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Old 07-22-2022, 12:19 PM   #1
marce002
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Default Uni-t UTP3315TFL-II stuck at 40V laboratory power supply

Hello

My 2 years old unit is showing and outputing around 44.33v , values are real comparing with my tester... current seems to be fine if could be tested passing CC to CV as usual, rotating knov volt does not change values at all.... always arround 44 vol,

PLEASE

what to test?? in the pictures i have checked
all is clean at 100%!! not blown components or traces of exploded caps or anything... most diodes are ok and transistors too i think..caps are good shape

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Last edited by marce002; 07-22-2022 at 12:42 PM..
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Old 07-22-2022, 01:44 PM   #2
stj
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Default Re: Uni-t UTP3315TFL-II stuck at 40V laboratory power supply

resolder all the front panel pots - they have hardly any solder on them!!
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Old 07-22-2022, 02:25 PM   #3
marce002
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Default Re: Uni-t UTP3315TFL-II stuck at 40V laboratory power supply

revised and they are almost perfect soldered...
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Old 07-22-2022, 03:44 PM   #4
marce002
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Default Re: Uni-t UTP3315TFL-II stuck at 40V laboratory power supply

it started to work fine again by itself, maybe the relay stucked or similar due to its sounds...tks for your help, and if you can confirm that a relay might have affected to generate this issue you are welcome..
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Old 07-24-2022, 02:31 PM   #5
redwire
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Default Re: Uni-t UTP3315TFL-II stuck at 40V laboratory power supply

A stuck relay is not the problem, that does not cause the output voltage to get stuck high.
I see many bad solder joints on the larger through-hole parts. Spend some time and resolder all of them.
Some pretty dodgy parts used, this Vreg IC (pic) seems to have been found on the road in china and put to use.

You can hit the unit with your hand, or tap the boards with a pen and see if a bad connection still exists. Because the fault will blow up whatever is connected to the power supply... it makes sense to actually troubleshoot and fix it before it kills something.
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Old Yesterday, 06:47 AM   #6
spiros.p
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Default Re: Uni-t UTP3315TFL-II stuck at 40V laboratory power supply

agree with bad solder.i have cheap axiomet linear psu and was full of bad joints out from the box..to92 transistor bad soldered and not triger the relay.booth of them i have two.resolder booth chance all the c(r)apacitors and is working properly.
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