Saturday, December 08, 2007

Distractions...

Unfortunately, this is not a gun post. Fortunately, it's just a photo-dump of what I've been working on for the last several weeks that's been keeping me off blogspot.

I'm not going to bother describing each and every photo, you can figure out what's going on. The chassis is marked 1936, a Fairbanks-Morse model 8A four band radio.

I'm trying to make this post collapsible, bear with me while I figure it out.

EDIT: Screw it, you'll just have to deal.












5 Comments:

Anonymous Standard Mischief said...

How do you plan on dealing with the capacitors? I'm just inclined to recap the entire radio with modern, better tolerance caps, but some people don't think that is the proper way to go about a restoration.

11:04 PM  
Blogger Dr. StrangeGun said...

I'm gonna orange-drop the sucker as soon as I have the scratch to buy an assortment.

I've already popped for a 5000/8 ohm transformer and a handful of power resistors and big caps to replace the old EM speaker with a modern one, and a reel of dial cord too... the aim is to get the darn thing runnnin', at least in AM, and hand it back over to the parents.

11:09 PM  
Blogger Dr. StrangeGun said...

Oh, and as far as the bigarse Aerovox 16mfd that popped, anything can go in it's place, really. I don't really know why they have such a large unit in place, the schematic shows it coming right off the output of a 5Y6, surely they could have gotten what's a simple power supply filter in a smaller package.

Then again, this *is* FB we're talking about, it was probably cheaper and worked just as well. Same reason the field coil for the EM speaker was designed in as the power line filter *smacks forehead*.

11:15 PM  
Anonymous Anonymous said...

A lot of competition in the market and lax safety standards. Look at the All American Five radios, They predate polarized plugs or grounded NEMA 5-15 outlets. Can you say hot chassis? Apparently the cost of a transformer was the difference between affording a radio or not. It also let people play radios in areas that still had DC wall power.

I also remember one type of radio that used a long resistance wire alongside the other two on the power cord to drop the voltage enough to run the tube filaments. If the end user wrapped up the excess cord in a bundle it might overhead and start a fire.

-Standard Mischief

4:02 PM  
Blogger Roberta X said...

As an IHRS member in more-or-less good standing, I have to comment. (The last three words are "Historical Radio Society.")

Hey, now, Anon, AA5s went to great lengths to keep your fingers away from the chassis! Some very high-end sets were acey-duesy, even some comms gear from National.

Doc, that's a good-lookin' radio! The big stud-mount 'lytic is very typical of the time, and 16 mikes (instead of the usual 8) is primo-luxe stuff.

Likewise, in the days before alinco magenets, it wasn't too uncomon to use an electromagnet for the speaker field, and if you're doin' that, it was considered efficient to use the magnet as at least part of the B+ filter choke. Works pretty well: the more current draw, the greater the field, and the largest variable load on the B+ is, you guessed it, the audio amplifier tube(s).

Serious recapping is an excellent idea, the old wax-paper jobbies are failure-prone, often in annoyingly subtle ways. Not merely changes in value as Std. Mischief alludes but DC leakage (especially problematic on the AVC line) and bizarre oscillation. In recent years, I've seen a lot of very-drifted carbon resistors, too; while the amount of leeway there is (generally!) even higher than the +/-20% typical of the components, it's worth checking.

Post photos of the finished project, please, if you have time!

8:31 AM  

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