shitty chinese psu kit

[m3vuv]

Would it be ok to use the 5v meter supply to power a usb socket for charging phones etc?.,or would it cook?

[m3vuv]

well i fed a 7805 from the onboard 7805 feed,fitted it to a heatsink,working fine charging my vape,happy days.

[m3vuv]

Well,i had a disaster with this,i connected it backwards to a charged 12v car battery( polarity wrong),now no output,any idears what to check in what order? TIA.p.s the 5v usb still works and meter reads ov.

[Gyro]

If you did that, buy another one. 

[MK14]

Well,i had a disaster with this,i connected it backwards to a charged 12v car battery( polarity wrong),now no output,any idears what to check in what order? TIA.p.s the 5v usb still works and meter reads ov.

That's why it is a very good idea to use quality bench power supplies and/or decent quality and/or professional, schematics or better, if you're making your own.
Typically, they will survive such mishaps. As it will have taken such issues into account, when designing the power supply.

EDIT:
I'm assuming the power supply is built to a decent standard, without lots of shortcuts, in its construction, with reasonably decent quality components. Without significant over-loading of those components, etc. Otherwise, the power supply will tend to be something which is very unreliable and may break, even if you only look at it in a funny way.

[m3vuv]

Firstly thanks to mk14 and gyro,that isnt what i am asking tho is it?,buying a new one is the easy option,and i live mostly in a world of skint as off work waiting for an operation!,cheers anyway Paul M3VUV

[MK14]

Firstly thanks to mk14 and gyro,that isnt what i am asking tho is it?,buying a new one is the easy option,and i live mostly in a world of skint as off work waiting for an operation!,cheers anyway Paul M3VUV

If it has got a (normally) reverse biased (power) diode, across (internally) the output terminals. Then that diode, may have gone short circuit, because of the reverse polarity.
If it hasn't, then you might have blown your PCB tracks (Maybe!!!!, lead-acid batteries, can give out huge currents) and/or burnt out a current sensing resistor, along the output section. Which also might mean the output transistors, have (probably) gone short circuit.
But I'm guessing, there are many possibilities.

I'd normally check the schematics, but there are so many different ones in this thread, I've given up on trying to identify which one, is the correct one.

[m3vuv]

So far all the emitter resistors were open,the diode mk14 is talking of was faulty as well,i have replaced those but still no output,all tracks look good but i beefed those up when upping the power output from it!,cheers m3vuv.

[Gyro]

Well if the emitter resistors are fried, then the pass transistors probably are too, and their driver transistor etc (cascade failure). It's basically a process of working backwards from the output until you weed out all the components that were damaged by all that reverse biassed current (hence the comment about buying a new one, it's the more expensive parts that suffer in such situations).

It would be best to check all components without powering up in between to prevent repeat damage, eg. Shorted pass transistors will take out a new driver.


P.S. Don't assume that, if the pass transistors aren't shorted, they are ok. Several hundred amps from a car battery can easily blow the bond wires open. At least do diode tests on their junctions.