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N_Cook

On 06/05/2016 20:05, wrote:
I have a computer that won't turn on unless it is warm enough. The
problem is in the power supply. If I use a blow drier to blow some
warm air through the exhaust holes in the power supply for a minute or
two the power supply starts working. I was told by someone here or on
the basics group that there is probably a bad electrolytic capacitor
causing the problem. I also have a CNC machine that has a servo amp
that acts the same. The machine must be on for a while and when the
cabinet that holds the servo amps gets warm enough inside the amp
start working and will work fine as long as the machine is kept
powered up. If the machine is turned off for an hour or so and then
powered back up the amp still works. But if the machine is off
overnight the amp acts the same as above. I replaced the amp so there
is no problem running the machine but I would like to repair this amp
so I can have a spare on the shelf. Anyway, it has only 3 physically
large electrolytic caps. I unsoldered one lead from each cap and
measured the capacitance with my Extech multimeter. The two 10 uf caps
measured 11. something uf and the 33 uf cap measured 37. something.
Could these caps be bad anyway? There are also three blue colored
dipped caps that have printed on them: .068K 250. I don't what the dot
in the .068K means but I don't think it's a decimal point. Maybe it
means lead free. There are also a couple 47 uf wound polymer caps.
Could either of these types of caps need to be warm before they work
properly? I have no schematic for this amp and have not been able to
get one. Furthermore, the company that makes this servo amp has ground
the markings off of any device with more than three leads.
Thanks,
Eric

I've seen a dot on ICs signifying PbF