4Ke PSU shot, replacing with a modded 5K PSU

[PMcC]

What a great forum...

My aging 4K power supply has played up once too often now and I have decided to replace it with a 5K supply. Just waiting on the arrival of some cable so I can bring separate DC feeds to each batch of eight channels and then I should get to finish mixing the last song of a new album.

Just wondering if anyone is in a similar situation and needs a bit of 'step through' to get back into operation. There is a bit of reshuffling the logic lines to make the thing work but nothing too mad. I've powered up 16 channels plus the centre section so far and all seems good.

[Matt Sartori]

What a great forum...

My aging 4K power supply has played up once too often now and I have decided to replace it with a 5K supply. Just waiting on the arrival of some cable so I can bring separate DC feeds to each batch of eight channels and then I should get to finish mixing the last song of a new album.

Just wondering if anyone is in a similar situation and needs a bit of 'step through' to get back into operation. There is a bit of reshuffling the logic lines to make the thing work but nothing too mad. I've powered up 16 channels plus the centre section so far and all seems good.

Very interesting,
in my short experience with 5K I thought it was a bit too over-engineered and complex to deal with (too many protections and so on) but it would be VERY good to see some pictures and/or a diagram of how you have connected it.

Mattia.

[PMcC]

Hi Mattia, the 5K supply is superbly engineered and beautifully partitioned into brute force Raw DC, individual 5A regulator cards and current monitoring sections.

I'll be offering up a full appraisal of the merging, with visuals as appropriate, paying particular attention to the impact this might have on the overall sound of the console, general reliability and serviceability.

All regulated outputs pass the load current through high current series diodes allowing paralleling of same voltage outputs with the attendant doubling, tripling etc of output current depending on how many outputs are paralleled.

Perhaps of general interest, the centre section alone consumes approximately 75 watts (minimal lamps on), the positive Audio rail draws 1.1A DC under same conditions, well within the 5A capacity of a single regulator card, mind you I've long since extracted the rear left and right mix bus compressor cards.

Eight channels consumes some 120watts, again with bare minimum LEDs and lamps on, and 1.26A of currents the audio + line. It's sobering to see how current consumption ramps up significantly with the dynamics sections gate LEDs in full flight.

For now back to finishing off the cabling...some heat shrink and flexible braided sleeving arrived today.

Back soon...

[PMcC]

Under preliminary tests...

[Matt Sartori]

Well done!
 
Mattia.

[PMcC]

Thanks for that Mattia, just a quick update...

The wiring looms that connect from the 5K regulators to the 4K console are now built and ready for attachment. I have decided to avoid using the BICC 19 way connectors, preferring a more direct connection at both ends of the looms, I know I will have to sacrifice a degree of interconnection convenience by adapting this approach but how often do we make the disconnect with the BICC looms anyway? When installed I'll take some photos to expose the detailing.

As a related aside, when the original PSU failed it took out a rip of group amplifier summing ICs (LT 1028), definitely not a 50p part :-/ plus the 10R local decoupling resistor on the positive rail on that card.

Also even though there will be five separate looms connecting PSU to Console, I have also decided to parallel the individual regulator cards together, a move that will lower the overall output impedance of the PSU as seen by any circuit connected to it...this is a good thing.

I should have more to report in a day or two.

Pat

[PMcC]

Stop the press...just finished wiring up the SSL 5000 series power supply to the SSL 4032 E series console, five separate looms in total so some reconfiguration needed at the console end (details to follow).

Powered up each section, one after the other with out smoke, always good and it has been running for an hour at this point with out any funnies so here's hoping.

Next up is a full on audition to evaluate the audio quality.

Pat

[PMcC]

Back to life...

[Matt Sartori]

Back to life...

Well done!!!
can't wait to see more pictures and hear some audio tests!

Mattia.

[xmax]

I would consider putting a current meter on each module, its the only way to truly
make sure everybody shares the load. Good work!

[PMcC]

Hi Xmax, that's a good idea. SSL describe a set up procedure based on voltages e.g. The Audio+ supply shoud be 19V so one regulator is set to this and all other Audio+ regulator voltages are differentially measured with reference to this value.

They specify a maximum deviation of 50mV from the ref. level but no mention of current hogging or sharing for that matter. I do like your idea of checking individual card currents all the same, no point in having a slacker amongst the ranks.

Pat

[waltzingbear]

current is the actual thing you care about. Setting to the 50mV spec *probably* does the job just fine. But measuring it directly does so with more assurance.

You'll need a good DC probe, probably hall effect. Repeatability is what matters, not accuracy, so you may be able to save a couple dollars on that spec.

And don't forget about thermal tracking. If the two supplies don't track well then the drift over time may cause mayhem. Been there, done that.

this goes for all shared supplies.

Alan

[PMcC]

Hi Alan, thanks for the input.

I may be wrong but my understanding is all individual regulator cards have power diodes in series with the output pass current of each voltage rail. The Audio+ rail for each card is say 19V as measured at the anode, the voltage at the cathode will be somewhat less than this and a function of actual load current.

If the cathodes are all commoned and one regulator card tries to deliver more current than all the others then it's series diode will have a larger volt drop than all the others. This is of course not possible as the other regulator outputs would have to drop in order to keep their series diode voltages at the lower current level.

Negative feedback holds the regulator output voltages at a constant value, this is the anode side of the series output diode. The cathode side is outside the feedback loop and therefore free to change with current load. Since the cathodes are all commoned they are all assuming the same voltage. If one regulator tries to runaway current wise it's series diode will try to drop a greater voltage than the other regulator series diodes implying all other regulator 'cathode side' regulator output voltages will drop. This is course impossible given the regulator outputs are held constant by negative feedback.

So it seems to me then that no runaway is actually possible. I may be off beam here but my view is the SSL engineers are/were extremely competent designers and why would they omit the whole current sharing issue from the set up manual if it was even remotely possible?

Having said all that I plan to measure the current from each card just to see his close they all are.

Pat

[waltzingbear]

I assume you are talking about the 5K supply, which I do not know. I was mostly refering to the 4K/6K supply, which does not include steering diodes in the supply, they did have them in the combiner box, about all that is in there. It does not prevent the supplies from blowing up.

In the 4K what can happen (in rare cases) is that the supplies do not track and one ends up supplying the current as they deviate in performance. This them goes into thermal overload and the 4K supply when out of whack can do all sort of nasty things to itself, (not the board, that is protected). Mostly they just blow up and shut down. Not fun. Or at least that is what I surmise from the postmortem. Which is why adding the fuses is a very good idea, can save a lot of money and time.

I just re read your previous post, the problem between the two systems is that here, I assume that the one supply goes off line and the other takes over and then has a current overload situation, because there are only two supplies. This causes the crowbar to throw and kills the one supply. You are dealing with multiple supplies which together can sustain the loss of one supply, the old 4K situation couldn't, depending on the size of the board. A much better scenario for survival.


Alan

[PMcC]

Hi Alan, that's a colourful raft of experiences you have had right there with the 4K supplies.

The move to the 5K supply, in my situation, is out of neccessity but it sounds like it might actually be for the better!

Pat