1937 American Bosch 670: The Gift That Keeps on Giving!

About 2 years ago, I found a 1937 American Bosch console radio, model 670, in an antique shop in Lithopolis, Ohio. It looked to be in really good shape and complete, so I forked out the $100.00 asking price, loaded it up in my rig, and took it home to the wife. She was starting to get the radio bug and it was around this time that she started confiscating everything that came through the door. So much for running a business for profit.

So, I get the radio home and unload it, and the wife just loves it! Of course, she wants it to work so I start separating the chassis from the case for an inspection. Besides the customary dust and cobwebs, everything look great. Little did I know that over the course of the next two years, this radio would be the bane of my existence.

First in order was recapping the radio. A mostly mundane job, I jumped right in, not really looking at the location of the caps in the chassis. Once I really started digging, I found caps behind the tuning mechanism, which Bosch called the “CentrOmatic”. If I would have known about the hide and seek caps, I would have immediately sold the radio.

Not being a quitter, I decided to test my sanity and get those caps out. After much agonizing and cursing, the radio was finally recapped. I reconnected everything and got her fired up. There was crackling but no real signal.

Okay, I’m thinking bad tube, so all come out and actually tested good. Now I’m wondering what I missed so I go back in with a bright light and a magnifying glass. Nothing seems amiss, so I just put her aside for the meantime to get some other shop work done. That’s where it sat for about a year. After all, I am the typical husband.

The wife and I decided city life wasn’t for us (As big a city as Baltimore Ohio can be) and found a house out in Liberty Township. After setting up shop again, I decided to tackle the Bosch. Remembering I was somewhat puzzled, I decided to get the oscilloscope out and do some circuit tracing. At that time, my O-scope was an old Heathkit model 10…an old CRT unit. It worked okay in spite of the focusing rectifier needing replaced. I plugged it in to warm the tubes and go inside for a bite to eat. Just as I am finishing lunch, Niki says, “Hey Gatewood, is there something burning in the shop?” Well, it was summertime and the farm just south of us had been burning brush for the last few weeks, so I didn’t think much of it. I told her no, that’s the farm down south, and went back to my desert.

That was stupid.

As I opened the door to the shop, an overwhelming odor of burnt wiring overcame me. Smoke was rolling gently out of the O-scope, so I hit the breakers for the shop, unplug it and run it outside. After inspection, I found out the transformer appeared to have shorted, starting a small fire. Luckily, I got to it before it burned down our palatial estate! Now that’s what I call timing.

Now I’m down an ocilloscope, which I don’t really use a lot, but I needed one to trace this circuit and I needed one bad. After informing the wife what a new (used) one would cost, it was determined we were too poor to replace it until tax time. Without a scope, I decided to go ahead and tinker with it again. I checked the tubes again and found the amplifier tube was bad. It must have died shortly after I tested it the first time. I ordered the tube and, hoping against all odds, I plug her in, fire her up and tune in a station. Hot damn, she worked…for about 55 seconds, then everything got really fuzzy. I recognized that sound immediately and remove the speaker from the cabinet. Yup, she had a blow out.

Speakers blowing out in old radios isn’t what I would call common, but it does happen. Without getting too technical here, my belief is that over time radio speakers seize in the voice coil and when they get a signal, they can’t move. Well, something’s got to give, and it usually the weakest point: The paper cone. My theory is tar from cigarette smoke and other environmental elements work their way into the voice coil area and, once the radios sits for years and years in heat and cold, that tar molds around the voice coil and the groove it rides up and down in and basically glues it in place.

Anyway, I digress.

Needless to say, the speaker has to go to The Speaker Shop in North Lima, Ohio. That’ll set me back another hundred or so. My wife is lucky to have a guy like me around…You know, the kind that will spare no expense to kiss her butt?

And the O-scope? Well, one of my customers came through and delivered one… a nice one and free of charge! It’s a Leader LBO-514 and it works amazingly sweet!