[davidff]

My recently recapped 42-1008 suddenly stopped receiving on the short wave band. It gets no audio at all when switched here. The broadcast, etc are all loud and clear. Is there an oscillator tube that may be bad or just need to clean the band switch? All suggestions welcome before I investigate.

[morzh]

If the oscillator tube were bad you'd get squat on all bands.
See if your band switch is bad or coils are open, or....

[hsusmann]

Try using some tuner cleaner on the band switch contacts.
Often the shortwave band(s) were not used much so those
contacts never got much wiping action and are thus
dirty.

I did a radio recently that did the same thing, once
I cleaned the switch contacts all was fine.

Herb S.

[davidff]

The tuner cleaner only made the broadcast and other bands clearer, nothing on shortwave except an occasional weak station, but it is a shortwave one because it does the usual drifting in and out. The schematic shows that the oscillator coil is the same one for both bands, but there is a SW "transformer" coil that shows on it also. Should I spray that also or could it possibly be open? Is there a way to bypass the oscillator coils? I know on other Philcos with 'Cap' tubes, you can bypass and attach a wire to the oscillator tube. Any assistance is appreciated.

[BrendaAnnD]

If you're getting even one SW station, your LO is running. Could be the antenna coil has opened up, this is not at all unusual.

[Eric T]

Do you have a signal generator to check it out with?

[davidff]

Unfortunately, no signal generator. I do, however have another chassis, which was the original when I bought the console. It had a bad transformer, so, I kept it as a spare after I found another chassis. The first chassis did receive clear shortwave reception before it started to do the smoking thing. What parts would need to be "swapped" to the new chassis? I can see there is the oscillator coil, and there is a "SW shunt", which looks like another coil according to the schematic and from what I can see.

[Eric T]

I'd still suspect the band switch contacts are dirty. I've found that most spray cleaners won't touch 70 year old switch corrosion. Use some Deoxit or q-tips with cleaner on it. If the SW contacts aren't bright metal, they are still dirty. But this is just a guess. It's hard (or impossible) to troubleshoot the actual problem without test equipment to be sure what's wrong. You're just grasping around in the dark.

You might just be in an area with lousy SW reception. The 42-1008 I did wasn't exactly brimming with life on the SW band anyway. My 39-45 gets way better reception overall than the 42-1008. Maybe you can try to hook up a long wire antenna to the external antenna socket and see if reception is any better.

[morzh]

Eric


He is not in an area with lousy SW reception, because he said that the other chassis did receive SW fine before it started smoking.
Maybe he is in an area where SW smoke chassis, but they are certainly not weak.

[morzh]

David


You don't want to swap the parts. If this is, say, a switch, it will take as much effort as building a whole new chassis from scratch. Exaggerating. Still pretty bad.

Clean the switch, clean the switch, clean the switch.......


then:

1) have you measured the voltages yet? If not do!.
2) In particular, if after the switch cleaninig the problem persists, see if the voltage is present on XXL (the very first) tube plate.
3) If the voltage is OK (well, typical plate voltage, not units of volts or a fraction thereof), check the continuity of both coils in the RF xfmr 35 (the plate winding will be OK).

[Eric T]

You don't want to swap the parts. If this is, say, a switch, it will take as much effort as building a whole new chassis from scratch. Exaggerating. Still pretty bad.

Not exaggerating much on this set. That band switch is three layers deep with fragile wires and components connected all over it, in a tight corner full of other stuff. You'd need one of those minimally-invasive surgery robot gizmos to do the work without breaking something else.

[Jamie]

Count me as another vote with Eric and Morzh... clean the switch. You are getting one station, even if weak.. that's good news. Clean the switch. You can go to a hobby store and buy an "eraser pencil"... it is like a regular pencil, but instead of lead, it is full of eraser material. You sharpen it like a pencil, then use it on the switch contacts. It will shine them up like new. And you'll be in business.

[morzh]

I would still apply some cleaner after that. Rubber and silver do not go together well. If, of course, the eraser material is rubber.

[davidff]

Thanks to all of you for your input. The station that I receive quite strongly is near the "amateur" marking in the far right side of the sw band. Regarding the cleaning, which of those areas on that complicated looking switch is for just the shortwave? I want to spend more time cleaning the correct band area.

Thanks again.

[morzh]

The switch will benefit from overall cleaning - don't clean just "shortwave".