1950s Zenith Tube Radio

[cpc24]

I found one like this not long ago. I got rid of the selenium rectifier just to be safe. All it takes is a 1N4007 diode. What values are on the new electrolytics you put in?

[CassetteMaster]

Very nice! Nice to see you show the inside. That thing is a selenium rectifier, AllAmericanFiveRadio knows well about those. As for the solder, did you try dapping new solder on it while the iron heated it? Cause the old solder might be hard to melt sometimes unless you "start it off" with new solder.

[coolbluelights]

@CassetteMaster hm that's a cool idea, but I managed to fix it without de-soldering that part. thanks for the comment! :)

[xscotty1990]

lol the cat is funny

[1xcalibur]

Hey Dan, I'm currently experimenting on the value of the new surge resistor you'll need to add when you swap from selenium to silicon rectifier. We need to keep the plate voltage on our 35C5s below 130V. Ohms law says it should be 440 ohms. I tried that and was getting only 85V at the plate. Lowered value to 240 ohms, and got it up another 10V. It'll probably end up around 100 ohms, but I'll let you know what I settle on for my Zenith.

[1938Silvertone]

It's a C725L -  1959 vintage.

[coolbluelights]

Thanks! someone else told me it was from 1960, so we're pretty close :-)

[watcher818]

Hi ,I've the same set. WIll get mod num for you. The Selenium might be ok. 2 schools of thought about leaving them , or replacing. They can stink really bad if they fail, but I have never had one fail, (cross fingers :)

The solder is regular solder. It takes a larger iron to get it hot enought to melt.

No need to remove the old can, Just ID the leads , then install new caps under chassis. WIll look original on top.

G Rabbitt..

[coolbluelights]

Thank you, it is a nice looking set!

[V8Jagnut]

nice. when i hear the word Zenith, i think of a POS carburettor.lol. you cat loves you.. yo should put that back in its box and leave it for 30 years and it will be worth a LOT and dont replace a thing or it will be worth less to collectors!! thats a nice old phone.

[coolbluelights]

ah, I think i'll have more fun working on it^^ and the new parts won't show anyway. I did make a video of that phone a while back^^

[V8Jagnut]

cool have fun.. and i think it could be tin solder or the heat sink is taking all the heat away.

[1944johndeerel]

@V8Jagnut i have a zenith carb and it actually works very well so they cant all be bad.

[V8Jagnut]

the twin thought down draft from the 70's on mercs and Opel's aren't the best ones from the best i found

[1944johndeerel]

@V8Jagnut yeah i cant speak for those

[edzgarage]

The solder on the capacitor could be silver solder. It melts at about 400 C. Lead solder melts at about 250 C. You could try a propane torch with a soldering tip to get enough heat. 30 watt iron wont do it with the high melting point and all the metal heat sinking. Check out Metcal irons. They are the best iron I've ever used. They heat instantly and can melt silver solder and heavily heat-sunk components.

[1xcalibur]

@edzgarage

[1944johndeerel]

im guessing late50's to early 60's the antenna you see is the AM loop antenna. it looks typical of a late 50's - early60's radio. i have alot of radios to fix, just havent had the time to get to them. let me know where you order the caps from,

[coolbluelights]

I'm actually thinking more like mid 50s because in the late 50s most radios went to the ferrite rod antenna. and the last patent date on the bottom label is 1951. I get my capacitors and tubes from antique electronics supply

[retrochad]

Also the metal device above the AM tuning capacitor is for operating the FM tuning coils. The AM section uses fixed inductors and variable capacitors and the the FM section uses fixed capacitors and variable inductors. There is a cam to move the metal lever up and down as you turn the tuning dial and this moves the coil slugs into or out of the coils.

[retrochad]

Very nice! This is a little earlier Zenith chassis than the similar model I have. Yes that device is the selenium rectifier, you can replace it with a 1n4007 silicon diode and 5 to 10 watt wire wound surge resistor (probably 10-47 ohms) between the power line and the diode's anode. You can experiement with different values to produce the appropriate voltage but the resistor helps protect the diode from a power surge. Also there is a paper capacitor under there that should be replaced.

[coolbluelights]

Thanks! yes I just ordered all new capacitors for it, hopefully I didn't miss any, and I'm going to hope the rectifier is good for now. but if it is bad I'll have to place another order. I'm not sure what the appropriate voltage would be though, how would I find that out?

[QueensJohnny]

You should replace the selenium rectifier before it fails. When they do it can be ugly. There is a risk of fire and the supposedly give off a horrid smell. To figure out the voltage just measure the output voltage of the rectifier if its working.

