Fluke 179 won't tun on

[stj]

Re: Fluke 179 won't tun on

is the battery good? i know it's a stupid question.

start at the board where the battery lead is soldered - i'v had the battery clips fail on stuff before.
i suppose there is a voltage regulator circuit we need to find.

[keeney123]

Re: Fluke 179 won't tun on

Pin#
1 - 13= 7.6V and slowly drops
14= 8.8V and slowly drops.
This slow drop, happens at the battery as well, measured from the COM.

Are you measuring right across the battery when in circuit?

[tibimakai]

Re: Fluke 179 won't tun on

I'm noticing some kind of yellowish deposit inside the case, specially at the bottom of the meter around the plugs area.
Could be a spill victim?

[tibimakai]

Re: Fluke 179 won't tun on

Pin#
1 - 13= 7.6V and slowly drops
14= 8.8V and slowly drops.
This slow drop, happens at the battery as well, measured from the COM.

[tibimakai]

Re: Fluke 179 won't tun on

I have placed the PCB in the case and that way I have turned the switch.
I'm trying to measure DJ Ricoh's measurements, but I'm having problem seeing those small numbers.
At pin #14 I have the battery voltage of 8.963V.
At all the pins I'm measuring above 7V. That is normal?
CD4069UBE

[keeney123]

Re: Fluke 179 won't tun on

Make sure the switch is actually making contact

[tibimakai]

Re: Fluke 179 won't tun on

I have turned to Ohm scale, with the switched installed.
I'm measuring pin #1&2 of the TI IC, which are the digital + and analog + and they are not getting any voltage. Basically, the TI IC is not getting turned on.
There is a 5 pin VDO(I assume) at the bottom right of the TI IC which also not getting any voltage.
The measurement,s should I take from the COM, right?

[tibimakai]

Re: Fluke 179 won't tun on

Later on, when I get home I will start measuring.

[keeney123]

Re: Fluke 179 won't tun on

So I have attached the micro controller info that TI has. Right now we are interested in page 6 for the pinout, page 9 for block diagram function and pages16,17,18 for terminal functions. If you look at these you will know where to test the frequency and supply voltage. I love TI they tell you everything.

[stj]

Re: Fluke 179 won't tun on

looking at page9, it can handle 2 crystals or clocks for some reason, and it has a reset/nmi pin that i would check is not stuck low.

[stj]

Re: Fluke 179 won't tun on

the display is a matrix, but has no drive circuitry, the driver is integrated into the microcontroller usually.
lcd requires a high frequency ac drive btw, if the mcu is dead or the crystal is dead you wont see anything.

[keeney123]

Re: Fluke 179 won't tun on

it's not a digital display, it's bare glass with nothing to short.
just a load of liquid crystal between oxide electrodes that probably have a reasonable resistance anyway.

So how do they turn on and off the segments of the liquid crystal display to show numbers? Do they not have a matrix coming out of the processor or in the display chip to enable the rows and columns of the display to turn on and off so they can change the digits of the display?

[stj]

Re: Fluke 179 won't tun on

stj it depends on how the lcd display dies. If a short inside the display the computer would shut it down before one would realize it was on. Also, if the power lines inside the display have somehow opened the display would not turn on. If one measures the input to the display and the designer did not shut down the power because of no return pulse train from the display with a bad display, one could measure and see that the processor is trying to turn on the display.

it's not a digital display, it's bare glass with nothing to short.
just a load of liquid crystal between oxide electrodes that probably have a reasonable resistance anyway.

[tibimakai]

Re: Fluke 179 won't tun on

I have tried, but it did not turn on.
Texas Instrument M430F437

[keeney123]

Re: Fluke 179 won't tun on

tibimakai after you fixed the open run to the 9 volt battery did you put the unit back together to see if it would work or where you just expecting to see the led lights to light. If you did not at least put in the selector switch you may of never turn the unit on and perhaps the designer also monitor the LCD display to see if it turned on. If you did not put the unit back together I would do this as you may have already fixed the problem without knowing it.

stj it depends on how the lcd display dies. If a short inside the display the computer would shut it down before one would realize it was on. Also, if the power lines inside the display have somehow opened the display would not turn on. If one measures the input to the display and the designer did not shut down the power because of no return pulse train from the display with a bad display, one could measure and see that the processor is trying to turn on the display.

