Service bulletin
Vol. 11
Subject: ZRM4 power supply capacitor
Date: 14/11/08
Initial Recipients: Chris Smith, Service, Tech support, David
Curtinsmith
Model: ZRM4
We have had some failures in the field of the internal ZRM4 SMPS.
When a failure occurs it normally destroys the bridge rectifier, SMPS
controller, rectifier capacitor and MOSFET’s. It also sometimes
destroys the transformer.
The failure of the entire power supply chain is due to the premature
failure of the rectifier capacitor. The reason for the premature failure is
due to a change in the ripple current rating of the capacitor
manufacturer that occurred around January 2008. Note, to this date,
units manufactured before Dec 2007 are believed to be unaffected.
A product recall is not necessary as the problem is believed to be a
relaxation of the performance specification tolerance of the capacitor,
and therefore only a small portion of units (not all) will be affected. In
most conditions, with most capacitors, the units are within spec. Only
a few units so far have been shown to be outside spec.
Production units with serial numbers above B00300001 will use a
better performance capacitor and will eliminate the problem.
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