Custom Circuits Ltd

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Testing facilities

Custom Circuits Ltd has all the necessary test facilities for measuring voltages and currents found in all types of equipment. These can be made using high accuracy multimeters such as the Fluke 287 combined with non intrusive current probes such as the Fluke i30. Signal and power waveforms can also be captured using a 4 channel, fully isolated Tektronix oscilloscope with both standard and specialist high voltage probes. Ideal for working on valve amplifiers with their very high operating voltages. Test data can be downloaded and documented when required.

Test equipment

  • Tektronix TPS2024 oscilloscope
  • Picoscope 5444B oscilloscope with AWG
  • Fluke 287 DMM
  • Fluke current probes i30
  • Picoscope high voltage differential probe
  • Peak atlas LCR40 passive component analyser
  • Peak atlas DCA Pro DCA75 active component analyser
  • Peak atlas ESR70 capacitance and ESR tester
  • Other DMMs, various
  • Insulation testers
  • Valve bias current measurement adaptors
  • Signal generators, various
  • Adjustable power supplies, ac and dc, various up to 300V
  • Valve performance curve tracer
  • Audiomatica loudspeaker response analyser
  • Martindale 2100 Portable Appliance Tester





Semiconductor Testing




NEW!!! Valve Testing


We now also have the capability to fully test Audio Valves using a computer controlled valve tester. This enables us to test any commonly available audio valve and determine that the heater functions correctly, the Transfer Characteristic is within specification and that where necessary, the valves performance is matched so as to ensure push-pull output stages are correctly balanced.


Typical preamp valve (ECC81 and ECC83) Anode Characteristics are shown below together with typical load and power dissipation traces in each case.