There's usually enough carrier on the speaker output even after the filter. At least my frequency counter doesn't have a problem measuring that way. I don't even need a ground reference.
"Jump Starting" with volume knob..
I repair amps, and I have seen this a couple of times: one channel is on from zero signal on up, and the other one "kicks in" at a low, but not gradual from zero volume like the other.
My suspicion is the lower stage transistors.
Semi conductors can semi fail in different ways.. some can produce steady
static, some can develop instability in the gain curve, making an amplifier unstable only at louder volumes, but measure and test perfectly..
maybe a small junction inside the chip, so the whole chip may be bad..
Hope this helps!
I repair amps, and I have seen this a couple of times: one channel is on from zero signal on up, and the other one "kicks in" at a low, but not gradual from zero volume like the other.
My suspicion is the lower stage transistors.
Semi conductors can semi fail in different ways.. some can produce steady
static, some can develop instability in the gain curve, making an amplifier unstable only at louder volumes, but measure and test perfectly..
maybe a small junction inside the chip, so the whole chip may be bad..
Hope this helps!
Might want to tidy up your wiring too if it's still like the pic. You have power wires and interconnects crossing speakers wires. Keep them all as far away from each other as possible. I would also either twist or braid the power wires.
I have just taken delivery of an irs2092 200W mono board (not a Sure product) but it was DOA. Fortunately the Ebay seller refunded me in full without requiring it be returned.
I have now ordered the following,
TDA7293 x2pcs 170W Mono Amplifier Board Kit | eBay
Less expensive and looks easier to fix.
I have now ordered the following,
TDA7293 x2pcs 170W Mono Amplifier Board Kit | eBay
Less expensive and looks easier to fix.
Some good news. After adjusting the pot resistor to as close to 265 ohms as I can (the damn thing is so sensitive!), it seems like it improves the issue a little bit.
1 Channel is still dead upon power up, BUT with the corrected resistor matching for both channel the dead channel comes alive at much lower volume. I didn't have to crank to reference level to kick-start it like I had to before. It definitely a lot less annoying and more use-able now. I'm now considering keeping these.
Now I only have time to test one board. Will test the other two later to confirm the improvement is replicable on other boards by just matching the pot resistors to 265 ohm.
Might also try ShangHai's recommendation later. In the mean time I'll try to email them to see what their official response is.
Thanks a lot for all the replies so far guys! It's been a huge help.
1 Channel is still dead upon power up, BUT with the corrected resistor matching for both channel the dead channel comes alive at much lower volume. I didn't have to crank to reference level to kick-start it like I had to before. It definitely a lot less annoying and more use-able now. I'm now considering keeping these.
Now I only have time to test one board. Will test the other two later to confirm the improvement is replicable on other boards by just matching the pot resistors to 265 ohm.
Might also try ShangHai's recommendation later. In the mean time I'll try to email them to see what their official response is.
Thanks a lot for all the replies so far guys! It's been a huge help.
The problem is that even if they were both at exactly the same resistance, that doesn't mean the frequencies are the same. The trimmers are there for a reason (fine tuning).
Now clean up your wiring like I suggested and see if that makes a difference. 😉
Ah, you're right. Adjusting the resistor value without checking the corresponding osc. freq is just plain meaningless.
According to this table from IRA ref design, the board I got is closet to the AMP7D-150 and they're using 300 ohms here if i read this correctly. This is only assuming that SURE has followed this reference design. But they have shown to change components here and there, mainly resistors, in their final design so the correct pot resistor value to yield 400khz can be 265, 300, or even something else completely.
My multi-meter only measure up to 20khz so I'll need to get a different one to verify the osc. freq.
Thanks!
According to this table from IRA ref design, the board I got is closet to the AMP7D-150 and they're using 300 ohms here if i read this correctly. This is only assuming that SURE has followed this reference design. But they have shown to change components here and there, mainly resistors, in their final design so the correct pot resistor value to yield 400khz can be 265, 300, or even something else completely.
My multi-meter only measure up to 20khz so I'll need to get a different one to verify the osc. freq.
Thanks!
Attachments
Actually ran into this blog post that uses the exact board I have (Sure 2 x 125w). And he uses 200 ohm to get 400kHz. So I'll also try that tonight.
He also showed how to adjust the gains/input Vrms, which is pretty cool.
Larrys Corner: Class D Audio amplifier - IRS2092S
He also showed how to adjust the gains/input Vrms, which is pretty cool.
Larrys Corner: Class D Audio amplifier - IRS2092S
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