Wanamaker radio

[stusnyder]

Here it is after the cabinet blaster. All I had on hand was black, so black it is. Now onto the speaker next.

[dieseljeep]

Originally Posted by stusnyder

I'm going to try the resistor since I already have it. I did a google search on this radio and found one other example at http://americanradios.perso.sfr.fr/Gallery.htm
He has a footnote about if anybody has any info on it, to email him. I sent him a email telling him what I know. So this seems like a scarce set.
I'm trying to get a rough date on this thing. By the type of tubes in it, I'm guessing 30's????

It's around a 1933-34 radio. The penta-grid converter tube came out around mid-1934. 6A7 and it's varients.
IIRC, the resistance line cord on these sets was a 160 ohm and dissipated 20 watts, over its length. Modern 120 volt mains require around 175 ohms.
If you're planning on using a 100 ohm dropping resistor, it's not enough drop. 100 ohm resistor will only drop 30 volts, you need a 51 volt drop.
Those tubes are getting harder to get. You don't want to over voltage them.

[stusnyder]

Originally Posted by dieseljeep

It's around a 1933-34 radio. The penta-grid converter tube came out around mid-1934. 6A7 and it's varients.
IIRC, the resistance line cord on these sets was a 160 ohm and dissipated 20 watts, over its length. Modern 120 volt mains require around 175 ohms.
If you're planning on using a 100 ohm dropping resistor, it's not enough drop. 100 ohm resistor will only drop 30 volts, you need a 51 volt drop.
Those tubes are getting harder to get. You don't want to over voltage them.

I looked up the latest patent number on the speaker, that was 1932 so your spot on there.
I searched for a cone for the speaker, could not find any with the correct depth. So I had to make one from scratch.
Next I got a few paper caps to replace and find a 25z5 in my tube stash.

[stusnyder]

Ok while I was finishing replacing the paper caps, I spotted a date on the inside of the chassis, stamped in black ink, April 15 1935. So I assume thats when it was built.
Now I have a question, on the 25z5, no pins are marked, socket is not marked either. Looking underneath, do they go counter- clockwise? And how can I tell which is pin 1?

[dieseljeep]

Originally Posted by stusnyder

Ok while I was finishing replacing the paper caps, I spotted a date on the inside of the chassis, stamped in black ink, April 15 1935. So I assume thats when it was built.
Now I have a question, on the 25z5, no pins are marked, socket is not marked either. Looking underneath, do they go counter- clockwise? And how can I tell which is pin 1?

The socket, viewed from the bottom, are clockwise numbered. The old UX base tubes, the thicker pins are number 1&6, for the 6 pin tubes. the 5 pin tubes don't have thicker pins, the 4,6 and 7 pin tubes do. The thicker pins are the heater or filament pins, depending on the tube number. The thick pin on the left would be pin number 1.

[stusnyder]

A update on this little set. I had to buy a 25z5 because I didn't have any. They came Monday. Got a chassis mount resistor with the aluminum housing from Moyers, I was in the area and stopped there.
Powered it up, just got some hum from the speaker. Took a closer look and saw one of the coils did not look right. Sure enough the surface was chewed up and it tested open. Luckily I got a slew of these carron repair coils.
So if need be I had one. Instead I decides to try to salvage it. Took off a few wraps. Reattached and tested, tested ok.
So I try it again. Got to one spot on the dial that sounded like it could be something. Started to adjust the one coil on the back and all of a sudden I heard something like jesus will save you! LOL. Found a station but it was off freq. because it sounded like sideband. Somebody had messed with the tuning pads on the tuner, because one was backed almost all the way out. So for now I set it by ear. I would like to do a alignment but I do not have a schematic or waveform pics and instructions to do such a alignment. I know one 77 tube is real iffy so I got 2 new ones coming.

[stusnyder]

I got the 2 NOS military 77 tubes today. Put them in and their was a difference. I did a general alignment on the set. Can pick up several stations across the band and it does not sound too bad. I consider this chassis done!
All thats left is grillcloth and 2 knobs.

[Olorin67]

Just keep in mind a resistor for a set like this will put out a lot of heat. Theres a reason they put it in the cord, to keep the heat out of the cabinet. I fixed a resistor cord set where I used a metal electrical box, with a 3 wire cord connecting to the set. Put the resistor in the outlet box. if I ever do that again, Ill do it one better by putting a isolation trans or GFCI in the box. I havnt tried the capacior Idea yet, but it would solve the heat issue.

[stusnyder]

Originally Posted by Olorin67

Just keep in mind a resistor for a set like this will put out a lot of heat. Theres a reason they put it in the cord, to keep the heat out of the cabinet. I fixed a resistor cord set where I used a metal electrical box, with a 3 wire cord connecting to the set. Put the resistor in the outlet box. if I ever do that again, Ill do it one better by putting a isolation trans or GFCI in the box. I havnt tried the capacior Idea yet, but it would solve the heat issue.

I used a aluminum bodied 50 watt resistor, which is riveted to the inside of the chassis, so the chassis sorta is a heat sink. I don't plan on using this radio much anyway. May just run it a half hour every few months. Some of the ones I got have not been turned on in 2 years or more.

[Olorin67]

Thats probaby fine... But its not a radio you would want to run all day.

[wa2ise]

Originally Posted by stusnyder

I used a aluminum bodied 50 watt resistor, which is riveted to the inside of the chassis, so the chassis sorta is a heat sink....

You could use a rectifier diode (without any filter cap) in the heater string. You just need the heater string to add up to about 83V. (2x50V) + (3x6.3V) = 69V, so you need s resistor to burn off another 14V worth (47 ohms 10 watts more than enough wattage), then the diode. Less heat. Put the diode's anode on the 120V source, and its cathode on the above resistor.

Why 83V? Power (watts) is voltage squared over resistance. The diode will half the power off AC. The heater string wants 24 watts, using a resistor will burn an extra 12 watts. The heater string looks like a 277 ohm resistor, and if we put the powerline direct on that, we'd get 51 watts, about twice what we want, so we cut that in half by using the diode. With the 47 ohm resistor, we waste only 4.2 watts vs 15 watts with an unrectified resistor.
That's a lot less heat. Only downside is you're using technology that didn't exist when the radio was made (well, maybe selenium rectifiers were around).

[dieseljeep]

Originally Posted by wa2ise

You could use a rectifier diode (without any filter cap) in the heater string. You just need the heater string to add up to about 83V. (2x50V) + (3x6.3V) = 69V, so you need s resistor to burn off another 14V worth (47 ohms 10 watts more than enough wattage), then the diode. Less heat. Put the diode's anode on the 120V source, and its cathode on the above resistor.

Why 83V? Power (watts) is voltage squared over resistance. The diode will half the power off AC. The heater string wants 24 watts, using a resistor will burn an extra 12 watts. The heater string looks like a 277 ohm resistor, and if we put the powerline direct on that, we'd get 51 watts, about twice what we want, so we cut that in half by using the diode. With the 47 ohm resistor, we waste only 4.2 watts vs 15 watts with an unrectified resistor.
That's a lot less heat. Only downside is you're using technology that didn't exist when the radio was made (well, maybe selenium rectifiers were around).

The main reason for the resistive voltage drop was for economy and the radio was built to be used on DC mains, common at the time, in the older areas of the large cities.

[stusnyder]

Look what I found, this sets brother! All intact and original. Now I got 2