Author Topic: Dead UT71E? Help needed to repair or discard it.  (Read 8051 times)

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Offline joeqsmith

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Re: Dead UT71E? Help needed to repair or discard it.
« Reply #25 on: June 23, 2016, 10:26:13 pm »
It's a UNI-T isn't it?   

It's a totally different from the 181a I had damaged.  U8 is your 3, U7 your 5.  You will need to trace everything out in that are.   I'm going to guess U1 at a minimum.   Hope I am wrong.

Even a $350+ UT181A is still vulnerable to transients?
How electrically robust is your meter?? https://www.youtube.com/channel/UCsK99WXk9VhcghnAauTBsbg
 

Online blueskull

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Re: Dead UT71E? Help needed to repair or discard it.
« Reply #26 on: June 23, 2016, 10:35:04 pm »
It's a UNI-T isn't it?   

It's a totally different from the 181a I had damaged.  U8 is your 3, U7 your 5.  You will need to trace everything out in that are.   I'm going to guess U1 at a minimum.   Hope I am wrong.

Even a $350+ UT181A is still vulnerable to transients?

Seems like my decision was correct. I wanted to have an OLED meter, struggled between a Keysight and a UNI-T. I ended up with a U1461A at more than double the price of a UT181A. Glad I made this decision.
 

Offline joeqsmith

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Re: Dead UT71E? Help needed to repair or discard it.
« Reply #27 on: June 23, 2016, 11:24:54 pm »
The Keysight I tested was far more robust than the 181A.  Not suggesting yours would be.  It's a different model and you would hope with the higher cost they would do a better job with it.   But like the Fluke 87V vs their cheapest 101 model, you just never know until you try them.
How electrically robust is your meter?? https://www.youtube.com/channel/UCsK99WXk9VhcghnAauTBsbg
 

Online blueskull

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Re: Dead UT71E? Help needed to repair or discard it.
« Reply #28 on: June 23, 2016, 11:35:55 pm »
But like the Fluke 87V vs their cheapest 101 model, you just never know until you try them.

Right. My F289 is now suffering from leaky MOVs. They leak ~17uA at 1kV DC. At lower voltage the MOVs are behaving well. Not sure if the MOVs will explode eventually, but I would rather replace the parts.
Fluke has yet to reply my service request on the leaky MOVs and the infamous super cap, and I will post upon receiving their response.
 

Offline joeqsmith

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Re: Dead UT71E? Help needed to repair or discard it.
« Reply #29 on: June 24, 2016, 12:39:29 am »
I have seen my fair share of MOVs coming apart.  :-DD  You have the PTCs there to limit it.  I did not take apart the 298 when I had it to compare with the 181.   Are there two in series or in a "Y" and just one of them is bad or didn't you check? 

They are supposed to warranty for life, or at least that's what I keep seeing posted.  Strange they would not just issue an RMA and get you a quote on repairs. 

The 181A used a coin cell battery.   They had some fairly good protection in the meter (not just for UNI-T but in general)  but the layout has a few problems which seems to cripple it.  Not a bad meter but I would have gladly paid another $50 to see it certified to the EMC standards, a more scratch resistant LCD cover, AC adapters for the charger and a spare battery.  Or even better, had used a standard set of batteries.   
How electrically robust is your meter?? https://www.youtube.com/channel/UCsK99WXk9VhcghnAauTBsbg
 

Online blueskull

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Re: Dead UT71E? Help needed to repair or discard it.
« Reply #30 on: June 24, 2016, 12:48:59 am »
I have seen my fair share of MOVs coming apart.  :-DD  You have the PTCs there to limit it.  I did not take apart the 298 when I had it to compare with the 181.   Are there two in series or in a "Y" and just one of them is bad or didn't you check? 

They are supposed to warranty for life, or at least that's what I keep seeing posted.  Strange they would not just issue an RMA and get you a quote on repairs. 

The 181A used a coin cell battery.   They had some fairly good protection in the meter (not just for UNI-T but in general)  but the layout has a few problems which seems to cripple it.  Not a bad meter but I would have gladly paid another $50 to see it certified to the EMC standards, a more scratch resistant LCD cover, AC adapters for the charger and a spare battery.  Or even better, had used a standard set of batteries.

I didn't check which one is leaking, and I do not want to desolder the board unless I know it is not covered by warranty.
My problem is, I bought the meter in China, and my local distributor didn't give me a formal invoice in English, so I'm not sure if Fluke USA will honor the international warranty.
I know Keysight definitely has no bullshit on international warranty, but I do not know how Fluke treats international warranty.
 

Offline joeqsmith

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Re: Dead UT71E? Help needed to repair or discard it.
« Reply #31 on: June 24, 2016, 12:53:58 am »
There is no local service center for Fluke in China?   That's a little odd being most are made there now.  I would have thought your local distributor would have handled it for you. 
How electrically robust is your meter?? https://www.youtube.com/channel/UCsK99WXk9VhcghnAauTBsbg
 

Online blueskull

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Re: Dead UT71E? Help needed to repair or discard it.
« Reply #32 on: June 24, 2016, 01:45:08 am »
There is no local service center for Fluke in China?   That's a little odd being most are made there now.  I would have thought your local distributor would have handled it for you.

The problem is I live in the US. Also, the version I got is not the Chinese F289C, I got the international F289.
 

