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Luxman L-100 woes

quadmatrix82

quadmatrix82

AK Subscriber
Subscriber
Hi all hoping to get some help on my Luxman L-100, it’s started blowing the main fuse and the w04 rectifier keeps shorting on the power supply board d901

outputs all test good as do the drivers, the amp is recapped excluding the main filter caps, confirming able to get ~57.5v +/- when testing the power supply new trimmers installed too I did notice adjustments hardly make a difference.

bias and dc offset are calibrated well with original trimmers and seem to hold steady.

The rectifier and 3.15a fuse blow on power on, any tips where I can look next to hunt this issue down? Thanks
 
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I can not confirm by the picture (sometimes, the silkscreen is wrong). You must follow the traces from the rectifier to the capacitors. There is almost no current delivered by this circuit. There must be a problem with one of the capacitors.
 
ecluser said:
I can not confirm by the picture (sometimes, the silkscreen is wrong). You must follow the traces from the rectifier to the capacitors. There is almost no current delivered by this circuit. There must be a problem with one of the capacitors.
Click to expand...

ok I will double check but pretty sure they are ok as they have been in place for a few years with no trouble until now (both 33uf 100v Panasonic FC)
I’m thinking maybe the power filter capacitors are failing? They are still original ?
 
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There is no relation between D901 and the main power filter capacitors. D901 is feed by another secondary output from the power transformer. Did you try the amp on a DBT? You might have a partial short at one of the outputs C07S~C10S on the regulator board. These outputs feed the front stage of the power amplifier. That stage doesn't draw a lot of current. Check C417, C416.
 
ecluser said:
There is no relation between D901 and the main power filter capacitors. D901 is feed by another secondary output from the power transformer. Did you try the amp on a DBT? You might have a partial short at one of the outputs C07S~C10S on the regulator board. These outputs feed the front stage of the power amplifier. That stage doesn't draw a lot of current. Check C417, C416.
Click to expand...


Thankyou! Good to know, I will check these and revert with an update
 
ecluser said:
There is no relation between D901 and the main power filter capacitors. D901 is feed by another secondary output from the power transformer. Did you try the amp on a DBT? You might have a partial short at one of the outputs C07S~C10S on the regulator board. These outputs feed the front stage of the power amplifier. That stage doesn't draw a lot of current. Check C417, C416.
Click to expand...
I didn’t try with a dim bulb, but I will now moving forward knowing there’s an issue,

I checked c416 and c417 they are new and seem fine.

As for c07s-c10s do you mean the 2sa653 and 2sc1161 Q901/2 TO66 transistors? I pulled these both and tested well on my transistor tester and with a diode check on the multimeter reapplied thermal grease and refitted for now
 
What voltage do you have at the collector of Q901, Q902, when the amp is on a DBT? You must put the amp on a DBT since the main fuse blows.
 
ecluser said:
What voltage do you have at the collector of Q901, Q902, when the amp is on a DBT? You must put the amp on a DBT since the main fuse blows.
Click to expand...
I will check and revert, wondering if it’s possible the new trim pots need re adjusting for the power supply voltage they didn’t seem to adjust much at all

Since last post I checked q907-8 while they test ok, the gain hfe is about 100hfe apart I might see if I can some better matched pair to replace them at least
 
ecluser said:
What voltage do you have at the collector of Q901, Q902, when the amp is on a DBT? You must put the amp on a DBT since the main fuse blows.
Click to expand...
Ok I have tested with the dim bulb, I used a 100w globe it stays bright and doesn’t dim, with the dim bulb the fuse and rectifier don’t blow, I don’t see any shorts on the power supply board or the main amp modules,
 
Make sure D901 is properly oriented on the board. Disconnect the wires at C07, C08, C09 and C10. What voltage do you get between C01 and C02 then?
 
If you disconnect the wires from the transformer at C01 and C02, do you have the same voltage between those wires?
 
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