Bell & Howell 16mm Projector Model 631

RM 1500 *excluding postage

FILMOSOUND Model 631
In great working condition. Regularly serviced.
Made in England
Origin : 1950's 
Included:
- transformer for 240V
- pairing speaker (paired design with projector)
- 2 x 16mm spools
- Bausch & Lomb SCOPE lens

All items/equipments included are vintage, original and fully functional.

Contact us for more information and close up photos. 
Email : qiyaoleong@gmail.com
Tel : 6017-5911978 

Background information:

Bell & Howell 640, 16mm Optical and magnetic sound (1957)
 

     After the war Bell & Howell machines were built under licence in the England by Rank-Gaumont at their factory in Mitchelldean, Gloucestershire. The 640 was the last British built blimp style Filmosound machine and was introduced in approx 1957. These machines used the original Bell & Howell picture head mounted on a well designed amplifier/scanner. To minimise noise whilst running the mechanism was mounted inside a wooden blimp cabinet with doors that could be shut during the show. 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

View  ACW Review on model 640(750k JPG)
View 630 Amplifier Circuit Diagram (164k GIF)
View 640 Amplifier Circuit Diagram (184k GIF)
(source:http://www.schimmel.talktalk.net/cine/)