Multi-tube fluorescent sign ballast mystery

I am helping a friend who owns a restaurant fix the marquee sign in his front parking lot. The sign was working fine for the last 3 years. The sign uses two separate banks of 5 linear 72" (F72T12/D/HO) tubes per ballast. The pin style is recessed the bi-pin. I think the voltage is

220VAC. Unfortunately, the label on the ballast has aged away and is now unreadable, but I am quite sure it is one of those pricey six tube ballasts rated at up to 36 feet. There are a total of two ballasts, one for each bank of five tubes, for a total of ten tubes. One bank of five tubes works just fine. However, on the other set of five, only the tube, the one physically closest to the ballast lights up. All of the bulbs have been confirmed to work by removing them and testing them in the working lower socket. I think this is just an open wiring problem. I now need to troubleshoot this bank of tubes while standing on top of a 12ft step ladder in the middle of a parking lot.

Troubleshooting Questions:

- Since one lamp still works, can the ballast be considered 100% good?

- Should I just use a meter to confirm 220VAC at each of the sockets?

- Can I use an inductive voltage tester to sense the voltage to the sockets?

- Should the bulbs be in or out of place when testing the sockets?


Reply to
Loading thread data ...

absolutely not

I have a sign that seems equivalent to "yours" ... several but not all of the windings of one ballast are out.

Most likely, you will need to replace the ballast.

for additional info see:

formatting link

Reply to
Tim Perry

Testing the lamps was a real good idea. I would go further and move all the lamps between ballasts with obvious expected results.

Could be wires from ballast to socket or sockets. I have seen wires burned open.

Since 1 lamp lights, the ballast is powered. My guess is the ballast. As you note they are spendy little critters. You could check filament voltage at each socket. (Voltage to ground may be high making this a hazardous test, especially standing on the top of a 12' ladder.) I don't know a good test for ballasts.

Nice links.

Reply to

The pin style is recessed double contact. The input voltage is 120VAC. The label on the sign ballast fell off but I took it home and looked it up. It appears to be a Rapid Start - Magnetic, Valmont 6G3959WF. From what I can tell this is a 4 lamp ballast. So that begs the question, what is that other 5th (working) lamp running on?

Sorry, I needed to get back OT (on topic) with this with you guys until I can understand it. Thanks.

Reply to

PolyTech Forum website is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.