Pinned by Durachko. Member arizonavideo has put much time and effort into researching the method commonly referred to as "overdriving" some of the lamps we use. Please proceed with extreme caution when experimenting with this method and heed all warnings. This is considered an extreme mod and obviously voids any and all warranties on equipment subjected to this procedure. Thanks for this summary AV.

This is a short guide to overdriving lamps and ballast.

The original thread is here:

http://www.lumenlab.com/forums/index.php?s...st&p=130435

Overdriving any lamp or ballast could cause the lamp to explode and break both lamp shells. If the light box is wood it could catch fire. Some lamps could also form a dead short which would normally be OK for ballast but an overdriven ballast will over heat and could catch on fire. You should use a fuse on the ballast.

I would never leave an overdriven light setup on when not in the room.

Overdriving a lamp will shorter a lamps life. There has not been a lot of long term testing so how much shorter is a bit of a guess. If your lamp bits the big one at 6 months don't cry too much. You have been warned.

Most MH lamps can be overdriven some to make them brighter and in some cases they may make better red and have a slightly better CRI

There is a few ways to do this. You can use a higher wattage ballast or add a cap to a ballast or use two ballast. The first part is about adding a cap to a ballast.

The cap is always added in parallel to the existing cap. It can be put on a switch for a high/low power setting but if you switch the extra cap ON when the lamp is lit it will make a spark on the switch contacts and this will shorten the life of the switch allot.

This is drawing of a parallel cap diagram.

Click to view attachment

The most common type if caps that can be found are motor "Start and run "caps. They look like this.

Click to view attachment

They need to be at least 360VAC rated or higher for a 400 watt or smaller ballast.


Durachko is demonstrating proper handling in this photo.

Click to view attachment


They will also stay charged (to around 200V) so if you handle them you can get a nice shock so they need to be discharged by shorting the leads. A plastic handle metal tool is OK for this, it may make a small spark.

The larger cap on the ballast like the 55uf or 24uf may have a drain resistor built in the cap. If it does it will list the size on the side of the cap in ohms. If it does the cap will discharge fairly fast after the power is shut off. If not the big cap will stay charged to around 200V if you touch the big one you will REALLY get a kick. If it has a drain resistor and the overdrive cap is connected in parallel , the extra cap will drain with the main cap.

Always treat a cap like it is charged until you discharge it.


All MH lamps will have the color temp go down if over driven. This makes using low color temps lamps a problem. It is best to start out with a higher color temp lamp, any 4500K to 6500K would be fine, and the CDM 150 with a low color temp of 4200k may be OK with a slight boost of power. It is best to not go to crazy with the over driving, 20 to 30% should give nice lux gains ad still have good life.

For 400 watt lamps there are two main types of ballast. I am only talking about coil & core ballast not electronic ballast. The S51 400 watt HPS and the M59 MH ballast. (The M135 PS ballast is almost exactly like the M59 except it has a starter.) These are the most common types and first up is the M59 400 watt standard MH ballast.

The M59 outputs 135V at 3.2A. Almost all of them come with a 24uf cap. If the cap on you ballast is 24uf then adding a 2uf cap will increase the power by about 50 watts and about 50 more watts for each 2uf of cap. (more like 50 watts -5 for each 2uf)

The M59 runs a little hotter than the S51 and also makes more noise. It has no starter so the igniter must be in the lamp. The LL 400 watt lamp will run on M59 ballast.


The maxim power you can get from the M59 is some where around 700 watts but you will not want to go that high. The ballast will make more noise the more power you draw from it and I think M59 is a little loud at 400 watts. It also gets really hot. If you over drive it, you have to put a fan on it and the lamp also needs to have active cooling.

I would not over drive the M59 past 500 watts. That would be adding a 4uf cap for a total of 28uf.


The S51 400 watt HPS ballast outputs 110V at 3.9A (or 4A depends on who you ask) It runs a bit cooler than the M59 and is fairly quiet. Most S51 ballast come with a 55uf cap (All the CWA that I have found) I have found that for every 4uf of cap the power goes up about 50 watts. (The second 4uf will give a bit less power like 50-5 + 50-5.)

