Copper Talk » Ask The Tech » Amplifiers » How do you know if you have a transistor going bad? « Previous Next »

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Sparkomatic
Intermediate Member
Username: Sparkomatic

Post Number: 288
Registered: 10-2002
Posted on Sunday, May 02, 2004 - 10:49 am:   Edit Post Delete Post    Move Post (Moderator/Admin Only)

Some people say that power transistors start losing power output over a period of time and others say that either a transistor works or it doesn't and there isn't any in between condition.
In the 20 plus years I have been in CB I have never burned a radio or amp up but I am curious.
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Bruce
Senior Member
Username: Bruce

Post Number: 1207
Registered: 9-2003
Posted on Sunday, May 02, 2004 - 11:34 am:   Edit Post Delete Post    Move Post (Moderator/Admin Only)

Spark YES they CAN " BE " going bad. Some transistors are realy a number of transistors bonded together and if a bond is cracked they will fail with changes like heat. Call it " Cold solder joints " but i seen it in the older VHF amps NORMALY they just go and thats it but it can happen ..... a 1307 fimal i had in a radio would go up and down in output as it got hot and hit it with cold spray poof good again........ yep enough to want one to become a bomb expert.
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Kc0gxz
Advanced Member
Username: Kc0gxz

Post Number: 785
Registered: 3-2003
Posted on Sunday, May 02, 2004 - 4:21 pm:   Edit Post Delete Post    Move Post (Moderator/Admin Only)

Bruce

You couldn't be more correct. For many years I was told and thought the same thing as Sparkomatic. Either they worked or they didn't work.

Then one day I came across a final (1307) in a Cobra 139-XLR that did just as you explained. Never again did I overlook the possibility of a final or driver breaking down internally.

Jeff.
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Kc8pcl
New member
Username: Kc8pcl

Post Number: 2
Registered: 7-2011
Posted on Monday, July 18, 2011 - 7:54 pm:   Edit Post Delete Post    Move Post (Moderator/Admin Only)

A transistor is like a light switch, it is either on or it is off, and they really don't like heat, unlike tubes that gradually loose output power over time.
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Onelasttime
Junior Member
Username: Onelasttime

Post Number: 11
Registered: 8-2011
Posted on Monday, August 08, 2011 - 7:05 pm:   Edit Post Delete Post    Move Post (Moderator/Admin Only)

They are not like a light switch. They seem to fail suddenly because of what normally takes them out. Usualy screaming high swr's due to bad ground feeding back up the power back into the transistor.

Heat slowly kills electronics.

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