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CAUTION:Remember that the High Voltage Circuit Cards operate up to 2000Vdc, and the HV capacitors can retain that charge for a considerable time. Any maintenance should be proceeded by removing the power cord from the AC or DC line. With the unit turned off let 5 minutes elapse until any disassembly occurs. This allows the Preamp's bleeder string to discharge the HV Circuit Card HV Supplies, and the associated capacitors, after which the HV circuit cards may be handled without fear of shock. No maintenance should be done with any input power (AC or DC) connected.
After noticing a problem with either abnormal or no High Voltage, a few clients mentioned that on older units circa 1980, they have had failures of the 1.0 ufd 2000vdc High Voltage capacitors on the HV boards. A few of these capacitors have failed, but usually only after many years of service. In 1989 we switched to a different capacitor. We now use two, 0.1mfd @3000vdc potted together in parallel. This yields a 0.2 mfd @ 3000vdc capacitor which is more than adequate for a smoothing capacitor. Indeed you may remove the capacitor entirely and the HV board and counter will still function fine. I however, prefer to have the capacitor in the circuit. We 'pot-up' two capacitors and provide HV leads to be soldered in place. The capacitors are glued to the circuit card with silicone rubber adhesive, (usually available locally), which is let cure overnight. We can supply the 0.2 mfd @ 3000vdc potted capacitors for $54.00 U.S. (each). If I have been made aware of other suggestions, I will post them here for anyone to see. If you have a suggestion you think might help please, E-mail to Applied Techniques Co.
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