Film-Tech Forum ARCHIVE: Sound Loss Need Help

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Posted by Martin McCaffery (Member # 37) on 10-13-2010, 04:41 PM:

Followup from a previous thread. Kelmar basement readers, CP650

As per previous thread, replaced power supply board in Kelmar.

All LED's on power supply light up. Basement reader lights up. No signal at the CP650. No digital, no analog.

Projector 2 works fine. CP is registering P1 and P2 correctly. Changeover is switching machines.

Have talked to Louis about it and we don't have an answer yet. Is there something blindingly obvious, or a secret I'm missing?

Posted by Kris Verhanneman (Member # 5562) on 10-13-2010, 04:49 PM:

What happens when you connect the signal (analog and digital) from projector 1 to the working input from proj2 on the CP650?

Sorry if this is a very stupid question...

Posted by Kenneth Wuepper (Member # 1174) on 10-13-2010, 04:59 PM:

Kris,

Your approach is valid.

In any troubleshooting situation you must start at some known to be working point and trace from there.

Since one set of input signals works and the other does not, if practical, exchanging the inputs to the processor is a valid test. It is also effective as it does not require additional or sophisticated test equipment.

KEN

Posted by Martin McCaffery (Member # 37) on 10-13-2010, 05:00 PM:

We discussed this possibility, but couldn't figure out on the fly how to rearrange the relays to trick the processor into thinking P1 was P2. And I don't want to take the chance of disabling both projectors so close to the show. If we haven't figured it out by tomorrow, I'll probably give it a try.

Posted by Scott Norwood (Member # 30) on 10-13-2010, 05:20 PM:

Does it work in bypass? I find it curious that both analog and digital are failing. That would indicate that it isn't the preamp or cell wiring that is bad.

Are the motor-start relays functioning properly?

Posted by Martin McCaffery (Member # 37) on 10-13-2010, 05:27 PM:

Scott: Yes, the motors are all starting correctly and registering correctly on the processor.

I didn't have it in the first post, but I did try putting the old power supply back in with the same result, even though it was working last night.

Posted by Mark Gulbrandsen (Member # 72) on 10-13-2010, 09:37 PM:

If in doubt always start at the power supply. If it isn't right nothing else is! FIRST... Check your DC power supply voltages at the test points with a DVM. You may find a couple of them to be low. I had a rash of CP-650 power supply failures earlier this year... about a half dozen of them all failed within a few months time. There is one particuluar version of supply that has problems with leaky electrolytic capacitors... Black tar looking stuff that comes out of the ends of the caps.You can get a new supply or just replace the half dozen bad caps and live happily after.

Mark

Posted by Marty Carr (Member # 5267) on 10-13-2010, 09:46 PM:

Just a thought on this. Did you by chance happen to switch the analog and digital wiring while replacing power supply?

Posted by Martin McCaffery (Member # 37) on 10-14-2010, 11:28 AM:

The latest update.

Projector 1 bad, Projector 2 good

Switched the digital inputs so #2 was in #1 and vice versa. Made appopriate changes to fool the system. #2 sound worked through Reader #1. #1 sound still did not work in Reader #2. So we at least know the Dolby Processor is working.

Made a similar test with optical inputs. Same results.

Hooked the new kelmar power supply #1 to the #2 supply. All LED's lit. Got digital from #2, but it would fail to SR and no sound out of SR (running loops). Put #2 back the way it was and was not getting digital, but SR was fine. Ran a new trailer, and rechecked the connections and got digital back on #2, but it is still iffy with loops.

What do I check next?

Posted by Tony Bandiera Jr (Member # 2365) on 10-14-2010, 11:38 AM:

Martin, If I am reading the steps correctly what I am seeing is that your analog reader in #1 is shot, and whatever the problem with the power supply was has killed the reader.

Kelmar readers suck IMHO and I would go with Comp. Engineering anytime, I (so far) have never had any fail on me. I have replaced many Kelmars though.

I sincerely hope, that when you were swapping the digital reader cables, that you powered down the CP-650. Otherwise you may have damaged the processor's reader inputs, the readers or both.

As for the Digital being iffy with loops, take that with a huge grain of salt. Loops are usually high wear, and if they are not threaded just right the instability of their motion will cause them to not read properly. A proper loop is one where you can thread the entire film path with room to hang the loop over rollers/spindles so it doesn't drag on anything.

Posted by Martin McCaffery (Member # 37) on 10-14-2010, 01:57 PM:

Yup, looks like we'll be doing some replacements. Going to need to call in a Tech. Louis is a little too far away so he suggested I put out a call here. I'll also put up a specific post, but if any of you can suggest a great Dolby tech, let me know.

Posted by Manny Knowles (Member # 1171) on 10-14-2010, 05:40 PM:

so...do we now have THREE threads for this one topic?

Posted by Martin McCaffery (Member # 37) on 10-14-2010, 06:23 PM:

One thing leads to another [Wink]

Posted by Martin McCaffery (Member # 37) on 10-16-2010, 01:25 PM:

The latest update anomaly:

This morning went to check the DCV input for the solar cell pre-amp. It was getting almost 12v, which is good. In the process I disconnected the both of the plugs on the pre-amp and put them back.

Viola! I am now getting a very low optical signal back through the processor (so low if I boost it to 10 can just barely hear it in the theatre) and still no digital.

Have I stumbled upon a dead pre-amp?

Posted by Richard Hamilton (Member # 321) on 10-16-2010, 02:36 PM:

Here's an idea...Call Dolby. They do have tech support.
Rick

Posted by Sam D. Chavez (Member # 1841) on 10-16-2010, 03:34 PM:

Martin,

You should have + and - 12 Volts at the solar cell board. Do you still have both voltages and a common back to the supply? Sounds like bad connections to me. Check the voltages at the power supply end as well while it's acting up.