Information needed : Bell & Howell 626 power requirements - UK Vintage Radio Repair and Restoration Discussion Forum

Zonnebloem · 26th Feb 2021, 8:18 pm

Hi all

I just bought a B&H Filmosound amp and it's due to arrive in a week or two. Now I'm trying to work out what it lives on ...

The seller says that (s)he has not tested the unit for want of the right cable, and that it requires 110V AC. The first statement I accept (I expect to have to some restoration work), the second I am beginning to doubt.

One thing I already discovered was that the 626 is apparently the UK-oriented version of the 621, and that can run off 240V AC without the need for a stepdown transformer. I also found some pics of the whole projector online and they show a 5-pin connector on the rear side labelled "200-250V AC or DC 6 AMPS". This struck me as pretty weird: if it accepts DC then there can't be an input transformer (so I reasoned), and while it's possible to feed DC into a rectifier circuit the output voltage at AC and DC will not be the same ...

Then I read on this forum (https://www.vintage-radio.net/forum/...d.php?t=169337) that the power converter of the B&H 640 (and maybe the 631) was a precursor of today's switching power supplies. Which is somewhat mid-blowing, but after drinking a bottle of Belgian beer to calm me down I conclude that:
* I don't need a step-down transformer
* however an isolation transformer would be a Good Thing and could save lives
* the 4-pin Jones connector for the amplifier power supply is probably wired up in a similar way to that of the 621 (about which there is plenty of information online).

Can anyone tell me if I'm on the right track?

Many thanks

Ed_Dinning · 26th Feb 2021, 8:35 pm

Hi, I did quite a bit of work with Bell and Howell projectors way back in the 60's and they always seemed to have "a transformer" connected to the projector by a jones plug.
I think this was a tapped transformer with an adjusting switch and you selected the best position so the attached meter read in the green band: as far as I know this was to normalise the local mains voltage so that the Lamp (110v) I believe received the optimum voltage

Ed

Zonnebloem · 27th Feb 2021, 11:25 pm

There's some nice pictures of the complete projector here: https://picclick.co.uk/Cine-film-pro...037653530.html

In one of the pictures there is a kind of patch panel to select the mains voltage, so it rather looks as if the operator was deemed to know what the local voltage was - plus there is a notice to say that the lamp must match the mains voltage! Else flash bang sorry folks, no film tonight.

The 626 was introduced in 1953 so it would be a bit before your time but this is what https://www.paulivester.com/films/pr.../bh_models.htm has to say:
"Similar to the 621, 240V operation without external transformer."

So indeed most B&H models would have needed a step-down transformer to be used in the UK but this one seems to have been an exception. At the same time it has to be said that the amp is not at all similar to the 621 model, it uses completely different valves for a start. (The 621 has a bunch of 6V6, while the 626 is mainly PL32s, which are more often found inside TV sets).

I'm beginning to wonder if it's one of those "transformerless" designs where the chassis is connected to the "neutral" wire, and let us pray that that wire is really neutral. You could get away with that inside the cabinet of a TV or radiogram, but I find it a bit hard to believe in the case of this machine. If the chassis goes live than the whole caboodle is live, which would make the projectionist's life excessively exciting.

P.S. the Jones plug is there all right.

Zonnebloem · 5th Mar 2021, 7:28 pm

Just heard that the seller has cancelled the deal, reason unknown, at least I didn't lose any money.

Thanks Ed Denning for the reply.

emeritus · 6th Mar 2021, 3:53 pm

110V bulbs were preferred when a brighter picture was needed. From memory at least 30% brighter than a 240V bulb of the same wattage. Projector bulbs of the era were typically only rated for 25 hours life, and this would be sigificantly reduced by even a small percentage overvoltage.

Herald1360 · 7th Mar 2021, 6:22 pm

ISTR the B&H projectors at college in the '70s being retrofitted with low voltage ellipsoidal reflector 250W halogen lamps for a significant increase in brightness over the original 1000W tungsten type.