[stj]

Re: Fluke 179 won't tun on

so scope the display pads - but i'v never seen an lcd just die - bad segments maybe but never nothing.

the msp430 microcontroller is ultra-low current.
you dont really need to turn them off.

[keeney123]

Re: Fluke 179 won't tun on

did anybody check the vcc and the crystal on the microcontroller?

stj here is another problem. If he is measuring this circuit without the selector switch in the circuit, all circuits should be off. I would think one would have to jumper the contacts of the selector to turn on the meter. If the meter is off then why did they not put in the selector switch "contacts" to switch the power from the battery so the battery is not being used when the meter is off? For all we know is everything is working correctly and we have a bad display.

First we have to know which pins those are. The Vcc pin. The crystal on the processor I believe I know where that is, but it may have a internal circuit for the oscillator or there maybe external components that set up the frequency. I do not know the processor number so I can not tell the pin outs. Even if one knows the number Fluke could of had this processor made just for them and they control the information on the chip. One really needs to have a schematic to troubleshoot a circuit and the data sheets of the chips. With processors one also need to know the program. Then one needs a logic analyzer to see where the program fails. Yes the basic things like Vcc and the oscillation could be checked. First one has to know if the selector contacts need to be jumpered to get the meter out of a stand by mode. Then one could connect a scope up to the display to see if the display is being turned on or one could see if the LEDs are turning on. That would indicate the processor is up and running.

[stj]

Re: Fluke 179 won't tun on

did anybody check the vcc and the crystal on the microcontroller?

[keeney123]

Re: Fluke 179 won't tun on

I have been thinking about this circuit we are looking at. This circuit appears to only measure if the possessor is up and running instead of if there is a voltage and if that voltage is correct. So you do not need to check that transistor out. So with that being said what we know is that if the processor is not turning on this Transistor/Cmos and you are measuring 6 volt at the transistor we have a problem. The problem is that there is some conduction going through this power up circuit. This then presents another problem. Did the designer mean for this to happen? I would say no because if the circuit in not up and running I do not want to drain the battery, however if I am in stand-by mode to conserve the battery I do not want to turn the circuit off completely so I can turn it on quicker with less inrush current. I would say your circuit is indicating that the meter is in stand-by mode. Have you verified that the 9 volt battery is actually 9 volts DC? If the battery is indeed 9 volts we need to understand why it is not coming out of stand-by mode. Stand-by mode would be used to measure if the instrument is being used or not. The designer would measure this from the input of the meter. He can do this in several ways. I would do it by using a comparator off of the input measurement . This comparator then would be monitored by the processor. If I did not read a high level then I would go into a count down sequence. After a certain time I would then put the circuits in stand-by. Also, once I measure a high I would then reset the count down clock. So what we can do is find out if the part number on the remaining chips actually have a data sheet or if fluke has prevented this from happening.

[keeney123]

Re: Fluke 179 won't tun on

To me, it seems like it is still connected. I measured right at the plastic.
Here is a picture taken with my phone, I can't really tell what is it, 1R?

I want you to measure between the two blue arrow to see if you still get 6 volts at the same 6 volt measurement. Then if you have a variable power supply. You could build it out of a nine volt battery and a rheostat. I want you to take out the resistor I have circled in blue. Measure the resistor you just took out. Find a resistor of the same value with-in 5% and connect it up to your variable DC power supply on the positive side. The other side of your variable supply, the negative, you want to connect to the negative side of the battery of the meter. Now take a insulated wire 28 gauge or bigger and solder it from the output between the resistor you have connect to this variable power supply and the input of the transistor where the other resistor had connected to the transistor. Make sure the rheostat is set to its maximum value. Which means maximum resistance so as little current will flow, you could put a switch in line so you can turn off the power to the circuit. The rheostat resistance plus the resistor in series should lower the current/voltage value enough so it will not harm the transistor. The maximum rheostat value should be 1.5 times the resistor value. So if the resistor is measured at 100 ohms the rheostat needs to be 150 ohms. After all this is done you can turn the meter to on position. The leds should still be off. With another meter you want to monitor the voltage from the ground to the transistor where you have connected the resistor. Slowly turn the rheostat, but do not let the voltage your monitoring go above 6 volts. If the transistor/cmos is good it should turn the leds on before you reach 6 volts.