KSGER t12 Solder station....AO4409 MOSFET alternatives please!!

[MisterKevster]

Hi....and new to this forum!!

Have one of these little stations....all good....then just yesterday get the glowing tip.
Found some references to alternatives for the AO4409....which is possibly(likely?) the culprit.

Hoping to order a small (<=5) quantity of a 'beefed up' replacement from my local RS counter here in Leeds.

Smallest qty of IRF9317/21 available is 20....which is overkill for me.
Found this Toshiba TPC8117....and hoping someone can confirm whether this might work as a replacement??

I've attached the specs for the 8117 from the RS site......!!

[wraper]

TPC8117 should be fine.

[MisterKevster]

TPC8117 should be fine.

....Great....and will it exceed the original AO4409...??

[wraper]

It should heat less.

[MisterKevster]

It should heat less.

....so hopefully longer lasting
Thanks again

[MisterKevster]

Aaaaggghhh.....TPC8117 not available until August '23....so back to square one!

It is possible to buy 5 of the original AO4409 (Amazon)....but was hoping to find something better/longer lasting.

[wraper]

You can use Si4459ADY. Limiting it to RS you severely limit what you can get, almost everything suitable out of stock there. Not to say their parametric search suck so it's pain to search on their website.

[MisterKevster]

You can use Si4459ADY. Limiting it to RS you severely limit what you can get, almost everything suitable out of stock there. Not to say their parametric search suck so it's pain to search on their website.

Thanks for this once more.....I agree that the RS 'search' sucks!!
I hadn't spotted that so much is 'out of stock' either.

[DavidAlfa]

Try parametric search, 30VDS, >=15A IDS, you should get quite a lot of parts.

[wraper]

You can use Si4459ADY. Limiting it to RS you severely limit what you can get, almost everything suitable out of stock there. Not to say their parametric search suck so it's pain to search on their website.

Thanks for this once more.....I agree that the RS 'search' sucks!!
I hadn't spotted that so much is 'out of stock' either.

Don't quite understand what du you mean. Si4459ADY is certainly in stock at RS. https://uk.rs-online.com/web/p/mosfets/1807996

[floobydust]

OP, add a back-EMF diode across the heating element to clamp spikes from the heating element and cable inductance, from damaging the mosfet.
Like here: https://www.eevblog.com/forum/reviews/t12-stm32-v2-1s-soldering-station-controller-schematic-etc/msg2777362/#msg2777362
The power supply is ~25VDC and the laptop mosfets rated 30V so there is no headroom there.

[MisterKevster]

]
Don't quite understand what du you mean. Si4459ADY is certainly in stock at RS. https://uk.rs-online.com/web/p/mosfets/1807996

Sorry for not being clear!.....I've ordered the Si4459ADY  that you suggested...thanks!
I was just observing that many other items are out of stock....or on 'back order'

[MisterKevster]

OP, add a back-EMF diode across the heating element to clamp spikes from the heating element and cable inductance, from damaging the mosfet.

1N5819s ordered....thanks!!

[thm_w]

OP, add a back-EMF diode across the heating element to clamp spikes from the heating element and cable inductance, from damaging the mosfet.
Like here: https://www.eevblog.com/forum/reviews/t12-stm32-v2-1s-soldering-station-controller-schematic-etc/msg2777362/#msg2777362
The power supply is ~25VDC and the laptop mosfets rated 30V so there is no headroom there.

The heating element is ~8 ohm, would there really be any spikes across it?
I guess when the tip is removed and inserted.

and the FET failed for some reason so maybe its due to what you say.

[DavidAlfa]

Check the handle internals for wiring damage, it's pretty common.
Also the socket can bend its pins while inserting.

Some tips fail shorted, already happened to me 3 times!
While soldering, started to hear some little bangs coming from it. Luckily the MOSFET survived.
I only burned it once when a wire broke and made direct short.

[floobydust]

That's a good point I forgot to mention.
Add a wrap of electrical/Kapton tape inside to prevent the aluminum handle tube from shorting the heater terminal. Or maybe put heatshrink on that pin.

[floobydust]

I don't know, never used the part.

[MisterKevster]

Aaaaggghhhh....I've made things worse !!!

Instead of sticking to what I (half!) know...I borrowed a solder rework station....and removed the AO4409.....and it was indeed shorted

Attempted to use the station to solder new SI4459ady.....without correct SOP8 'cowl'...for want of the correct word....and have succeeded in blowing 3 components off the board.
Returned to an old iron....and completed soldering chip before noticing this.
There's a pic below.

Looks like I've lost a resistor adjacent to pins 1 and 2 of the new chip.......thinking that is R21.
Further inspection shows R18....just below chip....now missing.
Managed to find missing D1.....top left of the chip....and there's a pic below!

Am I wasting my time (which I've plenty of!) pursuing this.....what do you think???
Perhaps I can buy a populated board....V3.x....??

[wraper]

R0 is not populated, R18 is 2k, R21 is 100k

[MisterKevster]

R0 is not populated, R18 is 2k, R21 is 100k

Thanks....are the resistors rated....as in watts???

[wraper]

Power rating does not matter. Size looks like 0603. But you can measure dimensions yourself to be sure.