I wonder though if temp spiked suddenly, enough to cook the part but not enough to heat up the PCB? Well, above what the PCB had already been cooked--it does have some discoloration. I'm wondering about sudden spike, then the transistor goes open circuit. Fast enough to blow the guts out, but not long enough to discolor the pcb above and beyond what it has already seen. Thermal compound and/or flux residue interacting with whatever leaked out of the power transistor when it went? Almost looks like is left over in the oven when a pie (high in sugar) has a spillover. Lastly, just to verify: the transistor is bad, right? Or is it still working? Shawn Upton, KB1CKT Test Engineer Allegro MicroSystems, Inc [log in to unmask] 603.626.2429/fax: 603.641.5336 -----Original Message----- From: TechNet [mailto:[log in to unmask]] On Behalf Of Guy Ramsey Sent: Tuesday, June 24, 2008 5:04 AM To: [log in to unmask] Subject: Re: [TN] Power amplifier growth Looks like less of a growth and more of transmogrification. Looks like Q100 got pretty hot. -----Original Message----- From: TechNet [mailto:[log in to unmask]] On Behalf Of Dave Elder Sent: Tuesday, June 24, 2008 1:01 AM To: [log in to unmask] Subject: [TN] Power amplifier growth Has anyone seen anything like this? The growth is on a 100W power amplifier that has been sitting, powered up, under load, on a desk, for six months. Dave http://sites.google.com/site/taitpcb/ --------------------------------------------------- Technet Mail List provided as a service by IPC using LISTSERV 15.0 To unsubscribe, send a message to [log in to unmask] with following text in the BODY (NOT the subject field): SIGNOFF Technet To temporarily halt or (re-start) delivery of Technet send e-mail to [log in to unmask]: SET Technet NOMAIL or (MAIL) To receive ONE mailing per day of all the posts: send e-mail to [log in to unmask]: SET Technet Digest Search the archives of previous posts at: http://listserv.ipc.org/archives Please visit IPC web site http://www.ipc.org/contentpage.asp?Pageid=4.3.16 for additional information, or contact Keach Sasamori at [log in to unmask] or 847-615-7100 ext.2815 -----------------------------------------------------