SSlmixed.com Forum
Tech discussion => 4K,6K,8K Series => Topic started by: Showcase on July 29, 2019, 12:38:52 PM
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Hi!
Trying to understand why this supply behaves like it does and here is some info:
* My -20 rail works for about 3-4 months, then a couple of 2N5886 is blown, I change them and then it works again, never any other rail breaks
* The -20 led is lit not as bright as the others and this is something that gets worse and worse, after last repair its even more faint (with also no load on supply)
* reuglator cards is checked and even switched out the -20 card but same same
* resistors in the -20 rail is checked and 2 was replaced when last serviced
I simply cant find any issues, the bridge rectifiers is hot, -20 more so than +, they are moved since ages up from the "railboard" and fitted in the chassi on the top chassi sides
Im not an electrician but managed fixing things having this console for 15 years . Can a bridge rectifier wore out and need replacement, ot is it working or not? Some tips of what to check?
/ Mattias
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as far as I am aware the main transistors need to be matched under load not off load.
also when changing things in the PSU it needs to be lined up again.
There are only 2 people I know that can do this effectively and have got the right gear:
-recycle audio
-graeme johns in London
Matt
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a little more info is also needed
-how big is your console (# channels)
-how many power supplies do you have on each rail
-have you measured the supply voltage over time to see if it is staying at the correct voltage?
what you describe is the -20V supply drawing more current than the +20V, it also sounds like the -20 is changing over time (the LED getting dimmer). You need to keep measuring this to see what is happening.
I tend to think that you have added more channels to this console? and you may not have the proper power supply for it?
Are the fans in the chassis in good shape? You want to pull lots of air thru there.
The rectifiers are probably fine.
There are resistors on the motherboard that control the voltage as well as on the regulator card, you could have a problem there.
But it sounds like you are drawing too much power from the -20V supply, plain and simple.
Cheers
Alan
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Thanks for replying guys!
Console has 56 channels
I have 2 PSU and a changeover unit, one PSU is working perfect.
This troublesome PSU has died again (-20) rail faded away, I switched off the fully working PSU first which killed 4 transisitors in the second PSU +20 rail
I have now replaced ALL resistors and diodes in the 20 rails, but only +20 rail works, regulator cards are fine but in this bridge rectifier for the -20 rail I found out maybe one diode inside is shorted see pic, I get readings in both directions to that point and Im no expert but it doesnt seem right?
Question is where can I find a good suitable Bridge Rectifiers? and do I need to change the rectifier in the +20 rail too for matching?
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As told to me from ex SSL alumni, the two supplies must be balanced with the change over or the one supply will work to hard and fail sooner than later.
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As told to me from ex SSL alumni, the two supplies must be balanced with the change over or the one supply will work to hard and fail sooner than later.
Ye I can see that has been a problem maybe, they were calibrated some years ago and honestly it got worse so thats why I learned how to at least service and fix these PSU´s myself.
Though V out and V trip is calibrated to 18.5 and v trip 22.5 , that isnt too hard to do yourself. And shouldnt this do the most of the balancing? And Im guessing but dont you need to run one PSU at a time, one rail at a time to balance a PSU? I think you need to do this first before using the changeover?
And I dont get why the second PSU get killed when switching off the first, isnt there somekind of inrush current trip (if thats the problem?)
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When I had this conversation I can remember him saying it has to be done underload with the changeover. So you can't do one at a time. Call Phil Nicolay he's on the tech list here.
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When I had this conversation I can remember him saying it has to be done underload with the changeover. So you can't do one at a time. Call Phil Nicolay he's on the tech list here.
Thanks alot, good input, will try to investigate in this further, much appreciated man!!
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According to the manual, the original bridge rectifiers were International Rectifier 40B20T's. These are 40A 200V bridges. I know that later they changed the bridge to one from another manufacturer when they issued the Fuse upgrade kit. Can't find any details re that though. Just get a known brand 60A 400V bridge and it should be fine.
Found the attached while looking, Adjustment procedure.
