The PHILCO Phorum

Schematic shows 5 lines coming out of it. Unit I am working with only has 4 lines.

They made an update to the chassis???

Part # says 32-7993 on the schem but stamped on top of item itself is 32-7993R

http://www.nostalgiaair.org/pagesbymodel...013346.pdf

The schematic shows the output center tap is connected to one of the primary lines so that might be done internally and you'll only see four leads....?

I had to sit with the radio and schematic and trace it out. Took me a few minutes but then I saw it. It appears you must be right.

40-216 band switch doesn’t appear to have any feedback when rotating. Well there is some but it is really small. Maybe just getting enough feedback from the waffer contacts.

I can see the end piece that is all metal and usually rotates up and over those bumps for feedback and that piece that moves is riding above the bumps.

I don’t see how this could even be moved down into a better position. The amount of space and what is needed to make contact doesn’t seem like it would be enough.

Plus I don’t see how if it used to ride fine that it would have moved that much further above the bumps.

Thoughts?

Design or QA flaw?

Can I fix?

Usually there are steel balls that ride over the bumps to provide the tactile feedback. Do you see holes in the rotating bar where a ball might have been located? There also should be a leaf spring to apply tension and press the ball against the locating bumps.

Don't see where any would go.

Is there a name for that part of a rotary switch setup?

That part is usually referred to as the switch detent assembly.

Is it possible that the whole shaft has shifted backwards so the rotating bar no longer contacts the bumps? There should be a groove with a lock ring in front of the switch bushing which prevents the shaft from moving axially. If the lock ring is missing then the shaft can move backward and the bar will no longer be in contact with the bumps.

Can you slide the shaft forward so the bar contacts the bumps?

I was thinking it would be "detent" as mentioned above.

I'm going to try and get some better shots and maybe a high res video to share.

Stay tuned.

Here is a little video. See if this helps.

I tried to add some lighting at the end but it was a tad bright.  

https://www.youtube.com/watch?v=oTnNGNHV...e=youtu.be

Part #30

Can I go 5w or should I really stay with a 2w?

http://www.nostalgiaair.org/pagesbymodel...013346.pdf

You can always use larger wattage. It's a question of having space for it, nothing else.

Wattage is not really an electrical parameter.

I guess I was thinking that wattage has a capping point to also make the resistor sort of a fuse.

If wattage gets to this level then blow up and save some other components.

No, it is not the way a resistor is used, with the exception of special "fusible" resistors.

And, most of the time, if the resistor starts heating unreasonably, this means some other components have already been damaged in the first place to make it overheat.
The wattage rating is not there to melt at certain point, but to provide a compromise between the space needed and acceptable heating. It is always better to have a resistor that heats less, meaning higher power rating, but then one might not have enough space to accommodate it, so a compromise is reached between "this heat should not damage this resistor and things around it" and "this resistor needs this much space" by using a resistor of 2W rating, which is sufficient instead of 1W, which would not be sufficient (damage to resistor or nearby components) or 5W, which is acceptable but too big.

The resistor I have is much smaller so I am good there. It is one of those white block ceramic types.

So I guess the next question would be is that type ok?

These are wire wound correct?

I've heard wire wound should not be used in some circuits.