Film projectors. Poor volume. - UK Vintage Radio Repair and Restoration Discussion Forum

highlander · 17th Apr 2011, 6:43 pm

I have an old Bell & Howell and a Debrie 16mm projector. Both of these were threaded up with film today for the first time in many years and strangely both suffer from a lack of volume even when turned up full. I would say they reach almost a 1 on a scale of 1 to 10 if that makes any sense to you chaps. Any ideas?

raditechman · 17th Apr 2011, 9:16 pm

1-Is the sound head optical system clean?
2-Is the exciter lamp focused OK?
3-Could be the Photo Cell.
What is the performance like if you feed audio into the line input? If the results from that source are OK your amplifier section is probably working OK and you can concentrate on the suggestions 1-3 above.
John

Lucien Nunes · 17th Apr 2011, 9:55 pm

What John says, but you might be able to glean a bit more information from the tone quality. If the sound is low in level but still has treble, it's unlikely to be a focus issue as almost any maladjustment of the exciter optic will impair the top response. Avoid tweaking soundhead optics unless you have tone and buzz track test rolls to line them up again. Are you certain that the film you are running has a properly modulated soundtrack?

Were they both working OK before being put away? How long since they were used? If it a number of years, and they had not been overhauled, it is likely that they have developed typical amplifier faults including coupling capacitor leakage.

Lucien

highlander · 17th Apr 2011, 10:32 pm

It's many many years since their last use, the B&H is from the late forties, the other about a decade later and the internal components of the amplifiers look original. The projectors were just given a good clean and a light oiling where necessary. When I first turned on the B&H I passed a fine piece of paper between the exciter lamp and the sound drum and that made a bit of noise through the speaker so I assumed that the amp was ok. No other input has been tried as yet so I guess that's a good place to start next weekend.

fidobsa · 18th Apr 2011, 9:54 am

Will you be going to the Scottish meeting? If so you could take them there to get some expert opinions.

Ian E G7OLT · 18th Apr 2011, 11:30 am

What model number is the Bell and Howell? Is it an L516 by any chance?

--
Ian

kalee20 · 18th Apr 2011, 12:46 pm

The L516 wasn't Bell and Howell - it was a British machine, part of Rank.

As to the problem - I'd suggest the usual wax capacitors. Excessive current draw as a result of positive grid can pull down the HT rail, and the photocell's excitation voltage has quite an effect on the cell output.

And of course, you don't want to fry the valves and transformers, so check those waxies!

PJL · 18th Apr 2011, 1:45 pm

I have a 1946 16mm Ampro I restored and there are plenty of capacitors to change! These amps are usually very compact, so I would not power it up again as the leaky capacitors will quickly result in over-heating.

Optical alignment is not difficult, just fiddle about till you get the best HF response, the typical quality of the audio recording is a different matter, but the roar from the fan and clatter from the film feed pretty much drown out the sound anyway!

Mine came with a load of pre-recorded films and we usually drag it out for Christmas to watch cartoons.

highlander · 20th Apr 2011, 12:06 pm

It's a Gaumont B&H 601, looks as if I will be spending some time on the end of a soldering iron. A lot to learn but there is no rush to fix it.

17th Apr 2011, 6:43 pm	#1
highlander Retired Dormant Member Join Date: Feb 2011 Location: Inverness, Highland, UK. Posts: 9	Film projectors. Poor volume. I have an old Bell & Howell and a Debrie 16mm projector. Both of these were threaded up with film today for the first time in many years and strangely both suffer from a lack of volume even when turned up full. I would say they reach almost a 1 on a scale of 1 to 10 if that makes any sense to you chaps. Any ideas?

17th Apr 2011, 9:16 pm	#2
raditechman Heptode Join Date: Feb 2007 Location: West London, UK. Posts: 867	Re: Film projectors. Poor volume. 1-Is the sound head optical system clean? 2-Is the exciter lamp focused OK? 3-Could be the Photo Cell. What is the performance like if you feed audio into the line input? If the results from that source are OK your amplifier section is probably working OK and you can concentrate on the suggestions 1-3 above. John

17th Apr 2011, 9:55 pm	#3
Lucien Nunes Rest in Peace Join Date: Apr 2008 Location: London, UK. Posts: 2,508	Re: Film projectors. Poor volume. What John says, but you might be able to glean a bit more information from the tone quality. If the sound is low in level but still has treble, it's unlikely to be a focus issue as almost any maladjustment of the exciter optic will impair the top response. Avoid tweaking soundhead optics unless you have tone and buzz track test rolls to line them up again. Are you certain that the film you are running has a properly modulated soundtrack? Were they both working OK before being put away? How long since they were used? If it a number of years, and they had not been overhauled, it is likely that they have developed typical amplifier faults including coupling capacitor leakage. Lucien

17th Apr 2011, 10:32 pm	#4
highlander Retired Dormant Member Join Date: Feb 2011 Location: Inverness, Highland, UK. Posts: 9	Re: Film projectors. Poor volume. It's many many years since their last use, the B&H is from the late forties, the other about a decade later and the internal components of the amplifiers look original. The projectors were just given a good clean and a light oiling where necessary. When I first turned on the B&H I passed a fine piece of paper between the exciter lamp and the sound drum and that made a bit of noise through the speaker so I assumed that the amp was ok. No other input has been tried as yet so I guess that's a good place to start next weekend.

18th Apr 2011, 9:54 am	#5
fidobsa Retired Dormant Member Join Date: Mar 2009 Location: Zala, Hungary Posts: 418	Re: Film projectors. Poor volume. Will you be going to the Scottish meeting? If so you could take them there to get some expert opinions.

18th Apr 2011, 11:30 am	#6
Ian E G7OLT Pentode Join Date: May 2009 Location: Byfield, Northamptonshire UK. Posts: 112	Re: Film projectors. Poor volume. What model number is the Bell and Howell? Is it an L516 by any chance? -- Ian

18th Apr 2011, 12:46 pm	#7
kalee20 Dekatron Join Date: Feb 2007 Location: Lynton, N. Devon, UK. Posts: 7,087	Re: Film projectors. Poor volume. The L516 wasn't Bell and Howell - it was a British machine, part of Rank. As to the problem - I'd suggest the usual wax capacitors. Excessive current draw as a result of positive grid can pull down the HT rail, and the photocell's excitation voltage has quite an effect on the cell output. And of course, you don't want to fry the valves and transformers, so check those waxies!

18th Apr 2011, 1:45 pm	#8
PJL Dekatron Join Date: Sep 2005 Location: Seaford, East Sussex, UK. Posts: 5,997	Re: Film projectors. Poor volume. I have a 1946 16mm Ampro I restored and there are plenty of capacitors to change! These amps are usually very compact, so I would not power it up again as the leaky capacitors will quickly result in over-heating. Optical alignment is not difficult, just fiddle about till you get the best HF response, the typical quality of the audio recording is a different matter, but the roar from the fan and clatter from the film feed pretty much drown out the sound anyway! Mine came with a load of pre-recorded films and we usually drag it out for Christmas to watch cartoons.

20th Apr 2011, 12:06 pm	#9
highlander Retired Dormant Member Join Date: Feb 2011 Location: Inverness, Highland, UK. Posts: 9	Re: Film projectors. Poor volume. It's a Gaumont B&H 601, looks as if I will be spending some time on the end of a soldering iron. A lot to learn but there is no rush to fix it.