Tag: Equipment Restoration
The HP3245A Universal Source (datasheet is copyright HP/Agilent) is a precision AC/DC voltage and current source that can provide a wide range of precise and repeatable voltages and currents up to +-100vdc and 100mA dc. It can also provide sine, square and arbitrary waveforms up to 1Mhz and 200vpp. Such an instrument is extremely useful in the lab for calibrating meters, driving current and voltage amplifiers and checking equipment. The particular units I have were built in 1992/1993 which means the electrolytic capacitors are approaching 30 years of age. I had decided to replace the RIFA line filter capacitors in (documented here) both my units and performed routine power rail voltage and ripple checking as part of that. For example:
+5.0840 4.4mv+15.194 30mV+18.625 29mV-18.691 28mV
The other power rails and HV Amp power supply also measured good, using an … Read More »
In a previous post, I had documented the condition of several RIFA Y Safety capacitors, showing clearly the cracked condition of the outer case. This condition is a precursor to the well documented failure of this style of RIFA capacitor. Reportedly, these problems have been solved since Kemet squired RIFA in 2007. Of course the equipment which contains these potentially failing capacitors is typically older than 2007.
For example, I recently replaced six (two from each instrument) of these capacitors from the following equipment:
HP 3245A (1992)HP3245A (1992)HP 3458A (1989)
HP 3245A (1992) Original RIFA Safety Capacitors. The line filter is on the bottom right.
HP 3458A (1989) Original RIFA Safety Capacitors. The line filter cutout is on the bottom right.
Each and every RIFA Safety Capacitor I removed from this equipment showed cracks in the case.
Cracked RIFA … Read More »
RIFA Safety Capacitor Failures have been documented by many of us who restore and maintain vintage electronics equipment. One very spectacular failure was caught live here: courtesy Dave Jones of the EEVBLOG. These capacitors were widely used in test equipment manufactured during the late 1980’s through the 1990’s. The general consensus is that the capacitors fail because the outer case (presumed to be a type of epoxy) develops cracks which allows moisture to penetrate into the body of the capacitor. This leads to internal short circuits which cause the capacitor to fail catastrophically. Because these capacitors are line to ground, they could see line voltage whenever a piece of equipment is plugged in, even when switched off. The crack network can develop to the point where large pieces of the outer case spall off, exposing … Read More »