I was trouble shooting a dodgy LCD panel on my Proton AC 620 now the spindle motor for the turntable has gone completely dead. This is a Philips based machine from ~ 1990 with the usual gang at the helm, TDA1541a, SAA7220 &SAA7210. I checked the motor and it works with 10v applied, the laser mechanism is also working. Checked all the wiring and grounds, compare what I have to the schematics....
. It is also a clone of a Dual CD player (don't recall the model number), I have been fidling with this thing for a few days now and feel like a fool but I would love to get this player going again, any advice?
. It is also a clone of a Dual CD player (don't recall the model number), I have been fidling with this thing for a few days now and feel like a fool but I would love to get this player going again, any advice?I think I found the culprit, seems a resistor feeding one of the op amps in the drive section died... and here I am thinking I must have carelessly destroyed one of the ICs or something. It was only 1.6 ohms so I jumped it out with a .6 ohm wire for the time being, player is working well. While I was in there I probed a capacitor case and saw huge voltage numbers on a few of the caps, is this normal?! I tried a few new ones and a couple remaining old caps, placed the probe on the top of the casing where the vent is stamped and saw 20V at one cap, 3v on another couple and ~ .5v on the rest??
S.Spielbergo said:
Re Caps: Yes, that's pretty normal - there is quite a lot of leakage to the can particularly when the cap is connected to relatively high voltages. The can is usually floating - not connected to either terminal and may have hazardously high voltages on it in some applications. (Snap-ins, radial types operating in HV supplies such as line operated switchers, and tube amplifiers.)
Don't operate it for long without that 1.6 ohm resistor, it was probably there to limit motor start current to a safe value or dissipation in the controller ic, or both..
I'll have to parallel the hell out of some higher value resistors as thats all I can find. Its weird that even my low powered caps show voltage at the case, good to know, thanks.
S.Spielbergo said:
You should be able to get these from digikey or mouser, but you would need to figure out what else to order to get to the minimum.
The original was probably a fusible type.
I found an apropriate resistor off of a dead IMac mother board, now I just need to find my stash of metalized poly caps for DC blocking of the opamps.
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