Uniden repair - part # help

[MB]

I sent two (BC250, SC200) of my scanners into Uniden for repair. Both lost their sensitivity by being used in the same vehicle as a 100 watt VHF-hi radio.

The online repair status shows Q-1 under the Parts Used field. Does anyone know what Q-1 is?

I hope they actually repaired them, I had to pay $50 a piece to have them fixed!

 

[MarkWestin]

Hello,

Although I'm not familiar with Uniden's parts list, Q universally means a transistor. In this case, it is probably some type of Field Effect Transistor (used as a high gain RF Amp). This would be the first active component in the signal path, and is before the mixer/local oscillator.

Mark

 

[MB]

I wonder if that is what it is??

I have always heard that the first thing that goes in this case is some kind of protection diode that is before the front end..

Does anyone know?

 

[Al42]

It could be either the first RF amp (Q1 would be a logical designation) or the protection diode - depending on the clamping voltage, the risetime of the signal that caused the problem, the frequency ... and a few dozen other things. But the protection diode protects the transistor, so whichever one goes a) you still lose sensitivity and b) the damage is in just about the same spot. ("Before the front end" is pretty much limited to the antenna and antenna jack - then comes the front end.) The reason for the diode isn't that the radio will keep working if the diode protects the transistor, it's that the diode is cheaper than the transistor.

 

[MarkWestin]

Hello again,

Diodes are usually given reference numbers like "D1" or "Z1" depending on the type and use. The odds are good that when you get them back, they will work better than or at least as good as they did before they were damaged, since they will be aligned after the part replacement.

Mark

 

[MB]

Hello again,

Diodes are usually given reference numbers like "D1" or "Z1" depending on the type and use. The odds are good that when you get them back, they will work better than or at least as good as they did before they were damaged, since they will be aligned after the part replacement.

Mark

Thanks for the help guys.

So it sounds like they just replaced the transistor. I wonder if there even was a diode protecting it? I just hope they work as good or better then they did.

So what does it actually mean to be "aligned". I have somewhat of a technical background, I have heard of this before but never knew what it ment.