FLUKE 8050A searching adjusting tip to set DC at 0000

[budm]

Re: FLUKE 8050A searching adjusting tip to set DC at 0000

And yet you still read it, LOL.

[Th3_uN1Qu3]

Re: FLUKE 8050A searching adjusting tip to set DC at 0000

Let the chairs fly!!!

Everybody, you should know that Greeks in general have a fairly short temper and hold their own idea until the end. You shouldn't get upset about it. In some cases, this can be a great quality, and it's certainly one that most of us Romanians lack, and we'd be in a totally different (and better) situation if we were more like the Greeks.

So everybody take a seat, leave this topic alone until something new happens, and let the anger dissipate.

[tom66]

Re: FLUKE 8050A searching adjusting tip to set DC at 0000

Until he kills himself, then it is no joke. I have met several reasonable Greek people. I have also met one Greek person (not Kiriakos) who is the most unreasonable, illogical idiot ever, but I treat him as the exception to the rule.

[Kiriakos GR]

Re: FLUKE 8050A searching adjusting tip to set DC at 0000

I have some updates to share.

I got some fresh 2500mA NiCD for my cordless power drill, and the old ones found a good home in my 8012A (NiCD qty 2), and the 8050A (NiCD qty 4).

What I do see as a problem is that fact that R26 (9.1 Ohm) stays very hot all the time at 74C = cooking up.
The R25 (12 Ohm) run a bit cooler at 43C, room temperature 22C .
The constant current PSU causes a constant flow of 300mA 24/24.

In the old days FLUKE could be happy with this design, but today I am not with it.
Other than the constant flow of 300mA the NiCD are all the time warm too.
The only option that I can think of is to add a second power switch so to turn off Mains completely.

[tom66]

Re: FLUKE 8050A searching adjusting tip to set DC at 0000

You decided not to use li-ion in the end?

[budm]

Re: FLUKE 8050A searching adjusting tip to set DC at 0000

If the constant current source is which is set at 1.25Vref/9.1 oHms = 137mA, that means the 9.1 Ohms resistor will dissipate 137mA x 1.25V = 0.17 Watts. What it means is that the LM317 is not working, instead of regulating the current, that is why you are getting 300mA flowing through the resistor instead. The LM317 has 1.25V ref voltage built in. Right now the resistor is trying to dissipate about 0.8 Watts of power (300mA is flowing through 9.1 Ohms, some may still flowing through the LM317).
the whole purpose of the constant current source is to limit the current flow to the set point as determined by the resistor, the current will force though the load up to the point where the Vload cannot be higher than the LM317 Vdiff.
So if the Vin is 15V and the Current is set at 100mA, if you short out the load, the max current will still be 100mA, the resistor (12.5 Ohms) will dissipate 0.125W (1.25V x 0.1A), the LM317 will dissipate 1.375W ((15V-1.25) x .1)
By the way, when power switch is activates, the resistors are put in parallel to provide BOTH the charging current and the operating current for running the meter. See post 24.
And of course the R25 (12 Ohms) will be cooler since less current is flowing through due to higher resistance than the 9.1 Ohm resistor, those two resistor are in parallel when power switch is activated.

[Kiriakos GR]

Re: FLUKE 8050A searching adjusting tip to set DC at 0000

I will try to replace the LM317 with another one so to investigate this possibility too.
What made to not suspect it as possible cause of the problem, is that all the voltages in the output are were you will expect them to be.

Tom@ I did manage to use another battery type successfully for all those weeks because I was not having spare NiCD at that time, now I do have.

[budm]

Re: FLUKE 8050A searching adjusting tip to set DC at 0000

The Voltage for the meter section is correct because they are generated by the switching power supply and it is important not to run the 8050A without batteries connected! plus the voltage of the batteries has to be correct since that will affect the -5 and -10V output. So I am not sure what happen when 7.2V batteries was used in place since the voltage of the batteries determines the voltage level into the power inverter which was expecting a little more than 4V instead of 7.2V, so we do not know as far as those output voltages are with 7.2V batteries in places. The -5 and the -10 may have gone higher also when 7.2V batteries were in place.
We will see when you try out the new LM317.

[Kiriakos GR]

Re: FLUKE 8050A searching adjusting tip to set DC at 0000

Unbelievable ... the LM which the meter was have on it, found to have one lead broken.

But now those resistors does not get hot any more and the charging current is at 100mA and 140mA with the switch off, but the LM317 runs hot 45C

The old one was LM317MP (attachment) and the New one LM317P+.

[budm]

Re: FLUKE 8050A searching adjusting tip to set DC at 0000

What voltage do you get if you put meter at the input pin and the output pin, then we can determine the power dissipation of the LM? Just multiply the voltage reading by 140mA to get the power. LM317P is the plastic tab without the metal tab for heat dissipation?

