I am trying to refurbish an Adcom GCD 600 [TDA1541A] I picked up cheaper than the chip set cost. The loader isn't working but when I put in on the bench and plugged it in the CD spindle motor started running before I powered it on?! I don't understand how it would get power as other functions clearly happen after AC is switched on. I know this is a vintage/nostalgia piece but does anyone know if this is normal for this unit??? Thanks for any ideas!
regards,
Steve
regards,
Steve
I'm not familiar with the player at all but what you describe doesn't sound normal.
First checks have to be all the rails, perhaps one is missing or perhaps a switched rail is staying on when it shouldn't.
Spinning motors can often be a sign of a PSU issue, or there could be a motor drive amp failure. Generally when a player is 'OFF' you'll find that (unless the switch is a mains on/off) that the player will be in standby and much of the circuitry could still be powered up.
First checks have to be all the rails, perhaps one is missing or perhaps a switched rail is staying on when it shouldn't.
Spinning motors can often be a sign of a PSU issue, or there could be a motor drive amp failure. Generally when a player is 'OFF' you'll find that (unless the switch is a mains on/off) that the player will be in standby and much of the circuitry could still be powered up.
So I just got hold of the service manual for this player. The electrolytic caps in the power supply seem to have the neg marked with a black dot. When I put a DMM to check polarity they seem to be only partially right! 2/3 have + pole in ground and that is how caps were in when I opened. Is the schematic just wrong. All my pin and header connections have ground as indicated as well as transistors [NPN/PNP] and +/- 15 voltage regs in supply. Should I just use ground to replace as they don't appear to be in series? If it was a short I would expect some + input be hot but I can't find one. Sorry my system fail is I power up system it blows fuses. Main transistors and V regs check OK [not shorted].Thanks for any ideas.
regards,
Steve
regards,
Steve
Schematics can have odd single errors but that is all.
Its normal to have lots of caps fitted with + to ground... it simply means ground is more positive than the voltage that will be seen on the - lead of the cap.
Ground is just a reference point and voltages can and will be above and below this point.
Its normal to have lots of caps fitted with + to ground... it simply means ground is more positive than the voltage that will be seen on the - lead of the cap.
Ground is just a reference point and voltages can and will be above and below this point.