shorted a good old CDP M95

[federikk]

hi all,
my cdp M95 (Sony, TDA1541) needs a set-up of focus & tracking gain every few year, because otherwise it starts skipping.

during the last set-up, I shortened with the oscilloscope probe the contact 15 (VDD2) and 5 (A GND) of the TDA.

given that they were a VDD and a ground i think "should be allright"... instead, now i've no output audio from line out, and only white noise from the headphone.

coaxial and digital out still works.

did i have burned my TDA? or there's an hope that's something else, like opamp or a capacitor?

thank you!
federico

 

[stephensank]

It's more likely that you simply fried a resistor or regulator on that supply line. Not very likely you cooked the 1541, but not impossible.

 

[anatech]

Hi federico,
Stephen could be right there. You may have killed a regulator or blown a thin ground trace. Fun to find.

What concerns me more is the constant attention that your CD player needs to keep running. Focus and tracking gain aren't very touchy adjustments, so maybe you mean the focus and tracking DC offsets? Those are touchy adjustments. Still, something else is going on there. I wonder if those trimmer controls have had it. They are only supposed to be adjusted a few times in their lifetime. You could easily replace them with the same or similar single turn controls and set them approximately where the original ones were. Fine adjusting them is as you have been doing.

I'm on the fence as to suggest you replace your CD player. It shouldn't need that much attention, maybe the head has become very weak. In any event, it's really old and might be ready for a massive sequence of failures anyway. Can you check the laser current and compare that to the value on the head? You are allowed a 10% increase in current before declaring the head unusable. Certainly if it reads that high or higher, I do recommend you replace it, or replace the head and disc motor.

-Chris

 

[federikk]

thank you all!
yess i know anatech, i've got a tired laser, but i've another one ready for the change, whenever it needs to be replaced.
more than this, one of the potentiometer (tracking gain) is a little noisy, and once a year/two year needs to be moved a little.

now, back to my fault:
i've a solid -4V on VDD1, where it shoud be -5V.
maybe that's the problem?? a voltage regulator?

thank you!