REVEALING THE ALARMING TRUTH
all the strange myths that have grown up around Hammond organs over the
years, there is one which is particularly illogical and decidedly unhealthy.
It is this; that a Hammond organ is Immortal, and will continue to Live
for all Eternity. The belief is that no matter how mistreated, or under-serviced,
it will somehow manage to survive just a few more gigs. And if it has
been oiled once or twice since manufacture, and has been occasionally
polished, then it will positively live for ever. If you own a tone wheel
Hammond, and find the concept distressing that your organ does have a
finite life, then you may prefer to log off now, and avoid the painful
reading that follows. This document is concerned with the increasing number
of serious technical problems encountered by us in our renovation work.
However well equipped our workshop may be, we are constantly obliged to
wrestle with new difficulties. New renovation techniques have to be developed,
which require specially made tools and machines, as well as hand made
spare parts. The ever increasing demands on the Hammond renovation specialist
is however only one aspect of the present situation; another aspect is
to make Hammond owners aware of the problems to be overcome, if their
organs are to survive. In this respect, there appears to be little or
no help to be sought elsewhere on the internet, where information is usually
what appears in old Hammond publicity material and service manuals. It
is easier to understand why this 'keep-me-happy information' is so abundant,
when one realises that the alternative is to consider the alarming nature
of the truth. The small, unattended problems of the past became big problems,
and more recently have become acute. In just a few years from now, most
of the important models will have become so decrepit that they will be
unplayable. Then, after a further period of neglect they will finally
be discarded. It is simple to summarise the present day situation for
models such as the A-100, the C-3 and the mighty B-3.
Caustic foam rubber residue on resistance wires
This magnified image, taken with special photographic equipment, should strike horror into the hearts of ABC owners. This is by no means a photograph of an exceptional case; every ABC organ that has been opened in our workshop during the last four years has looked like this. Using the match head for comparison, the thinness of the multitude of resistance wires can be appreciated. The different colours of enamel are codes indicating different specific resistances. The black bubbling mass at the bottom is the decomposing foam rubber. The caustic nature of this unpleasant substance reveals itself where a distinctive green tinge appears, as on the arching resistance wires that can be seen covered with it. Here, the protective enamel has finally succumbed to the aggressive chemical attack, hereafter the resistance wire itself is more easily eaten through. When attacked chemically, it is the copper constituent of the resistance wire alloy that produces the characteristic green colour, and such wires must always be replaced. On this particular manual, two wires were already eaten through, another wire disintegrated during the cleaning process and a fourth wire (the one shown in the picture) was so poor that it was removed and replaced. Organs are now turning up with many more than just four ruptured wires, and the situation is steadily deteriorating. There can be little doubt that what we term 'mad cow disease' is the greatest single threat to ABC organs, and it will be this, before anything else, that puts them in their graves.
As mad cow disease progresses, a secondary effect is bound to develop which is already in evidence here in Sweden, where an appreciable number of NGR organs are in existence. ABC instruments fall into a two distinct price groups on the open market, in which organs that are cleansed of the caustic strip are steadily becoming more valuable whilst those that have not are being avoided. It is very unfortunate that younger musicians, who would have the greatest long term benefit of NGR organs, are generally unable to afford them. Never the less, we would encourage any musician who is serious about his playing and his instrument, to make an NGR organ his objective, despite the unavoidably higher price.
The offending caustic strip on the inside of the covering plate. Note the indentation along the strip, where material has separated away and is now stuck to the resistance wires.
Palladium wire worn through, curling up and ready to short a tone on permanently.
When the wire reaches the contact, a tone is switched on and is impossible to get rid of, except by never using the drawbar to which that bus bar is attached. If the oxidised and unreliable key contacts tempt the player to use the bus bar shifter, which slides all 9 bus bars sidewards, all the curled up palladium wires find a contact to short against! Not only that, but all the contacts will then be poised above areas of the bus bars that have an accumulation of 35 years of dirt and hardened bus bar grease on them. Suddenly, half the keys will ceased to work at all, whilst a number of the rest may sound continuously. Clearly, there are lessons to be learnt here.
the Spirits Free
Generator filter capacitors of this older type must be replaced.
capacitors are now so very inaccurate (they are supposed to be within
1%) that the unevenness and breathy sound is disturbingly predominant,
treble boost or not. This is how the capacitors play their role; the signal
from each tone wheel and pickup assembly is far from pure, and contains
a host of overtones, undertones and signals leaking in from other pickups.
