Measuring was done at clipped point at approximately ~8.3vrms. This is kind clean sinewave but at very low volume - at 2-3vrms.
Both U202 + U204 - pins 1 and 16 are stable at all times and are looking basically the same.
There is difference between pin 2 and the outputs between the two chips.
At very low volumes when there is a clean sinewave both audio drivers are measuring/switching almost the same. But once u start increasing the volume and the output becomes clipped, U202 starts to behave awkward. It's like trying to switch but cannot develop proper wave. Pin 2 and the outputs pin 6 and 11 are nothing like U204.
Both U202 + U204 - pins 1 and 16 are stable at all times and are looking basically the same.
There is difference between pin 2 and the outputs between the two chips.
At very low volumes when there is a clean sinewave both audio drivers are measuring/switching almost the same. But once u start increasing the volume and the output becomes clipped, U202 starts to behave awkward. It's like trying to switch but cannot develop proper wave. Pin 2 and the outputs pin 6 and 11 are nothing like U204.
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In my experience with these amps, it’s crucial that all output transistors are the same and from a good known source.
Being that it’s been worked on before, I would not trust those output transistors to not be eBay/Amazon/alibaba
Being that it’s been worked on before, I would not trust those output transistors to not be eBay/Amazon/alibaba
The fitted are the original ones from the factory. I've only added 1 which was missing. It's from a reputable source Farnell UK, from which i've never have had any issues.
Also - transistors reads fine on the tester with almost identical parameters.
I don't think it's the outputs as i've pulled out IRFP264N from an old working amplifier and it behaves the same way as with the IRF3415P.
What are the real parts for SS-2662/ U200&U203 and SS-4141SM ?
Also - transistors reads fine on the tester with almost identical parameters.
I don't think it's the outputs as i've pulled out IRFP264N from an old working amplifier and it behaves the same way as with the IRF3415P.
What are the real parts for SS-2662/ U200&U203 and SS-4141SM ?
I will replace U200 + U203 + U201 + U290 and see if there will be any change. If not uc3706dw (U204 + U202) would be my next guess.
U201 (either the IC or components around it) wouldn't be a surprise. It looks like it's trying to go into protect but it's not latching.
Changed U201 and U290 with new TL072...same.
Sadly due to the mass chip shortage - LM6172IM are unavailable in my region. The next delivery is up to 18 months....
Sadly due to the mass chip shortage - LM6172IM are unavailable in my region. The next delivery is up to 18 months....
In post 21, you stated that pin 2 didn't match on the two driver ICs.
How does the output on pin 7 of U200 and U203 compare?
How does the output on pin 7 of U200 and U203 compare?