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Luxman L-100 woes

Do you have the correct rail voltages for the input and output stages of the left amp board?
 
sanjib said:
Do you have the correct rail voltages for the input and output stages of the left amp board?
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It appears all my voltages are correct. The L-100U (American model) has slight Power Supply board differences thaan on the widely available L-100 service manual. From my research my rail voltages are correct (on both power amp boards). Additionally when I swap the C11-C18 molex of each power amp board, the noise swaps channels. The noise does not follow along with one of the connectors.
 
You wrote earlier
"At the bottom of each power amp section there is the signal in connector essentially from the preamp section. At the top of each power amp section there is a connector with the audio output going to the relay prior to speaker output, and that connector also supplies the main power and filter caps. during troubleshooting I swapped the top connector on the power amp sections, thus swapping the main filter caps too and the noise did not follow the swap ( not unique to one filter cap). Hope this description helps."

By doing this you are also swapping the output. That means your output from the left amp is now in the right speaker and the output from the right amp is now in the left speaker. So, if you still have the noise in the left speaker that means, most probably the noise is coming from one bad filter capacitor which is supplying voltage to the left amp when it is connected in normal condition
 
sanjib said:
You wrote earlier
"At the bottom of each power amp section there is the signal in connector essentially from the preamp section. At the top of each power amp section there is a connector with the audio output going to the relay prior to speaker output, and that connector also supplies the main power and filter caps. during troubleshooting I swapped the top connector on the power amp sections, thus swapping the main filter caps too and the noise did not follow the swap ( not unique to one filter cap). Hope this description helps."

By doing this you are also swapping the output. That means your output from the left amp is now in the right speaker and the output from the right amp is now in the left speaker. So, if you still have the noise in the left speaker that means, most probably the noise is coming from one bad filter capacitor which is supplying voltage to the left amp when it is connected in normal condition
Click to expand...
Yes, I was aware that I was also swapping the output, but I'm also swapping the main filter caps at the same time. The filter caps are routed to each power amp board via the C11-C18 molex connector. Or at least that was my understanding.
 
What I mean is that by doing this connector swap if you still have the noise in your left speaker, that noise now is actually coming from the right amp. If you hear the noise in the right speaker after doing this swap you can assume that the filter capacitor is not the culprit.
 
sanjib said:
What I mean is that by doing this connector swap if you still have the noise in your left speaker, that noise now is actually coming from the right amp. If you hear the noise in the right speaker after doing this swap you can assume that the filter capacitor is not the culprit.
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Exactly! Perhaps my earlier explanation could have been better. When I swapped the connector the noise then appeared in the right channel. Indicating the filter cap is not the issue.
 
Okay, got it. At this point, my guess is any of the transistors as all of the capacitors are changed. First, it is better to check all solder joints and then each transistor, in particular differential pairs.
 
sanjib said:
Okay, got it. At this point, my guess is any of the transistors as all of the capacitors are changed. First, it is better to check all solder joints and then each transistor, in particular differential pairs.
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This had crossed my mind too. The only reason I had doubts is that in my continued troubleshootsing I swapped each of the power amp modules (They come out in their entirety), and the noise stayed in the left channel. It stayed in the left channel regardless of what power amp module I used on that channel. From what I can tell the noise follows and is dependent on where ever the left channel audio input connector is (the connector going to C09 and c10 on the power amp section). This is why I'm so perplexed.
 
When I swap the left and right audio input connectors at C09 and C10 on the power amp boards, the noise follows the left audio input connector. According to my swapping and troubleshooting, the noise is not specific to a filter cap or power amp board. Only to the left audio input connector going to C09 and C10. And as you noticed as well, there is not much going on between the main-in and C09 and C10 on power amp boards.
 
As I suggested in an earlier post, disconnect the input signal connector from pin C09 and C10. Connect C09 to the chassis ground and feed a signal directly to pin C10.
Have you done that?
 
SingleReel said:
When I swap the left and right audio input connectors at C09 and C10 on the power amp boards, the noise follows the left audio input connector. According to my swapping and troubleshooting, the noise is not specific to a filter cap or power amp board. Only to the left audio input connector going to C09 and C10. And as you noticed as well, there is not much going on between the main-in and C09 and C10 on power amp boards.
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Then it looks like the input signal connector cable.
 
The unit has a filter caps which designate to right and left channels?? Does this amp only have positive rails??
 
Pin C09 is connected to the ground through the amp board. What I meant, take one port from your signal generator, and the ground component of the port will go to C09 and the signal carrying part of the port will go to C10. Another thing, when you disconnect the left input signal port from the amp board you still hear the noise?
 
The Fuxtor said:
The unit has a filter caps which designate to right and left channels?? Does this amp only have positive rails??
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You are correct, it does not have filter caps designated to right and left. If I'm not mistaken it has two hot wires coming off each filter cap to each power amp board. The swap was technically not isolating one or the other, just the wiring.
 
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