Old console radio repair

[joeqsmith]

We saved my wife's grandparents old console radio when her grandmother had passed away.  It's nothing fancy and had not worked for years.   No one wanted it and it was going to head to the dumpster so crazy me decides to save it.       That was 25 or so years ago.   

I looked it over and one tube had leaked and the main alum elec filter cap was bad.   I could not locate a tube at the time and ended up changing the design slightly to use a different tube.  Many years later, I had gone to the Dayton Ham fest.  There was an old pickup truck sitting with bushels of tubes next to it on a table.  No one around.  I looked through the tubes and found two of the correct part.   There was a note stuck to the truck.  $1.00 ea, drop money in window.  They had left the window cracked and I dropped in a few bucks.  When I arrived home, I changed the radio back to original and installed the new tube.  The radio worked fine after that and I had not given it another thought.   That is, until last night.

We were listening to the radio and the signal was really poor.  So I pulled out the radio from against the wall and saw the original power cord was starting to disintegrate.   

I am a bit surprised that after all those year,  the radio still has all the original paper caps.   Today I gave it a good cleaning, pulled all the paper caps and installed a new cord.   Back in business.   

[james_s]

Looks good, what model is the radio?

I always replace all of those wax paper caps right off the bat, they're almost always way out of spec and they have a tendency to short and damage other much harder to obtain parts.

[drussell]

With knowledge gained only from YT channel Mr Carlson's Lab,  you should replace all the old wax paper capacitors before attempting to power it up. No if's no buts.

Shango066 would probably disagree with you.. 

My Precision E200 still has all the original Solar brand paper capacitors from when it was built in the 1940s.  It still works to specification.  The frequency dial is even still remarkably close to spot on in every range and I've never tweaked a single trimmer.

Generally, though, old paper caps should probably all be replaced as a matter of course during a restoration, even if you can leave some of them in certain parts of a circuit during a quick repair.  Anything where they are being used as a coupling capacitor from one stage's plate onto a grid or something, though, they certainly should go.  You can't have any leakage there.  In other places, a small bit of leakage current won't matter one bit.

[joeqsmith]

Appreciate the concern for the old radio.  It's been in operation since I've had it.  About 80 years on those caps.   I am fairly capable when it comes to doing my own repairs.  This radio is a fairly simple design.   

The radio was made by Crosley Radio Corp, model 718.  It still has all the papers and tags on it.  It has shortwave, there are notes about it's use.   

I have no plans to restore it.  I would say it's in fair condition.  Woods a bit rough, some water stain on the fabric covering the speaker. 

[chris_leyson]

I was discussing restoring an old radio with a colleague the other day and he mentioned a trick an old radio/TV service engineer had taught him. Paper caps will eventually absorb some moisture over time and one way to fix them was to heat up some candle wax in a small tin over say a 100W light bulb for example. When the wax has melted drop the paper cap in and watch the air bubbles "leak" out of the ends, when the bubbling stops take the cap out of the wax. If the candle wax is too hot you'll know because the wires drop off the end of the cap. Anyway, he told me he had managed to restore quite a few paper caps using this technique and he had tested them before and after with a Megger. I have a DAC90A that needs to have its caps tested so I might actually give it try. Just wondered if anyone else has heard of this technique.

[chris_leyson]

Sorry, I got carried away I should have said nice job well done, you've saved another piece of electronics history that's getting harder to find these days.

[joeqsmith]

I've never heard of anyone attempting to recover caps beyond reforming alum elecs.   I've seen paper ones short before and don't think you would do much with them after that.  May be a good experiment.  Please post about it if you make an attempt.   

My wife was telling her mother about me working on the radio.  She remembers listening to radio shows as a child on it.  The Shadow....  She remembers hearing about Japan attacking Pearl Harbor on it as well.  I'm glad I saved it just for the memories it provides.   

[james_s]

Yeah that's a unique story. I've had several antique radios, but never one that has been in the family since new, that's impressive.

