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HELP!!!

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John Swift:
Hi Stan ,

the only danger with a small reservoir capacitor and a large capacitor on the output
is when the stored energy discharges the wrong way through the regulator

the protection diodes shown in the diagram are also helpfull
with multiple power rails if there is a loss of input to one regulator

(hot swopping of power supplies and amplifier modules is all ways good fun !! )


     John

John Swift:
Hi Stan
just tested cellulose thinners on the edge of a sieg pcb and it does remove the laquer
I would expect acetone to work as well

not wanting to disassemble the board I've not tested it on the components

hope it helps


    John

John Rudd:
I would avoid getting solvent on the component side, it will remove the ink used for marking items like capacitors.....

Celly thinners is probably better suited than acetone as it is slightly less volatile...

2 cents supplied...

John Swift:
 Hi John 
you are correct ,  it would remove the markings

but if the solvent  helps removing the ic's without damage to the pcb , I would use it  ( we need to save the pcb at all costs)

since I would change the electrolytic capacitors any way ,  the loss of the markings isn't a problem

but as in earlier posts I would have tried the easy bits like the power supply first

        John

John Rudd:
Sure thing John.......
If ic's are to be changed I'd be inclined to add ic sockets of a decent quality as an aid to any future troubleshooting ( much easier to change a chip that is socketed than soldered direct). Assuming we are not dealing with smt devices... :doh:

Umm, just checked one of the fotos....They are smd devices...

Ok, no problems..You can either butcher the chip by cutting the legs and then removing the left overs...or you could fashion a desoldering bit from a piece of copper bar to fit on your big soldering iron..

(Without sounding patronising or teaching granny....you need to be quick in unsoldering/reflowing...prolonged application of heat will inevitably impair the bonding of the copper traces to the board...But I'm sure you know this already  :D)

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