Sick Proton ac-620 needs your help

S.Spielbergo · 13th January 2012, 10:50 AM

About a year ago my beloved Proton ac-620 cd player (great Dieter Rams knock off) went on the fritz, any disc inserted would just spin wildly (violently) out of control without being read. I have already rebuilt most of the pc board's analog and some of the digital section with only a bad resistor needing repair in the servo section. Its a great Philips based player from 1990 with the TDA1541 and cdm-4 mechanism so I hate to see it sitting there all slumped over on the "dead electronics" shelf. I have since tried a handfull of more modern players but have been unimpressed, build quality on modern equipment is unbelieveably chintzy. Any help is greatly apreciated guys.

stephensank · 13th January 2012, 04:29 PM

The first thing to do on any Philips based unit like these is to replace every non-Nichicon electrolytic cap in the unit, especially in servo, supply & syscon areas. Have you done this yet?

S.Spielbergo · 14th January 2012, 06:07 AM

I replaced all electrolytic caps during the rebuild a couple years ago.

stephensank · 14th January 2012, 04:01 PM

Well, having encountered this symptom only a few times, more than a few years ago, I can't recall the solution. However, the next steps I would take would be to 1)check laser current & focus offset adjustments, 2)assuming it's a philips or same style pcb, check for excess current draw on servo, drive & dsp chips via voltage drop accross the low value resistor feeding supply to each chip/group, 3)resolder all of these chips & anything else not 100% positively perfect looking, 4)unplug, replug & wiggle all connectors. After that, time to get out an oscilloscope.

13th January 2012, 10:50 AM	#1
S.Spielbergo diyAudio Member Join Date: Jul 2007	Sick Proton ac-620 needs your help About a year ago my beloved Proton ac-620 cd player (great Dieter Rams knock off) went on the fritz, any disc inserted would just spin wildly (violently) out of control without being read. I have already rebuilt most of the pc board's analog and some of the digital section with only a bad resistor needing repair in the servo section. Its a great Philips based player from 1990 with the TDA1541 and cdm-4 mechanism so I hate to see it sitting there all slumped over on the "dead electronics" shelf. I have since tried a handfull of more modern players but have been unimpressed, build quality on modern equipment is unbelieveably chintzy. Any help is greatly apreciated guys.

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13th January 2012, 04:29 PM	#2
stephensank diyAudio Member Join Date: Oct 2006	The first thing to do on any Philips based unit like these is to replace every non-Nichicon electrolytic cap in the unit, especially in servo, supply & syscon areas. Have you done this yet?

14th January 2012, 06:07 AM	#3
S.Spielbergo diyAudio Member Join Date: Jul 2007	I replaced all electrolytic caps during the rebuild a couple years ago.

14th January 2012, 04:01 PM	#4
stephensank diyAudio Member Join Date: Oct 2006	Well, having encountered this symptom only a few times, more than a few years ago, I can't recall the solution. However, the next steps I would take would be to 1)check laser current & focus offset adjustments, 2)assuming it's a philips or same style pcb, check for excess current draw on servo, drive & dsp chips via voltage drop accross the low value resistor feeding supply to each chip/group, 3)resolder all of these chips & anything else not 100% positively perfect looking, 4)unplug, replug & wiggle all connectors. After that, time to get out an oscilloscope.

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