Marantz SR5200 amp damaged center channel + DAC issues

[poot36]

Thanks for the info.  I will do the reset if necessary.  I have found out that me previous post about the I2C bus been shorted is incorrect.  Even though it is marked SDA and SCL on the board silk screen, based on the configuration of other chips I now believe that it is a SPI bus and it was still a clock line that was getting shorted out.  It now correctly detects digital input signals but I am still getting no correct audio out of the surround DAC.  I will do some more testing now that I have the digital input working as I can now remove the tuner and analog input board to probe the digital board.  I really hope my replacement IC719 is not fake.

[Chris56000]

Hi!

Does anyone mind if I join the party?

A seller was offering one of these "sold working with assorted intermittent buzzing faults!!" and at two figures I thought I'd join in as well!

Pics & repair–tales to follow when I get it!

Chris Williams

[poot36]

Well I did the reset and that did not change anything.  I probed around with the scope and got what looked like reasonable readings on the DAC pins.  I do want to confirm that the FILT pin on the CS4228A chip is supposed to be around 3.6V or so.  It is not listed in the datasheet and is a internal voltage supply to the chip.  I did try my 2nd CS4228A chip as I ordered 2 of them and managed to blow it up by using flux that I thought was for electronics soldering but was actually for pipe work.  There were sparks between the pins!!! Not fun.  Is there a modern replacement chip for this DAC?

[m3vuv]

base and drain??,is it a bipolar or mosfet?

[poot36]

@m3vuv I think you may have responded to the wrong post or I have not made clear that I have fixed the transistor amplifier section of the amp and am now working on the digital side of it now.

[Chris56000]

Hi!

I've had a quick look and there's no direct drop–in replacement that springs to mind'

There are still reasonable supplies of the CS4228A on eBay from UK and other sellers tho' – it's highly likely that's what's causing the faults on the one I've just bought!

Chris Williams

[mzacharias]

Well I did the reset and that did not change anything.  I probed around with the scope and got what looked like reasonable readings on the DAC pins.  I do want to confirm that the FILT pin on the CS4228A chip is supposed to be around 3.6V or so.  It is not listed in the datasheet and is a internal voltage supply to the chip.  I did try my 2nd CS4228A chip as I ordered 2 of them and managed to blow it up by using flux that I thought was for electronics soldering but was actually for pipe work.  There were sparks between the pins!!! Not fun.  Is there a modern replacement chip for this DAC?

I've had very good luck with UTSource. Takes a couple weeks or even more but never had a counterfeit.

https://www.utsource.net/

[poot36]

Thanks for the link, I will have a look.

[martinho1974]

I have the same problem in my sr 5200 marantz. Was it fixed with the exchange of the cs4392?

[poot36]

@martinho1974 I have not yet ordered the replacement DACs.  A quick test to see if your DAC is bad is try inputting a digital signal into the unit and if it does not detect it cs4391 could be bad.  If you remove it you will only lose the front right and left channels but the surround channels will still work I would think.

@mzacharias When you ordered off UTSource did you get the components from them or one of the cheaper alternatives they listed?

[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?