Month: November 2015

This one didn’t go up in a blaze of glory, but the potential was there…  The tantalum capacitors in vintage ARP synthesizers were of questionable quality when they were new, and now are disasters waiting to happen.  Good quality tantalum capacitors are a fire hazard when exposed to even brief voltages that barely exceed their ratings, but the dodgy tantalum capacitors found in ARPs seem to pose a fire hazard without any coaxing.  This failed capacitor on the Bass board of an ARP Omni 2, shorted the +15V rail to ground and caused the synthesizer not to work.  Fortunately it didn’t damage anything else when it vented out its magic smoke.  It is very important to replace every tantalum capacitor in an ARP synthesizer to protect your instrument.  We offer capacitor kits and recapping services for all ARP synthesizers.  Contact us to discuss your needs.

The ARP String Ensemble we have in stock rolled off the factory line in 1974.  Everything inside was original, including the power supply capacitors.  The ARP/Solina String Ensemble uses an unregulated power supply, with the varying voltages being generated by rudimentary resistor voltage dividers.  The filter capacitors in the original synth were 25V capacitors, on a 25VDC power supply.  This is bad news on many levels, good design practice allows for a nice buffer between the expected circuit voltage and the capacitor voltage rating, to ensure the capacitors maximum voltage isn’t exceeded, as well as to provide for a longer life of the capacitor.  A capacitor rated for 25V and run close to the maximum will last less than a capacitor rated for 50V and run at 25V…

So, we replaced all the capacitors in the power supply, with 50-63V rated capacitors.  We switched to radial capacitors, since the quality of the radials are better than that of the axials, and selected capacitors with a higher 105°C rating.  Now this string ensemble is good for another 40+ years!