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Part hunt. Release the hounds! 1

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itsmoked

itsmoked

Electrical
Feb 18, 2005
19,114
US
I have 5 high power ultrasonic driver boards in front of me. Sadly 4 of them have one of their 6 paralleled BJTs blown. They have crazy specs and seem to have been obsoleted by ON Semi around 2K.

They are MJ16018.
They were replaced by Semiconductor Technology's ST16018 also gone now.

They had crazy high voltage specs.

ice_screenshot_20180906-194138_jh7qfn.png

ice_screenshot_20180906-194239_s2hhia.png


V[sub]CEV[/sub] of 1,500V !!! I can't find a BJT in T0-3 over 750V in Digikey.

I know some of you have crazy web foo and may be able to churn something up. I've spent about 2 hours on it with nothing to show.

Keith Cress
kcress -
 
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Thanks IR.

Same problem I'm having. None of those will work in a TO-3 setup with massive machined heatsinks, with plug-in, screw-down, thru-the-back of the assembly setup.

Keith Cress
kcress -
 
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From my early days:

image_umhjdq.png


Not that it is a very good solution. But I hope that it will make any other solution - how awkward it may be - look and feel better.

Gunnar Englund
--------------------------------------
Half full - Half empty? I don't mind. It's what in it that counts.
 
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Another quick search led to: "Silicon NPN Transistor High Voltage Horizontal Deflection Output : NTE2365"

PDF =
It's not a direct replacement, for example not in a TO-3 can.

But the keywords "Horizontal Deflection" may be useful for turning up additional candidates.
 
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Hi Keith,

Here's a few which are still available:

BUX98C BUT35 MJ16018 MJ12005
All are somewhere in the ballpark for power handling, current, voltage.

Have you looked at conversion to IGBT switches if the BJT solution doesn't work out? A couple of IGBT packages could replace that paralleled BJT setup quite easily and probably retain the existing heatsinks. You'd need to do some tweaking to the drive circuit but there should be ample drive capability. What is the circuit config - a half-bridge driving a transformer?
 
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Thanks soooOO much guys!

Thanks IR I think one of those NTEs would maybe work if I replaced all the MJ16018s so they shared better.

VE1BLL, Scotty; You both found the same herd of poke-a-dot unicorns on opposite sides of the pond. I don't have to hope an oddball plays well with the existing other 5 on each repaired board. I'll gladly pay $20 bucks a piece. Well, my customer will, as these boards are irreplaceable. I've picked similar spec'd caps seen on the board below to replace the originals that now each cost $25+ with a minimum of 25 and 50 pcs with 19 week lead times... I'm hoping my subs fly. I gave the customer two 'repaired' boards today and will await his trying them before proceeding with repairing the remaining 3 boards plus cycling thru the four boards he still has running that are all likely about to age-out croak too. The machine is supposed to have eight of these but they're down to only four.

And that MJ16018 you found Scotty is not close - it's exact.

As usual I have no schematic for this thing.
20180906_163757_ear3np.jpg



Note the six TO-3 on the back at the top.

Scotty this thing takes in 120Vac and puts out the ultrasonic drive all thru the one Molex at the bottom. Why it needs six freaken transformers/inductors is beyond me. Why not just make a free running oscillator, boost it a few times and feed it to the transducer?

Oh and what's with the RTVed together MOVs at the bottom? (Across a typical bridge rectifier)

Keith Cress
kcress -
 
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Just another thought - I checked eBay, and found several auctions for the MJ16018 transistor.

When the Lunar Orbiter image recovery project began to rebuild 1960's era Ampex tape drives to perform modern analog-to-digital conversion of Lunar Orbiter images of the moon made in the 1960's, they found the spare parts they needed in a variety of places - including eBay.
 
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Indeed Com. I looked there and saw China and a package with extra pins sticking out the back and decided it was too risky but I see others now in the USA though they're "pulled" parts and the shipping is absurd. 2 weeks to actually get around to shipping them... Will be my fall back.

Customer handed the repaired boards to someone else.. Dang it. They put one in and it worked fine.. Yay!

Said the second one had something loose on it.. Say what??

Said when that one was added the first one stopped working. WTH?! I hate remote repair..

Keith Cress
kcress -
 
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Hey Keith,

Sounds like you're sorted for parts. [thumbsup2]

Are you sure the customer is playing fair with you here? Loose parts, and they put a newly a repaired board in and the another one stops working? Hmm... maybe I'm just a cynic. [neutral]
 
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I hope you're uniquely marking all "repaired" boards. Had an eBay equipment reseller hose me on one of my items... I know it worked when I sent it to him, but it suddenly had issues when he received it. Of course, he was willing to send me the bad unit back if I refunded his money... uh huh. I marked all further units, challenged any claims of faulty shipments, and never had a problem since.

Dan - Owner
Footwell%20Animation%20Tiny.gif
 
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Naw Scotty. This customer is a very good friend, diner at his home, we call just to talk. He's just stretched so thin it's painful. He works 12 hours a day 5 days a week and half a day on the weekend. So sometimes he hands things off to his brother, but that does make it a bit harder sometimes.

Yikes Dan. I'll remember that.

I used to sell a consumer product that was a bare-board ramping time-of-day 4 channel LED controller. Once I kept getting one back from a specific customer for warranty repair. I called them and found the board choked whenever she got off the couch in her bathrobe walked across the living room carpet and touched the board.

Keith Cress
kcress -
 
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She must have been exceedingly hot.
I'm sorry. The devil made me say that.

Bill
--------------------
"Why not the best?"
Jimmy Carter
 
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