MH Ballast Black Box PCB

Gideon Analytical Laboratories received several electronic metal-halide (MH) ballast black semiconductor diode, but it also permits current to flow in the reverse direction when its “Zener voltage” is reached. The goal was to expose the circuitry and reverse engineer the cause of failure of the three components that were failing at a high rate.

Failure analysis ensued. First, the zener diodes and fuses were exposed and potting material removed so that the circuitry was revealed. After analysis of the circuitry, a notable problem stood out. The configuration had no “soft” current limiting impedance for input line spikes. Input utility power has common surges and spikes. In a regular household, this sudden inrush of electrical current exposes unprotected equipment to damaging voltages. It can overheat motors, burn out lights and damage electronic components. In order to mitigate this potential threat, a surge protector is a good idea. However, all electronics should have some inrush limiting device to prevent these input power voltage spikes from damaging equipment.

In summary, failure analysis came to some important conclusions. There was a problem with the zener diodes. The zeners were rated for 410V (which was proper for this application) but the power handling capability is fairly light rating. They were bi-directional; that is they symmetrically clamp to the same + and - voltage potential. These zeners were not robust enough to handle power surges in the field.

Gideon Analytical Laboratories can solve your electronic failures, period. Why are we so confident? We have the best of both worlds: decades of experience in electrical engineering and chemistry combined with state of the art analytical equipment. Our successful diagnosis of electrical failures has helped hundreds of companies saving millions, (if not billions) of dollars. Trust Gideon Analytical Laboratories to help you. Get candid and accurate results in a reasonable time frame. Save time, save money, and avoid headaches. Contact us today.

potting removed circuitry revealed

potting removed circuitry-revealed

failure site on pcb

failure site on pcb

zener diodes

zener diodes

varistor to prevent voltage spike

varistor to prevent voltage spike