48V Problem

[Riff Raff]

Hi, I got an issue with the 48V on my 4000E.
The PSU seems not to be guilty, if I run the PSU alone, the 48V led is ok, but when the console is plug to the PSU, the 48V leds don't light up on the PSU and on the console.
Is there any fuse for that in the console ? or a card that I could check ?
Thanks.

[radardoug2]

Sounds like you have a short on the 48 volt line in the console or a faulty cable. You will need to fault find it. You need only a multimeter that will read ohms, but that voltage goes to every module, so it will be a big job finding the short.

[jimlfixit]

Hi Riff Raff. I am not technical, just a drummer and a wireman with SSL experience over 40 years but here are some of my thoughts on this:

1   48 volts just affects the mic channels, not the centre section, Keyboard etc right?
2   If so turn the console off and switch on various sections (8 channels at a time?)  but switch on the 651 and other stuff FIRST to prove it is not those units which don't have Phantom power.
3   Gradually switch on each bucket of 8 one by one to see if the problem is confined to a group of 8 channels.
4   Another option if non of the above works is that it may be on the patchbay ... see below.

I rewired a 6K SSL recently in Dorset, UK and found out that a mic input wasn't working because the bantam jack was not shorting (directly linked) to the SSL metal front panel as the console was 40 years old and the M3 screw had come loose (never, ever experienced that before). So tighten up the screws on patchbays A and B (mic sources and mic inputs) and see what happens.

I hope to document more SSL wiring soon as time allows. Firstly it will be the channel patchbay stuff.

PS: If anyone wants some 96 way DL looms made, contact me!

Hope this helps and good luck.

[Riff Raff]

It happend even when I switch on only the center section.

[jimlfixit]

Hi Riff Raff
As I mentioned, I am just a wireman and not technical. I read your latest message and have the following suggestions as a result:

1   Just unplug the 19 way Bicc PSU loom at the console end but keep it plugged into the SSL power supply (661). Turn the PSU on and see if it still shorts out without anything on the console connected. This will ensure that the lead is good (or not).

2   Plug the PSU loom into the console and switch off and on all the 4 pole switches (+20, -20, logic and 48v) one at a time (these include the 651 and channels in lots of eight)

3   The 48 volt power comes in on pin A of the 19 way Bicc with an orange 16/0.2 wire so, if none of the above work, I would get a ohm meter out and test any impedance difference between pin A on the Bicc input to the console to any other pins to see if there is a short. Also check between A and V I think, the main Ov in the middle of the connector and also any part of the chassis frame.

There is always a solution to this stuff!

Hope this helps and lets us know. Jim Lassen in the UK.

[Riff Raff]

Thanks a lot, I will try all that tomorrow.

[Dave Dicson]

Depending the console frame size, the bigger ones have 2 Bicc male power supply connectors under the patch bay with the DL's. One of the Bicc connectors doesn't have as many pins as the other one does. Are you in the right connector?

[Riff Raff]

It's only when I switch on the center section that the 48V led shut down on the PSU.

[horizonsound]

Possibly a short within the actual power switch for the centre section.

I was working on one of those on the weekend, and when the mechanical internals of them fail they can short out the poles.
In our case, one of the 18V lines shorted. It certainly let us know about it with a massive spark!

Test this by disconnecting MRAC M1 which carries power to the centre section. If it still shorts, it's the switch.

They are a real bitch to replace.

Anthony.

[Riff Raff]

Thanks I will try that.
I noticed that, when I switch on a 8 tracks frame, I got 43V on the XLR (is it ok to not have 48 ?), and when I switch on the center section, it goes down to 6V.
I got a plasma bargraph only for the LR output, and it doesn't work anymore since the 48v failed. So, yes, it looks like a short cut in the center section supply, even the sound still comes out from the LR output.

