My son and I are trying to resurrect a Zenith 8-S-154 radio from 1938, our first attempt at an old radio. We've replaced all the tubes. There get no sound from the speaker, but we get a signal from the speaker socket with an oscilloscope. How can we test the speaker? Is there any way we can connect a modern speaker to the signal current? Thanks.

Unfortunately the tubes are usually good and one of the last things to go bad. The radio will need some major restoration before it is powered up. The electrolytics will have to be replaced, the capacitors have to be checked and replaced (I always replace all of them) The resistors should be checked and replaced as necessary, the wiring needs to be checked. As you can see it is not just a simple matter to get one of these going but failure to do these steps can cause some serious component damage. Of course you could always fire it up the way it is using a variac or a dim bulb tester and hope for the best. If you feel you are competent enough to tackle this job the fellows on this forum would be glad to help you.

Dave

____________________________________________________________________
:My son and I are trying to resurrect a Zenith 8-S-154 radio from 1938, our first attempt at an old radio. We've replaced all the tubes. There get no sound from the speaker, but we get a signal from the speaker socket with an oscilloscope. How can we test the speaker? Is there any way we can connect a modern speaker to the signal current? Thanks.

:Unfortunately the tubes are usually good and one of the last things to go bad. The radio will need some major restoration before it is powered up. The electrolytics will have to be replaced, the capacitors have to be checked and replaced (I always replace all of them) The resistors should be checked and replaced as necessary, the wiring needs to be checked. As you can see it is not just a simple matter to get one of these going but failure to do these steps can cause some serious component damage. Of course you could always fire it up the way it is using a variac or a dim bulb tester and hope for the best. If you feel you are competent enough to tackle this job the fellows on this forum would be glad to help you.
:
:Dave
:Hi easyrider8 & Dave
Absolutly agree with easyrider8, I also always go through the set completely tubes, capacitors, resistors etc... thats the only way to be sure you don't damage something that is hard to replace or not possible to replace.
Mark

:____________________________________________________________________
::My son and I are trying to resurrect a Zenith 8-S-154 radio from 1938, our first attempt at an old radio. We've replaced all the tubes. There get no sound from the speaker, but we get a signal from the speaker socket with an oscilloscope. How can we test the speaker? Is there any way we can connect a modern speaker to the signal current? Thanks.

It's always tempting to replace all the tubes and hope that somehow fixes things, which it seldom does. When a radio doesn't play, it's natural to suspect the speaker, but that is seldom the problem either.

What's called for, in my opinion, is a systematic troubleshooting approach, which is very difficult and laborious to walk somebody through via the internet. Otherwise, you will likely be shooting in the dark, spending unnecessary money in replacing perfectly good parts, and possibly making a mess of things.

If this is your first radio to repair, you'd be best to get some hands-on help. Or, set this Zenith aside, read some books, and start with a 5-tube, AC/DC, post-war radio.

:Unfortunately the tubes are usually good and one of the last things to go bad. The radio will need some major restoration before it is powered up. The electrolytics will have to be replaced, the capacitors have to be checked and replaced (I always replace all of them) The resistors should be checked and replaced as necessary, the wiring needs to be checked. As you can see it is not just a simple matter to get one of these going but failure to do these steps can cause some serious component damage. Of course you could always fire it up the way it is using a variac or a dim bulb tester and hope for the best. If you feel you are competent enough to tackle this job the fellows on this forum would be glad to help you.
:
:Dave
:
:____________________________________________________________________
::My son and I are trying to resurrect a Zenith 8-S-154 radio from 1938, our first attempt at an old radio. We've replaced all the tubes. There get no sound from the speaker, but we get a signal from the speaker socket with an oscilloscope. How can we test the speaker? Is there any way we can connect a modern speaker to the signal current? Thanks.

I agree with the advice given. Read some books or info on radio repair. Expensive parts that might be hard to replace can be damaged if something is shorted, etc. I like the idea of getting a small ac/dc set to practice on. Zenith's are great radios, but can be quite complex. Good luck. Mark from Kalamazoo

Hi Bruce:
If this is your first radio repair I'm surprised because.... one usually doesn't have a stock of repair parts around unless they repair radios often... so where did you get all these old tubes from that you replaced? And what made you decide they needed replacing?
The fact that you have and know how to use an o'scope indicates some technical background.
Here's your schematic:
http://www.nostalgiaair.org/PagesByModel/444/M0025444.pdf
The first order of business is usually to check for proper supply voltages and replace all old tubular paper capacitors.
So firstly you should check and/or replace the power supply filter capacitors (c21 and c20)and to check for proper B+.
In this case your radio uses a field-coil-type speaker and it's used as a choke in the power supply. The input voltage to the field coil coming off the cathode of the rectifier is about +310dc and the other side of the field-coil is your B+ at +250vdc
If you get that far and still don't have audio you should replace each paper capacitor.
Then you can start doing some simple signal tracing like touching the center tap of the volume control to see if you hear audio etc etc.
Can you comfortably do these things that I've outlined ?