Radiola 28 (DC)

[Winky Dink]

That was too easy. I hadn't looked up the stations yet. Definitely the Detroit area, and definitely after 1934. Several of the stations' call letters were not in use until 1932-1935. I was puzzled at first about those starting with "C," but I remembered that in 1960, in the Washington DC area, I used to listen to CJBC, Toronto, on my first transistor radio.

In cleaning up the dial, under certain lighting conditions, I could see some erasures. The only one I could read was "WNEW." From metromedia.com, "In 1934 businessmen Milton Biow and Arde Bulova purchased a Newark, New Jersey radio station, WODA. They changed the call letters to WNEW for “the NEWest thing in radio”. Indeed, it was the newest thing.

The station was launched in a ceremony performed on February 13th at 9 pm by President Franklin D. Roosevelt. From the White House the president pushed a button and moments later a lamp illuminated in a New Jersey transmitter room. As the light shined, soprano Yvonne D’Arle sang the Star Spangled Banner and WNEW-AM 1130 officially went on the air."

The radio was in North Dakota 25 years ago, so apparently it is well traveled.


Regarding the hobby, my wife is actually supportive. After all, I gave up 25 years of avid golfing (which I sucked at) for vintage electronic restoration (which I suck at).

[Winky Dink]

Ultimately I'll be building or buying an AC power supply for this radio. In the meantime, I've spent 3 days trying to figure out the existing battery eliminator, which I thought would be very simple. In fact, when I started this project I thought that a battery radio would have three batteries, as simple as A-B-C.

I've been trying to trace circuits, but I'm often foiled because the lines runs into the "permanently sealed catacomb" and the wire colors are not readable. So please give me a clue. Here is a photo of the battery eliminator, an illustration of the same, the battery setup, and the continuity diagram.









(1) What do the power supply terminals 1, 2, 3, -A, -B+A, etc. represent? (Note to SciFi fans: don't tell me, "It's a cookbook!")

(2) The answer to the second question should be obvious, but I can't see it. After I connect the input to 110VAC, how do the electrons get into the black box? What are the input terminals supposed to connect to?

Anyone who can help me will be rewarded with total enlightenment during his or her lifetime.

- Winky

[Winky Dink]

I Broke the Code

I realize that this is obvious to almost anyone reading this post, but it took me four days to figure out this much. With the circuitry hidden in the catacomb and sparse identification of the visible components, I finally figured out what the resistors were doing attached to the bus bar and where to input the A voltage. Being an entirely visual thinker, I had to make many diagrams such as this…



…and then recognize the correlation between my resistance readings inside the catacomb to the series of resistors on the outside. Reminds me of the time I broke the Enigma code back in WWII.*

Now I can proceed to Code B and Code C.

- Winky

* Disclaimer: This is a joke. I didn't actually break the Enigma code, and I wasn't actually alive during World War II.

[Reece]

Ow, my head hurts! Excellent sleuthing.

[bgadow]

A really nice find. I spotted one about a year ago at a local antique mall, had all the tubes but no antenna (they always seem to be missing?) $65 but I just couldn't convince myself to dig that deep. Kinda wish I did because it was gone when I went back a month later.

I really like the handwritten call letters.

[bandersen]

Nice detective work

[toxcrusadr]

I'm very curious about this radio, particularly its tube compliment and manuf. date. It's a Superhet, which suggests late 20s at least, right? But the tubes are 199s and 00's - aren't those early 20's tubes? Anyone have an explanation of this weird beast?

[Winky Dink]

Off the top of my head--this model was manufactured from 1925 to 1927. The tubes are tubular, skinnier than globes, and placed too close together to allow globes or ST's to fit. Maybe that's why the seven X99s and one X20 seem outdated for this model's time frame.

[Winky Dink]

Slow progress on the Radiola. For me, the difficulty is trying to restore the Radiola 28 for DC operation when this one, and most of the other thousands of Radiola 28 battery sets, have had the AC conversion package installed.

As I puttered around the set I noticed several circuits seemed to have the wiring "wrong." I didn't appreciate the extent of the modifications for AC operation until I read the RCA radio repair course chapter on the Radiola 28 conversion package. I've put the chassis wiring back to the original DC state, including replacing the AC resistor strip with a DC connection strip. For the DC connection strip (DC bus bar) this is the only picture I found:



I puzzled over the RCA's circuit and continuity diagrams for several weeks before I realized that this highlighted section represents the DC connection strip on the back of the catacomb:



This is what I ended up making for a DC connection strip:



It fits, and I really hope I did it right. I thought it would take a couple of hours, but it turned into a 4-day project for me. Other than this, there are only a few other parts that need to be replaced, but so far I haven't been able to find values for any of the components in the original DC set.

[Winky Dink]

When I'm finishing an electronic restoration, I start procrastinating--finding unnecessary details to attend to--to defer the moment of truth: "What will happen when I power up this machine?" I still intend to build a DC power supply, but for the time being I'm going to use a store-bought battery eliminator.



