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June 2008

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Subject:
From:
"Upton, Shawn" <[log in to unmask]>
Reply To:
TechNet E-Mail Forum <[log in to unmask]>, Upton, Shawn
Date:
Tue, 24 Jun 2008 09:14:32 -0400
Content-Type:
text/plain
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text/plain (54 lines)
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/

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