The S51 has an igniter so will start most any lamp. It is an OK match for the HQI 400 lamp.

The S51 is larger and can make more power than the M59 and still be fairly quiet. It should be OK to run it at 500 to 550 watts if you have good cooling on it. I would still try to stay around 500 watts.


Durachko has has tested a dual S51 ballast setup and the HMI 575 watt lamp in his PJ with good results, for details see post #13 or look here.

Here

One important notice: this is a short "US only" guide to overdriving lamps. In a "regular world" outside US this idea of connecting capacitors in series with a lamp is totally unknown. This is due to 110V mains voltage in US, while in the rest of the world there is 220/230/240V, and a ballast is not a transformer, but just a single coil, connected in series with the lamp.

What you draw here is somehow bizzare, perharps it works, but seems to be an unstable solution, highly dependent on the quality of the capacitors and their condition, and these have often short life. With a "regular" series ballast if you want to overdrive a lamp, you just use higher power ballast, or take another small one and wire it parallel to the first one, and the total power will be about the sum of the both. And the capacitors will be connected parallel to mains on the input, as they are there for "power factor correction", not for a series reactance to limit lamp power. I'm not sure, but this seems to be risky, at least there is a risk that a blown capacitor will result in lamp and/or ballast damage. Or even a fire in the house.

Regards

Thank you Durachko for the sticky. My work will now live forever or until someone finds a lawyer!

Pepe: I wad hoping to not have a long discussion over how changing the cap value works but if you ask I will reply.

First you say "highly dependent on the quality of the capacitors" I have never seen any "quality" rating on a cap, 20 years ago they used to use a term called a "wattvolt" it had been a long time so that may not be correct but caps today are rated by voltage and temp. Most start and run caps are rated at 70deg C and most of the ballast caps are rated at 90deg C , the dry films are 100deg.

A 90deg C cap will be larger than a 70deg cap so it can dissipate more heat. The standard cap for most M59 ballast is around 360 VAC at 90deg C which is slightly higher than the 360VAC 70deg C (or 100deg)that most of the start and run caps are rated. The cap in the picture is a 660VAC which is a lot higher voltage rating than you need for a M59 or S51 but it is fine to use for all the ballast even the 1000 watts ones I have.

The S51 runs a 55uf cap with a 240V rating at 100deg C rating (If it is a dry film). A 360V cap at 70deg C is slightly over rated for the job.

For M59 ballast a 360V 70deg cap is slightly under rated but should still be fine. If you want you could use a 440VAC or a 660VAC for a M59.

For a S51 the 360VAC at 70 deg is slightly over rated and will live longer than you will.

The rating of the caps is taken with no cooling in a hot environment (full temp like 70deg or 90deg or 100deg) and run 24/7.

If you look at this schematic it is for USA 60Hz power but because the input voltage is much higher than the lamp voltage the setup transformer can be removed and a pure series reactor circuit is used. This makes the ballast smaller but can only be used with one voltage.

http://www.venturelighting.com/VLPS/Ballas...S/V90B1422H.pdf

The purpose of adding or subtracting a cap value is to have an easy way to adjust the power to the lamp. Adding a cap will screw up the power transfer function and the start up current will be higher than it should be. I have seen ballast makers list the same ballast for three different lamps a 400 575 and 1200 watt lamps and all they did was change the cap! This is not something new ou un-tried.

I like the idea of using larger ballast like a 600 watt or 1000 watt and under driving it for a much quieter and cooler system which I have done. This also gives a better start up current control.

Let look at you two ballast setup you were using with the S400DD lamp. You used a 400 watt HPS and a 150 watt ballast in parallel. What would you have done if it melted the lamp because of too much power? All you would have to do is reduce the vale of one of the caps or both to lower the power transfer and all would be fine.

I'm going to get to ballast paring after I talk about the lamps a little bit.

Pepe: It does look like adjusting the cap vaule may only be good for CWA and CWI ballast not the Reactor types.

I don't question this method works well, and I understand the principles behind it, I just doubt about durability and reliability of this approach. Capacitors are not durable, their values change with age and temperature, and your fine adjustments may not be that fine after a while.

