Radio Repair Best Practices

[Mister Mike]

Trimmer Capacitor Loosening Tool is Ingenious

Kudos to Yuri D for posting this ingenious tool idea five years ago. I just used it to loosen a frozen trimmer in a WW-II piece of Collins equipment. Worked like a charm.

[Quatsch]

Some things I've noted in getting antique radios to play;

One is resist the urge to turn it on/power it up untill a carefull visual inspection is made of the internals and safety devices such as fuses. If you open the case and find parts have been looted or mods have been made, or wires cut and hanging, you should address those first. If the fuse or fuses are open there's a reason why, it may be as simple as all the caps were empty so the sudden inrush of current popped the fuse.... or a transformer winding is shorted or a cap is leaky.

Also, if one doesn't have a speaker or headset plugged in, the audio output transformer may develop a very high potential that can short internally or shock an unsuspecting user, so have a speaker or headset plugged in.

Another is I've seldom run across anyone who has had to completely recap or reresistor a German ww2 radio (other than consumer radio such as the volksempfangers). A lot of the German mil radios may need repair, a tube or cap or inductor here and there, but nowhere near the degree US/allied radios do.

The allied radios usualy require a rebuild more or less and the greatest differences between allied and axis comms gear is often quality.
I've read where a Brit technician at the beginning of ww2 inspected a downed German bomber radio with its intricate castings and precision machining and gearing and was immediately impressed that the allies were going to win on this alone, the Germans were spending so much in man hours, money, and materials on making state of the art overengineered highest quality devices they'd spend themselves right out of the war, I feel this was mostly an accurate summation.

Side note;
Many German ww2 radios had cast and machined aluminum chassis and modular subchassis wich does make service a breeze, but the allies more or less used sheet metal stampings for radio chassis, more or less a cakepan and dropped the parts on top of that cakepan wherever they best fit. If an allied radio pooped out it could be replaced as easily as repaired as it was about as cheap, in the German case it made much more sense to repair their expensive radios than replace them.

Conversely, it's not uncommon at all for one to have to replace every wax/paper and electrolytic capacitor in, for one example, a Hallicrafters Sx-28 (used by fcc and the various branches of US mil for radio surveillance and monitoring throughout ww2) and most if not all of the resistors, many of wich will be twice their rated value or greater. Even if you find a cap or resistor that reads good in an allied radio, it is suspect. Most of this part failure/out of spec is due to being exposed to 70 years or more of humidity inflicted upon parts that likely were never meant to last more than 10 years, and were built just good enough to do the job when new. Attempting to "reform" the caps often ends in failure down the road so you might as well just replace all wax/paper caps and out of spec resistors from the start.

That being said, some allied ww2 electronics was made to a higher standard and thusly complete overhauls today are seldom needed, here I'm looking at Collins and the like and various transmitters that normally had nowhere near the amount of wax/paper caps to go bad as a receiver.

But in the German radio case, most caps and resistors are going to be good or at least serviceable, and better yet each part seems to have its value marked thereon, something unheard of in allied radio construction. Their high quality, wich in part cost them the war, is a great thing for collectors. Allied radio collectors may pay a lower price in obtaining their radio but a high price in getting their radios restored, with German radios it's usually the opposite.

Just some thoughts on the subject.

[Yuri D.]

Some things I've noted in getting antique radios to play;

One is resist the urge to turn it on/power it up untill a carefull visual inspection is made of the internals and safety devices such as fuses. If you open the case and find parts have been looted or mods have been made, or wires cut and hanging, you should address those first. If the fuse or fuses are open there's a reason why, it may be as simple as all the caps were empty so the sudden inrush of current popped the fuse.... or a transformer winding is shorted or a cap is leaky.

Also, if one doesn't have a speaker or headset plugged in, the audio output transformer may develop a very high potential that can short internally or shock an unsuspecting user, so have a speaker or headset plugged in.

Another is I've seldom run across anyone who has had to completely recap or reresistor a German ww2 radio (other than consumer radio such as the volksempfangers). A lot of the German mil radios may need repair, a tube or cap or inductor here and there, but nowhere near the degree US/allied radios do.

