Main LF and RF output down -8db

[perfectsnd]

Turned on my console yesterday and I started mixing and I noticed the LF/RF buss was showing significantly low level for material I know should be hitting the L/R pretty hard.  I put an oscillator into a channel and set the channel the level to 0 Vu. With the channel panned left or right, the main fader usually would show 0 db, but the main VUs were showing -8 db VU.  I pulled out the outboard comp on the PRE-VCA insert and no change. I tested the output of the Pre-VCA comp and they were were I expected. Post VCA output was also good (I tested by taking the out of the bay to a line input of the channel to show the VU reading).

I then tested LB/RB buss and the level hitting those were good on the main meters when I engaged the back buss and panned the channel fully to the rears.

I then brought up the center section and swapped comp cards with rear buss, but this didn't change anything so I am assuming my main buss cards are good.

I then tried to force a ton of level by overdriving to the LF/RF output, but the meter never went about 0 db VU when they should have been pinning.

Where can I check to figure out the problem? Has anyone experienced this before?

[walrus]

Been a while since I worked on a 4K, but what do you get if you dead patch the 2 track bus (i.e. break connection to all the 2 track machines).
Could something be loading down the main L/R outputs?

[horizonsound]

Fair point that Kevin, as all the stereo 2 track feeds are paralleled.

Anthony.

[perfectsnd]

I disconnected anything that was on the main L/R distribution on the patchbay, but nothing changed.

If I play a mix through the console, I hear distortion when monitoring back.  If I patch out of the post VCA send and come back in External to Monitors on ST1, the mix sounds fine, but it is 4.5 db down because of that patch point being an insert send.

Where else can I look? The back buss is completely fine.  I reseated the 024 and the 025 card in the center section. Those cards looked fine.

[walrus]

If patching out of post VCA Insert Out gives a good signal to an external monitor, but patching the Oscillator into Post VCA Insert Return gives poor signal on the main L/R outs, and there is nothing loading the main L/R outs, then the problem has to be on the 25 card.

[Edit] Thought it might have been the fusible resistors, but this would affect rears as well.

Problems with logic re the Slate signal, would again affect the rears.

[walrus]

Have you actually tried listening to the 2 Track output using another seperate amp/speaker of some sort?

The metering and monitoring all happen via the 24 card, and a fault on that would affect what you hear and see with desk, but would not actually affect the mix out.

[perfectsnd]

If I patch any of the 2 track outputs to my speakers, the level is way down and is distorted. If I take the the same signal from the Post VCA outputs everything sounds fine.

I tested my voltage at the center section and I am sitting at 17.84 so I might need to gain up my power supply. I installed a new power supply (81 Series Supply) about 4-5 month ago so I can easily just trim up the voltage. I don't think the voltage is the problem as everything was fine before.

[walrus]

Sorry to be perdantic, but did you actually try dead patching the M row of the Prgramme Outputs?

I can't think of anything else other than rats/mice have chewed wires and shorted them out, or the 25 card has damaged components on both the L *and* R driver circuits!

[perfectsnd]

Okay. Yes, I did dead patch the LF and RF via the patchbay and that got my LF and RF back full.

So what the hell is going on?  If I take out the dead patch, I lose the level.

Of course, none of the distribution is going to my stereo outs.  I can pick the main outs from the patchbay on the main LF and RF outs.

[walrus]

Do you have anything normalled to the 2 Track patch rows, like machine wall panels in the recording room? Could be a misplugged something on one of them.

Unfortunately now that I’m retired, I don’t have access to a SSL install manual, or I would suggest which 2 Track DL’s under the desk to disconnect to see if that helps narrow down the problem to in the desk or external to it. But I think that is the next place to look.

[Dave Dicson]

DL 31 & 32 are used for 2 track tape machines or whatever. DL 33 is used used for the main outputs to speakers & headphones.

[perfectsnd]

If found out that my convertors that were hooked up via DL32 were reversed on my convertors so the output were normalled instead of the input.

Once I corrected, my LF and RF came back to normal and my distribution chain was working as they should.

This mispatch seems to have been weighing down my master outputs.

[radardoug2]

So you should fire whoever did that! Was it you? This always looked like an excessive loading situation.

[perfectsnd]

Yes it was me. My main interface was having issues (Antelope Galaxy 64) and it have 64 channels of In/outs so I screwed up a couple of DB25 connectors.

I brought myself into HR and I reprimanded myself. Needless to say better markings went on the DB25s!