To test s/b on MJ15xxx's: Use a 65V lab supply, set the limit to about 7 amps. Connect to collector. Put 2.7 ohms (50W) from emitter to ground. Heat sink it too - on a separate sink. Apply 14V (pulsed or continuous, depending on cooling) to base. Monitor voltage across Re. If it spikes above 13.5V, your device didn't survive. To cool it for continuous operation or long pulses, mount directly to a finned heat sink and place the fins in an ice bath. Not too many of us have LN2-cooled cold plates but we can find ice in the freezer. Tc won't get above 10 or 15C as long as there is ice in the water.
For 2N3055's use 5.6 ohms and drop Vcc to 55V. Good ones will survive this. (2.5A@40V).
I would test ALL of them if the writing on them is in any way different. Test a couple of good ones for power, then measure Cbe. Check all of them against this reading unless the markings are absolutely the same. Meaure Cbe on your open unit and you could use it for a golden standard - it does appear genuine.
For 2N3055's use 5.6 ohms and drop Vcc to 55V. Good ones will survive this. (2.5A@40V).
I would test ALL of them if the writing on them is in any way different. Test a couple of good ones for power, then measure Cbe. Check all of them against this reading unless the markings are absolutely the same. Meaure Cbe on your open unit and you could use it for a golden standard - it does appear genuine.
I did suggest just that but got poo-pooed.
I've bought some On Semiconductor ones now from a reputable supplier.
I've bought some On Semiconductor ones now from a reputable supplier.
Another parameter that will weed out a lot of cheap die substitutions is how the beta holds up at higher Ic. 2N3055 and similar have Hfe collapse above 3A
Comparing to the originals I had at http://www.diyaudio.com/forums/solid-state/249168-3-failure-vibration-3.html
The insulating white material is missing.
Gajanan Phadte
The insulating white material is missing.
Gajanan Phadte
The white silicone material should be missing. Look at the pics linked and shown in posts 17,18 again. There is no silicone on ON-Semi product and the die of both examples is too small.
On ESP site, the coating on the counterfeit is patchy, as I mentioned in earlier post.
Gajanan Phadte
Gajanan Phadte
Genuine power transistor die were neatly soldered to a copper pad in the case base. Fakes just glue a small die onto the base
http://www.diyaudio.com/forums/parts/71367-fake-ing-motorola-transistors.html
Some useful info on fakes...
Gajanan Phadte
Some useful info on fakes...
Gajanan Phadte
- Status
- Not open for further replies.