Electronics > Repair

Fluke 289 not quite sorted.

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say:
I have also tried to identify some of the voltage supply ICs, which might be helpful:

U17 is a 5 volt regulator.
U42 19AI25 is 2.5V precision reference, which I believe is connected to COMM jack.
U44 is an adjustable supply set to 1.9V as per my calculation.
U21 is a 20V LCD supply,  I guess.
There is a U15 IC, which I could not locate but guess it's hidden under U42. I also guess it would be 3.3V (or 3.11V)  regulator.

U18 is a voltage supervisor IC, which shuts down the MS430 if one of the monitored voltage supplies fail.

Any correction/comments on the above data would be welcome.

ElecSeb:

--- Quote from: say on January 01, 2019, 01:05:17 am ---I have also tried to identify some of the voltage supply ICs, which might be helpful:

U17 is a 5 volt regulator.
U42 19AI25 is 2.5V precision reference, which I believe is connected to COMM jack.
U44 is an adjustable supply set to 1.95V as per my calculation.
U21 is a 20V LCD supply,  I guess.
There is a U15 IC, which I could not locate but guess it's hidden under U42. I also guess it would be 3.3V (or 3.11V)  regulator.

U18 is a voltage supervisor IC, which shuts down the MS430 if one of the monitored voltage supplies fail.


Any correction/comments on the above data would be welcome.

--- End quote ---

U42 is non existent to my idea, this should be U15 (look at leads of chips and regular naming).
U15 belongs to nothing else and it seems this is a multi-purpose PAD/IC.
U44 is 3.6V
U18 OpAmp


--- Quote from: say on January 01, 2019, 12:45:51 am ---


--- Quote from: ElecSeb on October 23, 2018, 08:24:52 am ---
Only thing I am missing at the moment is a comprehensive TP layout. IN earlier posts some mention TP which are unknown to me (cannot find them visueally and in Calibration manual they are also not mentioned).

Hope to add this info to this topic soon.

--- End quote ---

This might help :)

--- End quote ---

Nope, this I know, but read earlier posts, there are folks who are mentioning:
https://www.eevblog.com/forum/repair/fluke-289-woes/msg1380051/#msg1380051

say:
ElecSeb thank you for chipping in. IMO the list of TPs you are referring to is just a list and the crosses against some TPs reflect their absence on the board.

Since I'm on vacations now, I can't test the output of U44 but according to the datasheet its an adjustable LDO regulator. It's output is determined by the formula Vo=1.205 (1+R2/R1). In the circuit R1=1Mega Ohm and R2=0.562 Mega Ohm, therefore, the Vout equals approx 1.9V. I may be wrong but if someone could test the output, which is on pin5, we will know for sure. Or I will do that after ten days :).

ElecSeb:

--- Quote from: say on January 02, 2019, 12:15:38 am ---It's output is determined by the formula Vo=1.205 (1+R2/R1). In the circuit R1=1Mega Ohm and R2=0.562 Mega Ohm, therefore, the Vout equals approx 1.9V. I may be I'm wrong but if someone could test the output, which is on pin5, we will know for sure.

--- End quote ---

On R258 is the code: 562 (with a 4th char not readable, however it seems like an S). Just de-soldered one and it is 562 kΩ (0.562MΩ).
I calculate based on: 562kΩ

Which then leaves us with:
Vo=1.205 (1+(R1/R2)) -> Please be careful with formulas (see brackets)
Vo=1.205 * (1+(1MΩ/0.562MΩ))=3.34V (which is what I measure on my 3 boards -> 2.9V, 3.14V and 3.00V!!!)

So I think I can 100% surely say it should be between 3.0 and 3.34V

Your formula is faulty (should be R1/R2 furthermore first divide/multiply then subtract etc).

Which leaves us with the question, is your measurement 1.9V? Then there is a problem in your circuit.
Please answer the questions from my other topic before I can help you in giving you directions.

An update on my meters:
2 NXP chips are broken (short);
1 and possibly 2 MSP430 are broken (hope to use the 2nd to read program from with MSP programmer when it arrives, same for 3rd chip). Big chance they are all blown).

So for now I am stuck waiting for the programmer.

say:
@ElecSeb

You are right. I wrote the formula from memory and made a mistake. Thanks for the correction.

Since I'm currently travelling, I'm not in a position to check the TPs and resistances. When I return I will post a reply with requisite data. Thanks again.

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