[time-nuts] Fluke monitor
ernieperes at aol.com
ernieperes at aol.com
Fri Jun 4 06:42:21 EDT 2010
Just received a few hours ago my new Fluke monitor and just right now making the mods... I used 2SMD diode and the voltage on the CPU is 3,6 Volt..... hopefully will work properly......
Will report later on any problem.
From: GandalfG8 at aol.com
To: time-nuts at febo.com
Sent: Fri, Jun 4, 2010 11:57 am
Subject: Re: [time-nuts] Fluke monitor
In a message dated 04/06/2010 05:47:32 GMT Daylight Time, Leigh at WA5ZNU.org
fixed my fluke.l monitor.
This evening I got mail today from Bob Mokia:
The problem is too much volts on CPU (8051F330D).
ust have diodes 1n4148 etc at D1 and D2. Drop cpu volts to 3.6volts.
aximum volts from data sheet is 4.2 volts.
D1, D2, and D3 are zero-ohm SMT resistors in series from the 5V
egulator output. They are visible from the CPU board edge. Without
emoving the CPU board from the display, I was able to remove D1 and
ack a pair of 1N4148's in series from the D1 plus pad to D2, both right
t the board edge. I left D2 and D3 in place. I made the leads as
hort as possible, but still had to bend the parts up a bit to fit it in
As soon as I plugged it in, it worked. It's been on about 15 minutes
ow with no problems.
ongratulations on getting your monitor fixed.
hat's great news and very interesting, many thanks for sharing it.
ine are still packed away but I'm getting closer to being up and running
gain so will check them over when I can and adjust as necessary.
arking the component positions D1, D2, D3 presumably implies that the
esigner of the PCB allowed for this from the start so raises the question,"
hy wasn't it implemented as such?"
easurements I made following the initial confusion over supply
equirements did confirm that the display module will still function at 3.6
would have expected the contrast to require adjustment if the supply to
hat had also been dropped so perhaps the regulator output splits before
hat might also explain also why the option to fit the diodes was given in
he first place, instead of just using a lower output regulator.
erhaps the design of the original iCruze processor board was rather
lindly copied, with variation where necessary to accomodate the different
ackage and/or pin out of the 8051, but otherwise left the same and without due
consideration given to the voltage requirements of the replacement
lso of concern is the fact that your unit, and it appears some others
oo, did work as expected for quite a while before showing the symptoms you
hose symptoms then being consistent, at least without dropping the supply
oltage, suggests the possibility of some form of irreversible change, so
wonder if something in the processor itself, perhaps a protection device,
ight have been permanently damaged?
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