Film-Tech Forum ARCHIVE: Early Bell & Howell projectors

This is topic Early Bell & Howell projectors in forum Film Handlers' Forum at Film-Tech Forum ARCHIVE.

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Posted by Robert Crewdson (Member # 6256) on 05-30-2011, 07:49 AM:

I have a Bell & Howell 601, which is the UK equivalent of the 179.
My question concerns the cleaning of the optical system. The manual states that as well as the lens, which has one side facing the exciter lamp, and the other facing the sound drum, there is a mirror which can be seen by looking down behind the sound drum from in front and above the machine.

I have never been able to see any mirror, and I need to clean it to improve sound quality.

Is there anyone on here familier with these Bell & howell projectors in blimp cases, who can tell me exactly where to look, and what the mirror actually looks like.

Posted by Robert E. Allen (Member # 1351) on 05-30-2011, 11:19 AM:

Contact Ken Layton who occasionally posts on this forum. He may be able to help.

[ 05-30-2011, 03:13 PM: Message edited by: Adam Martin ]

Posted by Jeff Taylor (Member # 443) on 05-30-2011, 11:28 AM:

Ken's B&H 179 service manual has been scanned and is listed under the warehouse section of this website, and includes instructions for cleaning the mirror. Note, you should also check the installed exciter, as several would fit those models but you MUST have the one with the correct filament layout (vertical/horizontal/etc) to get proper sound. Make sure some helpful person hasn't installed the wrong one! Good luck.

Posted by Robert Crewdson (Member # 6256) on 05-30-2011, 01:48 PM:

I will check the exciter lamp, although I think it is the correct one. Unfortunately, the wording of the instruction manual for the 179 is identical to the 601; so no help there.

Posted by Bruce Hansen (Member # 281) on 05-30-2011, 04:48 PM:

If this is the projector that I thnking it is, without film around the sound drum, the excitor light should hit a small mirror right behind where the sound track (on the film) would be. The mirror is used to reflect the light that has just gone through the sound track, onto the photoTUBE.

Posted by Stephen Furley (Member # 1277) on 05-30-2011, 05:24 PM:

I've never actually seen the 601, but if it's like the slightly later 631, 636, 640 etc. then you can get better access to the mirror if you drop the amplifier out of the bottom of the projector. The photocell is mounted on the amplifier, and with that out of the way you can get to the mirror.

Sound was never the strong point on these older projectors, but they will run 'difficult' prints; I've never lost a loop on one.

Posted by Jeff Taylor (Member # 443) on 05-30-2011, 06:05 PM:

...and dropping the amp on a 1xx-3xx Bell & Howell is a 1 minute job if you're slightly careful to make sure it doesn't drop or damage cables. Unplug the cables, unscrew the four screws and you're there. The older 400 RCA's had a similar mirror arrangement, but I was always concerned about fussing with it as it was undoubtedly glued in and older than dirt, and never felt the need to touch it to improve the sound.

Posted by Phillip Grace (Member # 2262) on 06-01-2011, 01:44 AM:

Bruce has the answer here. The mirror deflects the light which has passed through the film onto the PE Cell inside the projector base. It can probably be reached with a cotton bud soaked in cleaning fluid.

Posted by Monte L Fullmer (Member # 2797) on 06-01-2011, 12:11 PM:

When I was in HighSchool AV dept in my Jr. and Sen. year, we had 179's 285's and a 399, and twice a season, I would drop the amps to clean the mirrors on a routine basis.

Amazing how dusty they can get with continual use.

-Monte

Posted by Jeff Taylor (Member # 443) on 06-01-2011, 12:38 PM:

...and the window on the screw off bakelite phototube enclosure

Posted by Robert Crewdson (Member # 6256) on 06-02-2011, 11:11 AM:

My thanks to all those who responded to my request for help, and a quick response it was too.
I have followed the advice, removed the aplifier, and cleaned the area where the mirror should be; remains to see if the sound improves when I get the chance to run it.

The 601, similar to the 621 and 631 in appearance, was the 1st to be built in Britain in 1947, under the supervision of B&H engineers from Chicago. It was a joint venture between B&H and Gaumont-British (British Acoustic Films). Optical sound, 110 volts.
Thanks again to all concerned.