Cine projectors do not seem to attract collectors in the same way as radios or still cameras. This is a shame because a sound projector offers a very nice blend of precision mechanics and electronics in one box (much like a tape recorder), this makes them interesting to work on. In addition if appropriate films are available then they are the best 'time machines' available, showing you what the original owners may have seen. At the end of the day no matter how old a radio is when restored it still only receives modern stations!
Safety film specifically aimed at the amateur was introduced by Pathe, France in 1922 with their 9.5mm format, a few months later Kodak in the USA introduced their 16mm gauge. Sound was introduced to 16mm in 1932 showing it was already leaving its amateur beginnings. To reduce movie making costs even further Kodak subsequently introduced the 8mm gauge.
WWII Bought a big boost to 16mm's fortunes both as a training and entertainment medium for the services. It was also in use around the world. 9.5mm by contrast was only ever really successful in France and her immediate neighbours, and was never taken up by professional users.
After the war several American designed 16mm machines were built in Britain under licence to serve the training market created by returning service personnel. Bell & Howell, Ampro and Victor were the biggest names. 9.5mm carried on in its traditional home market.
The following are a few examples from my collection:
Return to index
To cut costs there is no damping between the sprocket and the sound flywheel and the motor is not really powerful enough for the job. A centrifugal governor regulates the speed of the motor and is fed via a series rheostat. This must be only advanced far enough for the governor to take over to minimise wow. As the projector warms up the rheostat should be backed off to minimise the current through the govenor contacts. This is most definitely not a 'load and go' machine, it has to be driven and nursed. The fitted rheostats were a poor design and eventually fail, I now use an external Variac. The lens shown is not the original, but an 20mm F1.5 8mm design turned down in a lathe to fit the 7/8" barrel. The original was F2.8ish so didn't let much light through. It is said that the lens as designed was so bad that a washer was inserted to reduce it to F2.8 and make it tolerably sharp! The Son inherits the Gem's tight film path, but the film damage potential is worse since the flywheel must also be driven by the film, which goes through a 270 degree bend immediately before the sprocket..
The original amplifier as fitted to my unit is octal valve based delivering approx 3.5W from a 6V6GT into the 10" speaker built into the carrying case. Later units were fitted with miniature 8 pin valve based amplifiers and 8" speakers. It is rumoured that at least some of the amplifiers were built by Trix, then a well-known firm in the PA amplifier field.
The amplifier circuit itself is a bit strange - the first 6SH7 pentode was originally operated under starvation conditions (a prevoius owner has taken out the resistor that originally dropped this valve's heater supply to 5V), but the next was strapped as a triode. There is no feedback and the output gives 2.5% THD for 1 watt out. Why the 2nd stage wasn't used as a pentode allowing some spare gain and a bit of NFB I have no idea!
The projector does work and the results aren't actually that bad. You have to bear in mind that in 1951 few people had TV so the novelty of sound movies in the home was quite something. Eventually Pathescope folded at the end of the fifties, TV stealing their market for printed films and cheaper 8mm colour stock tempting the movie makers.
Restoration Problems: Governor, rheostat, gate, drive belts, claw etc. etc.
The following files are JPG's
View original Son data sheet (119k)
View 1952 ACW Son Review (305k)
Reflecting its American parentage these machines run on 110V and have switches that are up for on. The standard British 240V is reduced by an external (and very heavy) auto-transformer. Some other machines were built to run direct on 240V, but screen illumination suffered as the all the light from the less compact filament could not be condensed through the gate opening.
The 640 also features magnetic sound record and replay in addition to the standard optical, allowing the professional user or well-heeled amateur to produce movies with synchronised sound. Other models in the series were the 631, with optical sound only, and the 636 which was optical sound only with direct 240V operation.
