You don't have to be an Engineer to repair transistor radios. Basic Electronic Course and skills will suffice, along with being mechanically inclined. If you think that screwdrivers come in right and left hand models, then DON'Tattempt to repair small radios. Tools are pretty basic however, just requiring flat and phillips head variety screwdrivers, needle nose pliers, soldering irons (low wattage),a solder sucker, new solder, heat shrink tubing, and of course REPLACEMENT PARTS (New or tested 'good' from old scrap radios). There's lot's of good material on the web, just go look for it. Also, if you can, learn how to read and draw schematics (Circuit Diagrams). This will help you immensely. Most common parts replaced are the capacitors, especially those that couple one stage to the other. Most resistors hold up well in transistor radios since current and voltage are minimal. Transistors may become 'leaky' with age but again not too often. Earphone jacks are problematic and are among the first things checked when there is power but no sound at the speaker. Also breaking down frequently would be the Volume Control and it's On-Off Switch. Faulty battery clips (ie: 9 Volt Button Connector), or corroded battery spring coils and battery holders are notorious for 'Dead' sets. So, if you DON'T have any electronic training and/or experience, I think you should just collect and display these fine radios.
A good place to start if you are interested in LEARNING about ELECTRONICS may be a site like this:
http://www.kpsec.freeuk.com/study.htm
OR:
http://www.electronics-tutorials.com/receivers/receiver-basics.htm
I would practice soldering and de-soldering as much as possible BEFORE dismantling a decent, restorable radio. You can easily burn a perfectly good pcb (Printed Circuit Board), or overheat and damage perfectly good components. Knowledge of a VOM (Volt-Ohm-Meter) is extremely helpful and most likely required. A substitute Power Supply too, is extremely useful, and aids in having a non-depleting Battery Source (D.C. Voltage Supply or B+)
If you don't have a circuit diagram (Schematic) or 'Sams Photofact Manuals', then you will need to know the signal path from memory. Most AM radios have a very similar signal path and component layout. The signal is picked up by the Antenna (Ferrite Rod), and fed into the Mixer and Oscillator, through a 1st I.F. (Intermediate Filter) Stage and then through the 2nd I.F. (which is all shown as the Tuner), followed by the Detector Stage. Finally it goes into tha Audio Amplifier and into the Speaker.
Radio Receiver System
The power supply (not shown) is connected to the audio amplifier block.
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Aerial - picks up radio signals from many stations.
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Tuner - selects the signal from just one radio station.
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Detector - extracts the audio signal carried by the radio signal.
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Audio Amplifier - increases the strength (power) of the audio signal.
Loudspeaker- a transducer which converts the audio signal to sound.
On-Off Switch Volume Transistors Electrolytic Capacitors Resistors 9VDC Battery Lead
Loopstic Antenna Oscillator-Tuner 1st IF Stage 2nd IF Stage Fixed Capacitor Detector Earphone Jack
Speaker 3rd IF Stage or External Speaker
As far as cabinet disassembly is concerned, and rather than become repititious, check out this link from Sarah Lowrey's Radio Site:
http://transistor.org/restoration/restoration1.html
Perhaps you may like just cleaning and restoring the radios, and just put them on display. That is what I would recommend because de-soldering and soldering such tiny pieces does require skill and patience. Also, some collectors want their radios un-touched with no new parts added or replaced. The choice is yours. My radios are not all 'mint' but display beautifully. Getting them to work was an added bonus to me.
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