There is a K170 next to those three LEDs. Measure how many Ohms between its first and last leg when the power is off. Normal range no more than 50 no lower than 20. Also measure how many Volts between first and last leg of the nearby IRFP9240 when the power is on. Please verify its not a misplaced IRFP240.
All of the k170's measure between 38 and 44, the one you specifically asked me to measure is 42 ohms.
The irfp9240 flickers around between 0.05 and 0.25v, the other channel measures 5.39v. I assume that means a damaged/fried/doa component? Good job I have a couple of spares
The irfp9240 flickers around between 0.05 and 0.25v, the other channel measures 5.39v. I assume that means a damaged/fried/doa component? Good job I have a couple of spares
Sorry the one to the left never settles on a voltage, jumps around between 0.003 and 0.3, the one next to it is steady at 0.28v
That 9240 could be the problem. Check its insulation is not the problem first, then replace it.
Measures 100 ohms, I did have to remove the two 100 ohm and 47 ohm resistors as I'd bought 1/4 watt versions. Could I have damaged the pcb?
By the way also measure if the rectified DC source is as expected. In other words that there is equal but opposite polarity DC between the pins of each big reservoir capacitor.
That 100 Ohm completes the circuit to ground for the K170 current source energizing those three LEDs. You can verify that the PCB connections are still good around it if one of its legs has continuity to the K170 pins 2&3 and its other leg has continuity to ground.
I'll have to do that with the irfp240 and 9240 not attached to a heatsink I think, can't see how I can get to the capacitors pins otherwise
There is an alternative, you can measure on the diodes connected to them. I will show you.
No continuity between 100 ohm and any leg on the k170, got continuity between 100 ohm and nearest k170 leg on the other channel. Can I jumper it or connect the resistor straight to the nearest leg?
Even easier, you can measure between Rset resistors input pins and ground. Those Rset pins nearest to the 4700uF Nichicons. Represents what voltages are on those caps themselves for each polarity.
This one, could I cut the resistor lead and take it to the nearest leg?
An externally hosted image should be here but it was not working when we last tested it.
To K170 pins 2 or 3 i.e. gate or source. They are already shorted together by the board. There is a difference on how the mirror K170 is oriented in the other (negative) polarity. Don't copy its specific leg connection to the 100R in the positive.