Offline joeqsmith

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Re: Dead UT71E? Help needed to repair or discard it.
« Reply #33 on: June 24, 2016, 03:35:20 am »
Not sure why it would be a problem if you were the original purchaser and had the POP.    Are you using the new meter to check the old?  Curious if you really ran into the problem with normal use or if you where playing with the new toy and needed something to try it on.   If not, I am surprised you are using a meter like this on voltages that would damage the MOVs.   Let's here the real story...
How electrically robust is your meter?? https://www.youtube.com/channel/UCsK99WXk9VhcghnAauTBsbg
 

Online blueskull

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Re: Dead UT71E? Help needed to repair or discard it.
« Reply #34 on: June 24, 2016, 03:58:16 am »
Not sure why it would be a problem if you were the original purchaser and had the POP.    Are you using the new meter to check the old?  Curious if you really ran into the problem with normal use or if you where playing with the new toy and needed something to try it on.   If not, I am surprised you are using a meter like this on voltages that would damage the MOVs.   Let's here the real story...

The only symptom I saw is U1461A reads 17uA leakage current on 1kV insulation range. It is supposed to be 100uA, but it reads 117uA. I verified this with a uCurrent and another DMM.
On 500V or lower ranges the input resistance is perfectly 10M, so I guess somewhere inside the F289 is leaking at rated highest voltage.
When comes to real world usages, I only use my F289 on less than 500V DC, most of the time less than 50V DC, so it is not a practical issue. But I am concerned about whether long term degradation of the MOV can eventually lead to catastrophic failure.
 

Offline Flyfish

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Re: Dead UT71E? Help needed to repair or discard it.
« Reply #35 on: August 03, 2016, 09:13:51 am »
What ever happened with your UT71E?   I figured you would have the thing running by now or you hit it with a hammer out of frustration.

I'm curious as well, just thought to check back and see

Sorry guys for the delay. My hammer (the big one) is about to make presence.  And it's not because I wasn't able to fix it, or definitely discard the UT thingy. I'll explain myself:

I received the IC recently:

http://es.aliexpress.com/item/LSD0007-patch-QFP64-MSP430V103IPMR/32661954515.html?spm=2114.13010608.0.93.fifAzG

 After that, I read carefully the datasheet in order to figure out if it might (in my best wet dreams) come ready-to-work out of the box. But the datasheet is really hard for my english and electronics level, and, so far now, I'm not sure. That's all. I don't even dare to solder it because, if it isn't programmed, I'd have to de-solder it and try to programe it somehow. Too much motherboard warming and eye-hurting work.

Another sidedown is if, it's not programmed (as I really think), I don't even have the tiniest clue of how to do it, not to speak how to get that kind of firmware.

I have also checked the voltage in 3.5 and 5.5 after I lifted the shortaged legs from the IC and I resoldered the removed componentes, and they aren't so consistent. I need to do further checking.

So that's my thin advance so far. I'm stuck with the solder iron in one hand, and the hammer in the other.

Thanks for checking the thread. Don't fear, I'll have you updated as soon as I get some significant update.

Regards!
 

Offline joeqsmith

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Re: Dead UT71E? Help needed to repair or discard it.
« Reply #36 on: August 03, 2016, 10:24:59 am »
Thanks for the update.  Good to hear you were able to at least get a replacement part.   I would have guessed it was blank as well. I also would have guessed UNI-T programs them in-circuit. 

Quote
I have also checked the voltage in 3.5 and 5.5 after I lifted the shortaged legs from the IC and I resoldered the removed componentes, and they aren't so consistent. I need to do further checking.

There may be more than one bad part.   
How electrically robust is your meter?? https://www.youtube.com/channel/UCsK99WXk9VhcghnAauTBsbg
 

Offline iXod

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Re: Dead UT71E? Help needed to repair or discard it.
« Reply #37 on: August 03, 2016, 05:38:47 pm »
you just never know until you try them.

or, "you just never know until you fry them."  :clap: :palm:
 

Offline Macbeth

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Re: Dead UT71E? Help needed to repair or discard it.
« Reply #38 on: August 03, 2016, 07:58:56 pm »
After that, I read carefully the datasheet in order to figure out if it might (in my best wet dreams) come ready-to-work out of the box. But the datasheet is really hard for my english and electronics level, and, so far now, I'm not sure. That's all. I don't even dare to solder it because, if it isn't programmed, I'd have to de-solder it and try to programe it somehow. Too much motherboard warming and eye-hurting work.
You would not have to desolder it to re-program it, there is an 8 pin programming port labelled IO1. This is known as a "Bootstrap Loader" or BSL port for the TI MSP430 chips.

Of course if your replacement U2 hasn't been pre-flashed then the problem is getting the firmware to program it with! (and you would have to make a programmer too)

Anyway you have nothing to lose replacing the chip. If you don't have a hot air rework station then careful use of a scalpel from the top of the QFP pins, taking care not to cut the PCB or force the legs with a blunt scalpel to rip pads from the board. Then pick up all the cut off legs using a gob of solder on the tip. Some solder wick and flux would be handy to clean up and you will probably need them when you solder on the replacement too.

If you find yours is not pre-programmed then you need to find someone with a UT-71E and 'l33t cracking skillz then you can read from the BSL port of his meter!



(or you could ask UNI-T if they would send a pre-programmed one to you. You would be surprised, I got a replacement programmed 8051 MCU for my Maynuo DC Load and fitted it yesterday - worked first time!)
« Last Edit: August 03, 2016, 08:03:34 pm by Macbeth »
 


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