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Need help identifying an electronic component


Jan 6, 2020
Jan 6, 2020
Hi there, I am a newbie in electronics repair and in the midst of troubleshooting a power supply board for Yokogawa UT35A PID controller that experienced over voltage. The unit is rated between 110 - 230VAC.

During my observation, I have found a component which I am not able to identify. Linked a photo of it, appreciate if someone can tell me what is it and where I can source it online.

Many thanks.


Nov 8, 2019
Nov 8, 2019

Looking at the silver sticker on the part, it must be a progammable device.
Without the code inside, you are out of luck.



Oct 5, 2014
Oct 5, 2014
Big cap and mains input choke on bottom, opto on the left side, caps at top, I'd agree with Audioguru.

Especially since there is T1 written on the left hand side.:):)

Rarely , if ever, are these found as faulty in an smps.

How is the fuse on the left..?? (F1)

Just be aware some of these units require external components/circuitry to enable start.

Do you have a photo of the other side?

Excellent photo for diagnostics by the to share your method?
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73's de Edd

Aug 21, 2015
Aug 21, 2015
Sir LP640 . . . . .

Initially . . . just an utilization of a bit of digital and optical prestidigitation to optimize for maximun perceivabe resolution / interpretation of that partial photo submitted . . . being viewable better in critical areas, without that LARGE of an ORANGE circle

Seems like the HOT A.C. (Line 1) input is at the 2nd gold flashed PCB finger connection at the bottom left corner of the PCB. Its foil then routes up to the top terminal of the BLUE X capacitor and is afforded further electro - physical isolation by the two routed out slots in the PCB proper, located just above. The bottom lower gold flashed PCB finger connection is the N . . . . .COLD input side of the AC line.
And then it gets afforded a bit more anti EMI-RFI treatment with item [3] a special X capacitor of 0.47 ufd @ 275VAC rating.

The HOT AC input foil then further routes down to a series, low resistive value, input surge resistor item [4]. Then its into and out of the line choke [2] and into an ? unviewable ? fulll wave bridge block rectifier or being made up of of 4 discrete diodes, if so arranged.
( It / they must be physiclly located in the unviewable area, just below the LARGE side mounted E-cap. item [5] )

The outputted raw / unregulated DC voltage, is being of either . . . .160-170 VDC if ( Amerikanski/Japonie ) or 340-360 VDC if ( You Are A Peeing ), is being accumulated and smoothed out within the BLACK ? item [5] main E-filter.
That main HV filters output voltage then feeds over into the primary of your purportedly ? MYSTERY ? Black T1 Switch Mode Power Transformer as being item [6] .

With me being unable to see its foil path, somewhere, being series inserted either before or after passing thru the item [2] a contra-phase wound (phase cancelling) RFI- EMI filter choke in the AC power input , is being the bottom left corners item [1] chemical fuse. . . of a 800ma-275VAC rating.

All of the brains and accomplishment of switch mode drive generation and feedback / regulation control is being accompished within the UI power integrated circuit, positioned at the frontal foreground of that transformer and is so designated, as its being " U1 " nearby.

At the topside of that transformer is /are its secondary winding (s) output (s).

With your big ORANGE circle somewhat blocking view PLUS my not being able to "read" the boards bottom sides other foil paths.
I will now just opt to speculate the potential / possibility of the T1 transformers adjunct right side mounted diode . . . item [9] being used for creating the main low voltage output for that transformer, and to then be fed up the board to the largest E-cap item [7] for its filtering .
I suspicion the the two adjunct companion E-caps . . . items [8] [8a] might be for additionally derived lower voltage supplies.
Compare the voltage ratings specs on all three caps to be able to differentiate that possibility..
Two other unidentified sitting ducks are the transformers top left corners PC 2 which is for feed back of the outputted DC back to the U1 main IC, being used for regulation correction between a hot AC supply and the cold transformer isolated outputs supply.
At the power transformers right top corners U2, item 10, might be a related type xx431 series adjustable zener voltage reference.

At the boards VERY top left corner, I see one HEFTY power relay, with its 5VDC coil and and 8A/250 V rated contacts .
Additionally, located just below it, are being 3 separate minor relays (they have the casing profile of being reed relays) , as are used for lower power level switching.

TESTEE . . .TESTEE . . . ? ? ? . . . . . HOW DO YOU TESTEE ?

