A recently reported (T.J. Davies, R.G. Compton, J. Electroanal. Chem. 585 (2005) 63) two dimensional simulation method for the linear sweep response of arrays of randomly distributed microdise electrodes is applied to 'RAM (TM) electrodes' (S. Fletcher, M.D. Horne, Electrochem. Commun. 1 (1999) 502) in which thousands of carbon wires are sealed into epoxy resin producing random assembles of microdiscs. Theory and experiment are found to be consistent and it is demonstrated that the former allows the number of 'dead' electrodes in the array to be counted. In particular it is concluded by voltammetric means above that only ca. 30% of the carbon fibres emerging at the surface are electrochemically active. (c) 2006 Elsevier B.V. All rights reserved.