Electronics > Repair
Class D Subwoofer Amplifier Repair
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geoffagain:
Ok so Zener in circuit ZD201 is 1N4744 15v

The one I pulled from donor is also marked IN4744. So seems for whatever they're using 15V rather than 16V on this one.

Tested ZD201 out of circuit with my bench supply and a 1k resistor -

Seems ok, holds 15v upto the 20v I can supply. Not sure on leakage current.

I'm not measuring any current or at least very minimal under 15V  with a 1k resistor in series.

Approx >

0.5mA at 15V
1mA at 16V
2mA at 17V
3mA at 18V




 
Harry_22:
Measure the resistance  between D210 anode and pin 4 of IC201.
There are also C209 capacitor in parallel with the zener.
geoffagain:

Cheers for your continued patience.

Resistance  between D210 anode and pin 4 of IC201 - same behaviour as before with

D210 cathode and pin 4 of IC201 - rises quickly to OL then drops low then rises and settles at 9.6Kohm - perhaps still rising very slightly over time.

I'll pull c209 and see what my ESR says.

Harry_22:
But with Zener you had 0 Ohm. Am I right?
geoffagain:
Sure

ZD201 anode to pin 4 is 0hm
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