Custom power supply

[mikeg]

email me

[paully]

Power-One

Best, Paul

[matskull]

Can these type of psu improve or make worst the console's s/n ratio and dynamics?

My psu is down right now and my tech says if he can't easily find the problem he might bypass a large portion of the supply with some voltage regulator.
Anybody did that to an old psu before? Is it a good idea?

He also suggested that we could build a psu with those little switching psu.
If I change my original psu for something else, I'd like it to actually improve my dynamics and s/n ratio if possible, not the opposite.

[Matt Syson]

Hi Matskull
The desk and supply is not as faulty as your tech, get a new one.
Switching supplies on an 'old' desk not engineered for one (it would need checking out for noise pickup at least) is a bad idea.
Even a numbskull could repair a supply by diligently fitting a complete set of new components. Inefficient in terms of parts and labour maybe but not 'rocket science.
A 15 Volt 'standard' module wound up to 17 or so is good. A 24 Volt wound down to 17 is 'risky'. If it 'lets go' (possibly because it is being asked to waste far too much power as heat in the supply) it WILL trash the desk. A 15 Volt suffering a similar failure, which apart from being less likely, can probably be survived. Jim likes his smoke.
Replacing a supply will not necessarily change 'dynamics' or S/N ratio apart from the obvious situation of a faulty original unit.
Matt S

[matskull]

Originally Posted by Matt Syson

Hi Matskull
The desk and supply is not as faulty as your tech, get a new one.
Switching supplies on an 'old' desk not engineered for one (it would need checking out for noise pickup at least) is a bad idea.
Even a numbskull could repair a supply by diligently fitting a complete set of new components. Inefficient in terms of parts and labour maybe but not 'rocket science.
A 15 Volt 'standard' module wound up to 17 or so is good. A 24 Volt wound down to 17 is 'risky'. If it 'lets go' (possibly because it is being asked to waste far too much power as heat in the supply) it WILL trash the desk. A 15 Volt suffering a similar failure, which apart from being less likely, can probably be survived. Jim likes his smoke.
Replacing a supply will not necessarily change 'dynamics' or S/N ratio apart from the obvious situation of a faulty original unit.
Matt S

Yeah I decided to pass on the switching psu since it seems like they are noisy, I don't want that. But I seems like it's been done before though.

I finally found readable schematic for my supply so it should be easier to repair it now.

What do you think about the idea of putting some voltage regulator in there to bypass some of the pcb?

I contacted GRS to get a quote for a new psu, the one they make seem super solid and well made, easy to repair, mine is a mess inside it's scary lol.
They also said that their psu are 18V but after the diode it outputs 16V and is adjustable +-0.5%, does it sound risky to you?
thanks

[Matt Syson]

Hi
Switchmode supplies don't HAVE to be noisy but anything cheap probably will be.
Adding regulators is a silly idea.
Surprised if adding a diode drops 2 Volts but it should be fine anyway.
Diode drops for 'silicon' are up to 1.1 Volt and Scottky around 0.5 Volts (when they are passing a few amps).
Care to post the schematic?
Matt S

[matskull]

Originally Posted by Matt Syson

Hi
Switchmode supplies don't HAVE to be noisy but anything cheap probably will be.
Adding regulators is a silly idea.
Surprised if adding a diode drops 2 Volts but it should be fine anyway.
Diode drops for 'silicon' are up to 1.1 Volt and Scottky around 0.5 Volts (when they are passing a few amps).
Care to post the schematic?
Matt S

Good to know your opinion about the regulator, thanks.
I don't know exactly how the grs supply works but yeah they basically told me that it's a 18V supply that output 16V. As long as it's not risky...

Here's the schematic of my actual power supply.
The main bridge rectifier got shorted, I replaced it but I don't know what could have cause it to fail. I'm no tech, I just thought to check the bridge cause it failed in the past already.

