| Electronics > Repair |
| Marantz SR5200 amp damaged center channel + DAC issues |
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| martinho1974:
I already changed cs4228 and it did not work, it actually got worse. Only in direct source, it recognizes the channels passed more than 5 minutes, has sound but with noise similar to the sound of a helicopter. my doubt now is, will the substitution of 4391 will solve everything, or the 4228a having been ordered from china, very cheap, is false? |
| poot36:
If the sound is bad in direct mode you have way more problems then just the DACs (as direct mode disables all digital functions of the amp). If not I would go back to the original DAC and try replacing the cs4391. Do you have a scope to check the clocks and digital inputs to the DACs? |
| poot36:
Well I finally fixed it. I got in the replacement CS4391 and CS4228A a long time ago and fitted it but never had the time to test it. With the replacement chips in place I now had working digital input coming out for the FR and FL channels but no surround sound action. Checked on all the pins of the CS4228A and they were correctly soldered to the pads and no solder bridges. Also had sensible voltages on the pins as well. Checked to see if the chip was fake with the alcohol and nail polish remover trick and no paint came up. Tested for connection from the pins to where it connected on the circuit and found that pin 4 SDOUT was not connected. This resulted in the chip being put into SPI mode when it should be in I2C mode. Repaired damaged trace with a jumper wire and had correct surround sound action. Now I am dealing with some quiet humming/buzzing that is not affected by the volume control or mute-ting the audio. I suspect it may be caused by the temporary low value main amp filter caps I put in when I was testing the replacement power transistors as a attempt to reduce the peak current available so as to not blow up the replacement transistors. The interesting thing is when I took the original caps out of storage the tops were starting to bulge out like they were going bad. They still test at around there stated capacity based on one of the cheap component testers I have but I don't really like the ESR of around 0.10 ohm on one and the other was closer to 0.01 ohm. They are not shorted though. They are Samwha DL 85 C (M) 63wv 10000uF For Audio caps. They do charge up to 32V on my power supply and draw less then 0.5ma on my current meter so I don't know if they are bad or not. Should I replace them or not? |
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