I would never attempt to recover old waxed paper caps, even if you succeed they will absorb more moisture eventually. If one prefers to retain the original appearance it's fairly easy to re-stuff the old capacitors with modern parts.

[rsjsouza]

Pretty nice! I have a 1946~47 Philips BX462 that was bought new by my grandfather. Its housing is in excellent condition, most probably because it is bakelite and not wood. My dad restored it 30 years ago and replaced all paper caps with oil, but it is in need of service again - the electrolytic capacitors were never changed, thus this will be my focus when I get to it. I have good memories listening to Radio France International, Radio Nederland and BBC programs in the 1980s in SW.

[vk6zgo]

We saved my wife's grandparents old console radio when her grandmother had passed away.  It's nothing fancy and had not worked for years.   No one wanted it and it was going to head to the dumpster so crazy me decides to save it.       That was 25 or so years ago.   

I looked it over and one tube had leaked and the main alum elec filter cap was bad.   I could not locate a tube at the time and ended up changing the design slightly to use a different tube.  Many years later, I had gone to the Dayton Ham fest.  There was an old pickup truck sitting with bushels of tubes next to it on a table.  No one around.  I looked through the tubes and found two of the correct part.   There was a note stuck to the truck.  $1.00 ea, drop money in window.  They had left the window cracked and I dropped in a few bucks.  When I arrived home, I changed the radio back to original and installed the new tube.  The radio worked fine after that and I had not given it another thought.   That is, until last night.

We were listening to the radio and the signal was really poor.  So I pulled out the radio from against the wall and saw the original power cord was starting to disintegrate.   

I am a bit surprised that after all those year,  the radio still has all the original paper caps.   Today I gave it a good cleaning, pulled all the paper caps and installed a new cord.   Back in business.   

And it's a real radio---- with a power transformer, not one of those godawful transformerless things!

[james_s]

The transformerless radios were a great example of extreme cost reduction, and really they worked quite well despite the obvious shortcomings. Now over in 220V land I gather they used a resistive cord to drop the excess voltage but on 120V most got by without that. The All American Five as the design is often called was used in millions of affordable radios, bringing radio within reach of the middle class masses who may not have been able to afford the luxurious transformer powered consoles. Yes they have safety issues, but one has to remember that attitudes toward electricity and safety in general were different back then.

[vk6zgo]

The transformerless radios were a great example of extreme cost reduction, and really they worked quite well despite the obvious shortcomings. Now over in 220V land I gather they used a resistive cord to drop the excess voltage but on 120V most got by without that. The All American Five as the design is often called was used in millions of affordable radios, bringing radio within reach of the middle class masses who may not have been able to afford the luxurious transformer powered consoles. Yes they have safety issues, but one has to remember that attitudes toward electricity and safety in general were different back then.

Not in Australia!
Almost all our 240v ac radios used power transformers (the few outliers were derisorily christened "death radios").
There were also, a very few transformerless models made for the handful of places with DC mains ( both 240v & 110v).

The transformers for a normal mantel radio (the sort of thing which would sit on top of the fridge in thousands of households), were small enough to hold in your hand, so there was no size penalty.

With our smaller market, the cost savings for transformerless were pretty much an illusion.
Local tube manufacturers were set up to make 6.3volt heater tubes in large numbers, following the wartime buildup in capacity, & it was not worth it to setup parallel production of tubes designed for series filaments, neither was it economically viable to buy them from the USA, the UK, or Europe.

Added to this is that most series filament tubes were designed for 110v,  requiring, as you noted, a resistive power cord, or other means of dropping the excess voltage, all of which were clunky, either as large as the power transformer they replaced, or not made in quantity locally.

Add to that, the requirement for additional insulation, & it's no wonder they were rejected by manufacturers in this country.

OK, radios were more expensive than in the USA, but they would have been, anyway, as they were in other countries which did go down the transformerless route.

[Tomorokoshi]

It's amazing what UL approved back in the day!