Thanks - great information.

Thanks for coming up with ways to keep these old machines going.

Probably a dumb question - but if the kt859a don't get that hot why not eliminate the heat sink. Or use a heat sink for the TO-220?

Bob

A monster heat sink like that may make that part last literally forever.

Modern and still made replacement for the TO-220 transistor would be a BUX85 at less than a buck apiece.

I don't follow the 'running cooler' line, though.
Regardless of transistor type - this circuit is still dissipating the same amount of power. This power is dissipated as heat.
If incoming voltage is 230VDC, if adjusted voltage is 150VDC then this circuit is dropping 80 volts. If the current is 100mA (randomly high but believable value) then the power dissipated is 8 watts. This power dissipation is the same regardless if 2N3584 or BUX84 or any other type transistor. Since you have not changed the heat sink then the overall temperature should be nearly identical to that of a 2N3584. The BUX84 has slightly better Junction-to-case thermal resistance than the 2N3584 (probably comparable to one used above). But the 2N3584 has better case-to-sink thermal resistance (typical of metal can transistor). So, the thermal resistance is nearly identical. Unless the heat sink compound was dried out, I do not see any reason for the transistor to be any different in temp. And I see no reason for the heat sink to be at a different temp, either.

Now -- if the transistor being driven has a different gain then it is possible that one of the 2N3440's may be running slightly cooler. But most of their current is determined by biasing resistors.

do you guys learn this from just pinball or from your regular job?

I was in construction all my life and I missed out on this electronic stuff. Wish I could have learned it years ago.

Thanks for all you guys do here. We really need people like you on pinside.

Bob

Been working as an electronics design engineer for 30 years (same company the whole time). Currently updating design of high end communications equipment for satellites. 90% of the time through years has been for communications hardware design. Tons of miscellaneous jobs as well. Most fun was the monitoring system for people under home arrest. Had wireless ankle straps on the person (with anti-tamper), GPS tracking (that was fun to test), built in breath-analyzer (didn't get to test that one), cameras...lots of fun stuff while trying to out guess what the criminals would do (some of them are quite ingenious). Lots of experience with linear and switching power supplies on that job as well as solenoid drivers and mechanical stuff.
A lot of that stuff rolls over nicely into pinball and arcade electronics which is mostly generic stuff.

Based on what I have seen on the newsgroups and on pinside - there are quite a few electronics type people here... pinball must hold some form of attraction to us nerds.

Ed

Standard BUX84 and 85 transistors are with the non-insulated tab. It's a special suffix to get the version with the insulated tab (actual suffix varies between mfrs). I'll have BUX85G's (new On-Semi parts) in the near future as this looks like a good alternative to the increasingly rare 2N3584's.

Ed

Do you have any Bux in stock yet?

Another question,

Had some issues with a -22 Bally SDB. Replaced the 2n3584 with the rest of the HV Regulator components. Circuit went bad but can't figure why. Replaced the 2n3584 and the non-heatsinked 3440 and for a few seconds it output the correct voltage then nothing. R51 (22K) was very hot. It's new but already looks burned. What is the proper way to test the 3584 and the 3440 transistors? Other resistors in the circuit test at proper values as do the two diodes.

Yep -- BUX85's on this page:
https://www.greatplainselectronics.com/products.asp?cat=105

Had them for a few months with no sales... they were never listed on the website until tonight.

For current problem -- time to retest all three transistors. Only sure way to test is out of circuit.

Kind if figured. Probably the one I didn't replace was also bad. Now think I may have retried the 3584 and the other 3440. I hate re replacing things.

Thanks, will be ordering.

Could the lm323k be replaced with a 323t in a similar fashion to using the bux85 for the 3584 or is the pin config too far off?

By the way, my Meteor has a CPU repaired by you barakandl

LM323T might fit as the pinout would match. BUT the LM323T's thermal resistance is higher than that of the metal can LM323K's so the LM323T would run quite abit hotter. I don't think I would try that.

Hey, would this be a good addition to pinwiki?
As 2N3584's get scarce (only Central Semi making them now at greatly elevated prices). The BUX85 seems to be a viable alternative using method shown above.

I give it a yes vote. Good idea Ed.

I always use BUT11A without any problems.

- Ingo

Bumping cause this is good info and those new to the hobby might have missed a good piece of info. I've now got a few for when I do board work. Can't beat the price.