If you power up and test across the side terminals of the side mounted item 5 E-capacitor and find one of our prior mentioned voltage levels . . .all is possibly well with the units basic DC supply.
Then its being a question as if the switch mode aspect of U1 POWER I.C. is working.
A DVM in its lower DC voltage range and metering across Transformer associated secondary E-caps items 7 and 8a - 8b should show a supply voltage presence on a working unit.

A FURTHER CONSIDERATION . . . . . in the basic testing of Switch Mode Power Supplies

For any of our technically challenged, that can neither evaluate with a DVM or have prowess in the utilization and analyzing waveforms with an oscilloscope for accomplishing same .
I now offer a .no brains approach to ascertaining same.
The fast rise time variable square wave /or/ pulse trains that activate the inductors / transformers used in these types of supplies result in the additional outputting of higher frequency harmonics ( twice the frequency, three times, four times, five times , etc. ).
One then can see that some of the higher multiplied frequencies are extending on up and falling within the AM broadcast band.
Sooooooooooo . . . . an AM receiver brought in to let its internal ferrite antenna almost get in close enough to " kiss " that T1 transformer, should then have its speaker SCREAMING from that radiated signal. . . . . IF . . . the circuit is working / radiating signal.

ASIDE . . . .
I have started to initiate this info, times before . . . . but no one earlier, even acknowledged as to their even having a small POCKET sized battery powered AM band receiver.
Let me now Edd-i-cate all . . . . . on how this procedure is performed.


Matter of fact . . . lets get ALL participants that DO have that category of receivers, or can borrow one, run and get them and initially get them operating in their playing of a received AM band station.
Then tune down into the lowest end of the 540-1750Khz Standard broadcast band at ~ 540-600 and tune OFF frequency, from then being on any received station. Run the volume up to max.
In order to initially PRE-ACQUAINT you for what you are expected to be hearing, turn on either a TV receiver or computer monitor and let it warm up to producing a display condition.
Then back away a couple of yards / metres with the receiver in hand and start approaching the screen. At one point you should start hearing a febble whine from the speaker and finally a LOUD ROAR of "hash" / whining noise as you touch the unit s screen face...
Back away again to an intermediate area and start playing around with the different possible rotational positions of the radio, and you will then see that the received signal will be in variance to the positioning of the internally hidden ferrite loop antenna.
The broad side position of the loop and its 180 degree rotated complement position should produce the strongest received signal. AND at a VERY sharply defined 90 degrees from those positions, a very sharp null in signal should be perceived.
Concentrate on the position of maximum signal reception and replicate it when moving to your powered up unit and coming right on in to get as close to its " kissing" that T1 transformer unit.

An operating unit will cause that radio to WHINE. No reception of same, is indicative of no switch mode power operation.
With time , use and experience one can get some idea of fault analysis by listening to the specific noises.

By my prior mention of the presence of RAW DC at the item 5 main filter, you have cleared catastrophic failures of the input fuse or Full Wave Bridge rectifier and the internal power handling portion of the U1 I.C.

That then leaves the secondary winding of T1's winding(s) feeding into rectifier diodes that then feed DC smoothing E-caps associated with them.
If a diode shorts it typically will load down the transformer so severely that the output " whine " sound changes to a pulsing click as the unit repeatedly attempts to operate.
If an E-cap has developed ESR and associative capacitive decline effectiveness, the unit will work if its loading is shed, but with the reinstatement of that load, will cause the whines frequency to shift downward and go to the pulsing click sound.
If the supply is normally having to develop a HEAVY current in its operation, the timely onset of high ESR on the first E-cap fed out of a diode will cause that diode to run progressively hotter and the diode can fail . . .open circuit.
The unloaded condition causes the whine of the radio, but the supply output is receiving no DC from the diodes open circuit condition . Otherwise, normally loaded diodes fail shorted.
One is also able to hear the tone of the whine of the radio shift as different load levels change on the supply.

This procedure is applicable on the several types of switchmode power supplies one encounters, inclusive of the CFL lamps (they all whine ), LED lamps ( a select few are not being real strong whiners ) and the plethora of wall warts that have specs of 95-240 AC input given on their cases / labels.
The Ipad, Kindle units higher freqs used, sound almost like a bee.

So, now all run out and sample units for acquiring the familiarity of the sounds of normal operating units . . . . . OR . . . . . . that non working unit, that you are wondering about.



Thaaaaaaassit . . . . .

73's de Edd . . . . .

Just musing . . . . . . . Now, if a turtle doesn't have a shell, which is he being . . . . . homeless or naked ?

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Sep 13, 2016
Sep 13, 2016
Great stuff thanks St Edd. Now to get my Grundig Yachtboy working