Heavy-duty, vibration-resistant, 500W halogen lamps help to keep the voice coils safe. Excess electrical energy that could overheat the voice coils is absorbed and converted to heat and light by the lamps before that heat can get into the coil and blow the driver. Most of the time the lamps aren't even getting warm, so they are barely on and never noticed. But, all lamps do burn out eventually, even if they are barely ever on.

As each lamp fails, the remainder will glow more brightly. The good news is that the ore of the lamps that fail, the safer your woofers are. And these lamps are a lot less expensive than woofers!

To ensure the protection circuits were easy to service, we used readily-available, 118mm, R7S 500W 120V halogen lamps, which you can buy from most places that sell lamps or work lights (Home Depot, Lowe's, Harbor Freight, WalMart, Amazon, etc.)

Here's what you'll need and how to replace the lamps:

Buy lightbulbs on Amazon or Home Depot. You can also find them at any hardware or lighting store. 

Tools:

#2 Phillips or JIS screwdriver to remove the grilles (Not needed for VS21)

Allen Wrench to remove the driver(s) or cover panel (Be sure to use the right size to avoid damaging the bolt heads)

MkI woofers use 5/32" drive for flat-head or 3/16" for socket-head bolts. MK1 VS21 covers use 7/32" drive

MK2 woofers and VS21 cover panels both use 5mm drive

Wire brush, or similar, to scrub any corrosion or carbonization from the lamp holders

Recommended: Grease, such as marine grease or dielectric grease, to prevent corrosion and carbonization

The lamps are located behind the drivers, so it's easiest to access them by removing the drivers. Here are the basic steps to make the procedure as easy as possible:

1. Put the cabinet on its back
2. Remove the grille-screws and remove the grille (VS21: Remove the cover panel and skip to step 4)
3. Unbolt the driver and lift it out.
4. Locate the lamp sockets. Most cabinets have them attached to the inner port walls.
5. Carefully remove all the old lamps. The ends of the lamps can crack. Glass or ceramic shards may be present.
6. Clean the contact tabs on both ends of the lamp sockets with a wire brush.
7. Once they are clear of corrosion, etc., apply grease to the contact tabs. Also apply grease to both ends of the lamps. (You don’t have to worry about touching the glass because they are never as hot as actual lights.)
8. Insert the lamps into the sockets, one end first. The lamps are connected and held in place by the spring tension between the socket and the tube. The lamps should rotate smoothly when properly inserted. To check this, rotate the lamps, ie spin them on their contact axis between thumb and forefinger.
9. To test the contacts, flip the cabinet onto its feet and connect power and signal to the amp.
10. Short the red and black wires of one woofer together and play some bass into the sub’s amp. If you are performing this procedure on a double-driver sub, test each side separately.
11. All the lamps feeding those shorted wires should glow orange. (This will make the lamps HOT to the touch!)
12. If any don't glow, note which ones and, when the rest cool, check that they are centered on the fixture and making contact. It may be necessary to remove more of the carbon build-up to get good contact.
13. Repeat the signal test to confirm all lamps glow when their woofer wires are shorted.
14. Disconnect the signal and power from the amp and flip the cabinet on its back again.
    

While you have the drivers out, examine them for wear or damage. It's assumed that the woofers are working, but these examinations will give you some insight into their condition and life-expectancy.

• Check the cones, particularly where they join with the surrounds, to ensure they have not torn or separated
• Check the spiders, particularly where they attach to the coil-former, to ensure they have not torn or separated
• Check tinsel leads, particularly where they meet the cone, to ensure there is no evidence of burning or fatigue.
  

If you observe any of the conditions listed above, you may choose to take this opportunity to replace badly-worn woofers before they fail in the field. If there are no signs of impending failure, it's time to put the woofers back in.

15. Connect the wires to the woofers, red wires to red terminals, black wires to black terminals, of course!
16. Set the woofers in place and re-insert the bolts, starting each bolt by hand to ensure the bolts don't cross-thread.
17. Tighten the bolts in a star-pattern, similar to that used on wheel lug-nuts. Don't over-tighten. 4-5 foot-pounds is sufficient for T-nuts.
18. Check the gasket tape and re-install the grille. (On VS21, check the gasket tape and re-install the front cover panel.)
    

If you need to replace gasket tape, it can be found here: Buy Gasket Tape

If you need to replace a non-working lamp socket, they can be found here: Buy Lamp Sockets Option #1 | Buy Lamp Sockets Option#2

                          

Download PDF of information and process here: