Hello,
I new to working on electronics. I'm using tutorials, YouTube, and other sources to try to learn. I'm trying to resurrect a Proton D540 Amp and I'm stuck.
Here's what's up:
1. Unit powers on and lights.
2. Relay kicks in.
3. No sound.
Here's what I've done:
1. I checked both sides of the board for damaged components and broken soldered joints.
2. I replaced 2 capacitors that leaked from the bottom (capacitor plague?)
3. I've followed most of the power through the circuit
4. I've tested the resistors and capacitors around the plague
5. I've measured the transistors. Specs say order is B-C-E. Some seem reversed.Possible or bad?
5. I measure mv amounts coming through both A and B speaker connects when they are selected.
Obviously, as a newbie, I might have done any of these steps incorrectly!
What might I be missing? Thanks so much for any help!
Joel Kline
I new to working on electronics. I'm using tutorials, YouTube, and other sources to try to learn. I'm trying to resurrect a Proton D540 Amp and I'm stuck.
Here's what's up:
1. Unit powers on and lights.
2. Relay kicks in.
3. No sound.
Here's what I've done:
1. I checked both sides of the board for damaged components and broken soldered joints.
2. I replaced 2 capacitors that leaked from the bottom (capacitor plague?)
3. I've followed most of the power through the circuit
4. I've tested the resistors and capacitors around the plague
5. I've measured the transistors. Specs say order is B-C-E. Some seem reversed.Possible or bad?
5. I measure mv amounts coming through both A and B speaker connects when they are selected.
Obviously, as a newbie, I might have done any of these steps incorrectly!
What might I be missing? Thanks so much for any help!
Joel Kline
I am surprised nobody has come to your aid, I waited . Anyway - 1- all the voltages on the supply rails are correct----yes ? 2-specs say--B-C-E ---some seem reversed ? --- I take it you are using a multimeter diode test on them ? If so you should get a lowish resistance measuring --base to collector and base to emitter, unless there is a parallel resistor across them giving a different reading while in circuit ---- NONE of them should be a full short circuit. 3- the millivolts at the output could be DC offset , your lucky its not a full voltage rail value . To really test those BJT,s (transistors ) you would need to unsolder them and test out of circuit . But as I said if any are a full short circuit --or full open circuit while testing then unsolder them and check out of circuit . I do not have a schematic but I am sure somebody might supply one.
OK, first of all:
Are the pre - power bridge jumpers installed at the back? Super common issue in units set up like this.
If they are, attempt to verify both preamp and power amp separately (the old "divide and conquer" approach):
Attach a variable output level source device to the power amp inputs (like a phone or MP3 player), or another preamp.
Attempt to run the preamp outputs into another power amp or a line-level input or something.
Are the pre - power bridge jumpers installed at the back? Super common issue in units set up like this.
If they are, attempt to verify both preamp and power amp separately (the old "divide and conquer" approach):
Attach a variable output level source device to the power amp inputs (like a phone or MP3 player), or another preamp.
Attempt to run the preamp outputs into another power amp or a line-level input or something.
The transistors are very unlikely to be installed wrongly, but you can test for that if you wish.
You can tell with a diode test whether the the BCE pinout is correct. Reversing the transistor would measure differently.
Only from the base will there be two diodes to the other terminals, when they are forward biased. Since the base is not
the middle terminal, you can tell if it is in the correct place, at the left side.
You cannot necessarily see a bad component, most must be electrically tested.
You can tell with a diode test whether the the BCE pinout is correct. Reversing the transistor would measure differently.
Only from the base will there be two diodes to the other terminals, when they are forward biased. Since the base is not
the middle terminal, you can tell if it is in the correct place, at the left side.
You cannot necessarily see a bad component, most must be electrically tested.
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