The PHILCO Phorum
650X Shadow Meter question. - Printable Version

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650X Shadow Meter question. - audin - 01-27-2011

So I just got my 650X running. But the shadow meter does nothing. I opened it up (because it didn't look like any of the ones I see on the web. And because I was curious) and took these pictures.

http://www.flickr.com/photos/audin/tags/shadowmeter/

[Image: http://farm6.static.flickr.com/5180/5390133661_2d3aa2ae3e_d.jpg]

Is there supposed to be something to return the vane to the center position? A spring or something? The fact that the adjustment screw doesn't seem to go anywhere and that there is possibly the indication of something missing from the rear of the vane has me worried.

I have not gotten to the point of measuring the coil yet.

Re: 650X Shadow Meter question. - Ron Ramirez - 01-31-2011

Honestly...I've never had that type of shadowmeter open, but I would think if it is anything like the older ones (and the newer 1937-38 meters), that the vane should return to center of its own accord without the use of springs or any other help. Does the vane pivot freely? Sometimes they bind up, and then will not move freely.

I've only seen that type of shadowmeter on late 1936 model Philcos, and used as replacements on a few older sets. My 91RX has a shadowmeter like yours, but I know they weren't making them that way in 1932.

Re: 650X Shadow Meter question. - Chuck Schwark - 01-31-2011

One of my SERVICE TIPS:

http://www.philcorepairbench.com/tips/svctip01.htm

[Image: http://www.philcorepairbench.com/images/oldmeter2.jpg]
Should help you with info and re-building and adjustment tips.

Chcuk

Re: 650X Shadow Meter question. - Ron Ramirez - 01-31-2011

This shadowmeter is a different ballgame altogether, Chuck, and isn't really covered on your site.

Notice how different the coil is in Audin's shadowmeter compared to the older style and the 1937-38 style meters.

Re: 650X Shadow Meter question. - Chuck Schwark - 01-31-2011

I saw that Ron. Thought the older style info from Gary Tempest would be of
some help regarding vane pivots, coil, etc....

Have not run across any Philco service lit on that 'other' type older Shadowmeter.
Would like to add it to my Service Tip No. 1 page.

Chuck

Re: 650X Shadow Meter question. - Ron Ramirez - 01-31-2011

Yeah, I've never seen anything on this particular shadowmeter, either. It would appear that it was only in production for a few months. As I posted earlier, I've never seen one except on 1936 model Philcos made after December 1935. The exception is my 91RX chassis, and I am convinced it is a replacement. To clarify what I typed earlier, I *think* I may have seen one or two others on older Philcos, but like the one on my 91RX, I am convinced these were replacements. We know that the earlier shadowmeters look like the ones shown on your site.

Re: 650X Shadow Meter question. - audin - 01-31-2011

Sigh, I was afraid of that.

I've read over your great shadowmeter repair tips a couple of times, Chuck, but this one seems completely different.

The other ones seem to use a permanent magnet for centering. This one doesn't seem to have any such magnet (or even anything which may at one time have been magnetized). But the adjustment screw arrangement, to me, points at a spring centering mechanism.

I guess I will take it apart the rest of the way to see if there is anything which looks magnet-like. If not, i think i have a spring in my pinball parts collection which might be pressed into duty as a replacement. though it seems like it would have to be a very light spring. I suppose it is also possible the leaf spring which is there was just connected to the vane via a string...

On the other hand maybe i could retrofit a magnetic centering mechanism. hrm.

This is a '36. But i'm not sure when it was built. And i'm not sure if the meter is original. Though there isn't any obvious evidence that it isn't.

Re: 650X Shadow Meter question. - Ron Ramirez - 01-31-2011

So, I just looked this up in the Philco Changes in Models PDF I have available here:

http://www.philcoradio.com/phorum/showthread.php?tid=215

and I see that on November 1, 1935, the shadow meter on Model 650 was changed to part no. 45-2083. This is the same shadowmeter used soon afterward on the mid-season 1936 Philco models using shadowmeters: 635, 645, 655, 665. The shadow meter was also changed to 45-2083 on Model 680. No mention of a shadow meter change in Model 116.

So...I started looking.

I have a 655 chassis in a 645B cabinet. Oddly enough, it had an older style shadowmeter.

Then I looked inside my late version 116B, which came out in January 1936. Lo and behold, it had the same shadowmeter as Audin photographed above!

And the part number is...(drum roll please)...

45-2083.

Audin, take a look on top of your shadowmeter and tell us if it has a part number ink stamped on it. I would be willing to bet the number, if present, is 45-2083.

Oh, by the way, on Philco sets that received this shadowmeter, the resistor that was formerly connected in parallel with this shadowmeter was removed when the 45-2083 was added.

Re: 650X Shadow Meter question. - audin - 02-01-2011

You are quite correct.

The 8 is illegible, but clearly it is 45-2083.

[Image: http://farm6.static.flickr.com/5297/5406578358_dcf7d74548.jpg]

That also explains why I was unable to find the shunt resistor. I suppose that means that, because I have good audio from the radio, the meter coil is probably not open? Or is there some other way they avoided putting it in the critical path?

I'm unsure if it is actually connected correctly because this section of the circuit is "odd". There is a bakelite block missing and things generally do not match the layout as shown in the Rider. I haven't traced the whole area to see if it matches the schematic or not.

[Image: http://farm6.static.flickr.com/5135/5406254701_ae4061fb92.jpg]

Re: 650X Shadow Meter question. - audin - 02-01-2011

So, yes, the coil is not open. It reads about 500 ohms. I removed the unit from the radio and played with it using 2 D batteries. I was able to regain some function by placing a small rare-earth magnet on the rear end of the meter where the adjustment screw goes (after removing the screw). The magnet provides the centering force.

The shadow now varies from about full width to 1/4 width on a (very) strong station (my AMT3000 transmitter). I can't say it is terribly useful for tuning, but at least it moves. Icon_smile I'm not sure how well these things are supposed to work. On weaker stations it never moves at all.

Re: 650X Shadow Meter question. - Chuck Schwark - 02-01-2011

Remember, the Shadow Meter depends on the strength of the AVC action in the set. The better the aerial and ground, the stronger the stations come in and cause larger AVC voltage. The set was designed to acommodate an outdoor aerial for best performace and a driven ground.
Also, having the IF stage(s) adjusted properly vastly effects the Shadowmeter action. Poorly aligned IF causes low or nonexistant AVC voltage changes.

Chuck