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Conrad-Johnson It just sounds right

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  #1  
Old 06-06-2014, 02:50 AM
stargazerang stargazerang is offline
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Default LP125 M Trouble shooting

Hello

Last edited by stargazerang; 07-06-2015 at 09:08 AM. Reason: the pre is skewed towards the other channel
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  #2  
Old 06-06-2014, 06:51 AM
AudioGremlin AudioGremlin is offline
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Assuming all was well before the problem i.e all bias leds out. First check that the preamplifier is outputting a signaI, test by swapping over L&R outputs at the preamp if the other channel is working okay. Regarding the power amplifier I would also expect an led indication when a fuse blows. However it does no harm to simply remove the fuse & look, it may be obvious if it has blown, if not so you can easily check it for continuity with a multimeter if you have one.
Usually there are two fuses on tube power amplifiers, one for mains supply & the other for B+ (high voltage for tubes), your mains fuse is obviously okay so try to locate and check the B+ fuse as it may have blown due to a tube fault.

Last edited by AudioGremlin; 06-06-2014 at 09:03 AM.
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Old 06-06-2014, 09:47 AM
ronenash ronenash is offline
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Also you can try to replace the input tubes. If the LED at the rear of the amp does not light its not an output tube problem. Just make sure you do not put the input tubes from the faulty channel in the healthy channel. You do not want to cause damage to the good channel. There are a couple of fuses inside the amp but I suspect this is not the problem.

Most likely it either a preamp problem or an I put tube or phase splitter problem.
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Old 06-20-2014, 06:37 AM
stargazerang stargazerang is offline
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No problem

Last edited by stargazerang; 07-06-2015 at 08:52 AM.
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  #5  
Old 06-20-2014, 06:59 AM
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Briz Vegaas Briz Vegaas is offline
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Never switch tubes to trouble shoot. If you have a bad tube and move it to another position it can damage the electronics behind that slot as well. My dealer, who builds valve amps of his own, says always use fresh tubes to trouble shoot.
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Old 06-20-2014, 07:00 AM
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Myles B. Astor Myles B. Astor is offline
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Quote:
Originally Posted by ronenash View Post
Also you can try to replace the input tubes. If the LED at the rear of the amp does not light its not an output tube problem. Just make sure you do not put the input tubes from the faulty channel in the healthy channel. You do not want to cause damage to the good channel. There are a couple of fuses inside the amp but I suspect this is not the problem.

Most likely it either a preamp problem or an I put tube or phase splitter problem.
Not necessarily in my experience. Depends on whether you're using a 6550 or KT120 output tube. I've found that KT120s out and out die rather than going cherry red like the 6550s. But the KT120s don't take the fuse out. At least not the three that have died in my amplifiers. OTOH, I doubt it's the input tubes. They go noisy but rarely die. But the amplifier will usually still play albeit lacking dynamics, balances and will still be distorted.

Can you bias all the output tubes? Are all the output tubes lit? If one isn't lit or doesn't bias, you've found the bad tube. If not, maybe there's a bigger issue and there's an internal fuse blown. I'd definitely check with cj.
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Last edited by Myles B. Astor; 06-20-2014 at 07:03 AM.
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Old 06-20-2014, 08:45 AM
stargazerang stargazerang is offline
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Thanks

Last edited by stargazerang; 07-06-2015 at 08:53 AM.
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Old 06-20-2014, 09:26 AM
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Did you switch speaker cables and get sound in the right channel?

Then I'd check with cj. Usually they say that if the internal fuse blows, there's a bigger issue. But sometimes, they'll tell you to try swapping it out then too.
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Last edited by Myles B. Astor; 06-20-2014 at 09:29 AM.
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  #9  
Old 06-20-2014, 09:29 AM
stargazerang stargazerang is offline
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No issues

Last edited by stargazerang; 07-06-2015 at 09:09 AM.
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  #10  
Old 06-20-2014, 09:32 AM
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Myles B. Astor Myles B. Astor is offline
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Quote:
Originally Posted by stargazerang View Post
Meaning you using the right amp to drive left speaker and vice versa?

Or physically switch the cable for the left amp and hook it up to the right channel amp?

Both I have not done
The first: use the left amp to drive the right speaker and right amp to drive the left speaker. See if the problem moves to the other channel (or highly unlikely, maybe there's an issue with the connection at the binding post and unhooking the cable cures your ills.)
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