[Riff Raff]

Where is yhe MRAC M1 and does it looks like ?
Thanks

[jimlfixit]

Hi again.
Just realised that the centre section does have 48 volts but only for the Led at the top I think to show the power is on.
So, from the power 19 way round Bicc connector pin A, the orange 16/0.2 wire daisy chains across the 2 way,  4 pole switches and off to buscards etc.
The 651 48 volt feed goes to Mrac 1 (pin BD?), which is one of the two 104 way Mrac connectors plugged into the back of the 651. These are blue and have a yellow anodised backshell with two locating screws.

As Anthony mentioned, disconnect that to see if the short is still there and, as he stated, it could be one of the 4 pole switches which are not easy to rewire as everything is sleeved and would need to be cut off and replaced after so many decades. Access to these switches is also difficult but good luck and they do break down sometimes (along with the circuit breakers) so it is worth while having a few spares (Farnell/Newark or RS).

All this is from distant memory so bear with me if I may some details wrong.

[Riff Raff]

Thanks a lot.
I've found the MRAC M1 (Ididn't explore this part of my console untill today  )
So, with the MRAC M1 unplugged, the 48V short cut is still there. So I have to deal with that switch.
Since my console was a 48 channels and had been reduced to 32 channels, I have 2 switches that I can use to spare the faulty one. I will check that.
Thanks again to all of you for your precious advices.

[jimlfixit]

Hi Riff Raff
Good that you have a few spare SSL 4 pole double throw switches as spares but be patient as these may be frustrating to replace as Anthony mentioned as they were rubber sleeved decades ago and would be hard to access. SSL used H30 or H50 (3 or 5mm) Hellermann sleeves for this but you could replace them with heatshrink these days.

Another point: Sometimes and over time, various things can be dropped into the patchbay by mistake and there could be some loose screws or other metal parts which may be in there and I have seen a few over the years including XLR connectors lying around and loose.

If you need to access the switch, it is at the front of the patch and you may need to remove the Producers Table (horizontal grey material) to get access. If so, you may need to take out some of the patchbays (mostly user option rows) as well to gain access to the switches, circuit breakers etc.

If time allows, it could be a good time to remove any loose metal bits in there and vacuum clear the top side of the DL connector panel, especially as your console is so old. Also, maybe unscrew and put back the DL M3 screws as there would be a chemical reaction with the steel screws and the aluminium panel. If you remove the DL's and put them back, pull them down to notice the white cable labels on the wires as most of them will refer to the patchbay jacks (ie R16 is row R and jack number 16). If you do this, document the labeling as it may not be the same as your installation manual pinouts, assuming you are lucky enough to have a manual and it is accurate, which is rarely the case these days!

Here is a link to Farnell for the 4 pole switch which looked the same as SSL used but maybe a different supplier these days.
https://uk.farnell.com/multicomp/1m41t1b5m1qe/switch-4pdt-5a-120vac/dp/1550192

Good luck and if you have time, do what I mentioned above at the same time as it will save problems later on.

[horizonsound]

These are the actual ones used, available from RS Components

https://au.rs-online.com/web/p/toggle-switches/0316995/?relevancy-data=7365617263685F636173636164655F6F726465723D31267365617263685F696E746572666163655F6E616D653D4931384E525353746F636B4E756D626572267365617263685F6C616E67756167655F757365643D656E267365617263685F6D617463685F6D6F64653D6D61746368616C6C267365617263685F7061747465726E5F6D6174636865643D5E2828282872737C5253295B205D3F293F285C647B337D5B5C2D5C735D3F5C647B332C347D5B705061415D3F29297C283235285C647B387D7C5C647B317D5C2D5C647B377D29292924267365617263685F7061747465726E5F6F726465723D31267365617263685F73745F6E6F726D616C697365643D59267365617263685F726573706F6E73655F616374696F6E3D267365617263685F747970653D52535F53544F434B5F4E554D424552267365617263685F77696C645F63617264696E675F6D6F64653D4E4F4E45267365617263685F6B6579776F72643D3331362D393935267365617263685F6B6579776F72645F6170703D30333136393935267365617263685F636F6E6669673D3026&searchHistory=%7B%22enabled%22%3Atrue%7D