I tried to switch speakers same result, I also checked every connection twice.
The volume is around 65/70db, while if I use the other channel is 95/100db
The distortion don't change much with volume, bass are monstly absent and all the sound come pretty much from the tweeter
The volume is around 65/70db, while if I use the other channel is 95/100db
The distortion don't change much with volume, bass are monstly absent and all the sound come pretty much from the tweeter
I can ear the relay clicking when I turn on the amp but I'm not sure witch contacts I have to short
A resistor is a good idea for speaker safety. Your connecting the speaker directly to the output (L1 pin 13) of the amp to bypass the relay.
If that shows nothing then can you measure the DC voltage across D13 and D14 in the protection circuit. It should be nearly zero.
I would also turn the bias on this channel right down while working on the amp.
If D13 and D14 have no voltage on them then next step is to remove (isolate one end) of D11 and D12 and see if the fault clears.
If that shows nothing then can you measure the DC voltage across D13 and D14 in the protection circuit. It should be nearly zero.
I would also turn the bias on this channel right down while working on the amp.
If D13 and D14 have no voltage on them then next step is to remove (isolate one end) of D11 and D12 and see if the fault clears.
I shorted pin 1 and pin 4 on the relay board and now some sound come out of the speaker. (still some distortion but a lot better than before)
I tried to connect the amp directly to the speaker, pin 13 and pin 14, but in this case the sound will come out after I turn on the amp for only a second (as soon as the relay click it stop) and immediately after I turn off amp
Visually I can see that one relay is not working (it should be S3 in the relay board) but I wasn't able to effectively bypass it
I tried to connect the amp directly to the speaker, pin 13 and pin 14, but in this case the sound will come out after I turn on the amp for only a second (as soon as the relay click it stop) and immediately after I turn off amp
Visually I can see that one relay is not working (it should be S3 in the relay board) but I wasn't able to effectively bypass it
The fact it improves when you short the relay is suspicious. Have you tried using the other sets of speaker terminals as a test ?
Same effect with all terminals A,B,C.
This is how it sound with and without short on pin 1-4 (relay).
From the watt meter in the front I can see that the working channel is producing 1W while the other around 0.1W
This is how it sound with and without short on pin 1-4 (relay).
From the watt meter in the front I can see that the working channel is producing 1W while the other around 0.1W
Lets try and be creative with this.
When you look at the power meters at the moment of switch on (with music playing and the volume set normally) do they read the same or different in those few seconds before the speakers connect ?
Assuming they read different then you need to measure the DC voltage across D13 and D14 (or whichever channel it is) and confirm there is no voltage present.
When you look at the power meters at the moment of switch on (with music playing and the volume set normally) do they read the same or different in those few seconds before the speakers connect ?
Assuming they read different then you need to measure the DC voltage across D13 and D14 (or whichever channel it is) and confirm there is no voltage present.
When I switch on the amp nothing happen to the meter, the meter starts working after the protection go off. I think the meter board is also connected to the protection one
I tried to connect the amp pin 13 to the relay pin 1 with new cable (just to be sure there wasn't a problem) but that wasn't the issue
I measured bias and offset (with both trim at minimum) but now I have 0 bias and 230mv offset, if I touch the trims the value won't change
I tried to connect the amp pin 13 to the relay pin 1 with new cable (just to be sure there wasn't a problem) but that wasn't the issue
I measured bias and offset (with both trim at minimum) but now I have 0 bias and 230mv offset, if I touch the trims the value won't change
OK 🙂 That's a bit different to what was happening earlier where you said bias and offset were fine.
So basic checks. Measure and record what you get. This is to try and establish what the basic DC conditions are.
1. Amp OFF and measure all the 0.5 ohms in the bad channel just be sure nothings zapped.
2. The offset should be zero (measured between ground and L1. If you have 230mv then does that value change at all as you adjust VR1 ?
3. What is the DC voltage between Q8 and Q10 collectors.
4. Are the -/+ 63 volt rails on pins 3 and 4 OK
5. Are the supplies on pin 6 and 7 correct (haven't got the full circuit in front of me but they will be around -/+ 60 volts as well). That's the supply to the output stage, collectors of the outputs.
1. 5ohm are fine
2. it increase but not much
3. Q10 is fine Q8 too, but Q18 (we substitute this) seem broke while Q19 is fine
4. rails are +/-46V
5. yes
2. it increase but not much
3. Q10 is fine Q8 too, but Q18 (we substitute this) seem broke while Q19 is fine
4. rails are +/-46V
5. yes
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OK.
Why does Q18 seem faulty. What are the voltage readings on C,B and E ?
Q10 and Q8 may well be OK but its the voltage between the collectors that was an important reading (to help see why there is no bias current)
Why does Q18 seem faulty. What are the voltage readings on C,B and E ?
Q10 and Q8 may well be OK but its the voltage between the collectors that was an important reading (to help see why there is no bias current)
I'm just looking at those rails now. They sound low, perhaps because something is drawing more current than it should.
You will have to do this very carefully and methodically. Do you see R23 and R24, both 270 ohms. Can you measure the voltage across each resistor and compare the readings between the two channels.
You will have to do this very carefully and methodically. Do you see R23 and R24, both 270 ohms. Can you measure the voltage across each resistor and compare the readings between the two channels.
Listen 😀
What is the voltage between the collectors of Q10 and Q8 ?
We'll get to Q18 later 🙂
Across each resistor, Across not between 😛
What I want to know is whether there is more voltage across the ones in the bad channel compared to the good one. Yes 🙂
This will continue tomorrow (no doubt 😉) And don't blow it up.
There is just one voltage. Put one meter lead on Q10 collector and the other on Q8 collector. What does it read ?
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