Awesome! That old part was $5, now I can just buy 6 of this part for the same price. Thanks!

so can the bux 84 with the insulated tab still be used?,I assume they still need a heatsink

Yes, but the center lead - collector, will have to be folded up, solder a wire to the center lead and then attached the other end of the wire to the the tab mounting
screw to provide circuit continuity for the collector.

Yes the heat sink will still be required to be in place.

The metal tab, un-insulated. provides collector circuit continuity
when it is mounted, and the center lead is cut off.

thanks for the quick reply

Had people ask me what the "G" meant on BUX85G. "G" suffix simply means the part does not contain lead, it is RoHS (reduction of hazardous substances) compliant.

Unless I'm missing something major, it looks like this transistor is neither difficult to find nor expensive:

http://www.mouser.com/ProductDetail/Central-Semiconductor/2N3584/?qs=Ypxpq5eNvNUPDDXg7JlkXQ%3d%3d

Datasheet: http://www.mouser.com/ds/2/68/2n3583-3585-28734.pdf

Different strokes...

If it were me, the extra $$$ would be worth it for the peace of mind I'd feel knowing I used an exact replacement: no mods/hacks are needed, it is a known quantity with regard to long-term reliability and function, and it maintains the original engineering specs (which I won't second-guess as I am definitely not an engineer, just a self-taught hobbyist who realizes there is lot of stuff I don't know that I don't know).

In the end it doesn't really matter as long as the solenoids are clacking and the lights are flashing!

It's a matter of how much you are willing to spend and personal preference. Some people pay more to get exact same part that fits properly, some people just go for an electrical equivalent but a bit of a 'different' fit and at less than $1 each. No problem with paying more for an exact replacement, I also have these listed on my website but at much less than $10.90.

Regarding expensive - that's why I mentioned "Central Semi making them now at greatly elevated prices" above - they are at $10.90 each. Not long ago when Motorola was making these, new ones were less than a buck apiece. Central Semi keeps track on supplies and adjusts prices accordingly, they already increased their price by 3x in a short period of time.

Regarding tech specs - most of the BUX85G specs are better than the 2N3584's. BUX85G min gain is a hair less but BUX85G can withstand higher voltages and has a far lower junction to case thermal resistance. The slight difference in gain won't matter as that is already accounted for by Q22.

Same thing is going on with LM323K regulators. ST had them for less than $5 each at the time of LTB or Last Time Buy. TI is now sole survivor for making these and has them at nearly $30 each (new parts). I was fortunate enough to buy ~500 new regulators while they were still available and reasonable.

Thought I'd dig this up.

My HV section went on my lost world and didn't have any 2n3584 on hand. So I found this thread and ordered up a 10 pack of BUX85's. The install is easy and painless, clip the middle leg and install like a 2n3584.

I replaced the other HV parts, all caps and added some LED digital voltage readouts. Voila, a nice steady 190V.

BUX85 were $1.11 CDN each after buying 10.

IMG_20160202_165721_(resized).jpg

But turn that 190V down to save your Plasma tubes. The lower you can go, the better. Just enough to light all the segments.

what's with the LED monitors? I want to know more about those. that's pretty slick.

ebay.com link: DC 0 30V Blue LED Car Digital Display Voltage Voltmeter Panel Meter Gauge MiNi

$2 and free shipping

nice. These are kind of handy when you need to watch multiple voltages

I find the displays very handy, especially when you support your friends machines.

I got mine here ebay.com link: 10PCS 0 28 DC Digital Voltmeter Panel Mount LED Voltage Volt meter Red 2 50 30V

There are other listing that provide up to 100VDC if you want to see 43, 91....etc

Respect goes out to Clay....I saw it in one of his pics of a bench test rig

NICE!!! How did you fasten the LED-voltmeters?

I used two sided foam tape. A dab of silicone would work too or the pcb has screw holes.

BTW - you have to drill a hole in the SDB in order to run the wires to the back side

Thank you for the pic above Q21 replacement. I just did a rebuild of my board and needed to do that with the 3 leg replacement.

Small update and link, part number changed to the lead free version:

https://www.mouser.com/ProductDetail/?qs=vNc2DXHODiJ9fMJcu1Buag%3D%3D

BUX85G

And here:
https://www.greatplainselectronics.com/proddetail.asp?prod=BUX85G

^ the real MVP