It's amazing what happens when you power everything up. Fans come on, protect light comes on and voltages change. Okay here they are, two transistors still out and still no power light (related?)
Pin 1: 0.00
Pin 2: 4.95
Pin 3: 0.05
Pin 4: 0.56
Pin 5: 1.65
Pin 6: 3.44
Pin 7: 0.00
Pin 8: 12.56
Pin 9: 3.82
Pin 10: 4.24
Pin 11: 12.56
Pin 12: 11.90
Pin 13: 4.95
Pin 14: 4.95
Pin 15: 4.95
Pin 16: 0.00
Should I put the transistors back in? If so, any way to heat sink these or just do them very quickly. What wattage iron is good? I have 20 and 40 watt.
Pin 1: 0.00
Pin 2: 4.95
Pin 3: 0.05
Pin 4: 0.56
Pin 5: 1.65
Pin 6: 3.44
Pin 7: 0.00
Pin 8: 12.56
Pin 9: 3.82
Pin 10: 4.24
Pin 11: 12.56
Pin 12: 11.90
Pin 13: 4.95
Pin 14: 4.95
Pin 15: 4.95
Pin 16: 0.00
Should I put the transistors back in? If so, any way to heat sink these or just do them very quickly. What wattage iron is good? I have 20 and 40 watt.
The power LED will likely light up when you install the power supply FETs.
Re-check the voltage on 9 and 10. They should be closer.
With no FETs in it, Do you read essentially the same voltage on pins 9 and 10 as you do on the gate pads for the power supply FET?
I don't understand the question about heatsinking.
The 40w is likely better suited for this.
Re-check the voltage on 9 and 10. They should be closer.
With no FETs in it, Do you read essentially the same voltage on pins 9 and 10 as you do on the gate pads for the power supply FET?
I don't understand the question about heatsinking.
The 40w is likely better suited for this.
You said they were out and didn't say that you reinstalled them but many times people install/remove parts without posting what they did.
With no power applied, measure the resistance from the gate pads for each of the power supply FETs to ground (black probe on ground). Do they all read the same?
If not, what do you read?
With no power applied, measure the resistance from the gate pads for each of the power supply FETs to ground (black probe on ground). Do they all read the same?
If not, what do you read?
The resistance checks from ground to the gate pads are as follows.
From ground to:
Outside four pads = 129 k ohms
Inside four pads = 227 k ohms
Tracing the circuit back to pins 9 and 10 revealed that on the side closest to the IC, the resistance was the same. On the other side of the zener diodes however, it was as above. The resistors in the circuit are both 1000 ohm resistors so I don't see them causing a problem so is it safe to assume that the zener diodes are gone, or at least one? If so, I should probably replace all four. What about the two transistors (A1023). Will they be okay because I don't think they will be too easy to find.How do I find the values of these zener diodes? Should I test all four with a power supply and see if I can find the reverse breakdown voltage?
From ground to:
Outside four pads = 129 k ohms
Inside four pads = 227 k ohms
Tracing the circuit back to pins 9 and 10 revealed that on the side closest to the IC, the resistance was the same. On the other side of the zener diodes however, it was as above. The resistors in the circuit are both 1000 ohm resistors so I don't see them causing a problem so is it safe to assume that the zener diodes are gone, or at least one? If so, I should probably replace all four. What about the two transistors (A1023). Will they be okay because I don't think they will be too easy to find.How do I find the values of these zener diodes? Should I test all four with a power supply and see if I can find the reverse breakdown voltage?
Can you post a better photo of the power supply area of the board showing the 494, the drivers and the power supply FETs?
If you can take a high resolution photo, send me the original at the highest quality.
babin_perry@yahoo.com
If you can take a high resolution photo, send me the original at the highest quality.
babin_perry@yahoo.com
I have since repaired one of the traces and checked all the rest. The board had some corrosion on it when first opened. I just took some light (400 grade) sandpaper and cleaned it off to have a better look. Is there a better way to approach that kind of damage? Should I seal it up afterwards? The repair was also made prior to having all the resistance problems so it is not a factor right now. All resistance, like I said seems to be in the zener diodes. Any idea what the rating is going to be on them, I can't see any numbers on them. Thanks in advance.
You don't have to apply sealer to the traces. They will develop a thin layer of oxidation but it won't do any harm.
A brass wire brush works well. Sandpaper is generally difficult to use because there are lots of leads sticking up through the board.
There are two diodes per driver. Are those the Zeners that you're referring to?
A brass wire brush works well. Sandpaper is generally difficult to use because there are lots of leads sticking up through the board.
There are two diodes per driver. Are those the Zeners that you're referring to?
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