Vintage electronic equipment that's been sitting in an
attic, basement or storage for many tears will likely no 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 (made from
the 1920s - early 1960s) did not hold up well. Even back then they were the
first things to fail. Yes tubes did fail but many of them still function
perfectly today. You can't say that about capacitors even if NOS. So I will
conclude this paragraph with this statement:
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 during your restoration are usable. 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 & *Micamold capacitors. 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!
5) - Now check the resistors and replace those that that are off value.
6) - Clean controls and switches, see tech tip 17.
7) - Test and replace faulty tubes, see tech tip 14.
8) - Inspect your work, look for suspicious connections, potential shorts etc.
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 then 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.
Professional restoration, if it's worth restoring, let's do it right:
clean chassis, does not need to gleam or brand look new, just clean it up,
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.