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Thorn 200W HO SLI/H lamp on Parmar 175W CWA ballast

as per my picture post on this ballast one of the reasons I purchased it was to see how suitable it was for a 200W SLI/H lamp (specifically the HO type which has proven particularly tricky to run)

I theorised it would work quite well, and indeed I am pleased to report it does in practice as well :) the lamp struck up on its own without any ignitor thanks to the 330V OCV of the ballast

and ran up nicely and has been stably running for the past few hours now, its running at ~140V ~1.45A, which is pretty close to the official specs for a HO lamp of 145V 1.55A, and I think the closest anyone has been able to get so far :) and I think is an acceptable result for safely running the lamp

so I am very pleased with these results! I would like to try a GEC lamp on this setup as well, but I sadly dont have one of those in the collection (yet anyway! I know where to get one but they aint cheap!)

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Filename:	IMG_0452_3.JPG
Album name:	Lightbulbfun / My Lamps
Filesize:	3978 KiB
Date added:	21 Jan, 2022
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Comment 1 to 11 of 11

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FrontSideBus

[21 Jan, 2022 at 04:34 PM]

Interesting. Might have to pick up one. Does it seem like the ballast is complaining at all?

Lightbulbfun

[21 Jan, 2022 at 04:41 PM]

indeed! the ballast seems to be quite happy! input current is about 1A, and according to the datasheet for the ballast it should be 0.9A so thats I think thats within tolerance! and temp wise it seems fine Smile

a 175W Metal halide (and mercury) lamp is rated for 135V 1.5A so I am not pushing the ballast that far out spec anyhow Smile

FrontSideBus

[21 Jan, 2022 at 05:34 PM]

In that case I will deffo have to pick on up. Venture's eBay shop a few years ago were selling off normal reactor 175w ballast and I should have got one then. This probably better as you don't need an ignitor.

Lightbulbfun

[21 Jan, 2022 at 05:50 PM]

yeah, I dont think a 175W Choke ballast would work for this due to the aforementioned high re-ignition peak voltage issues, and the fact that a choke ballast is not a constant current device, I know others who have tried normal 200W SLI/H lamps on 175W Chokes and have run into the same runaway issues where the lamp voltage goes through the floor and the current goes through the roof as a result (because suddenly theres a lot more voltage being dropped across the choke)

one small thing worth noting is I had 12.5uF worth of capacitors on the go (which measure to 12.3uF according to the Uni-t DMM) I did order a 12uF Capacitor but the seller messed up and forgot to send it typically! just mentioning this as the capacitor is vital to operation of a CWA ballast and does direct influence lamp current, you can tweak the capacitor values to tweak lamp current, but you dont want to go too far out of bounds or you risk cooking the ballast of course!

FrontSideBus

[22 Jan, 2022 at 07:41 AM]

I ordered one. Will have to get the scope out and have a look when it turns up.

Lightbulbfun

[22 Jan, 2022 at 12:35 PM]

Awesome! I look forward to seeing the scope shots as I find those details very interesting! It would also be interesting to know if your 200W HO also eventually extinguishes itself when run on a choke with no ignitor, and if my theory about the high re-ignition peak voltage is true or if the lamp goes out on the choke for some other reason?

FrontSideBus

[30 Jan, 2022 at 05:44 PM]

I just ran my G.E.C 200w SLI/H on it and it's a no go. Started up nicely but after it warmed up the voltage dropped like a stone and the current shot up to 1.7a. I'll upload a screengrab. Flickered like a bastard too!

FrontSideBus

[30 Jan, 2022 at 06:27 PM]

Ooops! I cocked it up lol

Lightbulbfun

[30 Jan, 2022 at 06:30 PM]

Whoops! it is interesting just how much of a tricky bastard SLI/H lamps are to run properly, I dont think I have come across another lamp that has been this much of a bastard to find an alternative setup for! normally something can be figured out with the right combination of ballasts (and a Variac Smile

)

Lightbulbfun

[02 Mar, 2022 at 02:45 PM]

just a quick update on this setup after some more electrical measurements with some more equipment I was able to verify that my clamp meter (Uni-T UT210E) under-read somewhat, it can vary from about 50Ma to 100Ma, if not more depending on which range its in, I had my suspicions it was under-reading based on some previous tests I did but with the recent addition of some more test gear to my arsenal I was able to verify it so.

so in light of this, I reset this up (well like I really need an excuse to light an SLI/H lamp Smile

) and measured it up again with more equipment and I got a result that much more closely matches what FSB got with this setup so in the picture above it was likely running at 1.5A-1.55A rather then the 1.45A the clamp meter reports, so thats even closer to spec Smile

does mean that all my previous experiments and readings I took with this clamp meter where all a bit out!, at least I have managed to characterise the clamp meter now, so I know what to off-set the reading by more or less when I use it in future

Andy

[02 Mar, 2022 at 11:16 PM]

I have now found my spare clamp meter so might try running the lamp again with both meters attached to see how they vary. Will add my results in due course.

Comment 1 to 11 of 11

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