HISTORY:
This component has been pulled from a wonderful piece of test equipment made by KEITHLEY (USA), the 642 Electrometer. This equipment is from the 1980's ~ 1990's era, technically advanced (for the day) and designed to measure voltage, current and charge to extremely low levels (see one of the snapshot photographs from the User Manual)
Why "part out" such an instrument? I have decided to make this equipment an "organ donor" because a critical component is no longer with me, the remote head! To make measurements a wired head is required and without that, the instrument had no sensing abilities.
COMPONENT MANUFACTURER:
Clearly marked on the body of the capacitor as POTTER, reference to the 642 parts list and cross reference to the supplier of components shows this is definitely a POTTER & BRUMFIELD capacitor! Very well known electro-mechanical design and manufacturing USA company which had very humble beginnings and is now a highly respected name in the world of electronics across many industries including Military and Aerospace. To be truthful, I always knew the company was highly regarded in the world of relays but capacitors? I found some references to their manufacture of "other" components" but it surprised me to find these polyester capacitors (even from the 1980's) were Potter & Brumfield marked! Actually I suspect that Siemens AG might have been involved here because P&B became part of Siemens (Germany) around 1986, now THAT is a company well known for high quality capacitors ...
POTTER & BRUMFIELD - Polyester Film Capacitor
Value: 4.0uF
Voltage: 100V
Blue epoxy encapsulated
Circa 1980's (pull from the Keithley 642)
Body of the capacitor is printed...
POTTER
0109-5432
4 MFD 100 V
43-8341
Radial leads
Very short leads (4mm), removed from the PCB (NOT cut)
DIMENSIONS:
33.70mm length x 16.85mm height x 11mm thick
SPECIAL NOTE: I also have a 5uF capacitor from P&B with the same voltage ratings but it is actually SMALLER physically than this 4uF cap, weird?
TESTING:
Being a USED device of some age, I made a quick test of this capacitor
Value: 4106nF (4.106uF)
ESR: 0.85 Ohm
Loss: 0%
Well within the 10% tolerance
