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Vintage electronic equipment that's been sitting in an attic, basement or storage for many years will likely not be in proper working order even if NOS. I'm speaking here of tube type electronics and early transistor devices. Reason; failed or in various states of near failure, early paper foil and electrolytic type capacitors. Those made from the 1920s - early 1960s did not hold up well. Even back then they were often the first things to fail. Yes tubes did fail too but many of them still function perfectly today. You can't say that about the early capacitors even if NOS. So I will conclude this paragraph with this statement: Capacitors are the number one cause of electronic failures in vintage electronic equipment!
Here are the 10 steps I use in my Electronic restorations:
1) - I give a good visual inspection to determine if its worth restoring. Make sure special components; power transformer, dial, meter (if it has one) and any part that's not readily available for replacement. See tech tip 1.
2) - Once the decision is made to restore, I clean it up, why work with crusty, rusty or gaumed up chassis.
3) - I inspect, repair or replace bad wiring, secure loose mountings and take care of any other mechanical issues.
4) - Then I replace all tubular, paper foil capacitors. I check the electrolytics with a high quality capacitor tester that will apply full rated voltage during test. If you do not have such a tester, replace 'em! I also suggest that you look for and replace any and all *Micamold products, These look like mica capacitors but believe me they are not, some are even resistors.
5) - Then I check the resistors and replace those that that are off value.
6) - I clean all controls and switches properly, see tech tip 17.
7) - I test and replace faulty tubes, see tech tip 14.
8) - I then inspect my work, look for suspicious connections, those you may have neglected to solder and potential shorts.
9) - Power up slow with a "Variac" while monitoring the DC voltage and current draw at the plate or the screen of the output tube. If the voltage does not come up to the full specified voltage or excessive current is noted (more than 50 ma in most radios), there is a short circuit or low resistance path to B-.
10)- Once any functional issues are resolved, a full RF/IF alignment is performed.
*Micamold is a brand name for very poor quality capacitors and resistors. They have a black molded Bakelite body. Micamold resistors and capacitors look pretty much the same and should be replaced and NOS stock discarded whenever found.
Professional restoration or a "hack" job?
A good, professional restoration is a practice offered by some and there are those who don't think it matters how it looks under the chassis as long as it works. Some don't even care about the appearance of the exposed chassis areas as well. I'm here to state that appearance does matter.
Here are some of the repair practices that I refer to as a "hack Job":
1. Dirty crusty chassis and replacement parts that don't look original or even close.
2. Scabbed in capacitors and resistors. New capacitors installed in parallel with the originals
3. Wrong value parts used and hap-hazard wiring methods
4. Passing on or selling such "hack" jobs as restored.
Professional restoration, if it's worth restoring, let's do it right:
1. A clean chassis, does not need to gleam or look brand new, just clean it up, remove
house-hold dust, grease and crud. If rusty, there are methods to remove rust and improve appearance.
2. No scabbed in parts (that is old leads cut and new part pig-tailed in). The original capacitors and resistors should be unsoldered and new ones installed in the same manner with clean solder joints. Some terminal joints may have 3 or more components terminating at one point. If the components are scabbed in, this takes up more space, increases the possibility of shorts and makes trouble-shooting more difficult as it is hard to get a test lead where you want it and later repairs can be very messy.
3. Make sure you use parts of the right value. Some parts may be substituted with other values or multiple parts series or paralleled to obtain the proper value, but don't use a 25 watt resistor when only a 2 watt is called for. Such practice looks ugly and takes up space.
4. If you are unable to do such work as I describe because of lack of ability or proper equipment (or the use of), seek a solution. If vintage radio is your love, there are those who are more than willing to help.
© C.E. Clutter