[sdiy] White Lithium Grease for Heat Sink?

[mike ruberto]

Hold on I think I'm on to something. By being clumsy with the test
probe I managed to short out the Negative fixed regulator. Now both
rails exhibit the same problem. I guess it's the fixed regulators ;-)
DOH!

Mike

On Feb 16, 2008 9:24 PM, mike ruberto <somnium7 at gmail.com> wrote:
> Thank you Tim! It's good to know I can get away with it.
> Unfortunately, it's moot now as I just discovered that the pass
> transistor in this power supply isn't to blame at all.
>
> I think I could use some assistance with it. Here is the schematic.
> http://i108.photobucket.com/albums/n13/somnium7/gear/RX7PSU.jpg
>
> Problem is the +22V is very low. Initially it measured 6.5V on the
> output. I just swapped the big pass transistors - Q1 and Q2 with each
> other.
>
> Now I have -22V and +10V. Grrrrrrr.
> This is such a crap circuit design - biasing those fixed regulators
> like they did. Just kill the ripple rejection!
>
> I need to go take some voltage measurements around M301 and D302. If
> the problem is blatantly obvious to somebody please tell me. It would
> be hugely appreciated!
>
> Mike
>
>
> On Feb 16, 2008 9:15 PM, Tim Parkhurst <tim.parkhurst at gmail.com> wrote:
> >
> > On Feb 16, 2008 5:52 PM, mike ruberto <somnium7 at gmail.com> wrote:
> >
> > >
> > >
> > >
> > > I was wondering if I could get away with temporarily using white
> > > lithium grease for the thermal bonding between a power transistor and
> > > a heatsink. Any reason this would be bad?
> > >
> > >
> > > Mike
> > >
> > > _______________________________________________
> > > Synth-diy mailing list
> > > Synth-diy at dropmix.xs4all.nl
> > > http://dropmix.xs4all.nl/mailman/listinfo/synth-diy
> > >
> > >
> >
> > The main function of heat sink compound is to eliminate any air gaps between
> > the mating surfaces of the device and the heat sink. This is why you only
> > need a thin film of compound. In that respect, lithium grease should work
> > okay. It may not work as well as actual heat sink compound, but I think it
> > will be better than air(which is a surprisingly good insulator). You should
> > eventually replace the grease with proper HS compound, but it should be okay
> > as a stopgap measure.
> >
> >
> > Tim (meant to send the reply to the list) Servo
> > --
> >
> >
> > "Imagination is more important than knowledge." - Albert Einstein
>