Hello, I built this radio some years ago (using vintage parts) and figured I'd share it.

I had a mild stroke and cant recall the specifics. I'm looking for some schematics to help me recall what to do. Which is the A and B voltage, what the coil was and just how to operate it again. The tube is a UV-200A, I recall that it seemed to work better than the others I tried.

If I still cant get it going then I'd like to sell it or trade it for a crystal radio, something that would be easy for me to operate and enjoy. Thank you.

The radio is missing a plug-in coil. It should have at least two windings. One for the tuning range the other for the tickler. Also appears to be missing a grid condenser but it may be part of the Bradley-ohm variable grid leak. As a home brew radio possibly a plan was used and that included how to wind the tuning coil. It is known as a single circuit regenerative receiver, not unlike many commercially made ones of the era. It was common to place a metal foil shield behind the panel to prevent the hand form the effects of "hand-capacity" from de-tuning.

The radio will need an antenna but it must not be too long as that effects the regeneration and a short connection to ground, again too long a ground wire will effect how it operates.

Will need 6 volts at 1/4 amp and no more than 22-1/2 volts B+ Four alkaline "D batteries in series will light the filament for some 4 hours or so. A small 6 volt lead/acid utility battery will also work. Two 9-volt transistor batteries for the B+ will also work. The tube is the gas type soft detector and low B+ is essential. High impedance (2000 ohms DC resistance) headphones are a must. In fact for a 200a tube even higher impedance is better.

GL

Chas

There is a 5 screw terminal connector on the rear of the radio. Looking at it from the rear of the radio left to right, A+ A- NC B- B+. On the front panel the left most control I think is in series with the filament maybe used as a volume control. Also on the front panel the right most control is the regen potentiometer.
I checked some of my coils (AM broadcast with 240 PF tuning capacitor) and they seem to have compatible pin out but I'm not sure of the tickler polarity. Knowing the tuning capacitor value range and intended frequency range of the radio is required to select/construct a coil.

In case my above analysis of the battery connections is incorrect it would be wise to first pull the tube prior to connecting batteries for the first time. With the tube removed and batteries connected use a voltmeter to verify that the voltages on the tube socket pins are correct.

Would this work as a substitute ?

https://www.aliexpress.com/item/3256805756540732.html

Well, yes & no...

What you need to know is what is the maximum capacity of the tuning condenser... From the figure in pf or mmf (pico farads or micro-micro farads). The coil that will work with that condenser can be determined. At least a start, as one must make a or buy a coil form for the 4-pin socket. Then a fixed diameter of the form will be known. Calculations made base on that coil form diameter and the tuning condenser to arrive at an approximate coil to wind and what size wire. The Feedback winding can be estimated at 10 to 25% of the main winding.

If you want to guess on the windings, the number, diameter and turns can be taken from any of the many manufactured plug-in coils that were once offered from the 20's to the 60's.

Search World Radio History for 20's magazine articles based on a one tube radio in the 20's.

https://www.worldradiohistory.com/hd2/I ... search.cgi

The reason to search earlier magazines is the apparent maximum capacity of your tuner appears to be 500pf, modern vales are 365pf...

Your $16 for a China coil would be better spent getting an LCR meter ask advice from ARF members what is a better model...

I use older instruments so I do not have a pocket meter...

GL

Chas

Do this:

Measure the circle diameter of one of the rotating plates.

Count the number of rotating plates and count the number of fixed plates.

Post this information to this topic.

I will compare that data with one or more old tuning condensers I have then measure the capacitance to be sure. That, can be starting point to marry some odd plug-in coils I have to find resonance in the BC band using a grid dip meter or an RF oscillator, detector and 'scope...

Chas

I'm not seeing an RF choke in the circuit? There usually is one -- typically 2.5mh -- inline with one of the headphone output legs.

Chris

True, but it will work without one.

What the O.P. needs for the radio are coil specifications to work with the tuning condenser currently installed.