From frequency 44, these impurities are deemed to be so disturbing that
filters are used to 'cleanse' them. From 44 to 48 each signal passes through
a small transformer whose inductance is sufficient to trim off overtones.
From 49 to 91, a capacitor is added to each transformer, forming a tuned
circuit which boosts the wanted frequency and rejects all others. This
resonant circuit reacts to a specific frequency determined by the resistance
and inductance of the pickup and transformer, as well as the value of
the capacitor. When the mathematics are correct, the frequency of this
resonant circuit coincides exactly with that of the tone wheel. But this
clever balancing act of electrical parameters collapses when the capacitor's
value starts wandering. As the old style capacitors age, their values
increase greatly - we have recorded increases of up to 200%! - causing
poorly tuned resonant circuits which produce weak and impure signals.
The newer, maroon red capacitors do not exhibit this tendency to the same
extent. Since all the individual circuits are different, special equipment
is required to determine the optimum capacitance for each, after which
capacitors of the appropriate values are installed. This immediately has
two effects; one is mathematical and the other one is more spiritual.
Firstly, as if by magic, all 91 outputs from the generator fall exactly
into their correct relationship to each other. Secondly, the astonishing
clarity of sound produced by this operation is probably what prompted
the comment about the sound quality of an NGR A-100, likening it to the
view from a mountain top after the fog has risen. There remains, however,
an impressive grand finale, for now is the right time to add treble boost.
A truly spectacular organ sound emerges revealing a degree of soul and
character that only a tone wheel Hammond could produce; it's spirits have
been set free.
A so-called split (i.e. ruined) L-100. Why did they do it?!
Even if the amputation was conducted with surgical precision, which they almost never are, there is a host of reasons for holding these abominations in such contempt. To avoid dwelling on a long and tedious list of problems that might resemble a list of charges read out as a prisoner was led away to the gallows, let the point be proven by the existence of our L-100 graveyard. If you are looking for a Hammond, and a sawn-off L-100 turns up, our advice is to avoid it at all costs. There are, however, two factory-made split L-100s, the Porta-B and the L100P, which were designed to be dismounted and moved from gig to gig. It is doubtful, though, that the musicians using these models would entirely agree with Hammond's notion of 'portability'.
No-one would question the immense improvement to the sound of a Hammond organ brought about by connecting it to Leslie cabinet. But these too are ageing, and many are in urgent need of attention. For those who are reasonably handy, there are several service jobs which can be done at home by the owner, and details of these are found under Care of Leslie Cabinets. In common with Hammond organs, ever more problems are being encountered, some of which the owner could tackle himself, and some which he could not. In particular is the increasingly poor state of the motors, due mainly to insufficient lubrication. Whilst moderate wear can be taken care of with a thorough service (grade 4 job), severe wear can only be solved by replacing the axles and bearings, along with all the numerous different washers, spacers and springs. (Job grade 5). By comparison, problems with the windings are infrequent, and if more than one motor is burnt out in the same cabinet, this has usually been caused by the inadvertent connection of 110volt motors to a 230volt supply. When it comes to the speed control systems, a giant blind spot is exhibited by both those who designed Leslies and those who use them. It is incomprehensible how such a crude, dangerous and noisy arrangement can have been left unattended for so long. Not the slightest glimmer of modern technology entered the arena until the arrival of the model 760, which was unjustly greeted with derision rather than admiration. [The 760 and its superb walnut counterpart, the 770, have a remarkable number of virtues; after upgrading work has been carried out, they form the basis of our top-of-the-line Master Class series]. The mechanical clicks from the relays in the older models can be very distracting in quiet playing environments. If sensitive audio equipment is nearby, this is prone to picking up electrical interference from the relay's sparking contacts. There is also the question of the relay's terrifically high control voltage, whose magnitude has more in common with a Van de Graaf generator than a musical instrument. Since the task of developing a modern replacement for the old relay system is usually beyond the owner, the responsibility here is on the organ engineer, who should be routinely performing this operation on all Leslies passing through their workshop. We use thick film solid state relays incorporating a zero crossing switch, with a 5 volt control system, and have not sold a Leslie for 13 years without replacing the old system.