Zonnebloem · 7th Mar 2021, 6:39 pm

Apparently the filament of a 240V bulb is bulkier (makes sense - half the current for the same wattage), and the B&H optics did not capture all the light from the larger area.

emeritus · 7th Mar 2021, 11:57 pm

In addition, the shorter, fatter, filament of a 110V lamp than a 240V lamp of the same wattage, means that the 110V lamp produces more than 20% more light than the 240V lamp, and pro rata for lower voltages still.

broadgage · 8th Mar 2021, 2:54 pm

Agree, a lower voltage lamp filament of the same wattage will be more compact, and therefore more easily focused.
Also, if other factors such as design life remain constant, then a lower voltage lamp will give more light for a given wattage.

110 or 120 volt lamps tend to be more efficient than 220 volt or 240 volt lamps, if of otherwise similar design.
Alternatively the lamp designer might aim for the same efficiency in both 120 volts and 240 volt lamps, in that case the 120 volt lamp will be longer lasting than the otherwise similar 240 volt one.

wd40addict · 13th Mar 2021, 10:46 am

There was a desire, particularly in schools, to have a simplified design doing away with the large and heavy autotransformer. The reduction in light output was thought to be acceptable in these circumstances. Examples are the B&H 626 & 636 and the Ampro 'Educational'. Although the amplifier is an AC/DC design the Ampro casing itself is earthed and I would expect the B&H to be similar.

26th Feb 2021, 8:18 pm	#1
Zonnebloem Diode Join Date: Feb 2021 Location: Antwerp, Belgium. Posts: 4	Information needed : Bell & Howell 626 power requirements Hi all I just bought a B&H Filmosound amp and it's due to arrive in a week or two. Now I'm trying to work out what it lives on ... The seller says that (s)he has not tested the unit for want of the right cable, and that it requires 110V AC. The first statement I accept (I expect to have to some restoration work), the second I am beginning to doubt. One thing I already discovered was that the 626 is apparently the UK-oriented version of the 621, and that can run off 240V AC without the need for a stepdown transformer. I also found some pics of the whole projector online and they show a 5-pin connector on the rear side labelled "200-250V AC or DC 6 AMPS". This struck me as pretty weird: if it accepts DC then there can't be an input transformer (so I reasoned), and while it's possible to feed DC into a rectifier circuit the output voltage at AC and DC will not be the same ... Then I read on this forum (https://www.vintage-radio.net/forum/...d.php?t=169337) that the power converter of the B&H 640 (and maybe the 631) was a precursor of today's switching power supplies. Which is somewhat mid-blowing, but after drinking a bottle of Belgian beer to calm me down I conclude that: * I don't need a step-down transformer * however an isolation transformer would be a Good Thing and could save lives * the 4-pin Jones connector for the amplifier power supply is probably wired up in a similar way to that of the 621 (about which there is plenty of information online). Can anyone tell me if I'm on the right track? Many thanks

26th Feb 2021, 8:35 pm	#2
Ed_Dinning Dekatron Join Date: Jan 2004 Location: Newcastle upon Tyne, Tyne & Wear, UK. Posts: 8,194	Re: Information needed : Bell & Howell 626 power requirements Hi, I did quite a bit of work with Bell and Howell projectors way back in the 60's and they always seemed to have "a transformer" connected to the projector by a jones plug. I think this was a tapped transformer with an adjusting switch and you selected the best position so the attached meter read in the green band: as far as I know this was to normalise the local mains voltage so that the Lamp (110v) I believe received the optimum voltage Ed

27th Feb 2021, 11:25 pm	#3
Zonnebloem Diode Join Date: Feb 2021 Location: Antwerp, Belgium. Posts: 4	Re: Information needed : Bell & Howell 626 power requirements There's some nice pictures of the complete projector here: https://picclick.co.uk/Cine-film-pro...037653530.html In one of the pictures there is a kind of patch panel to select the mains voltage, so it rather looks as if the operator was deemed to know what the local voltage was - plus there is a notice to say that the lamp must match the mains voltage! Else flash bang sorry folks, no film tonight. The 626 was introduced in 1953 so it would be a bit before your time but this is what https://www.paulivester.com/films/pr.../bh_models.htm has to say: "Similar to the 621, 240V operation without external transformer." So indeed most B&H models would have needed a step-down transformer to be used in the UK but this one seems to have been an exception. At the same time it has to be said that the amp is not at all similar to the 621 model, it uses completely different valves for a start. (The 621 has a bunch of 6V6, while the 626 is mainly PL32s, which are more often found inside TV sets). I'm beginning to wonder if it's one of those "transformerless" designs where the chassis is connected to the "neutral" wire, and let us pray that that wire is really neutral. You could get away with that inside the cabinet of a TV or radiogram, but I find it a bit hard to believe in the case of this machine. If the chassis goes live than the whole caboodle is live, which would make the projectionist's life excessively exciting. P.S. the Jones plug is there all right.