By the way, my 250W lamp @ 380W is still doing fine, so I would recommend it over an overdriven 400W lamp, more light and less heat.

Regards

The most common lamps we have are the LL T15 400 watt standard MH and the old USHIO S400DD HPS conversion lamp. There is also the OSRAM HQI 400 and the OSRAM 250 watt HQI. All are good candidates for overdriving and all have a fairly high color temp of over 5000K

In the other testing I had a 400 watt lamp with a 38mm arc that took about 900 watts before the arc tube melted. It is worth noting that some lamps have the arc start to travel in an oscillating pattern. This is bad and makes the lamp useless for PJ use. The color and brightness will always be changing if the arc is moving.

One other thing that can happen is the arc will lay against the side of the arc tube. This is really bad too. The extra heat will melt the quarts and the lamp will fail or the extra heat will cause the quarts to age prematurely and crack. You need to look at the overdriven arc in the arc tube to see what it is doing. You need arc welding glasses to do this. Gas welding glasses are OK of you also have sunglasses on. I use full face arc welding helmet so my skin does not get burned.

If your arc is wandering you will see it on the screen and if your arc is on the side of the arc tube you could also see it in the arc image at the triplet which might be a better way to look at it for most people. The arc may change during warm up so you need to look at the real setup at the temp the lamp will be running.


The S400DD has been known to have arc wander with some lamps. The HQI lamps have the electrodes inset further into the arc tube and seem to have a much more stable arc. I have run the 400 watt HQI at 600 watts with no arc wander and some cheep China 400 watt "HQI" at 1000 watts and the arc stayed in the middle.


You may be able to drive it harder but I would run the S400DD at no more than 500 watts. It has a short arc 27mm so the power per MM of arc tube is already fairly high.

The T15 LL lamp should be OK to 550 watts from a power stand point but the M59 ballast is going to start to get really hot and noisy. I don't know how stable the arc will be. If you overdrive a T15 then please post your findings.

The HQI lamps have proven to have real stable arc's and can take some real power. I have run the OSRAM HQI 400 watt Fc2 lamp at 640 watts and all was fine (no reflector). Pepe is running his OSRAM HQI 250 at 380 watts on 400 watt HPS ballast and it is still working OK. I hope he keeps us informed of the lamp life at that power level.

The OSRAM HQI 250 at 380 watts just may prove to be one of the better setups because of the small arc and slightly lower power level might let you use a regular glass condenser lens

It may still be brighter for a 17” LCD to overdrive the S400DD to 500 watts with a condenser lens. You could get around 250 lumen or more. You will need a high heat condenser.

The OSRAM HQI 400 could be run at 550 watts or even 600 watts and be really bright but the arc is a little long for the smaller triplets. The color may be a little better than the S400DD. I did a fairly long test here.

http://www.lumenlab.com/forums/index.php?s...st&p=145895

AV,
I have a question regarding color reduction is there a guesstimate on color reduction % to watts? or a simple formula to figure it out. Which leads too, is it Kelvin # or CRI #'s that are reduced Or beter yet If I go for a 50 watt overclock with a 150 HQI using a 200watt ballist what would the guesstimate be % wise? Sorry if these are nubie Question but I've been waiting for you to do this summary. By the way I think what you have shown the DIY community is one of the most interesting reads and most informative plogs for a specific topic and weither the laywers get you or not (hopifully not) I will be using it alot.

Best regards, Joe


I think they should do a hall of fame for topics, you would have my vote

A heat-proof condensor is an issue, so far I have 4 or 5 lens cracked, at least one of them was supposed to be "heat proof", and it lasted couple of hours, all the others cracked just after 20-30 minutes. The last one I tried with this overdriven 250W lamp, and it also cracked, but it broke into 3 big pieces, that I could fix together using thin steel wire, and I rotated this lens to such a position, that those cracks do not cast strong shadows, you can see something only in the full white screen. The result is still better than no condensor. And a 250W lamp allows to make good use of a precondensor even with a standard OHP triplet, while a typical 400W lamp with a precondensor needs a bigger triplet, although with a standard one it still better than without a condensor.

