This is topic Crosstalk on old RCA 1040 in forum Film Handlers' Forum at Film-Tech Forum ARCHIVE.
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Posted by Harry Robinson (Member # 265) on 02-20-2001, 03:13 PM:
Well, my system's up and running at last. Things look and sound great with one exception. I'm getting a ratio of around three to one crosstalk between channels according to the ocillascope my friend and theater tech Mack Williams used to adjust the split lens and solar cell. He says ten to one is normal.The mix is center-heavy, with little to nothing going to the surrounds. Mack says we need to get the solar cell closer to the slit lens, but it is as far forward as it will go. He also says we can work with it to bring it closer, but we don't want to get too close to the slit lens because a bad splice can damage the solar cell.
Any thoughts on this?
Posted by Ken Layton (Member # 133) on 02-20-2001, 03:37 PM:
I am assuming you have a Kelmar stereo solar cell installed.The screw holes on the triangle shaped mounting plate are oversized and by loosening the screws sholud allow you to move the cell a little more forward. You shouldn't get the cell so close that bad/thick splices snag it. The top one third of the cell is where the slit light should be hitting the cell. The Allen head screws in the arm that holds the cell can be loosened and the cell rotated slightly up or down as needed. The small Allen screw in the cell itself can be loosened to slide the cell in the left-right direction, but don't do it with out a crosstalk test film and an oscilloscope!
How old is the slit lens? If it's the original wide slit replace it with a new C-1 (0.59 mil) slit lens
Posted by Paul G. Thompson (Member # 655) on 02-20-2001, 09:37 PM:
Mack is correct when he says he can work with it to get it closer. What he would do is probably loosen the three mounting screws that hold the whole solar cell bracket to the sound head casting. The holes are bigger than the screws, so he has lots to play with. Chances are, he will have to adjust the solar cell head so the exciter beam will fall on the correct portion of the cell itself. What Ken says also has merit. An old oil-fouled 1 mil slit is about as worthless as a penny sawed in two with a hack saw. It has flat runout up to 7khz if it is good shape, and if oil fouled, you'll be lucky if you get a flat run-out even up to 3 or 4 KHZ. The lense Ken is talking about has a much wider flat response. And, the availability for the old RCA sound heads is questionable. You might consider a cheap IR reverse scan kit for those. It's coming down the road anyway. No sense spending a small fortune for a set of new sound lenses because when the new cyan tracks hit, they will be worthless anyway.
Posted by John Eickhof (Member # 323) on 02-20-2001, 10:13 PM:
Hi Harry! Glad to hear that you're up and running!!! The face of the cell should be .040" from the film, if necessary, you may have to shim behind the clear cell mount and the black mounting arm to bring the cell closer to the film. Or you can remove the cell bracket and enlarge the three mounting holes to get it closer, I trust you have the narrow slit I sent you installed? Anyway, I have had this problem before on 1040 / 1050s and ended up placing a flat shim behind the clear cell piece! Good luck, let me know what you end up with! (A good 1040/1050 will end up with about a 7:1 ratio for signal to crosstalk, be sure the slit lens is focused with 9 KHz loop! Not 7 KHz! And that the azimuth is right on!!!------------------
John Eickhof President, Chief Slave
Northwest Theatre Equipment Co., Inc.
P.O.Box 258
Wendell, ID. 83355-0258
208-536-5489
email: jeickhof@nteequip.com
Posted by Darryl Spicer (Member # 711) on 02-20-2001, 10:15 PM:
If you are not doing it make sure to hook an analyzer up along with the scope. You want to make sure you get all the high frequencies that you can off of that cell otherwise your processor will not decode properly. You need to make sure you get a propper slit adjustment without loosing the highs.
Posted by Dave Ganoe (Member # 53) on 02-21-2001, 06:33 AM:
Speaking of RCA I have a 1050 with a kelmar stereo cell in it. Sound is really good except for one problem. During music it sounds as though it is sorta wavy or dragging a bit. I know what is causing it but don't know what to do to fix it. When the film is running and coming off of the sounddrum onto the top sprocket the film kinda rides up on the teeth of the sprocket then drops down into place. The causes the film to bounce between the upper sprocket and sound drum. Would replacing the sprocket be what is needed? Anyone else have this problem? The sprocket doesnt seem to be worn but I dont have something new to compare it to. Also the output from the cell goes to my preamp then to the input of a pioneer stereo receiver. Would it be possible to get surround sound if I were using a surround sound processor with the kelmar stereo cell? THanks for any replies/advice. Im still learning. 
Posted by Brad Miller (Member # 2) on 02-21-2001, 08:04 AM:
Dave, regardless of your alignment problem you should change the bearings on the sounddrum.
Posted by Harry Robinson (Member # 265) on 02-21-2001, 11:24 AM:
As usual you guys come through with some great advise. Just to wrap up a little bit, John Eickhof sent me the new slit lens some time ago. My high end is really good, no problem there. We are using the 9K test loop. I'm sure we'll be incorporating all the ideas in order to eliminate the crosstalk problem. Thanks for the 7:1 figure, John. We shoot for that.
Posted by Paul G. Thompson (Member # 655) on 02-21-2001, 12:00 PM:
David, I had that problem once in an old 1040. I replaced the sprocket, and the pad roller. (was worn lopsided). It takes a Wolk Pad Roller MNR4-22. Make sure the pad roller is adjusted to two film thicknesses. Your problem should go away. As Brad suggested, change your scanner drum bearings. They can be obtained from a local NAPA auto parts store, but you have to supply the bearing number from the bearing itself. I forgot what the number was.A couple of other things to check: When you thread up, as you place the film on the sprocket, pull it tight, than THEN BACK OFF a MINIMUM of ONE SPROCKET PERF. RCA and Simplex recommend two. The reason I say one or two is because some techs align the sound head with only one or two perf back-off's. If he aligns it with one, then back off one. If he aligns it with two, then back off two. Otherwise, some skewing could occur, especially if the scanner drum is badly worn. I always set mine to two. THEN close your lateral sound guide roller. It looks funky, but trust me - it is correct. NEVER run it tight. If you do keep it tight, it'll probably have a tendency to climb the sprocket, and possibly damage the film. Also, when the machine is running, check if the lateral sound guide roller is bouncing. If it is, the cushion roller has a blob of crud on it, or the roller itself could be shot. Then, lightly touch the end bearing cap on the lateral guide roller. If the bearings are shot, you'll feel it rumble.
And, keep that damned WD-40 away from your investment!!!
Posted by John Eickhof (Member # 323) on 02-21-2001, 03:29 PM:
Dave the 'rolling loop' or wow is most likely the two bearings on the sound drum shaft, These are a grade 8 number 202 bearing, install new ones with only one shield on them, lightly oil with 30 wt non dtergent oil, place bearings so shields protect outside from dirt. If the problem persists, the sound damping drum is low on viscuous fluid. These are hermatically sealed on the RCA. I have NOS replacements available. Another frequent cause may be the top bronze gear in the soundhead is about to fail. When the machine is idle, grab the upper sprocket and see if it rocks back and forth (CW & CCW)
if there si a lot of slop, say 1/8" or so, it's time to open the gearbox and see how bad the upper gear and the steel pinion is!
Have fun!!!------------------
John Eickhof President, Chief Slave
Northwest Theatre Equipment Co., Inc.
P.O.Box 258
Wendell, ID. 83355-0258
208-536-5489
email: jeickhof@nteequip.com