Testing magnetic ballast

[perpetual98]

So I've got a 26G bowfront in the master bedroom and it's got a 250W mogul14KK DIY pendant over it. The last couple days the halide hasn't fired up. I've jiggled the wires on the capacitor and it would fire up. Lately though I can't even do that. Is there a way that I can test the capacitor to see if it's shot? The ballast itself is warm, so I'm leaning towards the ballast being ok and the cap being bad.

Any advice?

[dakar]

Got a good digital multimeter? Check the output voltage from the coil, I'd have to double check, it should be around 250VAC, the cap can be tested the same way if your meter can do it (mine does), should be around 15uF, but I'd need to ballast manufacture and part number to be more exact and come up with a current potential from the coil to test for.

Now remember that a capacitor charges up to 66% of it's current potential and releases, charges back up, releases, and the cycle continues, where you interupt this cycle can lead to there being quite a substantial amount of current left in the cap at a stiff voltage, it WILL jump out and say hello if you aren't careful. Best to ground each lead before trying to test it.

Did you solder all your connections? Maybe as simple as cold joint somewhere... if not, break out the iron and get soldering, avoids a lot of troubles.

If there is voltage at the lamp holder, have you tested it with another bulb? I know the little conductor at the backside of mogul bases tends to loose it's springyness (that looks like a word) and can cause intermitant troubles.

[perpetual98]

I haven't broken out the Fluke yet to test it. I also don't have another 250W bulb to try, but that would be the easiest thing to try. I can try to solder the connectors on the cap. I do have that capability. :) Where should I be measuring 250VAC? Between the cap and the coil? It's an Advanced M58 Ballast if I remember correctly, but don't quote me. I can get that information later when I get home. Are 250W caps specific to 250W ballasts? I might be able to get a cap at work to try it out, but I'm not sure if we have any 250W ones laying around.

[jerryc]

sounds like a lose connection........................................ ...........

Testing a capacitor use a Ohm meter after shorting out put leads across the terminals the Ohm meter will go up and slowly come back to 0 reverse and
do the same if good you will get the same result.
Are if you wont to invest about 20.00 Thea make a capacitor checker.

As already stated Thea can bit real good believe me i got hold of a large
one putting together a pale-phase

[dakar]

Test the coil at it's output (before the cap), the output will be AC. I just checked my Advance H37 ballasts and the cap is rated at 22.5 uF @ 300V. Now the 250w pulse start ballasts I worked on last week had 15uF @ 300V caps, but the pulse starters may be different. Better to get the ballast number to be sure.

I cheat, my meter does capacitance, diodes, hFe (transistors), current, as well as the typical resistance and voltages. Really afraid of the day it dies, I've had it for like 20 years now and don't want to know what it'd cost to replace today.

[jerryc]

[I cheat, my meter does capacitance, diodes, hFe (transistors), current, as well as the typical resistance and voltages. Really afraid of the day it dies, I've had it for like 20 years now and don't want to know what it'd cost to replace today.[/quote]

Like always from 15 to 500 depending on whit you wont I gave 180.00 for the one i have after dropping the last off my ladder i love the newer digital amp/volt/Ohm meters

[perpetual98]

I've got an Advance 7C350P24 cap (I think it's a cap) that I could take home and try if you guys think it would work?

It says 35 MFD 240 VAC 50/60 Hz on it if that makes any sense to anyone

I've also got an Advance 7C550P24 that says 55 MFD 240VAC on it. These both came from HPS ballast systems though.

Won't work?

[dakar]

Looks like the standard for M58 Advance ballast calls for 15uF (MFD) @ 400VAC. Just looked at a few different datasheets and they all use than same capacitor. The Advance ballast part #71A5770 coil has an open circuit output of 300VAC. Think this is the more common M58 mag. ballast in use.

BTW the Cap part number is 7C150P40-R.

That HPS cap would not be a good idea, it'll likely melt down since it's not rated for the voltage.

[perpetual98]

Yup, you're right. I just looked at it. I've got an Advance 71A5790 coil. I'll try some things after dinner if I muster the energy.

[dakar]

I was close, but the 71A5770 and 71A5790 have the electrical specs. Only difference is the 5790 has 12" output leads and the 5770 has spade terminals. Took a few times going over the datasheets to find the difference.