The allied radios usualy require a rebuild more or less and the greatest differences between allied and axis comms gear is often quality.
I've read where a Brit technician at the beginning of ww2 inspected a downed German bomber radio with its intricate castings and precision machining and gearing and was immediately impressed that the allies were going to win on this alone, the Germans were spending so much in man hours, money, and materials on making state of the art overengineered highest quality devices they'd spend themselves right out of the war, I feel this was mostly an accurate summation.

Side note;
Many German ww2 radios had cast and machined aluminum chassis and modular subchassis wich does make service a breeze, but the allies more or less used sheet metal stampings for radio chassis, more or less a cakepan and dropped the parts on top of that cakepan wherever they best fit. If an allied radio pooped out it could be replaced as easily as repaired as it was about as cheap, in the German case it made much more sense to repair their expensive radios than replace them.

Conversely, it's not uncommon at all for one to have to replace every wax/paper and electrolytic capacitor in, for one example, a Hallicrafters Sx-28 (used by fcc and the various branches of US mil for radio surveillance and monitoring throughout ww2) and most if not all of the resistors, many of wich will be twice their rated value or greater. Even if you find a cap or resistor that reads good in an allied radio, it is suspect. Most of this part failure/out of spec is due to being exposed to 70 years or more of humidity inflicted upon parts that likely were never meant to last more than 10 years, and were built just good enough to do the job when new. Attempting to "reform" the caps often ends in failure down the road so you might as well just replace all wax/paper caps and out of spec resistors from the start.

That being said, some allied ww2 electronics was made to a higher standard and thusly complete overhauls today are seldom needed, here I'm looking at Collins and the like and various transmitters that normally had nowhere near the amount of wax/paper caps to go bad as a receiver.

But in the German radio case, most caps and resistors are going to be good or at least serviceable, and better yet each part seems to have its value marked thereon, something unheard of in allied radio construction. Their high quality, wich in part cost them the war, is a great thing for collectors. Allied radio collectors may pay a lower price in obtaining their radio but a high price in getting their radios restored, with German radios it's usually the opposite.

Just some thoughts on the subject.

Very good comparison of the technology from both sides. The period opinion is very interesting also.

[Quatsch]

Very good comparison of the technology from both sides. The period opinion is very interesting also.

Thanks for the kind words, and for sharing your experience in radio restoration.
I note that I made a mistake in this line however;

"But in the German radio case, most caps and resistors are going to be good or at least serviceable, and better yet each part seems to have its value marked thereon, something unheard of in allied radio construction."

What I meant to say is that the German components were marked as to their identity in the schematics, something the Allies never did.

[17thairborne]

What I meant to say is that the German components were marked as to their identity in the schematics, something the Allies never did.

That will be a big help to me when my radio arrives

[Val]

Removing the rust - what's the best method and ingredient to use? Share the experience.

[Quatsch]

Removing the rust - what's the best method and ingredient to use? Share the experience.

I've seen Hallicrafters cabinets that were well rusted be recovered almost to looking new by an electrolysis bath of some sort, can't remember the details but it involves water, a chemical, a plastic tub, and some dc voltage applied by wires. Keep in mind that is for a cabinet, not a chassis filled with electronics. Others have applied naval jelly if it's a severe case, or just a wire brush and elbow grease. Some guys remove the rust and then paint the case/chassis. I try to leave them if I can, and not remove the cadmium plating or whatever is present, but that depends upon just how much rust is present.

http://www.instructables.com/id/Elec...val-aka-Magic/

[Val]

Any luck with vinegar?

http://www.finewoodworking.com/item/...s-rust-remover

[Val]

It would be nice to hear Yuri's feedback what he used here to remove the rust.

http://www.battlefrequencies.com/res...storation.html

[jantar]

Electrolitic rust remowing

Hi !

I use it for a long time.
Cathode is a thing, which we need to rust remove.
Best anode is stainless steel sheet. Best size is as a r.removed thing, and arroud of this. But you can use only two pieces on the opposite sides, and the thing is in the midle.
They say : The chrome in the stainless will leach out during the electrolysis and form hexavalent chromium compounds in your electrolyte.
When you are in panic, you can use classic steel.

Electrolite - I use potassium hydroxide, but you can washing soda (sodium carbonate, Na2CO3)

Current is about 10A for decimetre square. The bigger distance between elektrods it is ( C and A) the bigger voltage must be for the same current.
Best results i have vith power source 0 -40 V, 0-100 A. You can use smaller current, but it prolongs the time.

And sorry for my english, I´am beginner.