The 640 was the 2nd B&H model offered in Britain with magnetic sound, the first was the 630 (known in US as model 202) introduced in about 1954. The 630 had an extra tall case to allow the amplifier mains transformer to be mounted well away from the sensitive heads/amplifier. In the 640 the amplifier was radically re-designed to avoid the need for this. In this machine a pair of UL84 pentodes form a power oscillator which runs directly off of the rectified 110V, and via a high frequency transformer supply the power to run the rest of the amplifier - a forerunner of today's switch mode PSUs. This solution is brilliant and achieves several desired features all at once:
A high frequency source is available to run the exciter lamp to eliminate mains hum, it can also supply the erase head and record bias. The pre-amp valve heaters are also run at HF to eliminate mains hum. No conventional mains transformer is required eliminating weight and a potential hum source. Although some parts of the amp are connected direct to the rectified 110V supply the inputs and outputs remain isolated giving the safety of a conventional AC design. A further pair of UL84's in push-pull give the amplifier an output power of approx 15W.
The above photo shows the 640 (left) next to the 630.
By modern standards the screen illumination from these machines is a bit lacking, but they still have some advantages: When showing 'thin' prints less light is desirable, also due to the small sprocket diameter and double claw shuttle they are kinder to shrunken film than their later siblings.
Sound quality is also first rate. but on my machine I found that despite all the care in the design of the amp mains hum was unacceptable. This was traced to a few inches of unscreened wire connecting up the tone control circuit, when replaced with screened lead the hum fell to the expected low level. It should be noted that these machines need a longer amp warm up than most since there is a double wait: First the power oscillator must warm up, then only once it is going will the pre-amp valves start to heat.
The original B&H projectors all needed regular oiling, this machine must be a fairly late example because the mechanism is sealed and greased. Unfortunately it still has the oiling tubes attached to the blimp, but going nowhere, it even came with an oil bottle. I wonder if the previous owner used to oil it and then wonder why he ended up with oil everywhere!?!
With the current glut of modern ex-school 16mm projectors on the 2nd hand market these older machines are being dumped, which is a pity since they still have a lot to offer. In particular there is very little plastic and no built-in obsolescence
Restoration problems: Hum, General clean out and greasing.
View ACW Review (750k JPG)
View 630 Amplifier Circuit Diagram (164k GIF)
View 640 Amplifier Circuit Diagram (184k GIF)
Like the 640 and 630 above the 8D644 also features full magnetic sound facilities. The series also featured the 8D642 which was optical sound only, and the 8D643 which added magnetic playback.
Noise levels were reduced by re-designing the intermittant to operate at frame speed rather than 3* as in the previous models. In addition the high speed brushed universal motor + governor was replaced by a quiet running, capacitor start, AC only induction motor. All this made a blimp unnecessary.
Improved lamp and condenser design meant that a 240V lamp could now deliver good enough results to make a 110V lamp and auto-transformer unnecessary. Lens barrel diameter was also increased to allow bigger aperture projection lenses. In the 70's light output would rise further with the development of 24V QI, lighting this was introduced with the TQ1 series alongside fully transistorised amplification.
There were also some weaknesses, in particular all post blimp B&H projectors have used a composite worm gear as part of the mechanism. The gear has plastic teeth moulded onto an aluminium centre, eventually the teeth crack rendering the projector useless. Replacement worms are available, and are now machined from solid plastic, but fitting them is fiddly and very time consuming. Any would-be purchaser of one of these machines should find out if the worm has been changed.
These machines suffer badly from mains hum, I have heard 3 different samples and they were all just as bad. The main problem seems to be the voltage doubler type HT supply fitted in place of the conventional EZ81 rectifier used on the older 644. On my machine and that of a friend I have beefed up the PSU smoothing to reduce the hum to inaudible levels. Fitting separate cathode resistors to the output valves is also beneficial, reducing the need for valve matching and allowing better hum cancellation in the output transformer. The output valves used are a pair of EL84's in push-pull giving about 15W.
Restoration problems: HUM, worm gear, dead bypass cap in solid-state magnetic playback pre-amp.