Often I have heard it said "I just bought a radio and plugged it in and all it does is hum."
I just wanted to share a few thoughts on how I would proceed in powering up and repairing old radios. This is not a exhustive procedure but is being posted to help. The other goal is to prevent damage to a priceless piece of history. Even though it is tempting, I DO NOT apply power first. My first step is to photograph all areas of the radio. The higher the resolution the better. This can aid in correcting miswires, restringing dial cords, and can be saved as part of the radio's history. Second I visually go over the entire set looking for burnt components, bare wires, signs of overload (oozing pitch or wax), and previous technician tracks. I also try to detect any burnt smells. Third I do what is called power conditioning. I have a 0-300 volt variable power supply that I connect to the B+ line of the radio. I slowly ramp the voltage up while monitoring current. I stop at 50 volts and let is sit there for several hours. I feel components to see if they are heating up and monitor current draw. Next I ramp up to 100 volts. I leave it there for 24 hours and monitor the set. Depending on the set, I'll go to 200 and then to 300 volts for 24 hours while monitoring. This ramping of voltage preconditions the filter capacitors and allows you to catch components that may short if power is applied after the set has been sitting for who knows how long. When power conditioning, on almost all the radios, I'll see that the current starts out at a much higher level than when I am at the end of the conditioning. I am not talking about the initial surge current. This is attributed to the reformation of the filters. Others suggest a longer time frame for reforming capacitors but I usually end up replacing them. My goal is to prevent overloading the radio when I finally plug it in. I next test all the tubes. If all is well I plug the radio in and monitor the B+ voltage and look for any signs of overload. Often the radio will hum and the B+ voltage will be low. I keep on hand several filter capacitors that are less that 20 uf. If you try to hang too large of a capacitor into the circuit you may blow the rectifier tube. Some handy capacitors to use are ac motor capacitors. The ones I use are rated for 370 VAC and can be used for much higher than that on dc (no problem at 500 vdc). I connect these capictors with jumper wires (watch out for old PCV oil filled ones. Bring them to your recycle station). This often brings the radio to life, but if it doesn't, it allows me to troubleshoot before changing any thing. I replace filters first one by one powering up the radio each time making sure nothing goes wrong. A good rule is if something has gone wrong check what you did last. Next I begin recapping one by one and powering the radio up each time. I usually start with the audio stages first. I replaced all out of tolerance resitors (usually 20%). When completed I do an IF alignment and then the RF alignment. I document what was done. This may seem like a lengthy proceedure but your radio may have been sitting for many years. You don't want to fry parts that may be impossible to get. I hope somebody finds this usefull.
MRO

oops no PCB's

I had a fellow HAM friend who was extremely diligent and careful on everything he built.
Every Heathkit circuit he built was like an advertisement for the product!
His procedures were very well thought out and through. Not the least of which was his process of building equipment from kits, such as Heathkit. He would read all the instructions from begining to end first. Then he would layout and count all the resistors, coils, capacitors, wires and other such components including screws washers etc. He would compare his count to the inventory of of parts listed in the instructions. Then he would proceed.
But his very interesting approach to avoid failure was this. He would wind each resistor or capactitor carefully around each binding post, solder it, and then cut off the tail ends of the leads from each end and place ALL the tails in a container. When he completed the entire wiring job he would count up all the saved tails (2 for each component including all the wires ) and then count all the components in the inventory and the number of wires used, double that number ....and if it matched his count for cut-off tails... then he knew... or felt certain that there were no scraps of short wires left in the circuit to cause shorts before powering up.

Boy that sure is diligent and safe... but I could never do it... lol

Hopefully he didn't drop a couple of tails on the floor and spend the night searching for them in the radio. It would be like putting together a puzzle when two pieces had dropped on the floor. Any ways I had seen that you do photography. Is there a good forum for photography. I have been cleaning out my fathers basement and have come across pictures negatives and slides of family and events that are from the late 1890's through to the 1980's. I have been archiving them on my computer and would like some pointers on cleaning and other misc things.
MRO

I think that the electrolytic re-forming idea is a great one that most of us overlook (though many old electrolytics are simply not able to be re-formed). However, as I always say, I do not think it is wise to power up the radio in any way with the old condensers in place. I think that it is wise to first test all condensers for shorts and leakage. Re-form electrolytics on the side if you wish--using a separate power supply, not the radio's. Then replace out of spec. resistors and faulty condensers. If you wish, then test tubes. Possibly test coils for continuity. Then, after all of this is done, slowly power up the radio. Slowly powering up the radio will reveal wiring errors by you, and will reveal a faulty power transformer, etc. I do not see the need for testing the radio's condensers by using its own power supply. Condensers are easily checked with a multi-meter in most cases. Leaving them in the radio and testing the radio to see which one is causing problems (replacing one at a time and powering up the radio after each one) just leaves the possibility for damaged transformers and coils, etc., due to a faulty condenser.

Thomas

This was just a method that I use. If you can glean something out of it that is fine. I have been using this method for a long time without problems. My main concern was for the person who just powers up a radio without taking any precautions. My running a separate power supply at or near normal B+ and monitoring current draw has worked fine for singling out potentially shorted caps. As I said, after I precondition I replace the filter caps first one by one to avoid the miswires that can make some real good toast. The preconditioning test with current monitoring can last a couple of days. But I'll take what you have said into consideration.
MRO

I also think you misread what I initially wrote. I use a separate variable DC power supply to do my pretesting. I do not use the radio's power supply for this process. You may want to read it again.
MRO

Ah.

T.

:I also think you misread what I initially wrote. I use a separate variable DC power supply to do my pretesting. I do not use the radio's power supply for this process. You may want to read it again.
:MRO

:Hi Mark.. thanks for dropping in on my site...
I have been at this exciting new-found artistic outlet now since about 1991.. and funny thing... I just never sought out a forum... I don't remember any .... there once was one ... on Polaroid transfer, which I'm known for.. but I don't know if it is still around... but there must be! ....sorry I just don't know them...
y'know it's funny cause I jumped into this very nice forum... right after starting this radio hobby in Sept... but... didn't for my photography.... curious.
Maybe because the net wasn't real big till about 95 when I built my own website... by then my learning curve had peaked.. so I wasn't seeking much help... however I am always advising emailers and guest-book signers about my techniques. And I do 1 on 1 workshops from time to time. I've been very fortunate to be invited to many places around the world teaching fellow enthusiasts and making new lasting friendships. In fact I'm going back to Australia for 3 weeks again in April.
But to answer your direct question... no I don't... lol
I'll be glad to help though if I can anytime. and my tel # is on my site too.

Thanks for the response. Great job on the photos and best wishes on old radio hobby.
MRO