I recently noticed, that my overdriven lamp got rid of that startup problem it had at the beginning, now it quickly ignites without any blinking or delay. And it didn't develop dark deposits inside arc tube, like my old 400W Venture lamp did within few first weeks of being overdriven to about 550W, so far this Osram 250W is clean like a new one. My average usage of the PJ is maybe about 1hr/day.

Regards

ndnjoeh: Thanks for the kind words and making me do the math

I have not found a good way to measure color temp so the best way may be just to look at the screen. The lamp could have almost any color temp and you could just adjust the RGB settings but if you have to lower anything this will cost you brightness.

Lucky for us OSRAM overdrives there lamps for us! (This is for all those who say that overdriving a lamp is a sin)

http://www.osram.dk/B2B/brochurer/intprodu...harge-lamps.pdf

page 40


This is a link to a PDF from OSRAM. At the bottom they list power levels and color temp for the lamps and some of the HQI lamps they drive the same lamp at two power levels.

One of the HQI 400

410W= 4600K
480W= 4000K

And another 400 watt HQI

400W= 5500
460W= 5300

And one more 400 watt HQI.

400W= 5900K
460W= 5200K

The color shift is a little all over the place. It may be a ramp up curve until the lamp reaches a certain pressure.

For the last set of numbers for a 14% power increases you get a 12% color shift. This is close to a .9 ratio. If this holds true for all lamps (this is a leap of faith) then the % of power increase will be close to the % of color shift.

A 150 lamp driven to 200 is a 25% overdrive so the color temp may go down by 90% of 25% or 22.5% or from 4200K to 4200 x 22.5% =9450K. 4200K- 9450K= 3255K.

I would think that the color shift will be more like .5 ratios not .9.

Either way the color shift is a fairly steep slope and can't be ignored.

As for condensers my 6x9 Pyrex is 50mm from a 1200 watt lamp with cooling and has been fine. Pyrex is good to 450deg.

It's in my PJ plog.

http://www.lumenlab.com/forums/index.php?s...st&p=171287

Thanks AV,
The color shift is alot more than I thought it would be. But with a 25% OC it would be a reasonal asumption that you would get that much reduction. By eye I have not noticed that much change, I need to take picts of the wall with the 150 ballast and the 200 ballast and do a side by side comparisan of white light.

I am a low tech DIYer (means no tools for electronics) Lamps are tested by eyes only. LOL, I was not trying to say kind words just facts. For a person in my situation ie: no tools or knowledge of lamps, what you have done is one of the best sources for a person like me to get the info I need to do a project of this scope. Cost wise I rank it right up there with SJ's monitor complilation.

Oh and I am sorry for making you do the math. The osram info helped out alot. I actually bookmarked it for 400w info more than the 150 info. I got lucky and purchased literishes s51 with lamp.

Thanks for all,
ndnjoeh

Using multiple ballast.

Using two ballast is another way to overdrive a lamp. Pepe was doing this to his S400DD 400 watt HPS lamp by adding a 150 watt HPS ballast to the 400 watt HPS ballast again in parallel and I have been doing this with my PJ for a long time.

I have done this trick with a few different lamps and ballast.

My 1200 watt PJ is using two ballast a 600 watt HPS S106 ballast and a 400 watt S51 ballast are in parallel with a switch to connect the two, after the first 600 watt ballast starts the lamp. The 1200 watt MHI lamp runs at 13A at 100V (I know this is more than 1200 watts but this is the non RMS readings that they use from the factory) The S109 makes 6A and the S51 makes 4A so I still needed to add some extra cap to bring the power up which I did by adding a 10uf to the S109 and a 5uf to the S51 for about 1200 watts of power.

The lamp did not always start with both ballast in parallel so I added a switch. One of the ballast must have the igniter removed so I removed the starter from the S51.

I also have a 2000 watt HQI lamp that needs 220V at 10.3A. I was going to use two 1000 watt HPS ballast which are rated at 235V at 6A but one of the guys sent me standard 1000 watt MH ballast so he let me have it cheep.

