Ultrasonic driver and fake transistors... - Page 1
Forum section: electronics / repair

author: coquinho
author_rank: Contributor
timestamp: June 04, 2024, 06:42:16 pm
content: Hi. I'm trying to repair my ultrasonic cleaner that had a short on a output transistor. Its a pair of MJE13009, from Fairshield. Also a bridge rectifier was shorted, flyback diode and fuse. I bought everything and replaced. Worked fine, but the transistors were heating up so fast, like in matter of one minute was about 80 to 100C on their dissipators.I found a similar schematic of the circuit driver from a Hackaday project, but there some diferences:• All component numbers are different on the board, but same values.• A resistor does not exist, R4, is just a jumper.• R7 on my board is connected between Base and Collector, not Base and Emitter.• My transistors are 13009, not 13007.Its about it, the rest is about the same so far I can tell.The transistor I bought seems fake, but I tried buying for other places, and they seem about same fake. I took a photo from they:Left is the originals from the board, that worked for years, on the right are the fake ones.So, what can I do? I'm a little lost on this. It seems that somewhat its very hard to find original transistors nowdays. What you guys suggest? Thanks for the attetion.

author: Harry_22
author_rank: Frequent Contributor
timestamp: June 04, 2024, 08:11:11 pm
content: Set up the circuit on fakes and when it works normally install ST13007(9) from ST Microelectronics or MJE13007(9) from ON Semiconductor.

author: wraper
author_rank: Unknown
timestamp: June 04, 2024, 08:29:10 pm
content: Transistors on the left are not Fairchild but something that tries to look somewhat similar. Transistors of the right have almost proper Fairchild logo, look 100% fake though. Also marking on the left suggests FJP13009, not MJE13009. Marking on the right suggests MJE13009. Although they're the same thing, ON/Fairchild does not seem to produce MJE anymore.QuoteIt's very easy if you don't buy from shitty places.

author: wraper
author_rank: Unknown
timestamp: June 04, 2024, 10:04:33 pm
content: Unless you buy from reputable distributors I suggest buying genuine Chinese branded stuff with no fakeryhttps://www.lcsc.com/products/Bipolar-Transistors-BJT_326.html?keyword=13009Or at least what's actually still in production, such as KSE13009, FJP13009...

author: coquinho
author_rank: Contributor
timestamp: June 05, 2024, 01:24:27 am
content: I found a pair of D209L NPN transistors on a old power supply, and they seem to no heat-up to fast, but they do heat up more than I wanted. Does anyone have any ideas that I could modify on the circuit to make a little more reliable? With 30 seconds on I can smell something coming from the heatsinks, maybe residual skin oil after handling and soldering on the board.I read on the same place that I found the schematic that this drivers are poorly filtered on the DC, because it has no capacitor after the rectifiers, but I don't know if it would make the transistor heat up less. Any suggestion would be good.On the first post like I said, the schematic has a little diferences, like on the schematic there is a 47K resistor polarizing (?) the Base to "negative" and other to "positive", but here both are connected to the Collector, like positive polarized (?)About the transistors, like all local market here, have about the same transistors, I could try other brands and have luck but it starts to becoming expensive like 5 USD per transistor and I would have to buy almost based on luck...

author: wraper
author_rank: Unknown
timestamp: June 05, 2024, 08:06:54 am
content: I don't think you can get less heating with other BJT transistors. So you either need to use larger heatsinks or modify the circuit to use MOSFETs.

author: coquinho
author_rank: Contributor
timestamp: June 08, 2024, 05:42:34 am
content: I managed to get good temperatures with original transistors and diodes, but the transformer is heating up to 105C that I can see with my CAT S60 Flir camera.I tried to add a filtering capacitor after the bridge rectifier, but it makes the transformer heat more. Ultrasonic drivers must run without filter caps? I also edited the diagram to look more like the circuit of my driver:What can I do to improve this design?

author: ArdWar
author_rank: Frequent Contributor
timestamp: June 08, 2024, 05:55:43 am
content: Did they really short T2 like that? I don't think it works as inductor either.

author: coquinho
author_rank: Contributor
timestamp: June 08, 2024, 08:58:06 am
content: I think that a least on my board, its just a inductor, the transformers is just like the ones on this picture of a driver board: