How do I know if my ballast is bad?
- A mercury vapor ballast consists of two
components: a transformer and a
capacitor. Sometimes it’s hard to tell
which is bad, so we suggest that each part
be individually tested.
- First, hook up the transformer leads
marked 120V and COM to the 120V
line coming in. Measure the output
leads marked CAP and COM with a
volt meter. They should read
approximately 240VAC. If not, the
transformer is defective.
- Next, attach the capacitor to the
CAP lead from the transformer, and
measure the voltage between COM
and the black capacitor lead. If the
capacitor is good, you will still read
240 VAC. If the capacitor is
defective, you should read 0-2 VAC.
Picture courtesy of Robert Huff Lighting, Houston, TX
- Next install the mercury vapor lamp in the fixture and measure the voltage between
the COM and black capacitor lead. If the lamp and capacitor are good, the voltage
will read approximately 15 VAC and ramp up to 130VAC in 5-10 minutes. If the
lamp is bad, the voltage will read 240 VAC.
**Note: we tested a 100W MV Advance ballast for our experiment**
| Mercury Vapor Troubleshooting |
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