Fluke 87V wont turn OFF

[AngraMelo]

Hey guys, got a cheap 87V from a dude over the internet.
Came with both fuses blown but the fusible resistor was fine.
When I try to power it off it just goes to uA mode.
I tried everything, cleaning the contacts, measuring all the capacitors and diodes... I though it was an allignment thing on the selecting weel but it seems more than that.
I do have a working 87V here and I check all the measurements and they are very close besides one smd diode.
The diode right above the battery jack reads 30Mohm on the good 87 and 3Mohm on the bad.

Im a bit lost, is that a function that I ahve to turn off? What else should I check?

I dont have the option to send it back to fluke because I live in Brazil and when the meter gets through customs they will simply charge me a insane ammount of money as if I were importing it.

any tips?

[lowimpedance]

 Your best bet would be to down load the original 83-85-87 series service manual, now this is of course not the 87V (which has no available schematic.) but will be better than nothing.
Compare the 87 schematic for the power supply section and the 87V PCB to see any similarities and hopefully there are.
 The 87 manual has a power supply test section for faults that might shed some light. Particularly as you have a good 87V to compare against.

The Fluke web site has the service manual for the 83,85,87 series.

[retiredcaps]

Came with both fuses blown but the fusible resistor was fine.

That is pretty standard with my ebay experience despite seller advertising meters as working.  When I tell them the fuses are blown, they don't believe me saying the meter turns on.  Obviously, they don't understand what the fuse does in a meter and probably shouldn't be using a Fluke.

When I try to power it off it just goes to uA mode.

Does the lcd on the meter show the correct annunciators in all positions other than off?  Does DCV rotary setting show DC on the lcd?

I tried everything, cleaning the contacts, measuring all the capacitors and diodes... I though it was an allignment thing on the selecting weel but it seems more than that.

Did you look under the selector wheel?  See

http://mrmodemhead.com/blog/fluke-83-dmm-repair/

What is the current draw when the broken 87V is on DCV and off?  Are they comparable to the working 87V?

[retiredcaps]

The 87 manual has a power supply test section for faults that might shed some light.

Modemhead's Fluke 83 blog entry that I referenced above goes through troubleshooting and measuring the 83 power supply.

[AngraMelo]

Your best bet would be to down load the original 83-85-87 series service manual, now this is of course not the 87V (which has no available schematic.) but will be better than nothing.
Compare the 87 schematic for the power supply section and the 87V PCB to see any similarities and hopefully there are.
 The 87 manual has a power supply test section for faults that might shed some light. Particularly as you have a good 87V to compare against.

The Fluke web site has the service manual for the 83,85,87 series.

I will look for them and check them out!

Came with both fuses blown but the fusible resistor was fine.

That is pretty standard with my ebay experience despite seller advertising meters as working.  When I tell them the fuses are blown, they don't believe me saying the meter turns on.  Obviously, they don't understand what the fuse does in a meter and probably shouldn't be using a Fluke.


Does the lcd on the meter show the correct annunciators in all positions other than off?  Does DCV rotary setting show DC on the lcd?

It shows the correct annunciators, the off position is the only one not working. It does show DC on the LCD when on DCV mode.
the current when on DCV is about 1.65mA
I cant measure the current when it is off because it will only turn of if I take out the battery.

[AngraMelo]

You meant the current when the selector is over OFF? If yes, than the current is 1.28mA

[AngraMelo]

I also looked under the selecting weel, both the good 87 and bad 87 look identical, from their spacing to their hight.

[lowimpedance]

The 87 manual has a power supply test section for faults that might shed some light.

Modemhead's Fluke 83 blog entry that I referenced above goes through troubleshooting and measuring the 83 power supply.

 Nice practical walk through the procedure.

@AngraMelo, follow the linked blog above rather than the manual to start with.

[retiredcaps]

I also looked under the selecting weel, both the good 87 and bad 87 look identical, from their spacing to their hight.

