Author Topic: SSL 4000 E Cut Problem  (Read 933 times)

Romaphonic

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SSL 4000 E Cut Problem
« on: December 04, 2018, 04:43:13 PM »
Hi! I m having a problem with the whole console right now... i could not find in the forum if someone had similar issue!

When i start cutting channels... as I accumulate cuts, the remaining channels start losing gain... i tried swaping modules, turning off some bucket, PSU is OK, but cant find the issue...

does anyone have any clue?

thanks as always!!!

bests

N

MarconeMusic

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Re: SSL 4000 E Cut Problem
« Reply #1 on: December 14, 2018, 03:34:49 AM »
Do you have led bulbs in the console?
I’ve heard of people with issues with leds that aren’t right. 
Only thing I can think of, by enabling more bulbs, more problems

Dunno?

WiktorTRS

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Re: SSL 4000 E Cut Problem
« Reply #2 on: January 13, 2020, 10:08:29 AM »
Hi, I have similar issue. I have noticed this during writing automation. When cuts are getting accumulate, levels slightly going down. Even a master fader. I started to use faders instead of cuts. It's annoying... Did you manage the problem?
Kindly regards,
Wiktor

Audioplatinum Service

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Re: SSL 4000 E Cut Problem
« Reply #3 on: January 13, 2020, 08:50:00 PM »
I had similar problem,and what I found..bad switch for 651 center section,losing -18V in centre. Check power switches under patchbay,maybe some of them had big resistance and voltage after switch is not correct.

Cheers,
Raf
Audioplatinum Service

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"A clean desk is the sign of a sick mind..."

WiktorTRS

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Re: SSL 4000 E Cut Problem
« Reply #4 on: January 17, 2020, 12:20:38 PM »
Thank you so much! I will check it in a couple days. Kindly regards!

WiktorTRS

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Re: SSL 4000 E Cut Problem
« Reply #5 on: February 03, 2020, 08:34:27 AM »
Hello,
I have done two videos just to clarify the problem:
This is the main video: https://youtu.be/MH3RrDHapeg
And this is an update: https://youtu.be/n65vcED7ot0
The problem only occurs when working with a computer. When computer bypass plugs are inserted everything works fine. So I suppose VCA's in a console area are ok.
Sorry for my awful English on these videos...
Kindly regards!

horizonsound

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Re: SSL 4000 E Cut Problem
« Reply #6 on: February 03, 2020, 10:08:03 AM »
My first thoughts would be the PSU, and the increased load pulling down the voltage rails?
Maybe check the rails as you keep pressing more cut switches, see if it is stable.

WiktorTRS

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Re: SSL 4000 E Cut Problem
« Reply #7 on: February 03, 2020, 01:48:25 PM »
Hi,
I have measured DC on computer rails (which should be +12v, -12v, +5v)
Here is the report:
NO CUTS engaged (normal VCA levels) -> +12.28v, -11.93v, +5.23v
36 of CUTS engaged (most visible VCA dump) -> +11.71v, -12.5v, +4.66v
ALL CUTS engaged (almost no VCA levels) -> +11.50v, -12.70v, +4.46v

So... Is it possible the Computer PSU doesn't have enough current efficiency?
Or some part in a computer has high power consumption?
Or maybe it is normal (I doubt it...)?

In Poland we have 230V AC / 50Hz just like in the Netherlands where the console comes from.
However all PSU's are set to 240VAC (GB).
I don't think that's the reason because regulators should handle the difference.

Thanks for the suggestion to measure voltages. However I don't know what to do next...
Wiktor

horizonsound

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Re: SSL 4000 E Cut Problem
« Reply #8 on: February 03, 2020, 07:16:17 PM »
Those 5v rail values look really low. I found the computer became unstable when it dropped below 4.8v.
It has a sense return line back to the PSU that should keep it constant.
How old are the regulators in your PSU?

Anthony

jimlfixit

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SSL 4000 E Cut Problem. An ignorant wireman take on this
« Reply #9 on: February 03, 2020, 10:46:53 PM »
Hi people
I read this post and the various replies a few times and here are my thoughts which may help (or not?).

I am not technical, just a wireperson and I can't fix anything unless I had instructions about what to change etc.

