TL;DR
What is the mechanical function of the transistor circled in red & yellow highlight imaged below?
Marantz SR18 in quite the state of disrepair lol
That said, 4/5 channels work and amp is used regularly at volume for hours at a time; so those channels are "solid" lol.
dc / power transistor bias are within spec and are not at extreme pot adjustments. yay!
Pre amp section does not work, last to "die" was the second zone RCA pre out...that no longer works.
The cpu side of the unit is broke; powers up fine, selecting input via knob "works", tuner wheel works (it indicates tuned, so signal is going that far in circuit), volume "works".
However all other buttons control primarily bass up or down. for example the A/D button increase bass tone control lol
So am firstly trying to get the RS Amplifier channel repaired.
After a excitement motivated repair attempt with only partial transistors replaced / tested properly the repair failed; however I think saved via current limiter bulb. The "precious" output transistors "survived".
That out of the way I've taken a more proper systematic approach and found a spoiled Toshiba C3426 (A1360; compliment). Fun having good circuits for simple resistance comparatives; that lead to the spoiled C3426.
That's all I see different from comparative measures of all transistors. I will replace the rest for which I have exact replacements just incase the originals are test passing, but otherwise spoiled.
So I've ordered a few pairs of C3426 / A1360; but time...
I have a few amps from around this "era", am not sure the purpose of this transistor other than is from power amp module of SR18; am wondering if I could find a good substitute in one of those of if this is a "unique" transistor / MUST be a direct replacement. ERR; First spare parts amp I checked had same ones! amp is nearly 10 years newer.
Imaged below is the location, circled in red & yellow highlight is spoiled transistor. Blue circle & yellow is compliment; it tests fine.
The resistor in blue is what measured wrong resistance in circuit (after replacing with proper spec new resistor); half the ohms, comparative to good channels resistor measures to spec in circuit...so traced it to transistor 2SC3423. Once removed the resistor measures in spec, cheap transistor tester indicates problem with transistor, hfe = 1.0 lol and this tester "measures" hfe on the high side.
Anyway, I cannot read the schematic yet so unsure the mechanical function of it within the circuit.
What is the mechanical function of the transistor circled in red & yellow highlight imaged below?
Marantz SR18 in quite the state of disrepair lol
That said, 4/5 channels work and amp is used regularly at volume for hours at a time; so those channels are "solid" lol.
dc / power transistor bias are within spec and are not at extreme pot adjustments. yay!
Pre amp section does not work, last to "die" was the second zone RCA pre out...that no longer works.
The cpu side of the unit is broke; powers up fine, selecting input via knob "works", tuner wheel works (it indicates tuned, so signal is going that far in circuit), volume "works".
However all other buttons control primarily bass up or down. for example the A/D button increase bass tone control lol
So am firstly trying to get the RS Amplifier channel repaired.
After a excitement motivated repair attempt with only partial transistors replaced / tested properly the repair failed; however I think saved via current limiter bulb. The "precious" output transistors "survived".
That out of the way I've taken a more proper systematic approach and found a spoiled Toshiba C3426 (A1360; compliment). Fun having good circuits for simple resistance comparatives; that lead to the spoiled C3426.
That's all I see different from comparative measures of all transistors. I will replace the rest for which I have exact replacements just incase the originals are test passing, but otherwise spoiled.
So I've ordered a few pairs of C3426 / A1360; but time...
I have a few amps from around this "era", am not sure the purpose of this transistor other than is from power amp module of SR18; am wondering if I could find a good substitute in one of those of if this is a "unique" transistor / MUST be a direct replacement. ERR; First spare parts amp I checked had same ones! amp is nearly 10 years newer.
Imaged below is the location, circled in red & yellow highlight is spoiled transistor. Blue circle & yellow is compliment; it tests fine.
The resistor in blue is what measured wrong resistance in circuit (after replacing with proper spec new resistor); half the ohms, comparative to good channels resistor measures to spec in circuit...so traced it to transistor 2SC3423. Once removed the resistor measures in spec, cheap transistor tester indicates problem with transistor, hfe = 1.0 lol and this tester "measures" hfe on the high side.
Anyway, I cannot read the schematic yet so unsure the mechanical function of it within the circuit.
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