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Old 11th October 2012, 02:17 PM   #1
ivtec is offline ivtec  United States
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Default Instrument Keyboad audio Fault?

Hi guys i have a Music instrument keyboard Technics Kn2000,that i few years ago have shorten the audio line out on the Left Chan,because of shorted cables.
last year i decided to repair it and i did re-pared it by changing Trans. A1015 and the left Chan on line out was working again,but since then when i switch on the power, it powers up but some times with no sound,i have to push power switch off and on button one more time or two times and some time 3.Besides that it works great,
I posted some pics of the circuit where i swapped the trans,A1015 should i look at anything else besides the transistor it self, that might not be the right specs i found this one on my electronic components scrap,Also on the Big Heat sink where the Audio Amp Trans are (D1266)can barely see the #'s looks heated up. thanks in advance.
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Old 12th October 2012, 10:59 PM   #2
ivtec is offline ivtec  United States
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Originally Posted by ivtec View Post
Hi guys i have a Music instrument keyboard Technics Kn2000,that i few years ago have shorten the audio line out on the Left Chan,because of shorted cables.
last year i decided to repair it and i did re-pared it by changing Trans. A1015 and the left Chan on line out was working again,but since then when i switch on the power, it powers up but some times with no sound,i have to push power switch off and on button one more time or two times and some time 3.Besides that it works great,
I posted some pics of the circuit where i swapped the trans,A1015 should i look at anything else besides the transistor it self, that might not be the right specs i found this one on my electronic components scrap,Also on the Big Heat sink where the Audio Amp Trans are (D1266)can barely see the #'s looks heated up. thanks in advance.

Hi guys i think i found the fault for the intermittent sound on\off,i found regulator 7805 with bad pin joints,for now is working fine, but i have my doubts that a regulator has any influence on sound,correct me if i'm wrong.
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Old 12th October 2012, 11:15 PM   #3
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Depending on the schematic, ittermittant power supply can really mess up a circuit. Sagged power supply and noisy power supply can hurt, also. Good stable supplies is step two of a debug routine, right after checking the fuses and the wall plug for power.
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Old 13th October 2012, 12:01 AM   #4
ivtec is offline ivtec  United States
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Originally Posted by indianajo View Post
Depending on the schematic, intermittent power supply can really mess up a circuit. Sagged power supply and noisy power supply can hurt, also. Good stable supplies is step two of a debug routine, right after checking the fuses and the wall plug for power.
Thanks indanojo; appreciate your input, there are 2 regulators on the right side as you see in the pic bellow,one is 7805 5v reg. the one i re soldered the other is 7905 you think the 7805 reg could be the one that cause the sound mute upon power on? thanks in advance.
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Old 13th October 2012, 12:55 AM   #5
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No schematic diagram, no opinion. However bad solder joints that can be spotted visually are one of the quick tricks of the experienced repairman. I'm not that experienced yet, thrashing around all the ways I have made a solder joint look good and have it still bad.
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