TQ3 grainy audio/ line out mod?

[Martin Davey]

Dear Forum,

My TQ3 (1695) is suffering from a sound fault. The audio is becoming crude and grainy, even through the line out DIN plug. I tried a new exciter lamp to no avail. I could have no idea what I’m talking about, but my suspicion is that the sound card (caps) are failing.

However I tend to use external amplification with my various projectors, and when one of my Elfs had a bad amp, I created a lead taking the feed directly from the solar cell, and amplify this instead, with a mic mixer inbetween , so avoiding the amp, and that arrangement works perfectly well.

I would like to do something similar with the TQ3, but as you know it's a far more complicated machine to take apart and outside of my ‘zone’. I did access the volume control card from the bottom and wondered if there is a feed from the solar cell that I can tap on to from there, thus abandoning the built in amp, and creating a 3.5mm plug somewhere.. I must point out that I have no idea of electronics, but can use a soldering iron (from my model railway experience), so I would need to be told in simple fashion where to solder.

The card has 5 wires going into it, 2 uninsulated which I have numbered..

I can’t see where the wires come from/ to as this requires disassembly.

I’m not interested in sending the projector away as it's not economical sadly.

If anyone has any ideas they would be most appreciated, thank you.

[Maurice Leakey]

Martin
Are you sure you have not got scratchy pots?
It's quite an old projector and the carbon tracks are not making good contacts with the sliders.
One way of curing the problem is to turn the pots each about a dozen times, this will lubricate by applying traces of carbon.
I hope my suggestion will work for you.

[David Strelitz]

...or a gentle spay of a contact cleaner.

[Nantawat Kittiwarakul]

Sometimes it would have to be a not-so-gentle blast of cleaner spray to get it work. And not only the pots, but also those connectors as well that would need some cleaning - or reseating at least.

By the way there seems to be too few components (and mostly passive ones) to be a complete amplifier circuit. Maybe there's some additional board hidden inside.

[Stuart Hilliker]

Hi Martin. Is your TQ3 Mag and optical? I had a similar problem with a TQ1. Repeatedly engaging and disengaging the mag head solved the problem. Dirty contacts once again causing problems.

[Maurice Leakey]

The 1695 is only optical sound.

[Maurice Leakey]

I am not an expert on Bell & Howells, but a friend is.
So here is another suggestion.
On this model the microphone socket serves two selections by means of a switch.
1) In SOF mode it sends the signal from the PEC to the amplifier.
2) In MIC mode its signal goes direct to the amplifier.
Over time, the plastic barrel of the socket may get small cracks which can cause problems with the switch.
It is suggested that a standard 1/4" (6,3mm) jack plug is inserted a few times.
It is hoped that this may affect a cure, but it's a long shot.

[Martin Davey]

Thanks Maurice, David, Nantawat and Stuart.

I did spray some cleaner into the pots and fed the ¼ jack into the socket a number of times. There is a little improvement overall with some of the distortion cleared but compared to testing the same film on a 1698, the 1698 is significantly clearer. Its not the high or low frequencies that are missing, but detail and dynamics, with sound being like a radio slightly out of tune.

Over the weekend I will remove what I think is the amp and look at the connections and see if the components look damaged, and try to work out what the audio connections are from the solar cell if possible. To isolate the amp is the last thing I want to do. I don’t want to dump the machine into a (never) repair corner as it was only serviced two years ago with a new worm drive and runs beautifully!

Nantawat - The item displayed in the photo was not the amp as you correctly pointed out, but just the control board for bass, treble and volume.

edit- I should point out that the 2 BH used are specialist models, with the audio on a 5 pin Din line out. When this is used the audio controls have no effect. The distortion is on the built in speaker, the external speaker and on the line out audio.

[Maurice Leakey]

.....I’m not interested in sending the projector away as it's not economical sadly....[/B]

It's a nice projector, but could be 43 years old. I consider it worth saving, even at a price.
I am sure that Kevin Brown would be able to sort it all out. He's been looking after my projectors for 10 years or more.
To save four car trips he has devised a special packing case with suitable cladding which he sends via Parcelforce.
For return, he will arrange collection by the same method, no need for a printer as the van driver will bring all necessary paperwork, including details of tracking.
I can thoroughly recommend Kevin.

[Martin Davey]

I’d thought I would just update this thread to complete it. This problem had been at the back of my mind since the original post, and the projector out of use. Since Christmas I’ve been learning a lot more about B&H’s to the extent I replaced the worm drive in one machine and overhauled the projection mech in another. I was advised of methods, by K Brown (with prompting from Maurice) in helping to diagnose the problem, the amp not being it as sound from the mic/ external source were fine. I de-soldered, and then re-soldered the connection of the cell to the sound circuit in case of a poor connection, which made no difference. Therefore the problem must be the cell itself, I presumed. Originally I was going to replace the cell with one separated from a scrapped TQ1, but this only had two wires attached, unlike the three needed on a TQ3. The thought then came of taking a cell from a TQ3 (turquoise) parts machine. However, rather than risk upsetting the line up of the cell with the scanning optics, I decided just to replace the entire sound block on the black TQ3 (with the exciter lamp, rollers, etc) and replace it using the turquoise example. Fortunately this fitted fine despite the black TQ3 being a newer machine. The exciter cover had to be the original one from the turquoise machine as the more recent black TQ3 cover would not attach to the older part. Once soldered in place all worked perfectly and the sound is as it should be!

Unfortunately I’m not able to inform Maurice of the successful transplant…