Please help me identify this component

[nearmitech]

I have come across this component on a circuit board. Its marked L3 and so I know it is an inductor. However the fact that it has 8 legs leaves me unsure of how to identify its value etc.
There are no markings on the body. Of the two circuit boards, one has this definitely defective.

Across the two pins that are used I am able to measure 27 ohms on the good board but not on the faulty PCB. Therefore it is imperitive I change this component to repair my device.

Any help to point me in the right direction would be much appreciated.

 

[FvM]

A ferrite pot core with adjusting screw and shield. Most likely a custom part, you need to determine winding configuration and measure inductance after disassembling it.

 

[Externet]

A tuneable transformer.
Smells like working at the switching frequency of a power supply for some oscillation/feedback/sensing.
I would mark its position and remove, pull the aluminium cover; inspect, make its pinout schematic and rebuild windings if unobtanium.
Come back with findings.

 

[D.A.(Tony)Stewart]

I recognize the design from I used back in the late '70's with the shielded single or dual slug core and the Bourns 10T trimpots with red-brown coating

You must match the design using a good part with the same schematic using an RLC meter.

It might look something like this. Murata and others in SMD format make them now in single slug to tune the differential and mutual coupling of the fixed coils. Look up how to measure mutual inductance with shorted secondary.

 

[D.A.(Tony)Stewart]

Alternatively, there is a "grey" surplus market, if you can afford the costs and have the part number.

This may not help find a part but at least explain "what is a coupled inductor?" and how is it used. (SMPS, IF Tuners etc)

It could be a Flyback, a Sepic or anything between two bulk e-caps with precision pots in an old-school but precision DC-DC converter.

ultimately, it's , L DCR and L/DCR ratio are critical and SRF from C must be sufficiently high.

Then the static DCDC output voltage is the 1st test and then a step load the final test to compare performance and stability.

 

[FvM]

1. try to understand the general circuit function
2. figure out the inductor/transformer connection, e.g. how many terminals

 

[D.A.(Tony)Stewart]

It might be easier for you to repair the short inside the can or on the board.

 

[FvM]

Across the two pins that are used I am able to measure 27 ohms on the good board but not on the faulty PCB. Therefore it is imperitive I change this component to repair my device.

Sorry, I missed the point. So it's clearly an inductor. If the winding is burned, you should re-coil it. But possibly only a broken wire that can be reconnected.

 

[eddwhatley]

Sir nearmitech . . . . .

Certainly would have been more helpful, if identifying the WHOLE boards function along with another photo encompassing the whole board top.

If L2 and L3 are being Low Radio Frequency circuitry related, those extremely physically humongous BLACK E-caps seem a bit out of place.
But with L3's 27 ohms DC resistance, that would seem to equate with a variable inductance that in conjunction with its resonating companion capacitor, to fall within the high ultrasonic ------------sub Low RF spectrum.
If that visible coils black surround is being a ferrite shroud, the internal adjustable slug is having only a very small tuning range.


73's de Edd . . . . .



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