Altman Shakespeare Lamp Contact Problems

[Les]

The community theatre where I was recently hired on has a few Altman Shakespeare's that have problems with the lamp sockets. The instruments sometimes "ghost" on and off, and it is evident that there has been some arcing on the lamp posts. Usually if you just take the lamps out, flip them and reinstall them, it will temporarily take care of the problem, but sooner or later it will happen again. These instruments are about 10 years old, so I don't know if it is just time to replace the sockets, or if there is a cheaper way of fixing this. My executive Director suggested using some kind of graphite or a contact cleaner, but I wasn't sure so I thought I would run it by you guys before I go and electricute myself or burn the theatre down. Any suggestions?

THX, Leslie Deal

[zac850]

Well, since you hired them, I could contact the place that you rented them from, and ask them what they suggest. Odds are they will send you new lights to replace the ones that are not working.

[ship]

Graphite is conductive so if you attempt to use it, be very careful about any of it which either as a liquid spray runs out of the socket, or as a powder... not sure what good the powder form would do since it would follow gravity and not apply itself to the walls of the socket. On Lighting Network there was a decent discussion about lamp bases to Sports Lighter fixtures and what chemicals and coatings work well on high temperature lamp bases. While I have high temperature spray on Graphite, I find it more useful for coating the insides of old Altman 360Q lens trains in making them move well. I am not sure I would trust graphite inside of my lamp base.

If a terminal shows arcing, the lamp base will also. Those little arcs prevent good contact with the lamp in forming a high resistance conductor. This resistance adds heat which in turn further melts down the lamp base and lamp's pins. Flipping the lamp over and putting a good pin into a bad socket will as you are doing work for a while in providing at least a cleaner surface area for contact. In this case, the bad part of the lamp base will just start melting thru the fresh pin at the same time as the bad pin than starts to melt thru the good part of the lamp base.

While you can clean the badness of the pins to some degree with a fine emery cloth as long as you than remove the scratches from the surfact with some chrocus cloth which is even finer in grit and don't try to remove anything but what is sticking up above the normal surface. Don't try to remove pock marks and pits because the pin than will be out of round and the larger amount of surface necessary to be removed to get rid of the holes will no longer be in contact with the lamp base. This than will force even more current and thus heat on other parts of the lamp base and pin which still do have a fair amount of contact. Also if your pin gets too small, it won't have good contact with the lamp base which will also cause arcing. I'm not sure how much effort this cleaning of pins will be worth due to the size of the pin and expense of the lamp. There is a nickel plating on the pin which helps prevent oxidation and heat damage to it. Once you sand that coating off or scratch it sufficiently, it will no longer provide a good contact either and probably corrode anyway which will start the problem all over again. There are coatings you can add to re-protect the pin, but to some extent such lamps due to the size of the pin are not worth the effort. A corrode and melted pin is useless, throw the lamp out before it goes into another fixture and destroys it's lamp base. Additional problems with bad contacts would be first heat on the lamp base which could destroy the pinch seal of the lamp in causing it to go bad faster, and the extra heat making the wire feeding the lamp base melt down where it hits the lamp base.

This is also true with the lamp bases. If just oxidation or a bit of charring, the contact might be able to be cleaned with a thinned out cotton swab so it fits into the hole with perhaps some peroxide or electrical contact cleaner applied to it, but the dia. of the pin hole is for the most part too small for much more than that amount of effort. If the lamp base at that point does not become clean, it's time to replace it. There are other tools you can use to clean the base but this should be the simplest in either working or not working. You cannot re-surfact the lamp contact, too small to be working inside of and too small a metal plate you are attempting to work on. By the time you cleaned the surface, the contact's metal would be too thin to resist the heat and current running thru it very long. I do frequently re-surface both lamps and lamp bases of all types but even I don't touch this type of lamp base - too small to work with and not worth the effort.

Fresh lamp bases are very necessary for these fixtures and 10 years is a decent amount of life they have had. Specifically on lamp bases the Altman #97-1580, a high temperature TP-22 base rated for 1,000w/250c in temperature sells for about $16.00 each from sources anywhere from Production Advantage to Altman themselves. Make sure your product has this part number no matter what source it's from because there is three other types of lamp base on the market Altman either sells or used to sell which will be a lot less effective in your fixture.
While Altman recognizes many other brands of lamp base you can get thru other souces - such as those frum Sylvania, Altman, Bender and Wirth, they do not at this point recognize the Ushio C3A lamp base which is often sold as a replacement lamp base for this fixture at a lower cost. The C3A is very popular amongst retailers because depending upon their discount factor with Ushio, the lamp base can be cheaper for them to purchase and in testing by respected users it preforms just as well. However as stated by a engineer at Altman about this lamp base, use of the C3A until such a time as Altman approves it will void the UL listing on this lighting fixture because both Altman does not recognize it in having tested it and the lamp base is itself not UL listed.

The extra $1.35 per lamp base normally the difference between the Altman and Ushio lamp bases is worth the extra cost. At one point I might also have taken apart lamp bases in combining two half good ones into one with good contacts. This was a long time ago and will have by doing so also voided the UL listing on the lamp base. The ETC fixtures are good in that they like an old PAR can's lamp base are designed to come completely apart. Unfortunately however as opposed to the cost for an entire TP-22 lamp base, just the contacts alone from ETC cost that much. The entire lamp base assembly would be more expensive.




One further thing to check is the fixture's plug. Make sure ferrules were used if a stage pin type and that the screws no matter which brand are tight.

I recommend on a stage pin plug that in addition to the 12ga ferrules that you purchase from a electronics supply or McMaster Carr some insulated 16ga ferrules for use with the 12ga ferrules inside the plug. Given the over twice the dia. of a 12ga ferrule on a 16 ga. wire, there is only marginal protection given to the wires above the screw clamping directly onto the strands. Often the 12ga ferrule given the lack of wires will just cut right thru the 12ga ferrule anyway than cut into the conductors anyway. In any case, the screw onto the wires with this size of ferrule will not sufficiently enclose all the wires to the extent that the pressure of the screw will clamp down on all of them to the same amount. Some strands of the wires will have more clamping than others thus a bad connection.

You can fold the wire over on itself by stripping twice the length and folding it back on itself but frequently with heat wire you won't be able to get the fold tight enough.

You can also strip the wire twice as long, than half way up strip the wire again for a 18ga wire in cutting strands, than fold the top part of the wire back on itself. This than often when folded has sufficient amounts of wire to fit with the fold into the 12ga ferrule.

In both cases, it's a question of folding the wire back on itself to act as a filler sufficient in filling up the larger ferrule with wire so that it's full of wire and does not just crush into the conductors.

The easier way to do it as above is with a insulated 16ga ferrule which has a PVC flare out coming off the metal part protecting the area close to where the wire is stripped from shorting to anything. The ferrule itself is proper for the wire but too small to reliably fit into the hole of the plug. Adding the 12ga ferrule as a sleeve over the 16ga ferrule than sleeves the 16ga one sufficient to both fit into the terminal and with the second layer of metal covering the wire, there is little chance that the screw terminal will cut thru one ferrule and than cut into individual strands of the lamp cord.

As always, give a tug to your wires once they are in the terminal to ensure sufficient pressure was put on them. 1/4 turn past finger tight might be an illusion if there was a ding in the screw's threads etc. in being tight in the screw but not tight in the terminal.