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Carbon or ceramic composition resistors – are quoted manufacturers leadtimes resulting in a “Surge” to look for alternative options?

The Firstohm SSR Series is currently offered with a manufacturers leadtime of only 12 weeks – while the unit price is significantly more cost-effective compared to carbon or ceramic composition resistors.

Allen Bradley - Hot Moulded Carbon Composition Resistors

Once known as the resistor of choice for designs demanding low noise, low inductance and pulse performance; the Allen Bradley - Hot Moulded Carbon Composition Resistors were the first point of call for professional audio designs and still to this day are considered by many as unsurpassed for certain applications.  Although since production ceased of the Allen Bradley - Hot Moulded Carbon Composition Resistors it has been a requirement to look for suitable alternatives.

Carbon Composition Resistors

If we consider the in-circuit performance attainable by using carbon composition resistors, it soon became apparent that it was not only audio applications where carbon composition resistors were a preference to other resistor technologies.  A solid uniform resistive element resulted in a resistor that could handle high surges, peak power or energy - example applications included power charging/ discharging, inrush current limiting, RC Snubbers, High Voltage Power Supplies, Fuel Ignition Systems, etc

The Ohmite OX/OY Series - Ceramic Composition resistor has long been viewed as the most suitable replacement to carbon composition.  As ceramic composition offers many of the associated features of a carbon composition resistor with a significant advantage in its ability not to drift due to moisture.

The Ohmite OX/OY Series is available in two power ratings:

  • OX Series - 1W Ceramic Composition Resistor
  • OY Series - 2W Ceramic Composition Resistor

However, with reported manufacturer leadtimes currently of 53 weeks for the Ohmite OX/OY Series - this has created a situation where many now have no option but to consider alternatives to ceramic composition resistors!

Firstohm Surge Safety Resistor (SSR Series)

Firstohm (First Resistor & Condenser Co. Ltd.) with more than 50 Years of resistor manufacturing expertise have developed their SSR Series (Surge Safety Resistor) which utilises an enhanced metal film and is designed solely for the purpose of replacing carbon or ceramic composition resistors. 

The SSR100 resistor is available in 1W @ 70DegC, 350V and with a Max Permissible Surge Voltage of 20kV and can be considered as a replacement to the Ohmite OX Series.

The SSR200 resistor is available in 2W @ 70DegC, 400V and with a Max Permissible Surge Voltage of 22.5kV and can be considered as a replacement to the Ohmite OY Series.

Firstohm’s in-house R&D department boasts an extensive range of high voltage and ancillary test equipment and are experienced in performing tests to international standards.  Furthermore, Firstohm can replicate customer specific test conditions allowing engineers to quickly gain confidence from the outset that any solution proposed by Firstohm warrants further consideration, in support of their own internal qualification procedure. 

Please contact us for more information such as to discuss your specific test requirements, request samples or enquire about price and availability.


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