Dear AudioKarma experts,
Recently I have bought at Japanese auction Nakamichi LX-5 cassette deck in quite a poor conditions and working on its repair and maintenance now. Mechanical part is already competed, everything works fine and the sound is expectedly very good! However, I have stacked with one very irregular problem with led indicator that I never came across before. Actually, the level meter for Right channel looks like "doubled" - means there are two "zero-points" in one row (at -40db and -5db) - please refer to pic.1 and when the signal is on they works simultaneously (pic.2). When the signal in higher than -5db, then these two indicator lines are overlapping so the led at -5db and further lit up twice lighter (pic3).
I thought this is a problem with a level meter driver IC and have already ordered one from China, but just in case I tried to connect the level meter assembly from perfectly working LX-3 and surprisingly got the same result! So, the problem is definitely not with the level meter indicator, but somewhere in level meter circuit on the main PCB board (pic.5). Unfortunately I have no schematic diagram of the the main PCB board (somehow it is missed in service manual) and I am not so familiar with level indicator electronic part, so I have just roughly checked the transistors, diodes, resistors and capacitors around and could not find any broken parts...
So, I would like to ask for a piece of advise from an expert who might know about such a problem or just a person with good understanding of electronics in general and led indicator circuits in particular - where the source of such a strange behavior could be and what should I check.
Thank you in advance!!!
Best regards
Recently I have bought at Japanese auction Nakamichi LX-5 cassette deck in quite a poor conditions and working on its repair and maintenance now. Mechanical part is already competed, everything works fine and the sound is expectedly very good! However, I have stacked with one very irregular problem with led indicator that I never came across before. Actually, the level meter for Right channel looks like "doubled" - means there are two "zero-points" in one row (at -40db and -5db) - please refer to pic.1 and when the signal is on they works simultaneously (pic.2). When the signal in higher than -5db, then these two indicator lines are overlapping so the led at -5db and further lit up twice lighter (pic3).
I thought this is a problem with a level meter driver IC and have already ordered one from China, but just in case I tried to connect the level meter assembly from perfectly working LX-3 and surprisingly got the same result! So, the problem is definitely not with the level meter indicator, but somewhere in level meter circuit on the main PCB board (pic.5). Unfortunately I have no schematic diagram of the the main PCB board (somehow it is missed in service manual) and I am not so familiar with level indicator electronic part, so I have just roughly checked the transistors, diodes, resistors and capacitors around and could not find any broken parts...
So, I would like to ask for a piece of advise from an expert who might know about such a problem or just a person with good understanding of electronics in general and led indicator circuits in particular - where the source of such a strange behavior could be and what should I check.
Thank you in advance!!!
Best regards
