[Guest]

A newbie question:

I have a 42-380 that I just replaced the electrolytics in. It powers up but I have no sound on any band. What would be the next logical troubleshoot? It also has a toggle switch on the rear of the chassis, what would be the purpose of this? The chassis was very clean for this year and the rubber covered wiring in pretty good shape. Must have been stored inside and in the dry.

Any help appreciated.

Chuck

[codefox1]

Assuming you have B+, and all the tubes light, most of us start by testing the audio section (you should get a little hum when the volume control is turned up and you place ascrewdriver on the middle leg of the volume control. If the audio is ok, work backwards with a signal generator to isolate the problem area.

In a set this old, for performance and safety you should replace all the wax bypass and coupling capacitors, not just the electrolytics. Do 'em one at a time.

Don't know about the toggle switch. Does it look like it was always there, or was it a modication by a previous owner?

[Guest]

It is near the antenna screws , could it be for an external antenna instead of the loop? All of the tubes do not light up. where do I check for B+ power? I also need to clean the tubes and sockets w/ cleaner.

[exray]

A common hack for old radios was to add a phono input. Often thats accompanied with a toggle switch. Do you have an 'unauthorized' audio jack on the back? Maybe thats it.

In that type of set ALL of the tubes should light up. With the loktal ones like those sometimes its difficult to see when there is heavy silvering on the inside top of the tube glass. Turn out the lights and look closely. Lighting up and B+ are not related.

You can check for B+ 'across' the new electrolytics that you installed. Pos on your meter to pos on the cap, neg to neg. There could be problems further downstream but thats a start.

[Michael Dennis]

A common hack for old radios was to add a phono input. Often thats accompanied with a toggle switch.

I've seen that on the back of a Philco 38-7. The giveaway was the fact that the chassis was bent near the switch.

Mike

[codefox1]

In a radio without a power transformer, your resistance across the line cord plug should be 150 to 250 ohms with the switch turned on and the set not plugged in. This is the filament load. If it is infinite, or a large number like 100,000 to 200,000 ohms you have a burned out tube or faulty connection at a tube socket, bad line cord, or bad/gummed up on/off switch. Measure this before you plug the set in. Of course, you will not generate any B+ if the tubes do not heat up.

I tried to post a similar message a few minutes ago, so if this is a repeat, forgive me.

[exray]

In a radio without a power transformer, your resistance across the line cord plug should be 150 to 250 ohms with the switch turned on and the set not plugged in. This is the filament load. If it is infinite, or a large number like 100,000 to 200,000 ohms you have a burned out tube or faulty connection at a tube socket, bad line cord, or bad/gummed up on/off switch. Measure this before you plug the set in.

Methinks you are referring to series string tubes? Schematic is on NA. I think your advice doesn't apply to this radio.


-ex

[codefox1]

Of course you re correct. My checkllst only would apply to models that does not have have a powertransformer.