[Kiriakos GR]

Re: FLUKE 8050A searching adjusting tip to set DC at 0000

As is the LM in the picture from left to right 2.6V / 3.8V / 9.1V as negative point I used the batteries negative.

[budm]

Re: FLUKE 8050A searching adjusting tip to set DC at 0000

I believe the input voltage to the LM317 is about 18VDC, that means if the batteries is at 4.8V, the voltage across the LM317 will be about 13.2V, so at 140ma, the powe dissipation will be about 13.2 x0.140 = 1.85 Watts, which will be quite hot, and will be hotter when power switch is turns on. I put heatsink on my LM317 for the 125mA current source for charging my 4.8V NiCad using 19Vdc power source.

[budm]

Re: FLUKE 8050A searching adjusting tip to set DC at 0000

Per your picture, measure at the Middle pin (Out) and the Right pin (output pin). At least you are getting the correct current reading now. Can you fix the broken pin by extending it with wire?

[Kiriakos GR]

Re: FLUKE 8050A searching adjusting tip to set DC at 0000

Temperature by K-Type thermocouple gets high up to 64C

There is heatsink on it.
About the old one I do not know if it works.

[budm]

Re: FLUKE 8050A searching adjusting tip to set DC at 0000

The LM317 has Thermal protection, 64C with that heatsink? At worst, the LM317 will shutdown, I think it will get even hotter when the case is put back together, you may have to get the TO-220 with metal tab instead. It also makes sense why the resistor get hot since if the ADJ pin is not connected, the LM317 will just let the current flow right through (with slight voltage drop across the LM IN/OUT) and the current is only limited by that 9.1 Ohms resistor.

[Kiriakos GR]

Re: FLUKE 8050A searching adjusting tip to set DC at 0000

I did play my last card on this game and soldered the old back.
Volts 2.65V / 3.9V / 10.13 temp 51C it runs far cooler than with the other one.
I am going to measure charging mA and be back.

98 / 136mA

It looks that today 9 June, this meter restored back 100% after all this research, thanks budm !! .

[budm]

Re: FLUKE 8050A searching adjusting tip to set DC at 0000

Base on you voltage reading, the Vin-Vout = 9.1 - 3.8 = 5.3V (Notes: right now your batteries voltage do not reach the full charge yet since you are only seeing 3.8V), so the power dissipation is about 5.3 x 0.14 = 0.74 Watt which is not too bad, it should get cooler as the batteries are at full charge, but when the power switch is on, then it will draw more current and heat up more.

It looks like the metal tab dissipates better heat than the plastic tab. I think you will be OK with the old one, it did not get damaged, just a broken pin.
At 50~60c. I do not believe the Jct of the LM will be @150c.

[Kiriakos GR]

Re: FLUKE 8050A searching adjusting tip to set DC at 0000

just a broken pin.

At the point where the pin was broken it was in a totally blind spot, and impossible to see with out extraction.

Always with a bit of motivation I am getting more productive.
Thanks mate.


Even Fluke have seen that on me.
http://www.ittsb.eu/forum/index.php?topic=518.0

[budm]

Re: FLUKE 8050A searching adjusting tip to set DC at 0000

Glad you found the cause of the failure.

[Totoro]

Re: FLUKE 8050A searching adjusting tip to set DC at 0000

Hello all,
I found this thread (and site) because a search led me here. The problem here is not exactly what I have but kinda close. Maybe someone can help lead me to a solution. Thanks!
I also have a Fluke 8050A-01 and it works fine except that the 20V and higher ranges have a negative voltage offset. I got this off eBay and expected to have to put new batteries in. I swapped out the dead Panasonic NiCDs (already a replacement) and used NiMH units. (I know that constant trickle charging can kill NiMH so I simply won't do that.) I let the batteries charge and was pleasantly surprised by a working meter with a nice contrasty display. But...
The 200mV and 2V ranges are fine (and so then the ohm and current ranges). But the 20V range sits at about -30mV (30 counts) with shorted input. And it can vary, sometimes as low as -10mV and sometimes much higher, even -100mV! The 200V range tracks with a 3 count offset and so on. Again, the 200mV and 2V ranges are fine and give correct values for test voltages, +, -, AC. So, I assume the A/D is OK.

I've probed all around and cannot figure out where the voltage is coming from. The voltage is zero right up to the A/D (R8).
A bit more info in case it helps. The +13V rail is rather low at about 9.8V. Other voltages are in line. I have replaced all of the power supply caps (Frolyt ERF series) but the voltages and symptoms are unchanged.

If anyone has any ideas, I would really appreciate it. Thanks to all in advance.