DX-302 Rf Amp

[Blackswan73]

I have a Radio Shack DX-302 with a bad rf amp transistor. Instead of desoldering the transistor and taking a chance of delaminating the traces of the forty year old pcb, I am considering just clipping the leads close to the TO-5 body, and soldering the new transistor to the existing leads. My concern is since it is a rf circuit, will this cause the circuit to pick up stray rf from the leads being too long?

B.S.

 

[prcguy]

There is no reason you can’t remove a part and not damage the circuit board. A desoldering station with correct size tip would be best but solder wick or a solder sucker plunger thing can also work well. The problem I’ve seen with solder suckers is people pushing down too hard with the sucker tip while heating the solder and grinding the soldering iron tip into the traces. If you approach it gently you will get great results.

 

[TAC4]

I have a Radio Shack DX-302 with a bad rf amp transistor. Instead of desoldering the transistor and taking a chance of delaminating the traces of the forty year old pcb, I am considering just clipping the leads close to the TO-5 body, and soldering the new transistor to the existing leads. My concern is since it is a rf circuit, will this cause the circuit to pick up stray rf from the leads being too long?

B.S.

Most of the time delaminating is a result of to much heat from the iron or poor quality control from the manufacturer country not
age. I have recapped tones of vintage SW radios and scanners
and delaminating does occur but it's not the end of the world.

Replace your transistor as you normally would, use a copper wick
instead of a vacuum solder sucker as it is more gentle and go easy on the heat of the iron.

If you do encounter delaminating don't panic just get a thin piece
of insulated hook up wire and make the same length and shape
as the trace and just solder it in at point A and B on trace side of the board. Done

Also all the electrolytic capacitors in that radio will need to be replaced in the near future. They are way past there service life.
Use good brand ones like Nichicon, Panasonic etc.

 

[merlin]

I think a bigger wory is pulling out a plated through hole. A proper desoldering tool, get as much solder off the connection as practical,
then use lateral force to loosten the leads.

all the electrolytic capacitors in that radio will need to be replaced in the near future

Back when these were made, Japanese, India, even Mexico used some good electrolytics, so low likelyhood for that need

 

[ratboy]

If you don't leave the leads really long, you're probably be OK. Electrolytic caps seem to vary in how long they last to a huge degree. I have a few 50 year old plus radios that have no problems at all with the original caps. Other have had the filter caps fail pretty quickly. And a couple of times, the filter caps showed no signs of problems until BLAM when turned on one day.

Don't even think about using a soldering gun, if you were. It's asking for trouble. I know, I've fixed a ton of stuff that has had "floating traces" from soldering guns and giant irons. You can get a cheap little 20 watt or so iron on Amazon or Ebay that works well, but a desoldering station makes life so much better. I scored my Solomon in great condition for the whopping price of $15 and $10 shipping. First thing I used it on was recapping my Kenwood TS-850SAT. My best Ebay deal ever!
Desoldering Station SL-928 - Sorny Roong Industrial Co., Ltd.
I giggle when I see the price of a new one is like $300!