5th Mar 2021, 7:28 pm	#4
Zonnebloem Diode Join Date: Feb 2021 Location: Antwerp, Belgium. Posts: 4	Re: Information needed : Bell & Howell 626 power requirements Just heard that the seller has cancelled the deal, reason unknown, at least I didn't lose any money. Thanks Ed Denning for the reply. Last edited by Station X; 6th Mar 2021 at 10:25 am. Reason: Political comments removed.

6th Mar 2021, 3:53 pm	#5
emeritus Dekatron Join Date: Jan 2012 Location: Brentwood, Essex, UK. Posts: 5,339	Re: Information needed : Bell & Howell 626 power requirements 110V bulbs were preferred when a brighter picture was needed. From memory at least 30% brighter than a 240V bulb of the same wattage. Projector bulbs of the era were typically only rated for 25 hours life, and this would be sigificantly reduced by even a small percentage overvoltage.

7th Mar 2021, 6:22 pm	#6
Herald1360 Dekatron Join Date: Feb 2007 Location: Leominster, Herefordshire, UK. Posts: 16,535	Re: Information needed : Bell & Howell 626 power requirements ISTR the B&H projectors at college in the '70s being retrofitted with low voltage ellipsoidal reflector 250W halogen lamps for a significant increase in brightness over the original 1000W tungsten type. __________________ ....__________ ....\|____\|\|__\|__\_____ .=.\| _---\__\|__\|_---_\|. .........O..Chris....O

7th Mar 2021, 6:39 pm	#7
Zonnebloem Diode Join Date: Feb 2021 Location: Antwerp, Belgium. Posts: 4	Re: Information needed : Bell & Howell 626 power requirements Apparently the filament of a 240V bulb is bulkier (makes sense - half the current for the same wattage), and the B&H optics did not capture all the light from the larger area.

7th Mar 2021, 11:57 pm	#8
emeritus Dekatron Join Date: Jan 2012 Location: Brentwood, Essex, UK. Posts: 5,339	Re: Information needed : Bell & Howell 626 power requirements In addition, the shorter, fatter, filament of a 110V lamp than a 240V lamp of the same wattage, means that the 110V lamp produces more than 20% more light than the 240V lamp, and pro rata for lower voltages still.

8th Mar 2021, 2:54 pm	#9
broadgage Nonode Join Date: Jan 2010 Location: North Somerset, UK. Posts: 2,129	Re: Information needed : Bell & Howell 626 power requirements Agree, a lower voltage lamp filament of the same wattage will be more compact, and therefore more easily focused. Also, if other factors such as design life remain constant, then a lower voltage lamp will give more light for a given wattage. 110 or 120 volt lamps tend to be more efficient than 220 volt or 240 volt lamps, if of otherwise similar design. Alternatively the lamp designer might aim for the same efficiency in both 120 volts and 240 volt lamps, in that case the 120 volt lamp will be longer lasting than the otherwise similar 240 volt one.

13th Mar 2021, 10:46 am	#10
wd40addict Octode Join Date: May 2009 Location: Stevenage, Herts. UK. Posts: 1,518	Re: Information needed : Bell & Howell 626 power requirements There was a desire, particularly in schools, to have a simplified design doing away with the large and heavy autotransformer. The reduction in light output was thought to be acceptable in these circumstances. Examples are the B&H 626 & 636 and the Ampro 'Educational'. Although the amplifier is an AC/DC design the Ampro casing itself is earthed and I would expect the B&H to be similar.