Problem Lights on #395 Floodlight Tower

Thanks for the quick reply.  This floodlight is not post-war; it was made in 1997-99, although it might be an exact post-war replica.  However, I have restudied the configuration and had it backwards.  Plus, I had remembered wrong how the 4 bulbs are connected.  It appears as you say.  But the only way I get the bulbs to flicker is when I reposition them.  So, it still seems to me to be a poor connection with the moveable bulb brackets.

Your tower looks to be made similarly to the postwar one.

It was not unusual for the lights to flicker while they are being repositioned, especially when tilting them up and down.
If they are bright when you are done, I wouldn't worry about it.

 

 

There are several places in this tower where the power is flowing through metal to metal contact surfaces.  If you have used a spray silicon, which is not conductive, you can loose conduction at these joints.  I notice in the picture that there is some corrosion on the blackened metal parts.  If there is corrosion in these conducting joints you will also have trouble. If you can get the speed nut off the rod under the tower you can take this all apart and clean out the conductive joints.  A very small amount of conductive grease in these conductive joints will probably prevent future problems.

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Normally, I have no problem understanding two wire hookup.

 

If you touch your test probes to two adjacent metal brackets, you should get the same voltage you are supplying to the terminals. The light bulbs are arranged intp two pairs, each wired in series.
The issue probably isn't the bulb contacts, it's probably the die cast metal light hoods. They have to make good contact with the bulb base, and with the sheet metal brackets.

Yes, I did get the same voltage.  I had set my test transformer to about 12 volts; the reading I got was 11.7, so close enough for gov't work.  My suspicion all along was that the problem was somehow related to the light hoods.  I did burnish the outside sides of the hoods where they contact the bracket, but that didn't solve the problem.  Perhaps, the problem lies within the hoods?

Yes, it could be oxidation inside the hoods.

Did you test the voltage right at the u shaped brackets that hold the hoods?

If not, it could be poor contact between the flat brackets and the u-shaped brackets.

 

You might also try bending in the U shaped brackets just a bit, so they grab the hoods tighter.

 

All four bulbs should be the same stock number. Off the top of my head, they should be #51 bulbs.

I did bend the U shaped brackets and checked the bulbs.  All bulbs lit at some point, but not at the same time.  I also replaced the bulbs with LEDs, which worked, but again not at the same time.  My next move is to see if there's voltage at the hoods/brackets.  But, as mentioned previously, I will need to study the hood interiors.  I need to become an electrical detective.

The bulbs should always light in pairs, never just a single bulb.

 

If a single bulb lights, then either the bulbs don't match, or there is an intermittent short.

Yes, I should have mentioned the bulbs did light in pairs.

Update:  I removed the bulbs from the hoods and used a fine rifling file to clean the holes on each side of the hoods, to include inside edges.  Also burnished the round thingies that the bulb base contacts.  Put everything back together - still no lights at all, not even flickering.  Checked voltage to hoods - all four got voltage.  So, I'm assuming the problem is inside the hoods?  If so, I have run out of ideas on just what to do.  Somehow, I have managed to get from "bulbs work intermittently" when moving the hoods to no action at all.

Bill

The led's were wired in series though the base contact. I believe they are diodes, and were blocking each other out.