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Old 12th February 2017, 02:36 PM   #1
vlucian is offline vlucian  Netherlands
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Default ARCAM alpha 5 problem

Hi,
I just bought an entire Arcam stack (alpha 6 amp, alpha5 tuner and alpha 5 cdp) for a good price but, unfortunately, the cd player has a problem: after some minutes it starts popping first in a channel then also in the other and slowly the noise become louder than the music itself. I spent some time to read about this issue and now I'm pretty sure it's the DAC. I measure the voltages (+/-5 and -15 ) and these are ok, I also replaced the infamous C416 with no luck. The gear wheel is damaged and must be replaced (another 10Eur or so).
My question is: does it worth? I mean, is it wise buying another cdp to extract the DAC (I guess it's cheaper than buying directly nos/fake chip - I already found a Marantz cd40) only to put it inside a machine with a design that proved to be faulty so many times? From what I read this player stays always powered ( SW402 switches off the +5V(s) supply, and grounds the reset circuit.) - could this be the cause for DAC failure?
Do you think I should maybe check other things too? (SAA7220 is also getting hot).

Thanks
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Old 12th February 2017, 02:50 PM   #2
Mooly is offline Mooly  United Kingdom
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I'm not familiar with the player and would have to look at the manual to see the chip set it uses but what I would say is that if the issue appears after a couple of minutes then its well worth trying some freezer spray on suspect parts.

Also check all the rails when the fault appears, not just with a meter but with a scope.

Faulty RAM can cause odd audible issues, in fact this was a fairly common issue on older players that had a separate RAM chip.

Rails and freezer spray
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Old 12th February 2017, 08:30 PM   #3
vlucian is offline vlucian  Netherlands
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I don't have freezer spray so I used a cooled piece of metal - the noise disappeared but then came back in a minute or so. I'm already looking for a replacement DAC but again: does it worth? What if the new dac will also be "baked"? I will try to use a large heatsink (now I'm listening with a big PIO aluminium capacitor "resting" on top of it and ... surprise, no noise!).
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Old 12th February 2017, 09:32 PM   #4
vlucian is offline vlucian  Netherlands
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So, I used a piece of aluminium that nicely resemble a heatsink and put also some silver grease as thermal pasta. So far so good. On the othe hand the measurement showed me some 5.3V (for both + and -). Could this be the cause of overheating? I think I will use some LM to obtain 4.9V using a separate transformer, what do you think?
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Old 12th February 2017, 10:18 PM   #5
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Maximum voltage on the Philips Chipset is 7Volts so no problems there. They draw 180mA so run hot to touch. They don't care about psu ripple as they are self regulating. They only need a modicum of smoothing. Have your re-soldered the pins? Could be all it needs.
Not sure where you get your -ve supply to the DAC from. it doesn't have one.
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Old 13th February 2017, 08:32 AM   #6
Mooly is offline Mooly  United Kingdom
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I wouldn't try adding separate rails. Check as Jon suggests that there is no problem with the soldering. Give the board a good push down as its playing to flex it slightly and see if the fault responds.
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Old 13th February 2017, 09:56 AM   #7
vlucian is offline vlucian  Netherlands
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Jon, what do you mean with "Not sure where you get your -ve supply to the DAC from. it doesn't have one." ?
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