400W UV Cannon

[Pete Alcock]

Hi All,

 

I bought a (Soundlab) 400W UV cannon off eBay for a bargain price. Dusty, bent, frayed lead etc. Fully refurbished it and it works fine, except the ballast hums and buzzes like hell for about 5 minutes until it warms up. It's made worse by the whole case resonating - annoying since it's going to be used for puppets in a church.

 

Could I replace the ballast with a better quality 400W model from Tridonic or similar? A google search reveals they seem to be popular with the "indoor hydroponic growing" community. Is a metal halide or high pressure soldium ballast the same as one for a big purple mercury bulb?

 

Thanks,

 

Pete.

[jonathanhill]

Is it worth giving Soundlab a ring for a replacement?

[musht]

Is a metal halide or high pressure soldium ballast the same as one for a big purple mercury bulb?

 

Kinda answered your own question there, can get a few combinations that will run HPS and MH on same ballast but Mercury Vapour is a relative but not the same as MH.

 

First hit on goggle

 

http://www.bltdirect.com/product.php?pid=5782&cat=487

 

76 quid , could get several 2-4ft tubes or 20W blacklight CFLs for similar money and get more even coverage with less hazard.

[csg]

Mercury vapour lamps ( like your blacklight blue lamp) simply require a choke in line on the live side of the lamp. Metal halide and HPS lamps generally require an ignitor. Mercury lamps are self starting and an ignitor will shorten life considerably. The chokes are generally not interchangeable due to different arc voltage and current.

 

Both systems can also employ a PF capacitor placed across live and neutral, but ive never seen a UV gun with PF correction.

 

The buzzing is simply being caused by the higher run up current during warmup - and you may well get it on a better quality choke. A suitable PF cap may help here as it will lower the current drawn ( I built external PFC units for some clay paky miniscans a few years ago, this quietened a couple of those with buzzy ballasts), alternatively mounting the ballasts on anti-vibration mounts with a suitable temperature rating may also help.

[Brian]

The rattle will probably be exasperated by being mounted in a flimsy sheet metal box. Could you use some self-adhesive sound deadening material, as used to quieten cars, to deaden the box? I've just fitted some to a fan-assisted convector and the change in noise level is quite marked.

[timsabre]

The rattle will probably be exasperated

 

I think you mean exacerbated. Although it could also be exasperated by being mounted in a substandard cheap box.

 

All the UV cannons I have come across are quite buzzy. If anything you are lucky it quietens down when it's warmed up. I would not waste your time and money changing the ballast as it will most likely not make any difference.

If you need silence, you need to look at LED or compact fluorescent UV fixtures.

[Pete Alcock]

Thanks for the thoughful responses. I will try adding a PF correction cap, and see about rubber washers or similar. I have hired a UV cannon last year (one of the cone-shaped ones) and that was completely quiet, even when just switched on, so I do think there are differences in quality with these things. As you say Musht and Tim, probably ain't worth spending out on a new ballast.

 

Cheers,

 

PA.

[Nicktaylor]

I have secondhand UV gun and it is totally quiet. The choke is a huge transformer that at a guess doubles the weight of the unit. At least it means it is not being driven too hard I guess. PS mine is the cone shaped one. It provides a lot more effect than my 4' UV tubes

[richard_cooper]

I inherited one of these square ones (although mine is showtec I think) and it sounds exactly the same as you describe. This one however is completely as new, probably because it's far to noisy to actually use! Strange really as they seem to go new for the same price as the spotlight ones that AC sell, which are the cone ones, that are next to silent!

 

Richard

[Jivemaster]

Transformers and chokes used to be vacuum impregnated with varnish to reduce vibration, can you brush some varnish or paint onto the lamination stack, see if it damps any vibration.

[bigclive]

Thanks for the thoughful responses. I will try adding a PF correction cap, and see about rubber washers or similar.

 

The PFC capacitor won't help with the buzz and may open a can of worms regarding inrush current. Rubber mounts are an interesting concept if there's no risk that they are going to let go and cause a big-heavy-choke-from-the-sky moment. Is it the choke that is actually buzzing or the case that is resonating with the magnetic field? If you turn the light on and then press round the outside of the case with your hands you will see if it's a case vibration issue. (Particularly where the choke screws to the case.)

 

Chokes are usually impregnated with resin to keep them stable as mentioned, but cheap chokes still make noise. Don't be tempted to stuff too much acoustic padding in there, since it's also thermal padding and possibly combustible too.

 

A row of 4 foot UV tubes does an awesome job of stage lighting. Just make sure the tubes have the wire guards over them and that people are warned of how fragile they are.