# Replacing a transistor when I can't find any info on it

I am attempting to repair a Sonix Ultrasonic Cleaner and I have found that the only parts that have gone bad are two power transistors, SIV300004. I emailed Sonix and they want to sell me the whole control board not just the part. And they didn't want to give me any more info like schematics or a data sheet.

I would need two control boards and they would cost more than this thing is worth. I have searched Google four a few hours and can only find a few references from others from years ago who are looking for the same part. I can't even figure out who makes this SIV300004, If I could I would contact the manufacture.

So I was thinking that maybe there is some way to figure it out from the circuit. Can that be done? If I were to draw out the schematics would I be able to figure out what specs I would need for a replacement transistor? How would I go about this. Or is there any other way to figure out what I can use?

Thanks for the help, Russ

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Yes. Give us the circuit and we will be able to spec a transistor for you.

AND a photo to go on with (and comment on thos below).

A copper side view of PCB as well would help muchly (for the terminally enthused to start in on).

If you have a working unit so much the better.
I you can tell us the supply voltage, power taken and frequency it would help greatly. That would be enough to hazard a good gusstimate. Even voltage would possibly be enough !!!

BUT the more you tell us the better.
For example, telling us that it was in a metal T03 case on a heatsink about xxx big and was made in 2008 or ... would help.

eg - like this? Yes? :-)

May be used elsewhere in system, too? Board level parts supplier here says

Item # Description Price
SS8G-PCA080 Generator Board, Acousti-pulse 6580 $91.91 SS8G-PCA120 Generator Board, Acousti-pulse 6580$91.91

and... . Transistor is about certain to be the same given the peep of part number seen.

Item # Description Price

SS8G-PCA120X2 Generator/Driver Acousti-Pulse/Dual \$165.44

You didn't tell us you knew board part numbers !!!! More photos

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The second photo is pretty much what I have and that is the transistor I need on the heat sink. I have two of those boards. Both of the boards have bad SIV300004s. There is a smaller board in the unit that also has a SIV300004 that I am pretty sure is good. Is there some test gear that can figure out the parameters I need from the working transistor? I don't have a curve tracer. I will try and run it with just the one board and see if I can get the specs you mentioned and I will also draw out the schematic and post it back here. Thanks very much, –  Russ Dec 8 '11 at 7:37

How nice! A while back our ultrasonic cleaner sprung a leak and I'm convinced also blew the TO-3 power transisters on both of the oscillator boards. A month ago there was nothing on the web regarding the SIV300004, other than an old USENET thread where the OP argued that SIV300004 was not an OEM or in-house number. Odd, the full name of the company is Sonix IV, and the semiconductor is marked SIV... hmm. Anyway, I was excited to find this current thread on the topic.

I have the exact same self-oscillating (the torroid is hard to see in the photo) SS8G-PCA120 boards in my Sonix ST-144 cleaner. From the Sonix literature, I know they oscillate at 60Khz. I'm fairly sure the output voltage is in the 400-480 volt range. I'd assume the transister must be low gain (<10).

So, I am also looking for advice towards a suitable high-voltage, high-frequency, low-gain replacement transister. Is it PNP, NPN, MosFET? I have no idea... I do believe this schematic for a different brand ultrasound unit is nearly identical to the Sonix circuit: http://www.repairfaq.org/sam/samschem.htm#schahv5

I hope I've contributed somewhat towards solving the mystery. And I await any further developments with anticipation!

Thanks all, Paul

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http://opencircuits.com/Semiconductor_Analyzer_Review is pretty cool, tells a lot but not everythging.

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I have one of those but I don't think it tells the whole story but I will take a closer look at it. –  Russ Dec 9 '11 at 1:08