[agfamatic91]

hopefuly you can get that radio working agan

[DrCassette]

Really nice radio! That solder drop is no special solder, you'll just need a hotter soldering iron to melt it. The metal the drop sits on acts as a heat sink, that's why it won't melt.

Your winter project is really similar to mine! Yesterday I found an old 1963 SABA Königsfeld 14 tube type radio at the dump. I'm going to fix that during the next time!

[coolbluelights]

Thanks! I think I'm actually going to leave that capacitor in and install new capacitors under the chassis. that will help preserve the original look. Good luck with your project! 14 tubes is a lot! :-)

[DrCassette]

@coolbluelights

The 14 is a part of the model number, luckily it has only 6 tubes in it :)

[coolbluelights]

oh ok^^ I was thinking wow those German radios are really serious! :D

[DrCassette]

@coolbluelights

The big top of the line models SABA offered back then sometimes had 14 tubes. The big radios had features like remote controls, automatic tuning with a motor turning the tuning capacitor, and that was all done with tubes only!

For example the "SABA Freiburg 14 Vollautomatic Stereo" had all those features.

[coolbluelights]

now that's the kind of legendary quality I expect from Germany :D

[1xcalibur]

@coolbluelights

[coolbluelights]

@1xcalibur hm your comments aren't showing up so idk what you're saying sorry...

[1xcalibur]

@coolbluelights

[AllAmericanFiveRadio]

C725L, That is the model number. I looked up the diagram. I'll send it to you to day.

[randomforum]

:D Nice radio, I hope you got that working. Lol, Chinese cardboard. But then all cardboards goes like that after 10-20 years :D

[BRENTHENRY1989]

take that Chinese cardboard! lol lol

[BRENTHENRY1989]

you could always use a propane torch? lol lol lol but you will melt way more than the solder! lol lol ah well i know you will figure out something, and the radio looks great, doesn't look like anyone has molested it, best of luck with it! and can't wait to hear it running again!

[coolbluelights]

Yeah I started to try the torch but there's too much stuff near the capacitor that could be burned. Thanks :)

[vwestlife]

Was that Jeremy Clarkson calling? :-P

That electrolytic capacitor might actually be welded to the chassis. Most collectors prefer to keep those "metal can" capacitors in place and install new capacitors inside the chassis, anyway, in order to preserve the original appearance.

[craig1974]

Yeah i dont think the filter capacitors are much to be concerned about. Just the old paper ones.

[joernone]

Re: Solder melting.

That solder blob is a grounding point. It's difficult for you to melt it because the chassis is acting as a heat sink...sucking away the heat. To get the job done you'll need a hotter iron. But as previously recommended, just connect a terminal strip to the underside of the can and solder the new e-cap to it.

[CrazyVolkov]

XD Way to symbolically get the Chinese cardboard box to fuck off - with your middle finger! Also, very nice radio score, but be wary that the oval speaker doesn't emit oval energy....

In fact, if Jeremy Clarkson were to smash a 1950's radio like this with an "oval" speaker in it....is that irony?

[craig1974]

That might be the same chassis as my Zenith G730 because it looks like the same dial set up. I will make a video of the insides for you. Man i really want an old large tube radio such as a Grundig, / Telefunken, but those things are really fucking expensive!

[umajunkcollector]

2:40 is a selenium rectifier, they go bad even if not used, more important to replace than e-caps. Do a little research on google about them, replace it with a silicone DIODE rated at least one amp at 1KV. Make sue you get the polarity right, pos to pos on E-cap.

[coolbluelights]

I thought that's what that is, thanks. I'm used to working on much older radios so I've never had to replace one of those

[krankiev]

LOL THE DAMN PHONE!

maybe you could heat up a piece of metal with a pencil torch and use that to melt the solder? I'm guessing you wouldn't want the torch in there directly.

FUCK CHINESE CRAP!

[krankiev]

nice old radio, that'll be sweet if just tubes and caps fix it :D

[Vinylrecordsneverdie]

Thatz a very nice Zenith! My 1961 Royal 2000 AM/FM transistor radio also has the copper bar on the variable capacitor too. To save you the hassle from removing the E-cap, just leave it in place and mount the new caps onto a terminal strip under the chassis.

[coolbluelights]

Yep that's what I think I'll do

[wilkes85]

WHOO! it came! awesome.

Lucky it survived those UPS apes lol

Very cool radio. I like the grille design.

And did that label say "Patented in Canada..."? cool, that thing must have originated in Canada hehe

And good idea drawing up a diagram where everything goes.

Hopefuly you can get that solder off, and if not, I know you'll find a way to get past it.