Replacement for mystery TO-3

Spiff59

Joined Dec 19, 2011
2
Hello all,I've been trying to find a cross-reference for an OEM transistor for a month now with no luck and thought I'd try here. The only reference to the elusive SIV300004 is one I found here in one of your UseNet archives. In that thread, the OP argued that the transisitor was not bearing an OEM or in-house number. I would disagree with that as the only place one seems to find the device is in a Sonix IV Ultrasonic Cleaner. The prefix "SIV" and "Sonix IV" are obviously more than just a coincidence.Anyway, I'm far from an electronics guru, but also am not a complete idiot. I was hoping someone could make an educated guess as to a replacement transistor from the info I can provide.The Sonix ST-144 has 120VAC going into a small Isolator or EMI/RFI Filter board (http://www.kabdental.com/small-dental-equipment/ultrasonic-cleaning-units/access15.jpg). The 120VAC coming out of that drives two SS8G-PCA120 oscillator boards (http://picasaweb.google.com/lh/photo/lW94RiELL4wFLEoNy_ZjRQ), one for each piezo transducer bonded to the bottom of the water tank. (There is a small torroid core wound with black wire that is difficult to see to the right of the larger transformer). I believe this circuit is almost identical to the schematic shown here: http://www.repairfaq.org/sam/samschem.htm#schahv5 Sonix literature states that this model cleaner oscillates at 60Khz. I believe the output to be in the 400-480 volt range. Now to expose my stupidity... would this be a PNP, an NPN, a MosFet? I need some sort of high-frequency, high-voltage, (low-gain?), device in a TO-3 can to replace these. Our cleaner sprung a leak and Sonix is completely unwilling to help. They wish to sell me complete boards at $125 each. (I did find them for$91 each online). The transformers test as neither open, nor shorted, the diodes test good (in-circuit), but the TO-3's do not test as good (out-of-circuit).Might anyone offer a best guess as to a semiconductor replacement that might save me a big chunk of change?Thank you very much.Paul

jimkeith

Joined Oct 26, 2011
540
I recall that I worked years ago with some Motorola developmental devices with approx this same high 3000xxx number--they were TO3, NPN, Bipolar (not darlington), Vceo about 400V--nothing magic about them other than early high voltage devices--medium gain--medium current (by today's standard). Probably can be replaced with TV flyback bipolar transistors--Good luck

MrChips

Joined Oct 2, 2009
20,882
You could try a BUX48 (or BUX48A) which is an NPN high frequency bipolar transistor rated at 850V (1000V), 15A, 175W.

Spiff59

Joined Dec 19, 2011
2
I was about to bite and order a couple BUX48A's, when I came across a parts list for a similar ultrasonic cleaner that utilized Motorola MJ8505 devices. Would you consider one more suitable than the other for this application?

MrChips

Joined Oct 2, 2009
20,882
They appear to have similar specs. BUX48A has a higher current rating 15A vs 10A. MJ8504 and MJ8505 appear to have shorter switching times. I would go with which ever is easier to get.