8mm Forum: Bell & Howell 642 Exciter Lamp

This is topic Bell & Howell 642 Exciter Lamp in forum 16mm Forum at 8mm Forum.

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Posted by Paul Mason (Member # 4015) on June 24, 2014, 03:14 AM:

Dear All,
I have recently bought a Bell & Howell 642 projector. All seems well but the exciter lamp is missing. The handbook says it needs a 6 volts 1 amp lamp and quotes a Bell & Howell part number I don't recognise. I have several spare G27 4V 0.75A lamps used in later Bell & Howells but no 6V version. Do I need a G5 lamp (this has the same P30s base)? Has anyone tried using the 4V lamp and how long do they last? All comments gratefully received.

Posted by Maurice Leakey (Member # 916) on June 24, 2014, 05:06 AM:

Paul
The lamp you need is a G/40. (6 volt 1 amp.)
The G/27 you have is for Elfs and Elmos, the later B&H projectors used the G/29.

Posted by Paul Mason (Member # 4015) on June 24, 2014, 06:17 AM:

Maurice,
Many thanks for your definitive answer. I should have said I have G29s as these are horizontal filaments not G27s with vertical filaments. G5s are definitely wrong as these also have vertical filaments. A trap for the unwary.

Posted by Dominique De Bast (Member # 3798) on June 24, 2014, 11:26 AM:

I was trapped a few months ago. I was wondering why the bulb I put as a replacement was not working. Maurice gave me the answer by explaining some exciter lamps only differ by the position of the filmament. Thanks again, Maurice.

Posted by Maurice Leakey (Member # 916) on June 24, 2014, 02:57 PM:

I have mentioned this a long time ago but I'll repeat it. A non-movie friend had acquired a Bell & Howell TQII which he wanted to sell on to me. When I had a chance to try it out the sound was so bad it was barely audible.

Obviously it needed some attention so I got the 1658 for £15, this was in 1994.

When I got the projector home I gave it a good check-over and discovered it was fitted with a G/27 exciter lamp. After replacing it with the correct G/29 it worked like a charm.

As Dominque said the lamps only difference is the position of their filament, the G/27 operates (Elf and Elmo) in a horizontal position, the G/29 for the Bell & Howells operates in a vertical position.

I still have the projector and over the last few years have spent £75 on routine maintenance. It's a useful projector as it also has magnetic playback capabilities.

Posted by Paul Mason (Member # 4015) on June 25, 2014, 05:46 AM:

I think the filament positions are the other way round
G/27 vertical, G/29 horizontal as can be seen in several Ebay listings.

Posted by Maurice Leakey (Member # 916) on June 25, 2014, 02:45 PM:

Paul
You are right, but I was referring to the lamps' operating positions in the projectors, not the filament.
In each position the filaments of the two different lamps are, of course, horizontal.

Posted by Paul Mason (Member # 4015) on June 26, 2014, 03:16 AM:

Maurice,
Apologies for not reading your post properly. I am not familiar with the use of the G/27 lamps. I suppose it would be rather difficult to focus a vertical filament onto a horizontal slit.

Posted by Paul Mason (Member # 4015) on July 01, 2014, 02:55 AM:

I have now fitted a G/40 exciter lamp as suggested by Maurice. It seems to be physically identical to the G/29 except for a slightly longer filament. Incidentally, according to the 1960 Bell & Howell book by Edwyn Gilmour the 600 range up to the 640 require a G/29. Bell & Howell then changed this to the G/40 for the 641 onwards before reverting to the G/29 in 1969 for the TQ models!! [Confused]

Posted by Maurice Leakey (Member # 916) on July 01, 2014, 07:58 AM:

The very first British made Bell & Howell, the Bell & Howell-Gaumont 601, used the G/19 or G/4. These were virtually the same as the G/29 but without the "skirt".

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