[SOLVED] Airvent 459318a - blown transistor identification / suggestions? - Page 1
Forum section: electronics / repair

author: Grytpype
author_rank: Contributor
timestamp: November 14, 2022, 04:00:41 pm
content: Hi all,I've got an old 240v AC extraction fan that recently stopped working. On the PCB, the only transistor had blown taking away with it the identification (most of it anyway - see attached).The units themselves are only £12 or so but I'd like to at least try and fix it.Does anyone know, or could suggest a replacement for it?Thanks in advance!

author: ingalopez
author_rank: Contributor
timestamp: November 14, 2022, 07:02:51 pm
content: Hi there,since the colector is attached to the + o the cap, and the emitter to the fan, I would try any NPN transistor capable of the current the fan may take. Just be sure it has the same configuration , tha is, the base is on the center.Good luck

author: Grytpype
author_rank: Contributor
timestamp: November 14, 2022, 09:12:49 pm
content: Will go through my stash of NPNs and try it out.Thanks for taking the time to reply!

author: Grytpype
author_rank: Contributor
timestamp: November 14, 2022, 10:32:02 pm
content: ...just tried a 2N2222A and it workedThanks again!

author: fzabkar
author_rank: Super Contributor
timestamp: November 14, 2022, 11:13:58 pm
content: As I see it, the PCB is powered by a transformerless, zener regulated supply, with a series AC film capacitor limiting the voltage by virtue of its impedance. This means that the transistor cannot be passing the fan current. Instead, it must be switching some other component, possibly a relay (or TRIAC??).Moreover, ISTM that the transistor should be a PNP type since it is switching the high side. :-?The fan is rated for 240VAC, 16W.https://www.airventventilation.co.uk/wp-content/uploads/2022/06/AIRVENT-TECH-SPEC-SHEET-459318A.pdf

author: floobydust
author_rank: Super Contributor
timestamp: November 15, 2022, 07:49:58 pm
content: I say the blown part is a small TO-92 triac, from the markings possiblyZ01-03600V 1A sensitive gate. Common circuit for bathroom fans, they use BT131-600 which would also work as a replacement. The fan motor works from mains, and the capacitive-dropper powers the low voltage MCU, humidity sensor etc. It might be the 800V part but I can't make out the last numbers.So I don't see a 2N2222 really working there, handling mains voltages for very long...These fan circuits can be powered up 24/7 so the capacitors don't last long - the dropper cap and the two electrolytics fail and cause oddball behaviour as well.

author: fzabkar
author_rank: Super Contributor
timestamp: November 15, 2022, 08:22:12 pm
content: Quote from: floobydust on November 15, 2022, 07:49:58 pmI'd say you were right.Here is a photo of the part:https://a.allegroimg.com/s480/116a82/b67973d54b37a39aca436ae4617e/Triak-Z0103MA-Z0103-1A-600V-TO-92-1411

author: Grytpype
author_rank: Contributor
timestamp: November 15, 2022, 08:48:47 pm
content: Thanks all! I ran the 2N2222A for 10 mins with no signs of overheating, explosions, portals etc but the fan didn't seem to react to the humidity or timer settings via the two pots which test okay - as do the caps. I wondered if, although 'working', whether it was behaving as expected with the wrong tranny in.I've ordered a TO-92 and will update this thread once in.Thanks again - great, and interesting, help all round!

author: Grytpype
author_rank: Contributor
timestamp: November 19, 2022, 01:39:18 pm
content: ...works perfectly with the TriacHappy Days!