I still pared them together to give me the 2000 watts I needed. I had to add some cap to get to full power because the standard MH does not make enough current.

You have to make sure that the input is in phase. If you reverse the input leads the two ballast will be out of phase and it will blow the breaker. I have done this just because I’m lazy and don't check the power cords.

So two 400 watt ballast will give 800 watts and so on. The voltage remains the same but the current is double.

It should be the most efficient to use ballast of the same type.

This also gives us a way to run low voltage high current lamps (HMI or MHI or HTI lamps). This is a big deal because many HMI type of ballast cost big bucks. There are also a lot of 72V and 60v short arc lamps that might work with two 150 watt HPS ballast.

We know that the S400DD can be run with a S400DD and 400 watt +150 watt ballast (Pepe is this right?)

Two 250 watt M58 standard MH ballast should give 500 watts and will be cooler than a over driven M59.

I also have run the lamps on larger ballast (1000 watt) using the higher voltage tap like the 208v or 220v on the quad tap ballast. The 1000 watt HPS ballast will run a 400 watt lamp if you use the 208 volt tap instead of the 110v taps. This cuts the output voltage by almost 50%. It is an easy way to drive a lamp to 600 watts and not have the ballast get hot and the ballast makes almost no noise. I had to change to a 400 watt igniter to get a spark and you will have to adjust the cap to set the final power level.

So with all or some of the ballast tricks here you should be able to find a way to run almost any lamp at any power level you wish.

Over driving a HQI lamp or under driving a HMI or even running a UHP short arc should be possible with a little work and a amp meter.

ok to break the limits a bit here.. anyone who could figure out what options there is for us european guys.. US is big but hey yer not the only one's building PJs =D

Im one of those fellas who's running my pj on 230V and i bougth a 10uF 450VAC cap and i wonder if i'll blow everything up if i wire it into my setup.. it arrived today and i wanna ask before i do something..

is the caps work to deliver a higher voltage to the lamp? or how exactly does the cap effect the chain

Just happened to drop in here AV and noticed where you put that crazy capacitor picture of mine. Nice!

And so I'm not adding a totally worthless post here's where to find my AV-inspired Dual S51's Driving a 575HMI.

Check here for additional info.

What is the feasibility of using this method to "upgrade" a ballast? I see here that you guys are getting good ballast stability at around a 25% overdrive, so here's my idea - I need a 150 watt setup, but don't want to pay that much, but there's several complete 100 watt kits on ebay for $20 shipped. A larger capacitor would add say $5-10 depending on the source. I haven't done the math out, but theoretically one could easily add/change the cap to essentially upgrade the ballast system to 125-150 watts. Add a bulb, and the total cost is ~$30-50...Anyone see this as feasible or find any glaring errors in my logic?

EDIT - had the wrong prices down

Long years ago I overdrove a 70W HPS on 1000W MH ballast. Wow! It burned super bright and pure icy bluish white.

Yesterday I ran a 150W HPS on a 400W HPS ballast... higher color temperature, 80 CRI (really nice). Fixture couldn't handle the heat though so had to unplug.

It's possible to get much better CRI while maintaining reasonable efficiency in public HPS fixtures by simply substituting a lower wattage HPS bulb. My test yesterday overpowered to 2.7x, but I predict that it will really start looking nice at 3x, with 4x being my limit.

Even running at 2x the CRI is substantially improved, without too much loss of efficiency.

And long ago I also ran a 100W MH on a 1000W MH ballast. Wow! Beautiful high CRI, white light at about 3700K, when unplugged I saw the arc tube had partly melted and bulged outwards!

I have found that the color temp always goes down when over driven.
Many lamps can take more power but you want to look at all the trade offs. If you over drive a lot and the lamp life is around 1000 hours then a HMI lamp would perform better for not too much money.

Out lamps run with a reflector which adds heat to the lamps so you have to add that in too.

A good paper about power control of HID lamps

http://ecmweb.com/mag/electric_hid_lamp_dimming/

note: the Fig 2 have error, must to say Switch Close for Full light output, Switch Open for reduced light output