Radiola 28 (DC)

[stusnyder]

It was hard to get this into the house without being noticed.


LOL The Wife????? I'm glad mine is not like that....she supports my radio hobble....Even goes along to the radio shows and flea markets looking for old radio and tv's. She said it cracks her up when we go to radio shows, mostly all men are seen and hardly any wives.

[Dangler]

Definately from the Great Lakes area. WXYZ and WJR are both out of Detroit. CKLW is Windsor. I used to listen to CKLW back in the 60's when I lived in Marion, Michigan.

That was back in the days when music was something worth listening to and something for your parents to complain about.

[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.

[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