29-01-2023, 10:35 AM
(This post was last modified: 29-01-2023, 10:39 AM by Lucien Nunes.)
I'm still not ready to start on troubleshooting that Wurlitzer because I'm very busy with MEET, so in the meantime here are some pictures to marvel at.
This is a Burge organ from the early 1960s. Kenneth Burge was an electronic engineer who was involved with some key players in the UK electronic organ industry, as the designer of Livingstone organs and later the founder of Wyvern Organs where he soon teamed up with Arthur Lord (ex. Compton general manager), to form a successful company still operated by Graham Lord today.
This organ, unlike the Comptons which use electromechanical generators and additive synthesis, uses electronic oscillators and frequency dividers to generate a set of frequencies, from which all the necessary wave-shapes are filtered. Thus there are 12 LC Hartley oscillators, one for each semitone of the top octave (actually one octave higher, as the oscillator outputs are not used directly) followed by six or seven stages of divide-by-two. Each oscillator and its dividers occupies one of the 12 PCBs in the central rack, as usual each stage using one half of a double triode. The PCBs are identical except for the values of capacitors, which vary somewhat across the frequency range to allow the optimum adjustment range either side of the working frequency
The signals are keyed at multiple footages by multiple key contacts and collected on a set of footage bus wires separate for each division. These are then filtered and mixed according to the selected stops by the tone-shaping assembly behind the stoprail. There is a chunk of filtering that is not visible in these pics. The final audio processing is done on the vertical chassis on the console end. The amplifier and power supply are at the bottom, on top of the relay and pin-patch unit that controls the stops. The generators therefore contain 49 valves (there is an extra divider stage on the C-generator on account of the 61st key), the tone forming about 24 valves, and the amplifier and PSU ten, for a total of 83 bottles. The two channel amplifier handles two divisions separately, driving two fullrange static speaker cabinets.
This organ is partly restored (e.g. amps and PSU fully overhauled) making it generally playable. It suffers from some contact problems through infrequent use, drifty and increasingly leaky paper caps in the generators, and needs a bit of fettling generally. It is a pity about the caps - they are high-quality papers that would have seemed like a robust choice at the time, but their drift, as much as their leakage, has started to cause trouble. A similar but smaller / cheaper organ by the same firm, made very soon after this one, has Wima polyester caps, which might have been cheaper but are still perfectly workable today.
This is a Burge organ from the early 1960s. Kenneth Burge was an electronic engineer who was involved with some key players in the UK electronic organ industry, as the designer of Livingstone organs and later the founder of Wyvern Organs where he soon teamed up with Arthur Lord (ex. Compton general manager), to form a successful company still operated by Graham Lord today.
This organ, unlike the Comptons which use electromechanical generators and additive synthesis, uses electronic oscillators and frequency dividers to generate a set of frequencies, from which all the necessary wave-shapes are filtered. Thus there are 12 LC Hartley oscillators, one for each semitone of the top octave (actually one octave higher, as the oscillator outputs are not used directly) followed by six or seven stages of divide-by-two. Each oscillator and its dividers occupies one of the 12 PCBs in the central rack, as usual each stage using one half of a double triode. The PCBs are identical except for the values of capacitors, which vary somewhat across the frequency range to allow the optimum adjustment range either side of the working frequency
The signals are keyed at multiple footages by multiple key contacts and collected on a set of footage bus wires separate for each division. These are then filtered and mixed according to the selected stops by the tone-shaping assembly behind the stoprail. There is a chunk of filtering that is not visible in these pics. The final audio processing is done on the vertical chassis on the console end. The amplifier and power supply are at the bottom, on top of the relay and pin-patch unit that controls the stops. The generators therefore contain 49 valves (there is an extra divider stage on the C-generator on account of the 61st key), the tone forming about 24 valves, and the amplifier and PSU ten, for a total of 83 bottles. The two channel amplifier handles two divisions separately, driving two fullrange static speaker cabinets.
This organ is partly restored (e.g. amps and PSU fully overhauled) making it generally playable. It suffers from some contact problems through infrequent use, drifty and increasingly leaky paper caps in the generators, and needs a bit of fettling generally. It is a pity about the caps - they are high-quality papers that would have seemed like a robust choice at the time, but their drift, as much as their leakage, has started to cause trouble. A similar but smaller / cheaper organ by the same firm, made very soon after this one, has Wima polyester caps, which might have been cheaper but are still perfectly workable today.
