Fluke meter acting up

[Tubetec]

I landed a consignment of used test equipment recently ,
all kinds of good stuff , temp probe kits , Peak Atlas LCR component testers , Fluke 177's and 1503 insulation testers , bags and bags of test leads , crok clips , probes and hooks .
Everything works to spec and aside from greasy paw marks, which clean easily , in like new condition .

One of the 1503 insulation tester meters has a minor issue , after 10 minutes inactivity on the volts scale it times out and switches off , like it should ,
but its supposed to come out of hibernation mode when any of the buttons are pressed , or if the dial is switched off and on .
Initially I found removing the batteries and putting them back in reset it and it works again , subsequently I found pressing any of the buttons then moving the dial makes it work again .

I took a look at Daves EEV blog and sure enough someone had a very similar issue with the 1503 , but instead of not turning on it wouldnt switch off unless they removed the batteries ,
he said he fixed it by cleaning the button pads ,but it was all bit vague , hit/miss . Anyway , next step is to remove the PCB .
I was just wondering if anyone else had similar issues with Fluke meters .

Another interesting thing revealed on EEV blog is that the 1503 meter actually has all the functions of its bigger brother , the 1507 built in , only difference is the 1503 is limited to 2.2 Gohms where the 1507 will read upto 10Gohm . Theres a couple buttons missing on the 1503 for the extra functions and the rotary dial is mechanically prevented from rotating to select 250,100 and 50 volt insulation tests . Other than that
the PCB's are identical.

 

[Tubetec]

I took out the board , cleaned the contacts , still the same on re-assembly , no big deal pressing any button then opperating the switch wakes it up .
The keypad switch contacts for the dieletric test and comparative modes are fully functional , drilling two small holes in the top panel would allow use .
Would the dielectric absorbtion test have any relevance for capsule measurement ?
obviously 1000 or 500 volt ranges are way to high for this .

 

[Tubetec]

Seeing as I was keeping the slightly sleepy 1503 meter myself I decided to modify it to provide the extra hidden functions on the 1507 .
I found a small semi circular channel behind the rotary switch with a corresponding notch which limited its travel , I used a small flat blade screwdriver to scrape away plastic material allowing the 200v,100v and 50v test settings be selected , works perfectly .
I also drilled two holes in the top panel over the DAR/PI and compare function switches ,they work too !

Funny thing is my modification seems to have fixed the original power on problem , switches on as it should now again .

 

[Tubetec]

Not quite 100% yet ,
It now powers on when you turn the the rotary switch on , but if its allowed to enter sleep mode it still requires a press of the lock button and turning the switch from the off to on position to restart it . I can live with that minor quirk

Later Ill file out the holes for the buttons properly , I can use a chunk of silicone self adhesive bump stop material to make the buttons accessible on
the top panel . I'll add a few pics illustrating things later.

 

[Tubetec]

I added dymo labels for the extra ranges ,
I cut a block of the translucent plastic into button shapes , thats visible on the left hand side button ,

The slight scrappyness around the new buttons was where the old owner had inscribed an ID code , not due to my handy work .
Took about 30 minutes with the zircon encrusted files to open the button slots , the boundaries of the holes are clearly lined out on the inside of the case so its easy to be accurate .The grey plastic grinds away with the file without any burrs ,
160 Euros in the difference between the 1503 and 1507 , well worth an afternoons tooling about !

 

[Tubetec]

I was thinking , might be interesting to use the insulation test to measure resistances with high voltage under load , then compare to cold tests with the DMM and LCR meter
Looks like a reasonable way to test caps for leakage also , the extra 50,100,200v ranges are handy to have

 

[Tubetec]

I took a selection of mil spec resistors ,1, 0.5, 0.25 and 0.1 % and went ahead and compared the Fluke 187 and four 177 series meters ,
resistance measurements were all in agreement to a very high degree.
I was then able to use the 1503 insulation test to measure a few of the higher value resistors under load ,
The 90k resistor I tested on the 50,100,200v tests gave a marginally different value, the value increased by 100 ohm as I went up the ranges
its a very tiny difference ,but these are best quality ,no expense spared mil grade parts , same test on resistors in the MegOhm range showed no signifigant changes , but load current was miniscule.

I'll dig out a few typical old out of spec carbon comp resistors from the junk box tomorrow and I can test them upto 1kV
I wouldnt be surprised if the standard component didnt hold up nearly as well as the high spec parts , why else do they cost the money ,
In any case we can afford the loss and exaggerate the test conditions way beyond what the resistors are rated to handle under real world conditions for the sake of proving effect exists and is measurable as a change in component value .

I was also able to use the oppertunity to refine the calibration on my XJW01 LCR meter , its spec'd at 0.3% , its now within a few handfuls of counts of the 187 on all resistance ranges with a 10,000 count display !
Many of the resisitors came to me labeled with accurate 5 digit values made on a proper LCR meter ,
Its nice to know all the meters are upto spec in the resistance range , but having both the LCR and the 187 readings very close is reassuring .
Low resistance and capacitance ranges are automatically handled better by the LCR with the sheilded Kelvin probes ,
the relative mode on the 187 ,which automatically subtracts the resistance of the test leads from the readings, its still very accurate down to a few tens of mOhms.

One of the nice features of the 1503 is the value is automatically held on the screen until the test button is pressed again , it has a number of compare modes that allow a simple component test to be done quickly and easily , you dont need to look at the screen, it beeps pass/fail
Examining coupling caps for leakage is another thing this unit most likely would do well .

 

[Tubetec]

The final detail I had forgotten was adding an extra hole in the top panel for the green led 'Pass' indicator , theres no sonic indication of pass/fail which would be a nice feature ,
Fluke went to the trouble of preventing light bleed from adjacent indicators , all trace of the green leds opperation was hidden until I opened the hole in the top panel .

So I can confirm that the 1503 does indeed include all the features of the 1507 except with lower limits on the max insulation resistance ,2 Gohm vs 10Gohm @1000v , not only that the mod is perfectly feasible with simple hand tools ,no spare parts from Fluke required , just a determination to get the job done.

I tested a foil cap 4u7 400v , it passed the 500v test with flying colours ,on the 1000v test I heard an arc inside the cap and stopped the test ,sure enough when I tested it again up to 500v it measured perfectly well , it had self healed

Best fun Ive had in ages ,I might have to refine my test methodology .