ARC LS First Run -- Light dims, must tweak head?

[GabrielET]

Read this forum a lot, but never posted before.

I have a first run ARC LS (#1468). The light dims, and I must lightly slap it on my palm or tweak (not twist) the head for something internally to make better contact, and then it returns to full brightness.

Is anyone familiar with this problem and its remedy?

Thanks

 

[cy]

Re: ARC LS First Run -- Light dims, must tweak hea

welcome to cpf, sounds like you have contact problems. kinda risky to fix. first you need to unscrew the bezel from the body without scatching the HA finish.

the board is covered with black epoxy which breaks off in chunks taking component with it, killing your board.

if you are able to get it apart without damage, then carefully scrape all contact surfaces and retighten.

 

[hideo]

Re: ARC LS First Run -- Light dims, must tweak hea

check this thread

Arc discussion

I had a flex failure in one of my First Runs after a minor drop to the floor and once I got the head loose and cleaned things up, it was just like new.

 

[cy]

Re: ARC LS First Run -- Light dims, must tweak hea

Please note my comments are for a first run with gold board. if your first run has a green or brown board, then you have a hybrid. those come apart with no problems and are easily moddable.

 

[CM]

Re: ARC LS First Run -- Light dims, must tweak hea

Flex failures on a non-hybrid board is a PITA to fix. Hybrid boards can be fixed using a piece of berrillium (sp?) located strategically. That requires disassembly of course.

 

[Dr_Joe]

Re: ARC LS First Run -- Light dims, must tweak hea

Gabriel,
Before you take it apart, have you done the obvious ?
Clean both battery contacts, (and battery !) and head and tail threads ? /ubbthreads/images/graemlins/thinking.gif

 

[GabrielET]

Re: ARC LS First Run -- Light dims, must tweak hea

Thanks all, for the input.

Yes, Doc, I've cleaned the contacts very thoroughly. My next question, is how do I actually get access to the board? I've done some looking around on the forum, and I seem to consistently encounter the need for a band wrench (I think that was the term), and where does one get that who lives 40 miles from the nearest town in the New Mexico desert?

I am certainly hoping it has the "green or brown board" Cy. What color is it if I'm in real trouble?

 

[cy]

Re: ARC LS First Run -- Light dims, must tweak hea

gold boards are covered with black epoxy and are risky to take apart. you stand at least a 50% chance of destroying a good board. just by taking apart.

 

[GabrielET]

Re: ARC LS First Run -- Light dims, must tweak hea

What is the preferred method of disassembly on these?

 

[louie]

Re: ARC LS First Run -- Light dims, must tweak hea

The only 2 Arc LS first runs I had developed these problems, and I actually was able to fix them both. I used a rubber strap wrench to unscrew the front bezel, as they are loctited on. Strap wrenches should be available at a hardware or variety store, often packaged as a small one and a big one for about $10. Mine came mailorder from Harbor Freight. (Harbor Freight Strap Wrench) Some people use these to open jars or change oil filters on cars, so I'm sure places like Wal-Mart would have these in tool, hardware, automotive or housewares.

From memory, after you get the front off, the circuit disc holding the electronics and LED is revealed, usually gooped with black epoxy and/or some kind of silver glue. This is where you have to be careful when getting the disc out to not break off chunks of epoxy that will take a circuit component off with it. I didn't have any problem, myself. Try tapping the disc out gently from the battery side. I actually chipped away at excess epoxy first. Interior scratches didn't bother me.
A "gold" disc will have gold circuit foils on the battery side, as opposed to a contact nub. Clean off any epoxy or debris from the battery side foils, especially the peripheral gold ring. I just used a jeweler's screwdriver. This has to make contact with the ledge in the body, and I think this is a major cause of intermittants. Arc seemed to hope that epoxy or loctite everywhere would hold the LED alignment, but I think it also caused contact problems. What I did was to take a very fine piece of wire (one strand out of a multistrand wire) and form it into a ring that sits on the ledge, then replace the circuit disc. This elevates the disc a bit, and I think provides a tiny bit of "bite" to the contact. Being extra cautious, I also put a small piece of tape on the gold foils that aren't supposed to touch the body ledge but are very close.
Practice aligning the LED before loctiting (if you must loctite the front bezel; it's not really necessary) by loosening the bezel and tapping the head to jiggle the disc around as you tighten the bezel. With loctite, you get a few tries before it sets up.

 

[mahoney]

Re: ARC LS First Run -- Light dims, must tweak hea

If you can't locate a strap wrench, take a couple blocks of scrap wood and bore a hole in each just barely smaller than the diameter of the LS head. Cut the blocks in half through the hole and you will have custom fitted vise jaws. Clamp the head in a vise between one set and clamp the other set around the bezel. A "handscrew" type clamp works best but a c-clamp will do. If you need more friction, masking tape or rubber tape wrapped around the LS will help. Heating the head will also help loosen the locktite. If the board is glued to the bottom of the bezel, don't pry it off. The odds of damaging the board doing that are very high. Been there... Just clean any gunk off the rim of the board where it makes contact and on the ledge in the head as well. Putting a ring of thin wire on the ledge as has been suggested is a good tip. If you can get a copper wave washer or make one from some shim stock, that is also worth a try.