Wht is this part about?

[berniedd]

Guys, this part is in the switching power supply section of a Sony thermal printer, in series between the line capacitors and the chopper transformer. As you can see, it looks like a power resistor in a ceramic housing. It is a siamesed twin made of a 12 ohm resistor and something else in series with it in the other half inside the common housing. This other something else is open-circuited, and I have no idea if it is also resistor or a choke. Any ideas?

[berniedd]

Re: Wht is this part about?

Sorry about the huge picture. This is my first time to post an image, and I thought it would come out only a small one. Imagine my surprise when it turned out this size.

[Wizard]

Re: Wht is this part about?

The pre-T220 transistor package have not made since 1985 (the thin tab) means you have a vintage electronic gear. What is it?

The resistor is just that, a 12 ohm with temp rating and max current load.

Cheers, Wizard

[i4004]

Re: Wht is this part about?

>What is it?

elephant!

he said what it is:
"switching power supply section of a Sony thermal printer".

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bernie, could you post pic of whole primary(or secondary what ever you're aiming at, but 400v cap should suggest it's primary) side of that smps?
i see it's in line with other coils, probably just another coil...

[berniedd]

Re: Wht is this part about?

Yes, it's in the primary side. I was just wondering about the design. I've measured 12 ohms between one lead at the bottom of the resistor to the top lead. This top lead is soldered to the other top lead, which goes through the other half of the resistor, before exiting at the bottom. It is this half of the resistor that's open. If it's merely a wire that's in there, why would it open circuit? I thought, maybe there's a choke in there too?

[i4004]

Re: Wht is this part about?

i thought you were asking about the black thing, but it seems you're talking about white thing, which indeed is power resistor.
and a blown one, according to what you just said.
you should have 12ohm between two contacts of the resistor that connect to pcb.

[Toasty]

Re: Wht is this part about?

Autopsy the bad side.

Does the board have a part number marking? R1, FR1, etc.

Could be a fuse.

Can you determine if its on the Mains side or output side?

[berniedd]

Re: Wht is this part about?

It's designated as a resistor, and I think the other half of the thing is a fusible link. This is the first time I've seen a resistor with a current rating (2 A) and a voltage rating (250V). What initially put me off was the label L52D, I thought it might be an inductance rating.

The resistor is on the primary side. I'm still looking for other defective parts down the line. I know there's another failed part because one of the line fuses was burned out as well.

[Toasty]

Re: Wht is this part about?

Check the transistor/FET next to it.

[hardwareguy]

Re: Wht is this part about?

Its an early fusible resistor. Follow Toasty's advise, check the transistor hooked up to it.

[Agent24]

Re: Wht is this part about?

Is it a fuse and a resistor in the same package or something?

[hardwareguy]

Re: Wht is this part about?

Yes, the part contains a resistor and a fuse wired in series.

The resistor limits the available fault current that flows in the milliseconds before the fuse link melts.

In theory this helps protect expensive parts like high speed switching FETs. In practice; all it does is prevent said expensive parts from catching fire or exploding when they fail short circuited so you can still read the part numbers to order replacements.

[stj]

Re: Wht is this part about?

it's a combined fuseable resistor & themal-fuse.

if you trash it then you could use seperate parts to replace it.