Right now I don't have the schematic in front of me (on phone),
but the lack of the 5.6 V signal not dropping coincident with no
Audio is the problem.
Part 1 is the lack of muting with no signal in, but the LED indicates that it is
supposed to be muting.
Part. 2 is that the circuitry at the ouput basiclly should come into play
When there is excess DC on the speaker. It may come into play for a brief
Period on power up.
Part 3 is that they are interrelated. Either should be able to mute the output.
The battery basiclly should force the system to think it's in current limit. It does't
In this mode,, you should be able to check to see if the transistors are functoning.
Shorts are common transistor failures.
Meanwhile, you can look at the E-B and E-C voltages with the battery in place and
The LED indicating UNMUTE.
When I get home, I'll try to figure out how to disconnect the DC PROTECT side.
Make sense?
OP said:In circuit, R3 has a resistance of 9.85k; according to the diagram, it should be 22k though? Is this meaningless, or revealing information?
op said:I think Part 1 isn't an issue - or have I misunderstood? When the LED is red, the voltage of ZD1 is 0. When it's green, it's 5.6V. Is this what we are discussing?
OP said:I did find a strange thing though, "RJ2", which is not referenced anywhere on the plan: it's a tiny resistor, with 1 black line only on it, which is situated between R18 and Speaker + on the board, just below R5. RJ2 is directly connected to Speaker +. The resistance seems to be 0 though, and I find it strange not to be on the plan, why would they add something useless to the PCB? I'm sure it's not, but I don't get it (and not sure if it "works").
OP said:When you ask whether there is sound or not, during the tests, would you want me to physically plug the speaker back in? Or is checking the voltage with the multimeter between speaker + and - sufficient?
What is the C-E voltage of Q3 when the 5.6 V is present?
What is the B-E voltage of Q3 when the 5.6 V is present?
With the LED green and the 1.5 V battery applied to the lifted R20 and speaker positive with the polarity that we discussed:
What is:
Q12, E-B
Q12, E-C
Q14, E-B
Q14, E-C
Q13, E-B
Q13, E-C
OP said:However, when the cable is plugged in, it used to stay RED until music was actually played, then it would switch green. But now, as soon as the audio source is plugged in (and the homecinema amp plugged in), it goes GREEN, music or no music. This could be due to the "jolt" somewhere?
1. Remove both L & R input plugs.
2. Measure the DC voltage at the ends of the output (disconnected leads) from your
source. Tip to shield. If there is DC here, then your source has a problem..
3. Turn on the sub and the source, don't connect the inputs.
4. Measure the DC and AC voltage from the shield side of the output of your source to the shield side of the input of the sub.
Is the gain of the sub up high?
The DC on the input to the sub WILL cause the LED behavior for sure.
Check the voltage across across R11 and R12 and between E-C of Q7.
Lifting of R15 and R16 will tell you if there is a problem with Q8, Q9, Q10 and Q11 There shouldn't be because there is no magic smoke in mute.
With it out of mute and R15 and r16 lifted, you should look at the voltage across R4 and R5. they should be identical.
You mean R20 lifted, not R21? I don't think it matters anymore, but you can leave it unconnected for now.
Pick up a 9V battery clip, a 9V battery and a diode (1N4001 or so) and a 10 ohm 1W resistor. Put the 9V battery positive lead in series with the forward biased diode.
Put two of your Ez-hooks at each end
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