Bell & howell 1695 volume problem

[Jon Byler]

Also, if you have never worked on an amplifier, review safety precautions. Amplifiers that are turned off and unplugged can still have dangerous electric charges stored in capacitors. Below is an example on Youtube of precautions to keep in mind.

The transistor amps can have plenty of energy stored in their power supply capacitors. Ask me how I know Always discharge them!

[Jon Byler]

Refer to figure 26 to show the volume and tone controls on the 1695.
Volume control is a 50k.
BHTQIII.pdf (film-tech.com)

Don't forget that this is likely and audio taper pot (has something resembling a log taper). It will matter which way it gets connected.

[Ed Gordon]

Here is and article on How to Wire a Potentiometer

[Chip Gelmini]

If all else fails

consider a speaker plug that connects a speaker near the screen

but just use the mail plug only that is not attached to a speaker

it should mute the problem for silent double perf prints

[Maurice Leakey]

Chip's suggestion may cause problems with the transistorised amplifier's output circuit as it has no load connected.
My earlier suggestion of blanking off the exciter lamp with a piece of cardboard was a better idea.

[Ed Gordon]

Chip's suggestion may cause problems with the transistorised amplifier's output circuit as it has no load connected.

Problems with with "no load connected" could be avoided by plugging in a headphone instead of a plug with no load on it.

Fixing the problem by replacing the defective potentiometer remains the best solution in the long run. As Jason pointed out, "I will probably sell this one so would like to try to fix it.seems to be working perfect other than this.".

[Jason Moffatt]

Thanks for the suggestions everyone, i’m pretty limited with electronics though.The volume still works ok as in it goes up and down with the dial, it just does not mute it at the 0 setting.i’m hoping it is maybe just an adjustment,if i get time i will have a look today. I may keep this one now as the worm does have fine cracks it could fail at any time.

[Jason Moffatt]

Ok i’ve taken the sound control unit (pictured) out and there does not seem to be a way of adjusting it anywhere. I have another identical 1695, if i was to swap the sound unit over would it solve the problem or is the problem somewhere else ?.

[Maurice Leakey]

I am not entirely sure of my following comment, but I have an idea that I have heard that some volume pots do not return to zero ohms.

So, in this case, there is nothing wrong with the volume control which I assume is as it should be for the projecting of sound films. I have hundreds of 16mm sound films but do not have any double perf silent so I have never discovered that any of my Bell & Howell models do have this problem.

Of course, the earlier valve models such as the 642 did have an off position on their volume control, this turned off the HT to their amp.

[Jason Moffatt]

Well i got round to swapping these sound control units around and it didn't make any difference so the problem is somewhere else in the machine.

[Simon McConway]

It's the two large capacitors on the other amp pcb that need changing.

[Clyde Miles]

jason, did you manage to source these caps and change them? regards.

[Jason Moffatt]

Clyde, no changing capacitors is beyond me. I’ll just have to put up with the problem.

[Jon Byler]

I highly recommend not ignoring this problem, and having someone competent replace the capacitors for you. problems like this tend to get worse with time, and there is a real chance that when the part fails, something else gets taken out too. or even worse, if the old capacitors start to leak electrolyte on the boards the circuit boards and other components may get ruined.

[Jason Moffatt]

I dont think its worth spending money to have work done on these bell & howells if they have cracked worm gears which could fail at any time. What if i was to swap over all the sound related parts with another identical machine maybe this would work without having to change capacitors etc.