RESTORING YOUR VINTAGE RADIO

Greetings to the forum. You'll notice that this is my first posting here. Love the site!

I'm a newly minted ham (just last week, as a matter of fact), but am not new to radio or electronics. I have always been intrigued by "Boatanchors" or those radios that have glowing components. I have fond childhood memories of sitting on the roof of my house with a makeshift antenna and my thrift store-purchased Hallicrafters S-38 shortwave radio, trying to pull in those far away stations. I'm also very much a fan of the process of restoration, be it an old firearm, a steamship, or an old radio. This thread really piqued my interest. Anyway...

I was interested to see that in the discussion of age-affected capacitors, Equivalent Series Resistance wasn't mentioned as a cause of leakage, bulging, venting and other failures. Although this may not be totally relevant to older style capacitors, these are often replaced with modern equivalents. An original capacitor that was replaced with a "modern" electrolytic in the '70s or '80s is again at the point where it could have an abnormally high ESR, and would need replacement again.

I think every electronics tinkerer, or troubleshooter ought to have a means of testing capacitor ESR. I built a meter based on this gentleman's excellent model, and I find it EXTREMELY useful... http://ludens.cl/Electron/esr/esr.html

Was wondering if any of you fellas are familiar with this, or what your experiences have been with this aspect of capacitor testing/troubleshooting.

Thanks!
Jason

 

Hi Jason:

Congratulations on your new ticket....and on knowing what an s38 is. I have an s38 (no prefix, meaning it had the dedicated BFO circuit) which I have restored to "gooder than new." condition with a radical capacitectomy.

Indeed ESR is a valuable figure of merit. Capacitors have gotten SO much better than the ones of yore.

Actually, ESR isn't normally a CAUSE of leakage...it's the RESULT of leakage.

I have a LEADER LCR740 which does a fine job of measuring ESR, as does any good component bridge. The ancient Heathkit Q meters did this well, too. (Alas, I rue the day I got rid o my old Heath....Ebay has discovered what they're worth. )

We're certainly open to any tips from noobies or oldbees!

By the way, the S-38, having a half wave rectifier, always had some hum...even when new. I have a cute little hum null circuit that will quiet down almost ANY half wave rectified receiver.


Eric

 

Thankee, Eric! You learn something new everyday! This forum's paying off already. I was mistakenly under the impression that an abnormally high ESR could lead to extra heat being generated inside the capacitor, which could cause leakage, bulging, possibly venting and capacitance changes, etc.

Yes, come to think of it, my S-38 did have a constant, sotto-voce hum. It was also renown for giving me a little AC tickles when I touched the parts of the case where the coating was chipped off. I always thought of them as love bites. Ha! I wish I could recall what happened to that old radio. I really cherished it.

 

Perhaps the ESR/leakage thing is a mutually parasitic malady. It's dielectric leakage that causes the ESR in the first place, but that in turn will cause overheating...and more dielectric leakage!

That "tingle" you feel is from the radio being an Ac/Dc model....the chassis goes right to the AC mains...if you have the plug reversed you'll get knocked on your keister. (Or plugging it into a house with non-standard wiring....more common than you'd think!)

Eric

 

I am a old tube radio repairman if you need info on repairing your boat anchor i can help you get it working. Be very respectful working on these radios!! tube type recievers have aprox. 350 volts+ transmitters can have up to 1500 volts b+ 73 Charles KG4NZW

 

Just finally got to this thread....Excellent intro there eric, with a fine modulated adjustment follow up by Glen.....
It really is an advantage having the original instruction manual, The manufacturers in the olden days assumed anyone using a ham RX aleady knew which end of the soldering iorn got hot, and understood basic hetrodyne theory, so the books usually included a detailed tune up and trouble shooting section. Unlike today, where we are pretty much limited to using warm soapy water and replacing a fuse if something goes awry...

 

CWX:

A good number of the "boat anchor" manuals, except for Heath and Collins, are available from BAMA at

http://bama.edebris.com/manuals/

The Heath manuals have been removed due to copyright problems. Although Rockwell Collins does enforce their copyrights as well, they have authorized the Collins Collector's Association to make the manuals available at no cost. Those can be found at

http://www.collinsradio.org/Archives/Collins_Radio_Equipment_Manuals.aspx

In addition, the information that was in the Riders series of books which go from around 1920 until the late 1950s can be found at

http://www.nostalgiaair.org/Resources/

Riders did have a lot of the amateur radio receivers in the information. There is service information and alignment information usually available. The procedures are somewhat abbreviated from the original manufacturer's manual. But, all the information that someone with even a little experience is available to do the alignment.

I do have a complete set of the Riders manuals, there are 23 plus an "abridged" Volume I - V. Also, I do have the Index volumes as well. But, it is usually MUCH easier just to go to Nostalgia Air and download the information than it is to look in several Index volumes and then go to the actual volume in which the information is located. The volumes range from about 4 inches thick to almost a foot thick!

Glen, K9STH

 

As another newly ordained ham, (I mean really, the ULS just posted my license 2 days ago) I could not resist the look of a Yaesu FT 101. So I bought one. What got me started on this hobby is I inherited a S-40A from my grandfather. God what fun, I must have turned that dial a million times. Even though I'm only a Technician, I just love to listen. Can't wait to get my General ticket and start talking!

73 John KF7KRX

 

Nice job, Eric! I am sitting here, at the "control point" of a quite modern computer, reading your thread, listening to a Perry Como LP (Yes, vinyl!) being played through a very interesting system that uses, of all things, tubes (6550's). It is also THX-certified. Your observations of hollow-state gear are spot-on.

Thanks again.

 

A fun tube, based on the 6L6 vacuum tube.
When you mentioned that tube, the first audio amplifier that I thought of was the Dynaco Mark III with KT-88/6550.

Shannon Parks at DIYTube.com designed a new driver board Poseidon for that classic amplifier!
http://www.diytube.com/phpBB2/viewtopic.php?t=947

http://store.triodestore.com/diytubemk3.html

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