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Shadow Meter wiring - Printable Version

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Shadow Meter wiring - dbrambert - 01-01-2014

   
Hello Phorum users:

I'm fairly new (about a year) to the hobby but enthusiasm is really bringing me forward. I have a Philco 37-630 with a shadow meter. I removed the chassis, then removed the shadow meter (which did not work) in order to change the bulb, and saw one of the wires just hanging. I can imagine that's the problem and I wonder if it's a ground wire that attaches to the chassis? I've attached a picture.

Thank you in advance,

Dave

RE: Shadow Meter wiring - Steve Chambers - 01-02-2014

I would think that this wire would be soldered to the terminal that's on the bulb socket. It's pointing almost straight up in your photo. With a good bulb you should measure continuity between that point and the wire that's soldered to the middle of the socket.

Steve Chambers

RE: Shadow Meter wiring - morzh - 01-02-2014

Look in the sch, if neither of the lamp's terminals is grounded (chassis) - then this is that spare terminal on the socket.
If it is grounded, take a meter, and in the female socket (where you plug that one) measure if the counterparts go where the sch says they should. Although logically there are no other option for this wire to go anywhere else other than to this free terminal.

RE: Shadow Meter wiring - dbrambert - 01-02-2014

The picture doesn't show it well, but the "free" wire is only half as long as the other ones, so I am wondering if it really goes to the other terminal of the light. Then again, I don't know at all which is why I'm asking!

RE: Shadow Meter wiring - klondike98 - 01-02-2014

Not sure this will answer your question but there is a service tip on Shadow Meters on Chuck's site at http://www.philcorepairbench.com/tips/svctip01.htm . If you look at the first picture of the "Newer Style" meter, it sure looks like the wire would connect to the terminal on the bulb socket.

RE: Shadow Meter wiring - morzh - 01-02-2014

Shadowmeters will usually have 4 wires: two are the galvanometer (vane movement) and two are the lamp.
In case one of the lamp's connections is through the chassis (clip-on) there may be 3 wires.

For instance in 18 the lamp is not grounded so there are two wires to it.
I do not have 37-630, but in 37-640 the lamp is grounded so it is possible it may use only one wire, but may also use two, depending on what kind of lamp socket it is.

This is it. It is a milli-ammeter with a light bulb.
Looking at it again, I am pretty sure this wire goes to that spare terminal. That is, I am sure. Without pretty.

RE: Shadow Meter wiring - dbrambert - 01-02-2014

OK so I'll solder that free wire to the terminal on the edge of the light socket. Thanks to all!

RE: Shadow Meter wiring - morzh - 01-03-2014

Make sure the wires in the socket are not shorted. Old sockets often have cracked and crumbling central contact insulator.

Also before you go to the trouble of screwing it back etc it makes sense to check it for being functional. You have already got the link to Chuck's site where there is info about shadographs.

RE: Shadow Meter wiring - klondike98 - 01-03-2014

Here's another item I saw that might be helpful down the road: http://philcoradio.com/phorum/showthread.php?tid=737 .

RE: Shadow Meter wiring - dbrambert - 01-11-2014

Hello gents:

I soldered the wire to the terminal as you suggested, but no go. Tried a few bulbs. I'm thinking that the metal terminal in the center of the socket is down too far to make contact with the bottom of the bulb. Should I put a small piece of metal on top of that to make the connection? I have a couple of pictures to show you what I mean.

Thank you,

Dave

RE: Shadow Meter wiring - dbrambert - 01-11-2014

See post above.

RE: Shadow Meter wiring - morzh - 01-11-2014

Repeat after me:

"Voltmeter is my friend, voltmeter is my friend".

Don't think.
Thinking hurts.
Measure voltages.

RE: Shadow Meter wiring - Warren - 01-12-2014

If after you check to make sure voltage is actually at the center pin I believe you can use a soldering iron and put a dab of solder their to take up the space.

RE: Shadow Meter wiring - BrendaAnnD - 01-12-2014

Warren, yes, you could do that. However, that pin is surely very close to shorting against the ground side of the socket. Even if not, there's not going to be any spring action left in it because the old rubber has taken up space between the coils of the spring. I've taken the pin and spring assembly out of other sockets and used them to replace those old ones.

RE: Shadow Meter wiring - Ron Ramirez - 01-12-2014

That lamp socket needs to be rebuilt. It's easy. Directions here:

http://www.philcoradio.com/tech/lamps.htm