When I mean look under, I mean to remove it and look under.  See

http://mrmodemhead.com/blog/fluke-83-iii-rotary-switch/

[AngraMelo]

I took it all apart, including the weel and cleaned it. I was not clear on the previous reply, I meant to say that I detached the weel from the board and check the contacts against the good 87 and they were identical, I also rubbed them with isoalcohool as well.

[lowimpedance]

If the meter functions correctly when actually switched to various modes but cannot be turned off then go through the external components associated with the power supplies for shorted or leaky parts.
It has to be one of those, and the 87V will probably be similar to the earlier series in respect to the supplies and how its turned on and off.

[AngraMelo]

To keep you guys updated:

Ive found a shorted transistor, it is a 3904 in smd format with the letters 1am over it.
As soon as I order a new one and get it fixed I will post pics for future reference if anyone has the same problem.

[lowimpedance]

Thanks for the update. Had to chuckle at the bit in your sentence "1am over it"  .
Sounds like you are well 'on it' now. 

[ElecSeb]

1AM   MMBT3904L         General Purpose Transistor NPN Silicon   http://www.onsemi.com/pub/Collateral/MMBT3904LT1-D.PDF

[AngraMelo]

hahahahahhaha I did not see that! I guess I was so glad Ive found something that Im making jokes without even noticing!

[AngraMelo]

Well friends, I changed the smd transistor and it still continues. I can still measure the short between base and emitter. I look at everything around it but I cant figure it out.
The meter still wont power off

[Psi]

Fluke sometimes will replace their meters even if you don't have any documentation.
Could try contact them.

[coromonadalix]

when the transistor was removed the meter did come off ?    you may have something failed who always drive the transistor on ?

could you take a picturs on the transistor section ?

what is the transistor pcb markings location ?


There is the model 87 service manual:  i think it sould be similar to the 87V serie in some ways.

http://assets.fluke.com/manuals/83_85_87smeng0500.pdf

Check section 5-10 page 83,  you have the Q3 transistor  mmbt3904  who drives Q8,  maybe you have something like the mosfet (Q8)  who can be shorted out

[AngraMelo]

Thank you for the schematic!

The 87V is rather different but Im found some similarities.

Here is a picture of the bad transistor that funny enough was replaced and is still bad...

[coromonadalix]

ok
When you removed the shorted transistor, have you tried  the meter ? is the meter stayed off ? or on ?

I would remove it again, and check the other nearby sot-23 transistor for short ?

Not sure about the 5 pins sot, maybe one is an regulator and the other an protection device,  could you write their markings ?

[AngraMelo]

Both the 5 pin smd's seem to be regulators.
The small one is marked: AQI
the larger one PCYI

The other transistors on upper left corner of the picture do not appear faulty.

I did not try the meter without that transistor. I will do that tomorrow and get back to you!

Thank you so much for helping me!

[coromonadalix]

I think the AQI  is an LDO regulator like :

AQI smd marking gives this :
    TPS71533DCKR
    MAX6745XKLD3
    BQ71533DCKR

and  PCYI  gives this :     TPS77050DBVT, TPS77050DBVR,  TPS77050DBVRG4, TPS77050DBVTG4

I maybe wrong   but ?  they are regulators in sot 23-5 packages

[ElecSeb]

Also something to check are the resistors around.
Found last weekend one in a fluke near a Q which was unlimited, preventing the Q from closing and thus one reason for problems.

[AngraMelo]

Exactly, I got the same results as your for the Q`s.
I will also check the resistor. I have a crazy pain in my neck from keeping my head down on the bench for too long. Ill take a look as soon as I get better!
thanks guys

[ElecSeb]

Sometimes it is difficult to distinct values, so you might need to desolder from the board.
In my case it was an 1MOhm...

IN your case I would start with the 01E, O1D and 01C around it.

Currently waiting for my orders to continue my repairs...