This is topic RCA Soundhead trouble in forum Film Handlers' Forum at Film-Tech Forum ARCHIVE.
To visit this topic, use this URL:
https://ft-forum.com/ft/cgi-bin/ubb/ultimatebb.cgi?ubb=get_topic;f=1;t=004187
Posted by John Westlund (Member # 913) on 11-09-2002, 01:58 PM:
The constant feed sprocket in our RCA 9030 is moving in and out as you advance the projector. I have also noticed a pulsating sound in the machine while it is running and on a couple occasions the machine wouldnt start when I flipped the switch. All that I could hear was the motor buzzing. After advancing the machine by hand a couple frames all was ok. I havent really noticed the machine feeling like it is binding when advancing it by hand but I will go in and check on that later. The soundhead has a Century SA on it.
Thanks
John
Posted by Adam Fraser (Member # 1074) on 11-09-2002, 02:23 PM:
As far as the motor goes, sounds like bad brushes or just a plain tired motor.
Posted by Gordon McLeod (Member # 33) on 11-09-2002, 03:45 PM:
Probably the brass gear or the steel pinion one has a problem and is jamming the motor
Posted by Roger Frazee (Member # 640) on 11-09-2002, 04:34 PM:
The motor problem sounds like dirty contacts on the centrifugal switch that operates the start winding. You can pop the end bell off of the motor and clean up the switch contacts.The sprocket shaft end-play problem indicates that a rebuild is in order for your gearbox. You can get new bronze gears, gaskets, shafts, and bearings from Wolk.
Posted by Sam Hunter (Member # 1119) on 11-09-2002, 06:08 PM:
Sounds just like the problem I have been experiencing with mine.
When you turn the motor by hand is it hard to turn?
Keep turning it and feel for binding.
I wish I knew something else worthwhile to say but if you happen to figure it out let me know.
Good Luck 
------------------
Samual Hunter Sr.
KC5ZSL
Posted by Paul G. Thompson (Member # 655) on 11-09-2002, 08:22 PM:
John, I agree with Gordon, as that was one of the points I mentioned in my communication with you yesterday. I also agree with Roger's thoughts in his last paragraph about the grearbox issue. By the way, did this trouble just start, or has it been an on-going problem? You might want to check to see if there is any bronze shavings in the oil, and check the backlash. Compare the backlash with the holdback sprocket shaft with the constant speed shaft. It is easy. All you have to do is grab ahold of the sprocket, and gently rock the motor shaft back and forth. It should feel about the same with both sprockets. Make sure the rag coupling is not busted all to hell, as it will give you a false backlash indication. Do this on several locations within a 360-degree rotation of the shafts.
If it feels like it is climbing, better overhaul the gearbox, it is ready to go kapoot!
If it easy for you to disconnect the drive from the projector for testing, it might be a good idea just in case there is an undetected bind in the projector head.
Posted by John Westlund (Member # 913) on 11-09-2002, 11:08 PM:
Tonight I checked and the backlash is much greater on the constant speed sprocked then it is on the holdback sprocket. Paul, what exactly do you mean by if it feels like it is climbing? I have just noticed the pulsating sound getting louder lately and found the problem with the constant feed sprocket moving in and out a couple days ago. Thank you all for your help espically Paul for the prompt replay to mye-mail yesterday.
John
Posted by Paul G. Thompson (Member # 655) on 11-10-2002, 12:38 AM:
John, the best way I can describe it is "It just doesn't feel right" - after a while, you get a feel for it. I will recommend you take Roger's advice..overhaul that gearbox ASAP. I would guess yours will last a week yet...if that long.
Actually, some theatre supply houses offer a repair exchange on them. It may be your fastest and best way out. Inspect your motor coupling to make sure it is good. If it is deteriorated, replace that, too.
Get the motor serviced, too. The starter switch is going bad. Probably because the contacts are burned up. Once they go, cleaning them will be short lived, and all it will do is buy you some time until you can obtain a replacement motor.
Starter switches are no longer available for those motors. I understand there are motor shops that will modify that setup, and the motor will probably run another 50 years.
Aside their shitty efficiency, I think that motor built by Robbins & Myers, along with the Leland's used on the Simplex SH10** were the best that were ever made. 50 to 60 years trouble free? That should say something... 
Your motor is worth having it rebuilt.
Posted by John Anastasio (Member # 607) on 11-10-2002, 07:51 AM:
I agree with everyone about the gearbox. I had a 9030 with a bad pinion gear and talk about pulsating! The entire projector practically walked across the floor. It can also bind, causing the problem you're experiencing with the motor. The original gears were made of brass. The new ones are bronze and are a lot tougher.