k214, not the same as in the 103. I hadn't thought to hunt for old stock transistors on ebay; I hope to find new product with comparable spec to the old. But I will check ebay now. Thank you again for your help and good ideas. vic.
 
#4
It is difficult sending manual as its 22mb, I dont think I can even email something so large so Ill try extract only the schematic but it seems its must different to your model then. Are those j77 and k216 fets used as outputs or something else, these you should also be able to locate from some ebay vendors at around 3 dollars a pop.
 
#5
I don't think the 103 manual is critical for me. The mosfets are part of the "driver circuitry" according to some poorly translated product literature. I found all 10 of the transistors for this amp on ebay (2 pair fets, 2pair matched BJTs, and one smaller pair BJTs)! They reside in a line mounted on the heat sink, in reflected pairs from the center. There is a single, very small transistor without markings mounted in the center on the heat sink and I have no idea what it is or what it's for. It has an offset metal clamp screwing it down on the sink, it's smaller than a kernel of corn. Any ideas?
 
#7
Interesting now I would like to see a schematic, anyway the small transistor is for temperature compensation, I wouldnt mess with it if its ok, what are the power Bjts on the heatsink.

Every single one in this range uses mosfets so Ill be surprised if this one doesnt, the other models have bjt drivers and mosfet outputs but seems this one has mosfet drivers and bjt outputs.
 
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#9
Bigred, you are spot on with the driver and output specs, that's exactly what's in my amp. I found a schematic/manual for the lv 101 here: Luxman LV101 Service Manual free download,schematics,datasheets,eeprom bins,pcb,repair info for test equipment and electronics, and it looks to be identical in layout but of lower power. It uses different transistors, but the same fets. At least the ones mounted on the heat sink.
I hope I am even working in the right direction here (I never described my problem here). I get no output at the speaker terminals, or the headphone jack. I get good voltage at the big caps. The spec sheet describes a bunch of other transistors throughout the amp; do I replace them all? Thank you all so much for your help so far. vic.
 
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