Electronics Repair (sci.electronics.repair) Discussion of repairing electronic equipment. Topics include requests for assistance, where to obtain servicing information and parts, techniques for diagnosis and repair, and annecdotes about success, failures and problems.

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Old February 5th 08, 02:01 AM posted to sci.electronics.repair
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Default Fluke 79 acting up

James Sweet wrote:

I invested in a moulded rubber surround for my 77, after repairing one
that had been jarred and the main SMD chip had loosened. Someone I know
managed to put his knee on his, while working on the floor, and also
dislodge the main chip. Both repaired after attending to the main chip.




I have the rubber surround, and it hasn't been jarred, it was sitting in the
closet where I always keep it.

I ordered a Fluke 187, I've wanted true RMS for a while anyway. When that
gets here I'll use it to try to fix the 77 and use that as a backup.


187,189 has been discontinued by fluke and replaced with a 287,289..

So beware of people selling you out dated meters.

get a 289, you'll like it!


--
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Can't think of any, that's why i'm here!"
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Old February 5th 08, 02:09 AM posted to sci.electronics.repair
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Default Fluke 79 acting up




187,189 has been discontinued by fluke and replaced with a 287,289..

So beware of people selling you out dated meters.

get a 289, you'll like it!




The 77 I'm replacing is over 15 years old, it still served most of my needs
just fine, all it lacked was true RMS. What do I care if a meter is out
dated?

Screw the 289, it'd cost me 3 times what the 87 I found did, and I can't see
anything extra it does that I need. That's a lot of budget I could use for
other hobbies.


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Old February 6th 08, 03:46 AM posted to sci.electronics.repair
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Default Fluke 79 acting up

On Feb 3, 2:15*pm, "James Sweet" wrote:
This thing has performed flawlessly for many years, but when I turned it on
today something was not right. The ohms range flickers random readings, with
no probes plugged in I get around 230K on the display, or 2.22M, depending
on the range, which would imply that the problem is ahead of the scaling
circuit. When I switch to the low ohms range, the reading starts around 240
ohms and then drops to -0.00 over a period of 10 seconds or so, frequency
reading works, but AC volts reads 70mV when plugged into a 120V outlet.
Something strange is going on! I realized that I don't currently have a
backup meter, I suppose I could use this as an excuse to buy a true RMS
Fluke, I don't think I can bring myself to buy a cheapie, except perhaps as
a backup. Anyone run into this?


The rotary switches get dirty over time. Take the meter apart and
clean the rotary switch with contact cleaner. If there's carbon
strips on the back side clean them with an alcohol soaked Q tip.
Also, clean the button grids on the circuit board with alcohol.

good luck

Bob
WC3P
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Old February 6th 08, 05:02 AM posted to sci.electronics.repair
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Default Fluke 79 acting up

The rotary switches get dirty over time. Take the meter apart and
clean the rotary switch with contact cleaner. If there's carbon
strips on the back side clean them with an alcohol soaked Q tip.
Also, clean the button grids on the circuit board with alcohol.




Tried it, no change. I covered all the easy stuff, including touching up any
suspect solder joints I found.


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Old February 6th 08, 09:05 AM posted to sci.electronics.repair
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Default Fluke 77 acting up

James Sweet wrote in message
news[email protected]
The rotary switches get dirty over time. Take the meter apart and
clean the rotary switch with contact cleaner. If there's carbon
strips on the back side clean them with an alcohol soaked Q tip.
Also, clean the button grids on the circuit board with alcohol.




Tried it, no change. I covered all the easy stuff, including touching up

any
suspect solder joints I found.



Have you tried, as a test, cable tie/s around meter body plus packing piece
plus folding wooden clothes peg wedges, over the main chip ?


--
Diverse Devices, Southampton, England
electronic hints and repair briefs , schematics/manuals list on
http://home.graffiti.net/diverse:graffiti.net/








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Old February 6th 08, 04:31 PM posted to sci.electronics.repair
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Default Fluke 77 acting up

Meat Plow wrote:
On Wed, 06 Feb 2008 08:05:14 +0000, N Cook wrote:

James Sweet wrote in message
news[email protected]
The rotary switches get dirty over time. Take the meter apart and
clean the rotary switch with contact cleaner. If there's carbon
strips on the back side clean them with an alcohol soaked Q tip.
Also, clean the button grids on the circuit board with alcohol.


Tried it, no change. I covered all the easy stuff, including touching up

any
suspect solder joints I found.


Have you tried, as a test, cable tie/s around meter body plus packing piece
plus folding wooden clothes peg wedges, over the main chip ?


How about baking it in the oven with Ricotta cheese and a good Italian
sauce?


Now then... don't be sarky

Ron(UK)
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Old February 8th 08, 05:03 PM posted to sci.electronics.repair
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Default Fluke 79 acting up

Jakthehammer wrote:

Correctly, the zener (or an IC reference circuit) are part of the A/D
circuit. You cannot design a complete A/D without Voltage Referencing.

Jack....



The reference may also be a separate IC. I've used a lot of them over
the years. Our telemetry receivers used a 10.000 volt reference in
multiple systems, so we used an external reference with a buffer so it
could be trimmed to exactly 10.000 volts.


A low voltage zener isn't suitable for a reference in a meter. The
knee is too soft, and they drift with temperature changes. If all you
want is +/- 10% tolerance it would be ok, but that level was obsolete by
WW-I.


--
Service to my country? Been there, Done that, and I've got my DD214 to
prove it.
Member of DAV #85.

Michael A. Terrell
Central Florida
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Old February 9th 08, 04:18 PM posted to sci.electronics.repair
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Default Fluke 79 acting up

On Feb 4, 7:58 pm, "James Sweet" wrote:
I want the 87-V I guess. I won't buy used though. While I got your
attention, do the digits on you 77 appear solid black? Mine look a bit
brownish and I don't remember if they were ever black. I've had it new
since around 1987 if memory serves me correctly.


There are a few authorized Fluke dealers within driving distance from me.
I guess I'll make some calls tomorrow and see what prices I can get. These
places don't sell to joe consumer so they usually have competitive
pricing.


I've only ever bought used, in this case it was a demo or some sort and
comes in the original box with accessories and warranty, I'm not gonna pay
another hundred bucks to get to break the shrinkwrap. I saw a surprising
number of new and nearly new Flukes on ebay, with many going substantially
below retail. For some silly reason, I dislike the new wedge shaped models
and prefer the classic style. I have no logical reason for that though as
it's a tool.

The digits are black on the 77, though some of the segments are a bit washed
out. I fixed that years ago by washing the zebra strips but it came back
eventually.


I had a similar problem with a 79. Fluke had a problem with the
cleanliness of the LCD Display contacts on some versions. Take apart
the meter & remove the LCD display. On a flat friendly surface,
carefully thoroughly clean the contacts with an eraser. Make sure no
residue is left & re install. Made mine look better than new.


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