Dr Bruce Griffiths wrote: > Didier Juges wrote: > >> Even though you may have to be careful about noise, and assuming the >> operating voltages are not exotic, you can probably find an >> off-the-shelf switching supply that will fit where the transformer and >> linear supplies were, with lots of room to spare, and significantly >> reduced heat dissipation. I am thinking about doing that with the 5370, >> considering how hot the rear heat sink runs. >> >> Didier KO4BB >> >> >> > > Didier > > Replacing the HP5370 power supply with switching regulators will be a > somewhat challenging exercise in ensuring that switching regulator noise > doesn't degrade the 5370 performance. Even verifying this will be > challenging. If you don't burn yourself on the external heatsink there > should be no problem with reliability of the linear regulators. > > Bruce > > Bruce,
I am not too concerned about reliability. Power transistors are designed to run hot. I am concerned about burning myself on the heat sink (it measures well over 60 degree C here), and overall power consumption and heat dissipation in the shack, because the instrument is typically running a lot of time. I have installed it on top of the short rack I made for my main instruments to maximize air flow, but as a result, the heat sink is quite exposed. Also, my shack is above the garage, and therefore the air conditioning is not too effective there (3 walls, ceiling and floor face non A/C spaces). I have not looked in detail, but I suspect the voltage drop across the linear regulators is a little too high and probably could be reduced. I may also look at simply putting a switching pre-regulator in front of the existing linear regulators (or at least the worst offender, I am sure the 5V supply must be loaded pretty well) to reduce the voltage drop and the heat, while keeping the good regulation and low noise of the linears. I have a box of LT1074 integrated switching regulators which require only a handfull of components to make a complete switching supply. A small fan would address the high temperature, but would not help with power consumption and dissipation. That would be an easy fix though. Didier _______________________________________________ time-nuts mailing list time-nuts@febo.com https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts