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Old 14th February 2014, 06:18 PM   #1
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Default Leak Delta 70

my delta 70 was running OK then one channel suddenly became very very loud. I could only use the amlifier with the balance contol fully clockwise. I isolated the fault to one plug-in board (not the pre-amp board). I have the circuit diagram, but need help to pin poibt the faulty component. I have checked the board for bad solder joints. Any suggestions please.
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Old 14th February 2014, 06:27 PM   #2
Mooly is offline Mooly  United Kingdom
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We would need to see the circuit for sure. Strange fault... could it be a floating ground to the volume control such that there is no attenuation on that channel... or a faulty control.
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Old 14th February 2014, 06:32 PM   #3
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Hopefully the negative feedback doesn't go through the pins of the pcb sockets!

Tony83: How was the sound ( when it was working well) ? A modern version with newer transistors sounds quite good.
What speakers are you using?
Cheers.
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Old 14th February 2014, 06:52 PM   #4
Mooly is offline Mooly  United Kingdom
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Looks like the NFB does go through the sockets. Lol... at least they are in the loop

Make sure (measure on ohms range with amp OFF) that point "A" (measure on R36) goes down to virtually zero ohms at minimum volume. Check that R48 is OK and that all the plus/sockets are good. Many of the electroylitics will be getting past it too and it would all benefit from a re-cap... but find the fault first.

Edit... measure the resistance above with respect to ground (the thick black line).
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