Hi everyone -
just finished connecting everything up on my f5, softboard works, dc protection works, psu work, one channel works, the last board put in - R7, R8 and R14 burned. Needless to say, gutted and confused. Any idea?
thank you
Philip
just finished connecting everything up on my f5, softboard works, dc protection works, psu work, one channel works, the last board put in - R7, R8 and R14 burned. Needless to say, gutted and confused. Any idea?
thank you
Philip
I guess you didn't test each channel separately and use an dim bulb tester.
Did the resistors burn on start up? Did you see if there might be a short of the
output mosfets to heatsink (punctured insulator, for example)
Is it possible your P1 and P2 were set to the 'wrong' direction?
Did you verify that P1 and P2 were at minimum value before powering up?
(i.e., check that the measured resistances at R5 and R6 were close to zero)
Please post some well-lit, in-focus photos of the board which might help others
spot what might have gone wrong.
Did the resistors burn on start up? Did you see if there might be a short of the
output mosfets to heatsink (punctured insulator, for example)
Is it possible your P1 and P2 were set to the 'wrong' direction?
Did you verify that P1 and P2 were at minimum value before powering up?
(i.e., check that the measured resistances at R5 and R6 were close to zero)
Please post some well-lit, in-focus photos of the board which might help others
spot what might have gone wrong.
hi Dennis - no each board was tested in turn. The first one connected and is ok. the second one blew. Yes - they blew up straight away and smoke came out. I didn't check anything in advance, just connect it and power up. i'll check R5 and R6 later on. Don't know how to check the others though
Those are a little high if the pots are turned all the way down, but I don't
think that is the cause of your problem.
Just for fun: Can you measure the resistance between output and ground for both
channels?
I would suggest looking for shorts on the bad channel. Also photos of both front and back of the board will be helpful.
think that is the cause of your problem.
Just for fun: Can you measure the resistance between output and ground for both
channels?
I would suggest looking for shorts on the bad channel. Also photos of both front and back of the board will be helpful.
hi Dennis - thank you for your help. Looking at the circuit diagram, those resistors are connected to the JFET. I'll check the voltages V+, V- and ground How do i check the transistors?
I suggest going over the boards carefully to verify all parts are in the right place
and that the soldering looks fine.
Your output to ground (ie, the pos and neg outputs) should measure about 30 ohms.
You probably then want to take the board from the heatsink and further inspect the
bottom. Check in particular the insulator pad and the condition of the mosfets.
There are some tutorials on testing mosfets with a multimeter but I think you need
to desolder them from the board first.
and that the soldering looks fine.
Your output to ground (ie, the pos and neg outputs) should measure about 30 ohms.
You probably then want to take the board from the heatsink and further inspect the
bottom. Check in particular the insulator pad and the condition of the mosfets.
There are some tutorials on testing mosfets with a multimeter but I think you need
to desolder them from the board first.