Re: bn44-00338b
I'd love to see a schematic with some voltage readings of other pertinent areas. If someone has one of these that they could take some readings one it would be most helpful.
Thanks, Terry
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Re: bn44-00338b
Hi Guys,
I installed a new MOSFET and have no change. Do any of you have a suggestion for where to look next?
Thanks, Terry
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Re: bn44-00338b
I ordered a new mosfet. I get back to you once I've replaced it.
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Re: bn44-00338b
No, I have not tried that. Do the voltages indicate it is faulty?
I don't quite follow you. INV pin is 1.1V which is higher than 0.45V and lower than 2.675V. I don't understand the term hysteresis nor how to check for that.
Thanks, Terry...
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Re: bn44-00338b
Hi Bud,
Any more suggestions as to what I might check to help get to the bottom of this issue?
Thanks, Terry
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Re: bn44-00338b
Hi Bud,
I'm still hoping to fix this with some help. I hope you can find the time to take a look at my findings and make some more suggestions. I could just buy a replacement but then I won't learn anything.
Blessings, Terry
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Re: bn44-00338b
Here you go.
Edit; adding a shot of the bottom where I replaced the FSR...Last edited by still4given; 10-03-2014, 09:30 PM.
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Re: bn44-00338b
I'm attaching another partial of the schematic with the voltages to hopefully give a better picture of what's going on.
Thanks, Terry...Last edited by still4given; 10-03-2014, 08:50 PM.
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Re: bn44-00338b
Exactly the same, everywhere. I bought more than one IC so I even swapped in a second one. No change. The docs say the IC compares the inverted and the non-inverted inputs. I'll assume the inverted in the INV pin but I don't know which pin is the non-inverted. Something is not sending the correct voltage or current to make the IC happy. Have you had the chance to mark down the correct voltages for each pin on the IC? That would be very helpful.
Blessings, Terry
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Re: bn44-00338b
Hi Bud,
I hope you are still monitoring this thread. My replacement IC finally arrived so I installed it. That wasn't the problem. I still have exactly the same voltages I show in post #17. For some reason the IC is not turning on. I have read through the docs for the IC and though I understand it a little better, I'm not sure what to look for as to why it is not turning on. Any other things you can suggest to look for?
Thanks, Terry
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Re: bn44-00338b
You're right, I didn't notice that.
How is this circuit supposed to work? Obviously 23mv won't turn on the MOSFET but what happens when the MOSFET turns on? Looks like it will force positive voltage onto the ground? You can see I don't understand how an SMPS works.
So you still think the IC is the problem? I ordered some but likely won't see them for a week or so, coming from Hong Kong.
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Re: bn44-00338b
Hi Bud,
Looking closer at the circuit made me suspect DP803. I'm not sure exactly how that diode is supposed to work but with my DMM on diode test I get 0.026V in both directions. Seems it ought to be open in at least one. That could explain the 4mv on pin 4.
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Re: bn44-00338b
I sat down this morning and took some voltage readings of the IC and the MOSFET. I don't understand that circuit well enough to know what it is supposed to be doing so I am attaching them. Hopefully you can see where the problem is.
Thanks, Terry...
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Re: bn44-00338b
IC referenced to pin 6
Pin 1 60k
Pin 2 47k7
Pin 3 inf
Pin 4 1R
Pin 5 20k
Pin 7 8k6
Pin 8 14m
DP802 checks fine
RP822 1m2
MOSFET checks OK with diode meter.
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Re: bn44-00338b
Pin 18 has 0.723V and pin 16 has 5.28V. All other pins have 0.0v
Your right. I rechecked the bridge and it pulses on DC. The 42V was an AC measurement.
Yes, my measurements were with no other board connected. Taken on my bench with the board upside down so I could get to all the nodes.
Thanks, Terry
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Re: bn44-00338b
DC voltage on the main cap is 160V. No 24V or 13V. 42V on the bridge.
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Re: bn44-00338b
How do you measure each pin with the boards all plugged in? I had to have the bottom exposed to get to them. Can I test the PSU simply plugged in on the bench?
Thanks, Terry
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