[time-nuts] LPRO-101 Heatsinking

Neville Michie namichie at gmail.com
Mon Jan 12 03:20:45 EST 2009

The LPRO is shown to run down to 18 volt supply which reduces the  
power dissipation, see the graph in the manual.
Like Mike I put one on to a heatsink and used a tiny under-run 12V  
fan to cool it.
I placed a thermistor on the heat sink and controlled the fan to keep  
the heat sink to about 37C.
I insulated the assembly so it can handle low temperatures.
It hold this within +or- 0.05 degree, which is a tremendous assist to  
the non-ovened XO.
It also reduces the power demand to about 7 or 8 watts.
There is a small burden on the MTBF specs, but in my book quite  
When I finish building some more gear I will get the improved  
performance data,
cheers, Neville Michie

On 12/01/2009, at 6:07 PM, Michael Baker wrote:

> Hello, Timenutters--
> I only have experience with four different LPRO-101
> units, but with respect to heatsinking, all 4 behaved
> identically during my testing of them.
> It appears that the LPRO-101 units do not require
> much heatsinking.  I experimented with a variety
> of heatsinks and discovered that just bolting them
> down to a 1/8" thick flat sheet of aluminum roughly
> 8" x 10" (no fins, just a flat sheet) kept the
> case of the unit and the aluminum sheet below
> 105 deg F.  That is relatively quite cool as far
> as electronic circuitry is concerned-- only
> slightly warm to the touch.
> The 4 units I tested were powered by a regulated
> 24VDC supply and the aluminum sheet was kept vertical
> and had good air flow around it.
> I also experimented with a heat sink that is very
> nearly the same size as the base plate of the LPRO
> units but only has ten 1/2" tall fins that are
> quite wide spaced on it.  With that particular
> very minimal heatsink the highest temp reached after
> 4 hours was only 97 deg F.
> I put a teeny 12 volt CPU fan about 2" from the fins and
> ran it on 6 volts DC to keep the blade speed waaaaaaay
> down (and essentially silent).  After two hours had
> elapsed, the heat sink and case were still only
> ever so slightly above room temperature.
> Bottom line seems to be that the LPRO units must have
> at least some minimal heatsinking but they do not
> require much.  The four units I tested came to me
> with their base plates covered with a very thin layer
> of some sort of a pale green heat transfer material
> so I did not need to apply any of the typical
> messy white "moose-poop" zinc-oxide and silicone grease
> heat transfer paste.
> Mike Baker
> Gainesville (Micanopy) Florida
> ---------------------------------------
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