Just picked up a 1930s Battery operated Coronado
 

Hello everyone, today I just picked up a 1930s vintage battery operated Coronado Radio of which I don't know the model number and I'm trying to locate the service literature for it.

It is in really decent shape yet, but someone at some point in time wired a power cord up to the antenna hookup and I'm hoping no one actually attemped to plug it in that way otherwise this radio may be a shelf queen, it looks really clean underneath as well and looks like there was no servicing done to the radio (except to the battery cables and the addition of the power cord onto the antenna hookups.)

what kind of batteries were used to power this radio and does anyone have any idea which model this might be?

pictures below.

I used to have one. It wasn't a stellar performer and the cabinet was beat up so I got rid of it. I think it took 90V for the B+ supply and 1.5V for the A supply...the A supply voltage is easy to confirm by googling for the data sheet for 2-3 of the tubes and using the lowest filament voltage. (The audio outputs of battery radios often used a tube of double the A battery voltage with a center tap...the ends of the center taped filament would be jumppered together to halve the opperating voltage and double the current)

I got it mostly as a curiosity piece as I've never owned a battery powered tube radio set before, and thought it would be an interesting piece to try and fix up.

That power cord hookup to the radio's antenna terminals almost certainly would destroy the radio (not to mention possibly starting a fire) in the blink of an eye, if the plug were to be inserted into an AC outlet. Why on earth would anyone do anything like that?

It's a model 650A-B-C in Riders vol 8.
Those are 2 volt filament tubes using 90 volts B+. Chances are, the antenna coil might not be damaged, if 120 ac was applied. :scratch2:
It's easy to build a power supply because it uses only a A+ & B+ source.
Doesn't use a grid bias supply.

Yeah, I checked the antenna coil and it still had continuity so I think it's fine yet. It does have AVC which is good.

Despite Jeff's dour predictions , capacitor C1 would save the antenna coil if AC was improperly applied to the antenna terminals .

Indeed you are correct, when I tested C1 between the antenna terminal strip, and the antenna coil, C1 measured open.

I did some research and I figured out that this radio is a Coronado Model 650B which was a rebadged Arvin "Phantom" Series Farm Radio Model 628B.

I thought that was kind of interesting.

I like the cabinet!

Go to your local dollar store and get 10 9V tranaisistor radio batteries to use in series for B+, and some D cells for the filaments. The 9V batteries can be clipped together in series using their own terminals, and then the first and last ones can have wire leads with alligator clips soldered to them, which you can connect to the radio's power connector. For the A battery I'd use 2 D cells in parallel.

Before you apply power you may want to do a basic replacement of capacitors, especially any electrolytic capacitors, the AVC filter, and the audio grid coupling capacitors.

The reason these radios sound worse than normal radios, is the audio output stage is necessarily very low powered, so the speaker is designed for efficiency rather than sound quality. They can be okay though. I like yours because of the fancy grill design and late 30s deco cabinet.

The radio might not work because the filament voltage should be 2 or 2.2 volts. Those tubes are probably a little tired and need the proper voltage.
I have a Coronado model 550 tombstone made by the same company, but using a single 33 tube in the audio output. It originally had a magnetic speaker that sounded lousy. I installed a PM speaker and output transformer.
Not much audio output, but doesn't sound bad. :thmbsp:

How do you parallel "D" batteries? is it positive to positive or negative to negative?

Both at once...

OK, so I take it that a battery clip like the one in the link below won't work in my case?

https://www.radioshack.com/products/...battery-holder

I didn't realize there was a capacitor in the antenna circuit to protect the coil in case the latter were inadvertently connected to 110v AC power. This will teach me not to say anything like what I said in my post without being sure of the facts.

It's easy enough, unless you have the schematic in front of you!
A lot of sets don't have that capacitor, so it could've been detrimental.
They probably included it because of lightning strike is more common in rural areas.