17-07-2019, 05:13 PM
I have washed and checked the board both visually with a magnifier and point to point with a continuity tester, found nothing.
Thanks to all for the valued suggestions, however the problem is still not resolved.
The two 0.56 ohm resistors R8 & R9, measure 0.23 ohms in parallel after allowing for the resistance of my meter leads. I don't have alow reading ohm meter.
The TIP31 transistor is properly connected. When it was OC is when the 100 ohm resistor R6 burnt up and the 5v rail was at 12v.
From turn on it takes 12 seconds to get up to 5.146v, the same time it takes to recover once any load is taken off, tried with a 30 ohm load and it is exactly the same, voltage drops to 9 mV as soon as any load is placed on it.
The 12v supply stays at 11.99v no matter what the 5v supply does.
L4 is a ferrite toroid wound with thick enameled wire and is connected properly.
Looking like I am beaten, hate that, and a buck module will be the only way out.
I will however persevere if I can get any further advice.
Thanks to all again, Sam.
Thanks to all for the valued suggestions, however the problem is still not resolved.
The two 0.56 ohm resistors R8 & R9, measure 0.23 ohms in parallel after allowing for the resistance of my meter leads. I don't have alow reading ohm meter.
The TIP31 transistor is properly connected. When it was OC is when the 100 ohm resistor R6 burnt up and the 5v rail was at 12v.
From turn on it takes 12 seconds to get up to 5.146v, the same time it takes to recover once any load is taken off, tried with a 30 ohm load and it is exactly the same, voltage drops to 9 mV as soon as any load is placed on it.
The 12v supply stays at 11.99v no matter what the 5v supply does.
L4 is a ferrite toroid wound with thick enameled wire and is connected properly.
Looking like I am beaten, hate that, and a buck module will be the only way out.
I will however persevere if I can get any further advice.
Thanks to all again, Sam.
Boater Sam.
