Film-Tech Forum ARCHIVE: SRA-5 Schematic/Help Needed

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Posted by Matt Close (Member # 996) on 08-24-2004, 07:15 PM:

Does anybody have a schematic or technical info on the Dolby SRA-5? Mine blew a fuse and now doesn't pass through any sound! [Eek!]

Any help and advice is welcome too! [Big Grin]

Posted by Daryl C. W. O'Shea (Member # 1303) on 08-24-2004, 07:44 PM:

Replace the fuse. [Big Grin]

Actually, there is some documentation in the manuals section. Not sure what it is, I don't have time to download it on dialup here.

SRA-5 and the SA-5.

edit: thought I had pasted in two SRA-5 links, not one for the SA-5

[ 08-24-2004, 09:13 PM: Message edited by: Daryl C. W. O'Shea ]

Posted by Steve Guttag (Member # 268) on 08-24-2004, 08:23 PM:

The SA-5 is a CP-100 stereo surround adapter...

The SRA-5 was made during Dolby's dark years on documentation...it and the Cat 113C were done around the same time. There is virtually no doucmentation on the schematics of the unit that I am aware of (though there must be some, I don't think they have ever made it to any sort of publication).

Change the fuse and in the mean time wire around the SRA-5. In a CP-200 type installation, the sound must pass through the SRA-5 and it will indeed nix the sound. It is good to have a bypass fanning strip handy just in case.

Steve

Posted by Matt Close (Member # 996) on 08-24-2004, 09:06 PM:

I was actually using it with a JS-200 Ultra-Stereo processor. What a huge difference it makes over the USL SR card!!!!

Anyhow, I have now discovered that if you power down the SRA-5, you here the sound that has been passed through the cards for a split second until the caps discharge...... I know it is the processed sound I am hearing because you can't hear it if the cards aren't in. So, I guess I am looking at a control/logic problem. I see there is a CD4052 chip in there for signal switching, but I don't know what goes where, or what rails should have what on them to trigger what!?!? [Roll Eyes]

... if you get the drift..... so I am hoping someone either has schematics or has struck the problem before..... Even the pinouts for the CAT280T cards would help, so I could see where the signal is making it to before it is interrupted.

Posted by Matt Close (Member # 996) on 08-25-2004, 12:36 AM:

Don't worry ... Found the problem holding the 'inhibit' leg high on the CD4052. All good now.