Age is now taking its toll on the Leslie's audio system, as well as the mechanical components. The increasingly poor treble response of the V-21 driver is misinterpreted as 'charming softness'. The reality is that old age, oil from the treble rotor, and heat from the speech coil, are all contributing to the gradual deterioration of the membrane's phenolic material, whose high frequency performance diminishes as the membrane loses its suppleness. For use at home or in churches, the V-21 may still have its purpose, but the final phase of 'setting the spirits free' consists of replacing the old driver with a newer alternative having better efficiency, especially above 5kHz. In addition, the greater power handling capacity of modern drivers is useful, considering the greater volume levels common today. To fulfill the requirements of certain stage musicians for very high volume, we use two large, high efficiency drivers in a twin adapter. For more volume, we would recommend double Leslie cabinets, and if even more volume than that is sought, we would advise seeing a hearing-specialist! There is an odd problem now creeping into the picture, which places undue strain on the treble driver - the cross-over network of the older models incorporates a double paper capacitor, the value of which is now gradually rising (in the same manner as those on the tone wheel generator filters). This upsets the careful balance of the network's components, causing bass to leak into the treble circuit. The intended cross-over point of 800Hz is very low for a treble speaker to manage at all, and lowering this point still further places great strain on an old driver. This capacitor should be checked. De-solder the red and black wires first. The two values should be 7.8uF and 12.5uF, and if these have increased by more than 20% or so, they should be replaced. Modern bipolar capacitors are quite good enough, and their low price allows bunching several together to achieve the correct values. (Use 4.7uF + 3.3uF and 10uF + 2.2uF. 50volt rating is sufficient)
or 60Hz? BEWARE !
50 Hz versions existed as long ago as 1937.
Considering, then, that as long as seventy years ago the problem of 50Hz contra 60Hz was solved competently and elegantly by the organ's own creator, is it not beyond belief that 60Hz organs are still finding their way to Europe by dubious means, instead of staying where they should be; in the USA ! ! Once having landed on these foreign shores, these poor 'illegal immigrants' have to suffer the indignity of hideous back-street botch jobs to convert them to 50Hz, after which they are sold to gullible customers who are unaware of their low value. All the electromechanical components are different - the synchronous motor, the generator, the start motor, and the vibrato scanner, and 60Hz spare parts are unavailable in Europe, should work ever have to be done on them. If you are considering buying a Hammond tone wheel organ, avoid being the 'gullible customer' - insist on seeing the organ's registration plate. If it says 60 Hz, beware! Be especially suspicious if the plate is 'conveniently' missing or has been tampered with. Remember, there is no shortage of Hammonds in Europe, so buy a 50Hz model. There is, however, a shortage in professionally renovated tone wheel models.
(a) Three un-insulated fuse holders are placed on the metal side of the power supply chassis, which is screwed to the floor of the cabinet. The 5mm spacing between these fuse holders is very unfortunate, being exactly that of the fuses themselves. If you have to replace a fuse, always, always pull out the mains plug first! Then check visually that you place the new fuse correctly in its holder, and not in the space between two holders, in which case the metal caps will form a direct short in the power circuits, and they are no longer protected by a fuse! BANG! Fetch a torch, get on your knees, and watch what you are doing.
(b) The lack of louvres degrades the sound pitifully, but you can improve things yourself by installing sound shields. Cut out six pieces of hardboard, all slightly longer than the rectangular openings where the louvres are supposed to be. Screw these to the inside of the cabinet, using 7mm spacers to create a gap between the hardboard an the cabinet, so shielding off the rotor's direct sound, but providing an exit slit for reflected sound. The spacers at the centres of the treble shields must be less than 7mm, or the rotor will scrape just there. Job grade 2.