Anyway, some of the SSL's being talked about here could be 40 years old (I was there from 1980-87 in the earlier days).

So, wires will get brittle over time, some solder joints may go cold and some switches which are not used much (the high standard Highland versions are great though) may get oxidised.

Therefore, after all of this time, it may be worth resoldering some solder joints (especially if they look 'frozen') and flick some switches off and on which haven't been used for a while (if you don't use the fog lights on your car much, they may not work ... I have had that problem before).

Just some thoughts which may prove useful. Also, cover your console when not in use to stop the dust getting into the fader slots and around the pots ... prevention is better than cure right?

I will shut up now. Bye all.
« Last Edit: February 03, 2020, 10:49:16 PM by jimlfixit »

WiktorTRS

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Re: SSL 4000 E Cut Problem
« Reply #10 on: February 04, 2020, 06:29:50 AM »
Anthony,
Thanks for tip. PSU comes from 90’ decade so probably regulatots too.
I know there are feedback lines and in this case the voltage shouldn’t change value at all (if regs work properly)
I tried to compensate all voltages (including +5v) by trimming „V out” pots and it’s possible to get the
5, 12, -12 on computer rail but it doesn’t have any influence to VCA levels.
P.S. Your 4k building project is amazing. Congratulations!
« Last Edit: February 04, 2020, 06:46:59 AM by WiktorTRS »

WiktorTRS

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Re: SSL 4000 E Cut Problem
« Reply #11 on: February 04, 2020, 06:43:02 AM »
Jim,
Thanks for your suggestion.
I will check VCA ribbons. They look awful. Some connectors doesn’t look good too. Maybe there is a leak or short.
Console itself is ok becouse it works with computer bypass terminators.
Regards,
Wiktor
« Last Edit: February 04, 2020, 06:48:37 AM by WiktorTRS »

WiktorTRS

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Re: SSL 4000 E Cut Problem
« Reply #12 on: February 06, 2020, 10:44:11 AM »
After hours of researching I found dead germanium diode AAZ17 in Analogue Input Board of Studio Computer.
There are  actually two diodes between 0V analog and 0V digital rails. I am not an educated electronics engineer, rather an amateur but it seems to me that circuit ensures that the voltage difference between 0V an. and 0V dig. does not rise above the forward voltage of those diodes and strictly 0.45V. When one of them is blown (does not lead in either side) the voltage may increase. Thus, the voltage may vary on the common rail of VCA ribbon input.
I hope this is the cause of the fault.
I attached piece of diagram.
Just bought the diode on ebay and I'll let you know if it works as soon as the diode arrives.
Kindly regards,
Wiktor

waltzingbear

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Re: SSL 4000 E Cut Problem
« Reply #13 on: February 06, 2020, 07:02:06 PM »
you could replace it with a Si diode which you probably have around to test.

But my guess is that the diode being blown is indicative of a problem else where. I do not know that part of the computer or have a schematic, so....  You still have the 100 ohm resistor to keep things in line. for testing you could even short the diode/resistor, that circuit is there to keep ground loops under control. Not a big deal for testing.

Alan
Alan Garren
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WiktorTRS

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Re: SSL 4000 E Cut Problem
« Reply #14 on: February 07, 2020, 07:23:27 PM »
Hi Alan,
Thanks for your tip. It was very helpful! I have done short in place of blown diode as you suggested and VCA's returned to normal !!! :-) I can engage as many CUTS as I want and it's stable!
I can't wait for the diode to come. However,...
1) Something caused damage of diode
2) Without the short there is 0.45v - 0.58v difference between 0V an. and 0V dig. (depending on number of engaged cuts). A current is extremely low (less than 0.01 mA) Maybe this is the normal behavior of this circuit.
Anyway I'm f....n' happy!!!
I will let you know as soon as I finish the repair.
I am very grateful for all your hints guys.
Kindly regards
Wiktor
EDIT:
I decided not to wait and put two Schottky's diodes in place of old germanium. VCA's are super-stable!
One more time I thank you very much for your help.
Regards
Wiktor
« Last Edit: February 07, 2020, 08:20:24 PM by WiktorTRS »