Interesting...because when I ran Dolby Tone in that theatre yesterday I made a note that Left and Right trimpots were INTERACTING!

Raising Left also raised Right and vice-versa.

I've got an hour to spare while waiting for the current show to end. What should I check first?

I'm willing to bet that the solar cell isn't wired in to the processor correctly.

This is a Dolby CP-45 and a Kelmar LED Reverse-Scan (Analog only) in a Westar (Century R-3).

As far as interacting is concerned, I would have a tendency to think the cell common wire might be broken or improperly connected somewhere.

An ohm meter will be very helpful to have and use.

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I went over and had a look-see during intermission and here's what I observed...

Solar cell wiring (Kelmar PC 7929 AT-1200 LED Kit) is as follows...

1 L+
2 Earth (jumpered to #5)
3 L-
4 R+
5 Earth (jumpered from #2)
6 R-

On the D9 connection to the CP-45 Projector 1 Input the connections for L+ L- R+ R- are in the right pins. There is no shield wire attached to the body of the D9 connector, and the Earth connections don't terminate anywhere on the processor input.

FWIW this D9 connector isn't like the others we are using. The others I've seen all look like a breakout card and they use L+ E L- R+ E R- so this one is different. Still, it seems to be wired up correctly (with the exception of the shield wire not being soldered to the body of the connector).

Also...what do you make of jumpering the Earth connections on the solar cell? From what I can tell, it's not actually connecting to ground anyway...that connection is only happening on the solar cell side.

When running Dolby Tone, the little LED's on the SR/A card start dancing around and freaking out...they don't give any steadiness. I suppose I could try swapping out boards to eliminate the circuitry.

Also, the hum is more of a buzz appearing only in the left channel. I've heard DTS timecode before and it was a lower pitch than this buzz that I'm hearing. DTS was more of a motorboating sound and it tended to remain constant (i.e. you'd hear it throughout the movie). This noise is more of a high-freq razzing sound that comes and goes.

Want to hear this sound? Smile with your lips parted. Teeth together, move the tongue away from them and make the sound of the letter "Z" in short spurts and you'll probably hear what I'm hearing.

Note: Playing the movie in MONO seems to get rid of the problem as a temporary work-around.

In those silly countries that require that the shield be tied at both ends for RFI reasons..then the shield should only be connected directly at the processor end, at the reader end, connect a capacitor between the shield and the reader "E" terminal.

Steve

Presently the shield is going to Earth (#5 on the cell) and that's what is jumpered at the moment to #2.

Steve

Please double-check this for me and let me know if this is correct/incorrect...

LED CELL >>> DB9 ON PROCESSOR

#1 Left + >>> Pin #1
#2 Left E >>> Pin #???
#3 Left - >>> Pin #2
#4 Right + >>> Pin #4
#5 Leave Open (Earth, same as LED terminal #2)
#6 Right - >>> Pin #5

Shield Wire floats on LED end >>> Pin #6 (Earth) on DB9

Ground the processor/rack with a brass lug...can I make one if I can't buy one here buy using a brass nut & bolt?

~Manny

"Don't forget to drink your...Ovaltine!?"

--Ralphie, "A Christmas Story"

Steve

The hum was triggered by the platter motors. Yikes!

Rewiring the solar cell to the P1 DB9 (and grounding) per Steve's directions took that hum away.

I got most of the ground loops out of the audio, but once in a while they come back and plague me when someone plugs in a little space heater to warm their feet in the sales office. For a while, I thought our call letters were KHUM instead of KAPS!

One of my biggest nightmares has always been keeping the KAPS rf out of KBRC's audio. But when the weather changes, the RF says, "I'm back!"

Nothing like listening to Paul Harvey's "The rest of the story" super-imposed on top of Elvis Presley.

Our building is old. So old that in some areas, it was wired with Romex without a ground. How in the hell can I deal with that without spending a king's ransom to cure? We even had an electrical contractor come in once, and when he walked away, he shook is head in dis-belief.

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