Author Topic: Fluke 787 repair  (Read 1614 times)

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Offline MiroS

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Fluke 787 repair
« on: November 08, 2018, 01:56:28 pm »
Hello,

I am looking for Fluke 787 schema / servie manual, can somone help me please?

 

Online coromonadalix

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Re: Fluke 787 repair
« Reply #1 on: November 08, 2018, 11:30:41 pm »
I dont think there is one available ?

Fluke docs i've seen are the Calibration manual and the User manual with google fuuu has you may did yourself ?
 

Offline ElecSeb

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Re: Fluke 787 repair
« Reply #2 on: November 09, 2018, 05:41:08 am »
You might describe your problem?
 

Offline retiredcaps

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Re: Fluke 787 repair
« Reply #3 on: November 09, 2018, 05:48:08 am »
I am looking for Fluke 787 schema / servie manual, can somone help me please?
You won't find publicly available one.
 

Offline MiroS

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Re: Fluke 787 repair
« Reply #4 on: November 09, 2018, 08:15:55 pm »
787 is cmpletely dead, but I belive it can be repaired. There is smoke dust all around protection circuit . PCB looks intact. I believe power supply circuit is dead.
 

Offline ElecSeb

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Re: Fluke 787 repair
« Reply #5 on: November 10, 2018, 06:55:39 am »
High quality pictures would help.
 

Offline MiroS

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Re: Fluke 787 repair
« Reply #6 on: November 11, 2018, 04:23:04 pm »
Pictures of this 787
 

Offline Twoflower

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Re: Fluke 787 repair
« Reply #7 on: November 11, 2018, 04:49:03 pm »
Wow, that is a severe damage in there. Even the rotary switch is deformed (in the picture in the upper right). That means the overload condition was persistent for some time. A look to the range switch might be useful and could indicate a problem there.

But the front end seems totally fried. It's hard to see, but the discolored PCB might indicate to be carbonized -> lower than usual resistance. The input protection might be totally gone and I wouldn't trust this anymore. And without having the possibilities to test each individual part a full replacement would be required.
 

Offline retiredcaps

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Re: Fluke 787 repair
« Reply #8 on: November 12, 2018, 01:11:51 am »
This thread shows why you need to remove the rotary switch.

https://www.eevblog.com/forum/repair/fluke-787-repair-any-idea/
 

Offline MiroS

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Re: Fluke 787 repair
« Reply #9 on: November 12, 2018, 11:04:06 am »
Nothing wrong under rotary switch. Yes input protection has been partialy destroyed; one od sidactor thyristor P3100EA,  transistor marked as 1AMZ , transistor 81J, one 1K resistor. I think this is not a big deal. The ink is that multimeter is dead  and I belive it is OK in general but power supply circuit is damaged. That a schema or service manual would be usefull.  Maybe some can give me a tip which components are resposible for it?

Failed components are marked of picures

However I see that 81J is bad, I cannot find datasheet for it. Maybe someone will know what it is actually? I think it is NSN transistor, but maybe I am wrong and diode ?
« Last Edit: November 12, 2018, 11:07:45 am by MiroS »
 

Offline ElecSeb

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Re: Fluke 787 repair
« Reply #10 on: November 12, 2018, 08:29:12 pm »
Start with identifying the power IC's.
Then figure out if it are adjustable ones, what are the resistors around (to calculate Vout).

Then measure the outputs, following by finding the root cause of not having Vout.
I do not have an 787, but this is what I did with my 287 and 289
 

Offline dardosordi

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Re: Fluke 787 repair
« Reply #11 on: November 12, 2018, 08:48:49 pm »
This thread shows why you need to remove the rotary switch.

https://www.eevblog.com/forum/repair/fluke-787-repair-any-idea/

Missed this post. That's the first place where I looked (fixed my Fluke 323 clamp meter with some scrapping of the carbon it had there from arching).
 

Offline MiroS

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Re: Fluke 787 repair
« Reply #12 on: November 16, 2018, 12:07:06 pm »
RESET pin is low therefore 787 is not  starting. i will try to find treset control trace, hoprfully without to desolder all chips on pcb .. or anyone knows how reset is controlled in 787?
 

Offline ElecSeb

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Re: Fluke 787 repair
« Reply #13 on: November 16, 2018, 05:41:37 pm »
What is the output of power LDO U2?
(And if existing what are the other LDO/power  IC's producing?)
 

Offline MiroS

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Re: Fluke 787 repair
« Reply #14 on: November 17, 2018, 11:10:44 pm »
Output of U2 is 4.987V, input 6.7 V. I measured current from battery, it is 70 mA. I think it may be too high.
 

Offline MiroS

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Re: Fluke 787 repair
« Reply #15 on: November 17, 2018, 11:13:32 pm »
Q7 is quite warm, marked as 6KE NK. Hard to find what it is.
 

Offline ElecSeb

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Re: Fluke 787 repair
« Reply #16 on: November 18, 2018, 10:13:16 am »
Unknown to me.
When looking on other sites/google photo's I see different types (but too unclear to exactly read the type either...).

May be someone on the forum with the same device might give an alternative which is identifiable...
 


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