Luxman R-1050 Left Channel not working
Hi, I've been reading through this forum, but I'm not sure if I have a similar problem. I was able to grab my dad's old 1050 before he tossed it because it wasn't outputting any sound anymore. I did a little research and decided to replace all of the fuses on the amplification board and Bam! it's alive! however, I can not get any audio to come out of the left channel. I have tried both the A and B outputs, and my headphones, and no audio comes out of the left channel for any of those outputs. The left channel LEDs on the front also don't light up, but the right channel LEDs do.
I'm a novice when it comes to audio equipment repair, but I do have some basic electronics and soldering knowledge. Does anyone have any suggestions as to what could be wrong here?
Thanks.
Hi, I've been reading through this forum, but I'm not sure if I have a similar problem. I was able to grab my dad's old 1050 before he tossed it because it wasn't outputting any sound anymore. I did a little research and decided to replace all of the fuses on the amplification board and Bam! it's alive! however, I can not get any audio to come out of the left channel. I have tried both the A and B outputs, and my headphones, and no audio comes out of the left channel for any of those outputs. The left channel LEDs on the front also don't light up, but the right channel LEDs do.
I'm a novice when it comes to audio equipment repair, but I do have some basic electronics and soldering knowledge. Does anyone have any suggestions as to what could be wrong here?
Thanks.
Got a multimeter? That's the minimum you'll need.
Also, no audio as in no audio at all? Not even the tiniest bit of hiss?
It's no surprise that the level meter is not showing anything, the signal is tapped off pretty much right at the output.
Have you checked the fuses again that you replaced? If one channel was presenting a dead short because e.g. the outputs are shorted, they may have blown again right away.
If so: Poke around the outputs (Q109/110) and drivers (Q107/108) with the diode test, noting down what you find. Also check their emitter resistors.
Looking at the schematic, I can see a few potential trouble spots.
There's a VD1221 bias diode (D102) in the current source circuit, which is the kind of type that occasionally goes intermittent or open. Some other components may not appreciate that. The current source transistor (2SA915) also is one of those NEC jobbies in rectangular case that have a tendency to go leaky (but should not cause the whole amp to blow up).
The bias transistor is a 2SC945, which is a TO-92 case type, not entirely ideal when it comes to thermal coupling to a heatsink (which is important for thermal stability). Verify that it is firmly attached; any thermal grease is likely to be entirely dry at this point.
There also are some electrolytic caps on the rails, which when dried out could have the amp oscillating and should be replaced (C107-109). Specs on C109 also are unclear - the schematic says it's a 2.2 µF 50 V, which would be foolishly undersized for a nominal 48 V DC, while the parts list states a 500 V type, which seems unrealistic, so better look at what it actually is. I would have chose the same value as C108, i.e. a 100 V type.
Speaking of electrolytics, C103 is only a 10 V type and polar to boot, it would be easily damaged during a fault condition. I would ideally see a 50 V bipolar type here if it can be made to fit at all. C104 could also be increased in value and voltage rating easily - if a 47 µF 25 V fits, use that.
Hmm, the big 10000 µF ones are rated at only 50 V. Granted, that's probably WV, still seems a tad tight in the long run. If any of them gets appreciably warm after some operation, it may exhibit excessive leakage.
Do not buy components from questionable suppliers on eBay if you can help it, especially unobtainium transistors. Find more easily sourced alternatives.
Also, no audio as in no audio at all? Not even the tiniest bit of hiss?
It's no surprise that the level meter is not showing anything, the signal is tapped off pretty much right at the output.
Have you checked the fuses again that you replaced? If one channel was presenting a dead short because e.g. the outputs are shorted, they may have blown again right away.
If so: Poke around the outputs (Q109/110) and drivers (Q107/108) with the diode test, noting down what you find. Also check their emitter resistors.
Looking at the schematic, I can see a few potential trouble spots.
There's a VD1221 bias diode (D102) in the current source circuit, which is the kind of type that occasionally goes intermittent or open. Some other components may not appreciate that. The current source transistor (2SA915) also is one of those NEC jobbies in rectangular case that have a tendency to go leaky (but should not cause the whole amp to blow up).
The bias transistor is a 2SC945, which is a TO-92 case type, not entirely ideal when it comes to thermal coupling to a heatsink (which is important for thermal stability). Verify that it is firmly attached; any thermal grease is likely to be entirely dry at this point.
There also are some electrolytic caps on the rails, which when dried out could have the amp oscillating and should be replaced (C107-109). Specs on C109 also are unclear - the schematic says it's a 2.2 µF 50 V, which would be foolishly undersized for a nominal 48 V DC, while the parts list states a 500 V type, which seems unrealistic, so better look at what it actually is. I would have chose the same value as C108, i.e. a 100 V type.
Speaking of electrolytics, C103 is only a 10 V type and polar to boot, it would be easily damaged during a fault condition. I would ideally see a 50 V bipolar type here if it can be made to fit at all. C104 could also be increased in value and voltage rating easily - if a 47 µF 25 V fits, use that.
Hmm, the big 10000 µF ones are rated at only 50 V. Granted, that's probably WV, still seems a tad tight in the long run. If any of them gets appreciably warm after some operation, it may exhibit excessive leakage.
Do not buy components from questionable suppliers on eBay if you can help it, especially unobtainium transistors. Find more easily sourced alternatives.
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