[perpetual98]

OK. I'm getting 303VAC between the Com wire (going to the bulb) and both terminals on the Cap. What next?

[perpetual98]

And I appear to be getting the same voltage in the socket. Is it the bulb, or is something not 'firing' the bulb?

[dakar]

I'm assuming you tested for voltage at the socket as well and are seeign the 303VAC too right?

To test the cap, remove the cap from the circuit and discharge it to ground, If your meter will test capacitance see what it comes up with, if not then set it up to measure resistance around 2K ohm should do, the resistance should ramp up and down (you may have to bump up the range).

[perpetual98]

I tested it both ways. It's got a capacitance (is the the right term?) of 15.3uF and when I run the resistance my meter goes from low resistance up to around 650 kohm and then bounces back down and repeats. 650 might be the range of my meter, or the setting I had it on. It's a Fluke 177 that I 'borrowed' from work.

[dakar]

Good news and bad news..and better news.

Good news, ballast and cap check out fine
Bad news, bulb it likely toast

Better news, you can now effectively troubleshoot magnetic ballasts.

[perpetual98]

That stinks. Although I think I can get a bulb for cheaper than a new ballast, so that's a good thing. That bulb is only a couple months old too. I'll snag a generic 250W bulb from work and bring it home and try it out. It should look pretty cool, it'll probably be around 2100K. lol

[dakar]

Where'd you get the bulb from, any warranty? I know Marine Depot is where I have been getting our halides mostly because have a 12 month pro-rated warranty from the date of purchase. Though you have to ship them the dead bulb and wait for it to be tested and they'll credit you with the balance or knock it off the price of a replacement.

[perpetual98]

I bought it directly from Hamilton. I'd probably be hard pressed to find a receipt though.

[perpetual98]

I think in the interim I'm going to take my 250W pendant down and hang my 150W Brinks HQI pendat retro until I can figure out what's wrong with the 250W jobber.

[dakar]

Ah HA, so I'm not the only one who has eyeballed those Brinks jobbers for chaep <$30 sitting on the shelves of WallyWorld adn HD. Anything good in them? Come one show us your hacks!

Angel found all the stuff to get our OLD digi working yesterday, so we'll be able take some pictures again (albiet far lesser quality) until I can tear down the newer one, and see if i can fix it, or permanently let the smoke out.

[perpetual98]

Can't beat a $7.44 halogen fixture that you can ALMOST pop a 70W halide into stock or with a little modification a 150W bulb.
You need to grind/cut/snap some of the metal so that the bulb fits in, but it's a super quick mod once you figure it out.

[dakar]

Got it... same thing I did with that knock off halogen -> 70w MH hack. BTW did you attach the ballast to the fixture or remotely?

Initially I was thinking you were hacking on the Brinks MV fixtures, they've been taunting me for a while now to grab one just to take it apart to see if the ballast was good for anything else.

[perpetual98]

I have the ballast remotely mounted. The thing gets pretty darn hot the way it is. I haven't looked at the MV fixture. I don't know enough about the ballasts to see what the difference is. I might try to get my 150W up tonight after work because the few things that I have in my bowfront have already shown signs of fading because they miss the halide light and the PC bulbs that are over the tank are good enough to light things up to see, just not good enough for much else.

[perpetual98]

I got my 150W pendant up last night. I need to get some more chain so I can lower it a bit as it's about 12" or more off the water right now, but at least I have some decent light over the tank again. It's amazing how much brighter the 150W 14,000K bulb is than the 250W 14,000K bulb. The 250W seemed to fluoresce stuff better though. I moved a couple frags around in the tank to see if they brighten up more.
Oh yeah, I brought another bulb home from work and tried that in the 250W pendant and that didn't fire up either. Something is causing the SE bulbs to not fire. I might just leave the 150W pendant up if the corals like it. :)

[dakar]

Hmmm wonder what you've got going on there with that ballast... was the bulb you brought home a MH or something else? HPS, MV need a higher surge of power to fire the probe to actually start the bulb, hance the bigger caps.

[perpetual98]

It was an M58 metal halide bulb made by Sylvania.

[dakar]

Maybe the ballast has just given up the ghost and will no longer push enough current to fire the bulb(s), of course that is the only thing we didn't test for was max load being output, think the Fluke meter you had could measure it without burning up, but I'd need to double check both the ballast outputs and the meter...