Film-Tech Forum ARCHIVE: SMART MOD-2C will not switch from digital to analog when dts drops out

This is topic SMART MOD-2C will not switch from digital to analog when dts drops out in forum Film Handlers' Forum at Film-Tech Forum ARCHIVE.

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Posted by Dave Williams (Member # 299) on 09-21-2000, 06:33 PM:

I have a Smart Mod 2C that will not switch from digital to analog when the DTS cuts out.
Also there is another problem, when it powers up in the morning the right surround speakers have a loud hiss. This goes away after you cycle the power a few times, but comes back if there is a power outage and cuts out for any lenght of time.

Any ideas on what is up here?

Dave

Posted by Gordon McLeod (Member # 33) on 09-21-2000, 06:40 PM:

Power supply or the regulator on the eq board for the surround
The not switching issue is a problem between many processors and the DTS units
I would be tempted to change the RC ratio on the format boards input but Oscar will tell you the consequences as noise imunity will change as well

Posted by Dustin Mitchell (Member # 372) on 09-21-2000, 10:23 PM:

I'm not a technical guy, but I've had that DTS prooblem between a Mod 11c and a DTS 6D before. The problem is not nescessarily in the SMART. The DTS unit has to send a 'signal' back to the sound processor to tell it to switch when the digital drops out. The signal may not be getting there, either because:
a) its not being sent, or
b) there is a broken/loose cable between the DTS and Smart.
Then again it may be in the SMART, I don't know. Good luck.

Posted by Oscar Neundorfer (Member # 458) on 09-22-2000, 09:59 AM:

Hi Dave,

On the failure-to-switch problem, it is hard to say where the fault is at this point. We need to do some simple tests first. I am assuming you can manually switch the MOD IIC to any format you want.

Remove the db25 connector from the MOD IIC. Manually switch the MOD IIC to DIGITAL format. Then take a jumper wire and momentarily ground pin 13 (upper row, left end pin)on the MOD IIC db25 connector. Verify the the MOD IIC has gone into either STEREO SR or A format. (Whether it goes into SR or A will depend on a jumper setting on the format card.) If this test works, then the MOD IIC is probably OK. PLEASE NOTE: it may be difficult to get a good connection on the db25 connector. You need a small enough piece of wire to go into the pin 13 hole and actually make contact with the pin.

If the first test fails, then do the same thing except you will momentarily ground the STEREO SR or STEREO A format terminal on the back of the MOD IIC. If this works, then the problem could be a defective MOD IIC motherboard trace or solder connection between the db25 connector and the format terminals.

Also, disassemble the DB25 connectors on both ends of the DTS interface cable and inspect the solder connections. Look for broken wires. Repair as needed, or order a new cable if the cable has problems.

Regarding the problem on right surround, my best guess is that the surround eq card is at fault. Pull the card and look at the back of the card (solder side). See if there are 2 diodes soldered on the solder side of the card. If they are not there, then this board needs to be modified. Or, we will be happy to send a replacement board. Contact me for details. Without the modification, the board will SOMETIMES be prone to latch up the voltage regulators on power up. This will result in a noise on one or both surround channels.

Hope this info helps.

------------------
Oscar Neundorfer
Chief Engineer
SMART Devices, Inc.

oscar@smartdev.com

Posted by Oscar Neundorfer (Member # 458) on 09-22-2000, 10:17 AM:

Dave,

One more thing to check. Remove power from the MOD IIC. Now, pull the format card. Look for a jumper near the upper edge of the card, a couple of inches in front of the gold edge connector fingers. The jumper pins are labeled OPT DEF which stands for Optical Default. The jumper should be on 2 of the pins, either A or SR. This jumper determines whether the MOD IIC goes back to A or SR if digital fails.

------------------
Oscar Neundorfer
Chief Engineer
SMART Devices, Inc.

oscar@smartdev.com

Posted by Karen Hultgren (Member # 395) on 09-22-2000, 03:04 PM:

Check the pulse from DTS player to the CP. Use a DTS setup disc and meter. After the disc plays, eject it. You should see a pulse to low on the analog line. Which analog line? That depends on how the disc is programmed. If using the DS1 disc, each DTS channel is programmed to go to a different analog backup channel. This is used to test the pulse lines from DTS to the CP.

Movies discs each are programmed to default to whatever analog format the film was mixed in. If it is in "SR", that is the format the DTS will pulse to (in the event of a DTS drop-out).

The "hitch" comes in when the CP you have does not have "SR". In that case you will have to make a modification to the DTS logic card so that the "analog" pulse will always to sent to "A" Type. Depending on the model of DTS logic card, it will mean either moving a programming jumper to "A" -or- doing a trace cut & adding a jumper. Please send me an email and let me know the model of DTS player (2-drive or 3-drive) and model of DTS logic card you have = it should be D???

Karen at DTS
khultgren@dtsonline.com