[time-nuts] Fluke monitor
brooke at pacific.net
Wed May 12 17:41:10 UTC 2010
Is the wiring to the monitor exposed such that you can touch it? I
think mine died because of static zap to the exposed wiring.
Leigh L. Klotz, Jr WA5ZNU wrote:
> On 05/06/2010 12:29 PM, Arthur Dent wrote:
>> "But now here is the finding..... The monitor board has the 7805 SMD
>> version and
>> I was feeding from +12Volt and after a while the SMD voltage
>> regulator overheated
>> and started to drop the voltage.... and it was the reason to
>> receive/display garbled
>> msg.....the display is built into the same box as the gpsdo..... the
>> temp of the gpsdo
>> was around 45 Celsius, so inside the box the temp also was elevated
>> so no wonder
>> why the SMD voltage reg overheated...."
>> Glad to hear you were able to find the problem. Quite often you can
>> use a can of spray
>> coolant to identify thermal problems like this one. The regulator is
>> rated 0.5A but the
>> amount of power it was asked to dissipate caused the thermal
>> shutdown. It was working
>> just the way it was designed.
>> One suggestion I would make is to epoxy a small heatsink onto the
>> chip to make sure
>> this doesn't happen again. The 75 ohm resistor you're using will
>> probably take care of
>> the problem permanently but even a small heatsink cut and formed from
>> a soda can
>> wouldn't hurt.
> My fluke.l monitor stopped working today after one overnight session.
> LH is connected at the same time and is reporting good data from the
> I currently think that it's perhaps a clock speed issue, not a voltage
> issue, because I'm getting 5V out of the regulator right now and it's
> not working.
> Here's how I got here:
> The monitor is a recent model and has the regulator. I left it on
> overnight, in its original case and out in the open, hooked to a 13.5V
> supply. I had it on a ammeter the whole time, and it never draws more
> than 0.02A. The backlight is fine and the display works.
> It says "No Message" and occasionally gives garbled displays of other
> Once it said "No Message / PowerSupply Fail" but not again.
> Turning it off for an hour didn't help.
> I tried it at a lower voltage (8V) and it works some, alternating
> between "No Message" and some data or otehr every few minutes, but the
> data doesn't appear to be accurate (claiming 2D/3D mode when it's not,
> including question marks in numeric fields, etc).
> With 12.2V-13.5V in, I get 4.99-5.01V from the square via on the left
> of the board to the 3 round vias next to it, yet I still get "No
> message" or garbled data.
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