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How NOT2

nomadradio

Analog Retentive
Apr 3, 2005
6,935
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Louisville, KY
www.nomadradio.com
Just a quick post to pass on a humorous and sad bit of sabotage found in a Cobra 2000 today.

You really should bolt down the final BEFORE you solder the leads to the circuit board.

wUbFzv.jpg


A friend sold this radio, and the buyer complained that it stopped transmitting.
He forgot to mention the sabotage he did to it.

Always bolt the transistor down to the heatsink before you solder the leads to the pcb foil pads. This guy soldered them first, but in a position that pulled the transistor body away from the heat sink.

No mystery behind this "no transmit" complaint.

73
 

I have seen a few over the years the same way. . audio chips pulled apart by bolting them down after a solder job. so many have came by me also and I was just a small repair in my garage from home. so I know with your shop you have seen a bunch of them like this.
I saw a 7222 audio chip that was split in half by soldering it to the board then bolted it down tight.

that one was bad enough just not fully seated.
 
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The same goes for making sure the heat sink (if it has one) is also tightened down and in proper position before soldering any leads. Remember, no strain...no pain...
 
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I suspect that the final that was being installed was used, removed from a junk radio.

The leads were probably too short to comfortably reach the foil pads. And the foil pads look a bit shorter than they were originally, as well.

I think the poor schmuck was just trying to make the leads reach the foil pads.

73
 
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Oddly, I’ve seen several manufacturers that purposely added lead extension wires to the finals in some of the early 23 Ch radios. They deliberately cut the leads short on the transistor and left them straight. After mounting they wrapped several turns of solid wire around each transistor lead, then soldered and cut the wires to the desired length, no bending involved. I since used that same method occasionally whenever I applied a used transistor with short legs.
 
About the only way you could mess this simple job up some more would be to put the final in backwards. The person who soldered that final in needs to have their soldering iron (or cigarette lighter) taken away and a 15 minuet time out in the corner to think that butcher job over some more. If any effort was made to tighten the screw, they probably cracked the nice ceramic insulator too.
 
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