Re: HannsG HW173D dead. Recap = new fault.
Ahh, that makes sense now.
Looking at page 14 and figure 24, I'm going to assume pin 1 is getting 160V DC.
Pin 2 is GND.
Pin 3 is vcc. C123 has already been replaced, but there is still fluctuating voltage across that cap.
Pin 4 is feedback via optoisolator.
So, on pin 3, the voltage is coming from the tertiary winding. It goes through R104 and D102 in figure 24. Here are the possibilites (if my schematic reading skills have improved - and using the schematic reference designations).
a) R104 is bad. I believe R104 corresponds to the resistor just right of the big Capxon cap. Unsolder one leg of R104 and measure the ohms and compare it to the band color.
b) D102 is bad. I believe D102 corresponds to D110 on the power board. You can test this "in circuit" to see if it is shorted. Put your multimeter on diode test. Put black on one side and red on the other. Record reading. Now reverse probes and record 2nd reading.
A good diode should measure between 0.4 and 0.7V one way and 0L or "1" the other way.
It might also be worth testing the diode (D12?) just above the C123 cap in case I picked the wrong diode on the power board.
c) If R104 and D102 (D12?) are okay, then the chip itself is bad.
Originally posted by Rtech
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Looking at page 14 and figure 24, I'm going to assume pin 1 is getting 160V DC.
Pin 2 is GND.
Pin 3 is vcc. C123 has already been replaced, but there is still fluctuating voltage across that cap.
Pin 4 is feedback via optoisolator.
So, on pin 3, the voltage is coming from the tertiary winding. It goes through R104 and D102 in figure 24. Here are the possibilites (if my schematic reading skills have improved - and using the schematic reference designations).
a) R104 is bad. I believe R104 corresponds to the resistor just right of the big Capxon cap. Unsolder one leg of R104 and measure the ohms and compare it to the band color.
b) D102 is bad. I believe D102 corresponds to D110 on the power board. You can test this "in circuit" to see if it is shorted. Put your multimeter on diode test. Put black on one side and red on the other. Record reading. Now reverse probes and record 2nd reading.
A good diode should measure between 0.4 and 0.7V one way and 0L or "1" the other way.
It might also be worth testing the diode (D12?) just above the C123 cap in case I picked the wrong diode on the power board.
c) If R104 and D102 (D12?) are okay, then the chip itself is bad.
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