As we seek workable solutions to ever more problems with the old style Hammonds and Leslies, sometimes questions arise which we would appreciate help with. Should any visitors to this website be able to assist us with any of these matters, we would be very pleased to hear from them.
* Replacing generator filter capacitors. To answer this very specific question, we seek contact with someone who was actually concerned with the manufacture of Hammond's tone wheel generators. As outlined elsewhere on this website, we put much effort into the intonation of the generator, partly by accurately determining the exact capacitor value required by each pickup/transformer to produce ideal LCR resonance. We believe that the superb results produced by this lengthy procedure justifies the all the tedious work. Our question is this; did Hammond pay this much attention to the accurate resonance of each individual circuit? This would have involved measuring and analysing each circuit, and then selecting an ideal capacitor from a systematically arranged assortment of carefully measured capacitors. The older, yellow capacitors are marked "0.105uF". Did they have the great uniformity and accuracy implied by this? If so, were the coils and transformers manufactured to such a fine degree of accuracy that only one value of capacitor, 0.105uF, need to be stocked? After 35 to 65 years of ageing, they have now increased by up to 200%, which makes nonsense of resonant accuracy. Hence our confusion.
* Accurate felt guillotine. Increasingly often, organs are encountered with excessive side play of the keys, due to wear in the key comb felts. Riveted to each finger of the key combs is a small rectangle of high quality, woven felt, which we must learn how to replace before our stock of new key combs runs out.

A new B-3 key comb.

The length of each felt is about 9.5mm, but needs to be of no great accuracy. The width, however, must be exact; too narrow, and the key will flop from side to side. Too wide, and the key will stick. Thus, 9.5mm strips of felt must be cut from a roll of suitable felt, and each strip must then be accurately cut up into rectangles of width 9mm to 11mm, according to the key comb concerned. The B-3 has two different widths on the same key comb, which is just about discernible in the picture. The guillotine must be equipped with a screw adjuster, which determines the width of each cut piece of felt. Trial and error will show what width produces a suitable compromise between floppy and stiff key movement, after which a large number of identical rectangles can then be cut. A second tool is then required to punch a 3mm rivet hole in the dead centre of each rectangular felt, and a third tool to rivet the felt to the key comb. The tubular rivets, which are 3.2mm x 6mm, are available to us locally. We do not know if tools answering to this description are available ready-made, or if they can be adapted from ready-made tools, or if they will need to be specially made.


Top octave generator I.C.s Several attractive Hammond models from the 70's and early 80's have a top octave generator consisting of two separate I.C.s which are becoming hard to find. The Hammond part numbers are 075-047242 & 075-047243. Other commercial equivalent I.C.s have the following markings; S2555 & S2556, MC1183 & MC1184, MM5832N & MM5833N. Does anyone know where these can be obtained? Or has anyone designed a one-chip replacement board? [Note to technicians; these two I.C.s become noticeably warm under normal operating conditions, and their life-expectancy can be extended by fitting I.C. heat sinks]


Transistor tester/characteristics meter. These appear to have fallen from fashion, since all we can find on the market are small test boxes of the 'go/no go' kind. We need a universal instrument that can measure the performance of different transistor types, with an accompanying transistor data manual, against which the health of ageing transistors can be compared. We especially need to measure Hfe of power transistors like the 2N3055, in order to produce matched pairs. Does anyone know where we could get hold of such an test instrument? We have a very good AVO valve characteristic meter, and it seems odd that we are unable to test transistors to the same degree of sophistication as our valves. Perhaps AVO made a transistor tester?

Is there an equivalent to this fine instrument, but for testing transistors instead of valves?