I have an originally battery-operated Radiola 28 receiver-- no antenna, no speaker. It is an early model, but was produced after RCA discontinued the 877 "protective tube." It had been converted to AC with a Model 104 speaker. I have found no part numbers or values for any components except the grid leak condenser, for which the Radiotron UX199 information states, "One to five Megohms."

I have reversed the wiring changes from the AC conversion, but several components were also changed. The conversion involved replacing the rheostats for filament voltage and volume and elimination of a dual capacitor in the B+ supply circuit. I can work around the rheostat changes, but I have no clue what to use for the missing capacitors. For that matter, I don't even understand the function of the capacitors in a DC power line.

This is the best diagram I had to work from, with the missing condensers circled:



Here are the missing caps on my own diagram, on the B+ 45 and 90v lines:



So, approaching one issue at a time, I'm asking what I need for the missing condensers. I've done all the continuity testing in the chassis and the catacomb, and it seems to be okay. I checked the values of all components I could measure without opening the catacomb, and this is what I got:



If I can replace the missing condensers, or if I find that I don't need them, then I'll apply the power and start checking voltages--first without the tubes--and proceed from there.

Finally, I've reworked RCA's Radiola diagrams into something more understandable to me, and if anyone's interested, here are links to my diagrams:

'A' Voltage through chassis:
https://picasaweb.google.com/lh/phot...eat=directlink

'B' Voltage through chassis:
https://picasaweb.google.com/lh/phot...eat=directlink

'C' Voltage through chassis:
https://picasaweb.google.com/lh/phot...eat=directlink

Battery diagram through chassis:
https://picasaweb.google.com/lh/phot...eat=directlink

'A' Voltage through catacomb:
https://picasaweb.google.com/lh/phot...eat=directlink

'B' Voltage through catacomb:
https://picasaweb.google.com/lh/phot...eat=directlink

'C' Voltage through catacomb:
https://picasaweb.google.com/lh/phot...eat=directlink

[bandersen]

Yikes, what a project! I never heard of an 877 tube before so did a little research. It appears to be equivalent to a modern thermistor like a CL-90 I think.

[Winky Dink]

The Radiola 28 went operational yesterday. With eight pricey tubes at risk, I was a bit skittish about the power supply connections. Dave Snow at Antique Radios Inc. was very helpful.
Reception is good, but the audio quality is poor. The volume rheostat is a component for AC operation and it only works on very weak stations, so I put a 1Meg pot on the speaker. When I get some idea of specs for the original DC rheostat, then I'll work on replacing it. There are also a couple of condensers missing from the 90-volt and 45-volt lines (B voltages).

This is a 40-second video of the set's on-bench premiere. This is the best audio I can get so far.

https://picasaweb.google.com/coldrb/...eat=directlink


And some pictures (I feel like I'm showing pictures of the grandkids to roomful of strangers).
The ARBE III connection to the terminal strip:



The ARBE III in the battery compartment:



The Radiola 28 with the convertible top up (It's old-fashioned, so you have to raise the top by hand):



The next project is finding an antenna or building a replica. My woodworking friend who replaced the feet for me is eager to work on antenna. I'm hoping to find someone with an antenna to get some detailed photos and dimensions.

[mstaton]

Nice work and awesome radio! Saw that on CL for the longest time and I've been tempted to buy it but I'm glad you got it and made it work.

[Winky Dink]

I've got the Radiola up and running, and the rotating antenna actually works. The signal is noticeably stronger/weaker as I turn the antenna. The problem now is that it actually receives only one station, and I can look out my window and see the antenna towers less than two miles away.

Previously, even without the antenna, I could receive the usual five or ten local stations. Now I've examined the chassis thoroughly for visible defects, redone the continuity testing, retested all the tubes, juggled tubes to put the strongest performers in key positions. To my knowledge, since the last time it was working properly, the only thing I've changed is to modify the volume rheostat to the original DC configuration pack the power supply wires into a tight cable.

So here are the symptoms: Strong reception of KTIK 1350 and a much weaker image of that signal at around 1250. Below 1250 KHz I have absolute silence--no signal, no noise.
Above 1350 I get noise--a buzz--that gets louder as the frequency increases. I have no way to guess what the frequency of the buzz is.

I've managed to resolve a lot of issues with this restoration, but I'm stumped here due to lack of knowledge and experience. Can someone please give me some direction?

Forever Grateful,
Winky.

[Electronic M]

Are you sure the antenna is connected right? I had two seemingly identical Zenith wave magnet antennas come with a console, and the plug on the nicer looking one was wired so that it would short the AM signal out on the console I got it with. It took me forever to find what a double check of antenna wiring could have found in 5 minutes.

If the antenna is right recheck your other work, if your other work is right put it back to the last configuration that worked and then change one thing back to present condition at a time checking performance between each step.