In my experience with transistors, none dealing with ballasts, but several other high voltage and/or high current applications, it is uncommon for transistors to fail open.=20 It's not unheard of but is in the minority. Regarding your direct question, I don't know whether there is some sort of protection built into the transistors you used as a replacement, but I highly doubt that there is any. Regards, Jim =20 > -------- Original Message -------- > Subject: [EE]transistor dies open circuit > From: cdb > Date: Thu, January 05, 2012 1:55 pm > To: >=20 >=20 > At work I repair some ballasts that use 2 * TIP41's, these die on a=20 > regular basis often burning a nice hole in the PCB at the same time as=20 > disintegrating. >=20 > After trying catch diodes (didn't work), I experimented with replacing=20 > TIP41's with BUJ 302a from NXP, these have a breakdown voltage of around= =20 > 1kv. >=20 > The other day one of these repaired ones died, but one BUJ died O/C betwe= en=20 > all three pins, and the other O/C between CE and S/C between BE. I've not= =20 > seen a transistor used in transformer multivibrator circuit fail O/C=20 > before. Is it possible NXP have some form of internal resistor or perhaps= =20 > this is a result of some inherent manufacturing technique of high breakdo= wn=20 > transistors? >=20 > Obviously failing open circuit is much much safer than short circuit. >=20 > Colin > -- > cdb, 6/01/2012 > =20 > -- >=20 >=20 >=20 >=20 > colin@btech-online.co.uk >=20 > --=20 > http://www.piclist.com PIC/SX FAQ & list archive > View/change your membership options at > http://mailman.mit.edu/mailman/listinfo/piclist --=20 http://www.piclist.com PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist .