Some help/advice with our stereo channels.

[bradholland]

Hey Guru's
Last year we went and bought our SSL 8000gb from a nascar truck in nashvile.
We've slowly commissioned it back into life and have never gotten to the 4 stereo channels.

Started to mess with them last week and they dont work. I have done quite a bit of tracing (my methods you will probably find questionable, but I'm not an ssl tech so have winged it!)

OK, this is how far I got.

2 of the channels permanantley have the overload lights on and none of the 4 seem to have any output.

Connecting a cd player to the inputs on the back of the desk if we smashed the gain all the way up we could hear some quiet but very distorted signal coming through.

To check a few things like connections I did the following:

1. Pulled channels out and hard connected the pins on the edge connector on the backplane direct from line in to the buss out on the lower card connector. sound came through just fine. so we ruled out anything wrong with connections.

2.placing the channel into a different slot and then using one end of a test cable in the edge connector I put the other end onto some points of the channels board. right where the mono switches of the channel are. signal was good and the channel otherwise then worked as expected. eq etc and everything were fine. the gains did not work which told me I was injecting the signal post gain stage.

Because of this I suspect there are problems with the input card i think the board number is: 82E201N0189

A photo of the board is attached.

Perhaps someone could tell me if this is a common problem and where I should start looking. as a quick test (we had a spare channel) I swapped all the NE5534N op-amps out that didnt seem to fix anything.
Just some guidance where to start and what to replace first would be great. the caps dont look bulging and nothing seems burnt.
as I said, all 4 boards seem to exhibit the same problems. we dont knwo when they were last used, its probably just the caps, right?

thanks guys

Brad 

[sintech]

I'd check all your voltage rails feeding to the stereo channels are good as a first port of call.

[bradholland]

oh yeah, should have mentioned that.
They all checked out ok, as per what the manual said should be present on the edge connector.

[sintech]

Hi, looking at the schematic, you should apply a 1k test tone to the Left and right inputs.

Scope at R127 you should see if the signal for the LHS is reaching this point, R128 for the RHS.

Unfortunately don’t have a stereo channel to play with but to my eye, that’s the pre-cut outputs of T1 and T3 input hybrids.

You need to know these are working ok.

[bradholland]

thanks sintech. going to check that in the next day or so.

should I not find signal there, what am I looking at?

[sintech]

Hi Brad, I’d be highly surprised if you don’t have signal at this point, and I’d then double check and pull the hybrid and see that pin 1-2 is receiving the input from the upper bus card.

The Gain switch is interactive with these hybrids, so bare that in mind. (Trim and Balance are found later in the circuit)

If all is good at that point, continue to the input of T6 (LHS) and T9 (RHS) you could clip the scope at R25 and R49. You should have the same but the Cut button should be interactive.

If all is good here.. I’d personally jump to the output of the circuit and then scope back if no signal was present. The Panning arrangement sits between the two stages.. and looks understandably complex!

These look like the standard Input output Hybrids that SSL used in the 5k, GFX 384 series? if so you can get replacements from the SSL webstore.

[michaeldtech]

I am in the same sitch with some stereo modules in a SL6056. 
Silly question, do you have them assigned to LF/RF at the top?
I would also check if the VCA's are making it to the computer.  I am still testing mine with them bypassed with the ribbon jumpers.
I have been familiarizing myself with the placement of specific components along the signal path with a second module in my hands because once it is on the extender it is tough to see the component labels under the actual components.
I am figuring that the overloads are a chip on the VCA board and just following signal path along the channel for the other problems.  The 1986 console will have to be completely recapped of course as there have been some burned fuse resistors already and some channel paths are slightly attenuated.
Mike