Annoying HUM

[John Burgess]

I am in the process of fettling a Ricoh sound 8 St8 mm sound projector (tube amp). Changed the lamp from tungsten to halogen, amplifier all good now, here’s the bad bit , turn on amplifier , you can hear it faintly breathing through the speaker, switch on motor and the hum starts , checked earthing and obvious loose connections, it will not go away. Switch motor off , no hum !!
I was hoping someone with more electronic knowledge than me can help with this problem.
Thanks in advance John

[John Burgess]

Forgot to mention, it’s an induction motor.

[Steve Klare]

Hi John,

It sounds like your sound head is picking up stray magnetic fields from your motor. Very often there are inductors in series with the head which can be reoriented to pick up the same field and cancel out the one picked up by the head (hum-buck coils).

This would just look like a donut coiled with wire dangling out in space near the head and connected in the head's wiring.

Also, on a machine this old, electrolytic capacitors really should be many years past replacement. I worked for a power supply company that wouldn't sell a unit from inventory with filter caps more than 5 years old, yet here we all are with electrolytics old enough to have grandkids!

This could be at least a contributing factor.

[John Burgess]

Hi Steve
Many thanks for your kind reply. The caps are all good and replaced not long ago. Regarding hum buck coil, I think Eumig used them on their heads, I used to have one and moving it around could lessen the hum. I will check out the head on the Ricoh to see if they have a similar arrangement.
Will report back with my findings.
John

[Steve Klare]

Best of luck!

There is also a human factor that can play a role here. Living with modern electronics, there is often no hum at all and then we turn on something 50+ years old and find it disturbing even if it is doing as best as it ever did.

Everybody loves an antique car until they apply the brakes!

[Brian Harrington]

My ears perk up anytime I hear of a Standard 8mm only sound machine. I'm not at all familiar with Ricohs, and a google search also turns up new digital projectors as well as 8mm. I see lots of silent models, and the only sound one I found was for Super 8. Unfortunately, the Super8Database doesn't list Standard 8mm-only machines, obviousy. What's the model number? thnx.

I get the feeling Standard 8mm sound was never that popular. It is rare to see a single-gauge projector for sale, and the amount of Standard 8mm sound films for sale is very limited.

[Dominique De Bast]

Brian, you may like the picture posted here : Ricoh Sound 8 up and running - 8mm Forum (film-tech.com)

[Brian Harrington]

OMG what a gorgeous projector -- now I want one. Thnx Dominique. You can see just from the picture that it is a heavy-duty, quality machine. I can't believe I've never seen one before. It's too bad that the industry gravitated towards cheaper and cheaper machines for their slick salesman to pawn off to unsuspecting customers!

John, is this the same one from that 2021 post? Sounds like you had already fixed the hum. What capacity did it have originally?

I bought some Standard 8 silent features a while ago mounted on 1200 foot reels, with a 16mm hub. I fabricated a quick-and-dirty long-play unit, using a rewind as the feed, and an Elmo ST-1200 as the takeup, and watched them on a Bolex 18-5. It worked, but it is not a permanent solution. I then cut them down to 400 foot reels.

I've read old posts here about Chip Gelmini's setups. I'd love a self-contained Standard 8mm machine with larger capacity, though. None of my silent-only machines, even in Super 8, can handle anything more than 400 feet.

They talk about it here, with a pic, starting on page 19: https://www.worldradiohistory.com/Ar...nd-1963-12.pdf

They didn't mention capacity, but looks only 400 foot.

[Dominique De Bast]

Brian, this projector handles large spools. But is uses rare and expensive 100 v 500 w P28 (Continental Europe reference, I don't know the Anglo-saxon one) bulbs. Also, as far as I know, there is no zoom lens or a very bright one.

Spare part finder – Van Eck Video Services (van-eck.net)

[Brian Harrington]

Dominique,

Thnx. That's the problem -- many take incandescent bulbs. I've converted a few B&Hs to halogen with mixed results. Some are impossible to align with the frame hole, because the socket/lamp holder for halogen is too large. Others I've aligned as best I could but I think the bulbs weren't designed to focus on a Super 8 gate and/or they need to be moved further back but there's no room.

I've never seen a B&H Standard 8mm sound machine, except the one they branded for Sears called "The Soundstage 8" or something like that. A few others are mentioned in that article I linked to above. The Eumig Mark S is supposed to be one of the best.

The Elmo FP sound version (Elmo TP-8) is nice, as I have the silent version. It would be my favorite Standard 8mm machine (that I have) if it weren't for the 25mm lens. I had to remove the zoom portion since they're impossible to take apart and clean. They made the diameter of the barrel so small that no other lens I have will fit, even a tiny B&H lens from a 200 series Standard 8mm machine from the 50s. And no the Bolex 18-5 lens won't fit, either. I'm still using the incandescent bulb it came with, but I plan to convert it to an EJM halogen when it blows out, since I have an Elmo FP halogen donor machine, and it is very easy to swap in the lamp assembly -- at least it looks that way. That being said, it is still just 400 feet.

John,

Sorry we hijacked your thread!

Now back to the regularly scheduled program, folks!

[John Burgess]

Hi again
Yes that’s my Ricoh in the previous post. I had just put the larger arms on and tried it out, the hum then I had cured. I haven’t used it since then and gave it the once over last week and noticed the hum but this time when motor switched on. These old machines should be run on a regular basis .
Still investigating this new hum, there’s no hum buck coil on sound head Steve, the plot thickens .
This may be old tech but it’s built like a tank, no plastic, no electronic wizardry no auto thread. That’s why I love St 8. I can run a feature non stop for a little over 2 hrs with valve amp sound ! Doesn’t get much better
John

[Steve Klare]

Understood!

If I ever build my dream-theater, the last stage of the sound system will be two tube amplifiers!

(-keep that booth nice and warm all winter long!)

I'd want there to be some kind of a process getting the whole setup going, and the soft red glow of the heaters warming up would add to that.

[Brian Harrington]

Yup, and that's why shiny discs and digital projection don't float my boat -- there's ZERO charm in it.

[Paul Adsett]

Yup, and that's why shiny discs and digital projection don't float my boat -- there's ZERO charm in it.

I'm sure a lot of us feel that way, otherwise we would not be on this forum!

[Steve Klare]

If I wanted it to be easy and efficient, I'd watch "movies" on an I-Pad like most people!