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According to the manual, the original bridge rectifiers were International Rectifier 40B20T's. These are 40A 200V bridges. I know that later they changed the bridge to one from another manufacturer when they issued the Fuse upgrade kit. Can't find any details re that though. Just get a known brand 60A 400V bridge and it should be fine.
Found the attached while looking, Adjustment procedure.
Ye I tried to do a search on the 40B20T but couldnt find anything... good to know thanks... I had a pretty robust Semikron SKB 30A/1200V rectifier around and put it in for now and at least the PSU is up and running again.
So... from your attached line up procedure... it seems they are calibrated one at a time... logic... didnt know they were to be matched as close as 0.1 V though, I need to be more careful there perhaps to not get an imbalance
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I must say...
I matched my 2 PSU... but when firing up the whole console the voltage dropped to just under 17 Volt (But still matched)
Sounds fucking amazing, less headroom it seems, dynamic range narrowed down, sounds not disted but a bit crunchy, but most noticable the dynamic range/headroom is very much flattened, as a guitar amp more, love it !
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I always wondered about the 220 versus 120 on the power on the SSL. In the UK they run 220.
They say a Marshall sounds best at 220....
Do we have a thread on that?
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Europe has standardized on 230V but the tolerance allows the UK to still run at 240V like we always have, and France Spain Italy etc can still run at their original 220V.
There is definitely a thread somewhere re 240/120 but it might be at GDIY.
Providing the overall cabling is specced for the current, then there should be no difference between the two. Watts/VA/VAr don't care about the volts if the current is available.
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Ye but underpower the whole console should be a different matter, it def got another vibe too it, for many to the worse I guess but I liked it :)
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-20 rectifier exchanged to a 70 AMP 800V Semikron, PSU´s seems to run fine again, but the -20 rail seems a bit hot running, at least the rectifier, I read this " the large filter caps frequently play a role in overheating the bridge. If the capacitor develops a "bulge" at the top of the part"
Since it has been a problem with the -20 rail for a long time now, and I dont know how old the filter caps are, but at least 15 years running almost daily, I think I need to replace them question is i dont get what uf I should get, here is 2 pages from the SSL manual telling the same or different??
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Fit the same size and voltage rating. You can go up on the voltage rating if you cant find the same. Dont fall for the internet hype about fitting bigger.
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Fit the same size and voltage rating. You can go up on the voltage rating if you cant find the same. Dont fall for the internet hype about fitting bigger.
Ye but the SSL manual, as I read it says 2 different vaules 1000 000 uf or 100 000 uf ? Look at the pic, for me its more than one way or the other, voltage is less problem
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1000,000uF is One Farad!
I think it is a misprint and s mre likely to be 100,000uF.
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1000,000uF is One Farad!
I think it is a misprint and s mre likely to be 100,000uF.
Ok thanks, much appreciated
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It should be written on the cap that is in there.
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The CF661E schematic specifies :-
100,000uF 40v (for the +20V rail)
100,000uF 40v (for the -20V rail)
22,000uF 25V (for the +7V rail - logic)
1,500uF 100V (for the +48V rail - phantom)
220uF 450V (for the +250V rail - bargraphs)
Anthony.
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I putted these in, KEMET stunning 37 000 hours lifetime at 85 degree, they were on sale for just above 30 euros each in Swedish elfa.se, so I think I go for 2 more for the other PSU :D Rectifier bridge is alot cooler too
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lovely caps and you could have been having leakage from one of them causing the rectifier to run hotter.
But the failing 2N5886's are after the cap and their failure is probably not connected to a leaky cap.
The supplies need to be calibrated under load in the working conditions that they will be experiencing in the real world. One thing you can do to make this easier is add test points to the changeover unit. (to me this should have been done at the factory)
A lead from each of the inputs to the changeover diodes gives a convenient monitoring point under load. To set them up measure each supply and get them close, final trim can be measuring from one test point to the other. What you want is both of them at the same voltage, exact level is unimportant, and measuring the difference gives the best resolution. You can monitor this over time and see if the regulation is holding or drifting, which is what I suspect. If the difference voltage goes over about 0.7 volts then the current sharing starts to shift from both to one. Hence your problem.
Good luck.
Alan