Uni-T UTP3313TFL - Just killed it...

[Bicurico]

Hi,

I was messing around with a dumpster score (barcode reader) and powering it up with my lap power source, a cheap Uni-T UTP3313TFL.

All was working, but then the wires connecting to the barcode reader were intermittent (too thin diameter to get better contact) and after a while, suddenly there was no power up.

I looked and noticed that the power source went to C.C. mode with 0.0V and 0.0A (occasionally changing to 0.1V or 0.1A).

Reading the manual, this is the mode, where you short + and - to set the maximum current.

I turned the power source off and measured GND against + and there is some resistance. It seems to me that some diode must have broken?

Any thoughts on how to repair this?

The device is under warranty and it should NOT break from what I was doing. But then, I should have used a better contact instad of an intermittent one. Also, I don't feel like going through all the support issues, which probably end up costing more than a new power source.

The problem with the repair is:

a) I have no knowledge on how these things work.
b) It is highly compact device with difficult access, unleass I tear it completely apart, but it does have a lot of glue around.

Any ideas are welcome.

Regards,
Vitor

[SaabFAN]

Sounds like the problem the Korad Power Supply had: Short the leads out by banging them together in rapid succession and the pass-transistor was killed.

Call Uni-T and tell them what you did. This is a fault that either has been fixed already or is going to kill a lot more devices.
Maybe you even receive a new one free of charge.

In the case of the Korad there were some videos of people showing how to install the revised board with the pass-transistor.

[IanMacdonald]

A bench PSU that pops its clogs as easy as that is not fit for purpose.

The series pass is the most likely candidate. Though, they more often fail s/c than o/c.

[Bicurico]

Thanks for your quick feedback posts!

I am relieved that it is not my fault and that a protected bench power source should be able to handle the usage I gave it (I have it for little more than a year and used it perhaps 6 times).

I just opened a RMA. Hopefully they repair or replace it.

I just remembered that I had opened it before, because the plastic of the front panel broke where one of the screws goes in. As a result it looked a bit off and tilted. Because I wasn't into going through RMA (how to prove that it already arrived broken), I glued the broken plastic bits. Hopefully they won't use that to refuse warranty...

Anyway, seems kind of a bad product. I guess, you get what you pay for, still I hoped to get something slightly better...

Regards,
Vitor

[Bicurico]

Update:

Under warranty I received TODAY a brand new replacement unit!



It took 5 weeks, but 1 week was due to the shop being closed for holiday, so they did manage to process the whole RMA within the 4 weeks they claim it can take.

Regards,
Vitor

[vlx]

Hi Bicurico, I want to buy a Uni-T UTP3313TFL and I have question to a person that owns this unit.

Do you have on this unit a spike on power-up if the source is powered when in change ?

I noticed in this review https://youtu.be/k7oSBPHgQK8?t=439

that when powered the Unit has a spike in 24V that is stabiling to 15V.
My concern is that could fry my components.

Thanks

[Bicurico]

Hi,

I never tested that, so I don't know.

However, it doesn't seem a good proceedure to attach the DUT before switching on the PSU. I always turn on the PSU, set the desired Voltage and Current and only then o I connect the DUT.

Let me know if I misunderstood your question.

Regards,
Vitor

[vlx]

Yes, that was the question.

Even if is not a good practice, a "nice" unit would save DUT from your mistake.
Connecting the DUT after the unit has been powered needs an extra switch or might imply other risks depending on how handy you are

Bottom line, would you recommend this unit?

Thanks

[Bicurico]

I am honestly not the right person to ask.

I know too little about PSU's and I have not used mine often, to have an opinion, other than:

GOOD:
- It was the cheapest I could buy locally
- It is easy to use
- It came with a small instruction booklet
- It seems to work as specified
- The broken unit got replaced by a brand new one

BAD:
- I broke one and I don't think it was my fault - so I either got a faulty unit, had bad luck or this model has a bad design...
- Not programmable (but what do you expect at this pice)

I know this does not help you, but on the other hand, I am not going to attach one of my equipment to then turn on the PSU, to see if it indeed produced a spike that may have killed my equipment.
Doing this excercise without a DUT, may not represent the real thing, either.

Regards,
Vitor