[sameal]

as much as some may disagree with this statement, turn your desk off when not in use.

when i "interned" (laugh track) at a local "studio" (laugh track) they left there little trident on all day and night. the power supply just sat there, cooking. eventually i noticed one day it wasn't on and went back to investigate. after being scrutinized for being back in the wire mess of the racks i calmly explained to them how there piece of equipment was no longer working.

apparently the power supply heated up the solder joints and the melted solder touched the case. burn marks all over the place. lucky enough it wasn't a crispy critter and was repaired.

[Matt Syson]

Hi
There is no particular reason for this unit to fail although it does need decent heatsink compound on transistors and rectifiers. And tight screws.
Matt S

[adamboon]

Allen&Heath RPS11 is worth a look. Big, Dumb and Strong.
I think PSU's affect performance a lot more than most realize!

[matskull]

Originally Posted by Matt Syson

Hi
There is no particular reason for this unit to fail although it does need decent heatsink compound on transistors and rectifiers. And tight screws.
Matt S

Maybe there wasn't enough thermal paste on the rectifier... now there is.
Right now, with the console disconnected from the psu, the -16V indicator light turns on a lot faster than it should, normally it should light slowly after I switch the psu on, now it lights instantly.
The voltage seem to go through the psu too fast.
When I plug the console into the psu, it blows the -16V fuse.

[Matt Syson]

Hi
The supply is moderately complicated and there are serious amounts of current available. This can trash components pretty quickly if there are any mistakes. The actual voltage won't hurt you (apart from the mans tags of course) but you need a tech who knows what to do and have suitable test gear available. The fact that one rail comes up 'faster' than usual and blows fuses indicates it is still faulty. It may actually have been started by a desk fault.
From your comments about 'adding regulators' and 'switchmode designs' you need to find someone better. GRS offer a 'easy way out' but a bit heavy on the wallet.
Properly working supplies in themselves have relatively little effect on the audio unless the desk is also faulty.
The definition of 'properly working' is low impedance output (say 150 milliOhms DC to 30KHz or greater), and output noise less than say 1 millivolt RMS 20Hz to 150KHz or better.
Most supplies designed for mixing desks should manage that quite easily.
Matt S

[matskull]

Originally Posted by Matt Syson

Hi
The supply is moderately complicated and there are serious amounts of current available. This can trash components pretty quickly if there are any mistakes. The actual voltage won't hurt you (apart from the mans tags of course) but you need a tech who knows what to do and have suitable test gear available. The fact that one rail comes up 'faster' than usual and blows fuses indicates it is still faulty. It may actually have been started by a desk fault.
From your comments about 'adding regulators' and 'switchmode designs' you need to find someone better. GRS offer a 'easy way out' but a bit heavy on the wallet.
Properly working supplies in themselves have relatively little effect on the audio unless the desk is also faulty.
The definition of 'properly working' is low impedance output (say 150 milliOhms DC to 30KHz or greater), and output noise less than say 1 millivolt RMS 20Hz to 150KHz or better.
Most supplies designed for mixing desks should manage that quite easily.
Matt S

I emailed another tech company just to get their opinion and a quote, I'll see what they say...

What in the console could cause a power supply failure and how can I know that something's wrong inside the console?
Can a simple bad cap or something like that cause that much problem or would it have to be more serious?

IF there is a problem in the console, is there a standard procedure to find it or do we have to check every components from every channels?

I'm still debating if a new psu is a better option or not.
Let's say mine breaks every 2 year, costing 200-300$ of repair everytime plus a 2 weeks downtime. Let's say a week in the studio is worth 400$, it means that a psu failure cost me around 1000$ every 2 year.
So a new 1500$ psu takes 3 years to pay for itself and should normally operate better for a couple of years.

I could also repair my actual psu and have a backup in case of a failure.

[Matt Syson]

Hi
Isn't Sonotechnique in Montreal?
If it is repaired and serviced properly there is no good reason for it to fail any more than any other supply.
Matt S

[matskull]

Originally Posted by Matt Syson

Hi
Isn't Sonotechnique in Montreal?
If it is repaired and serviced properly there is no good reason for it to fail any more than any other supply.
Matt S

I think you are referring to Solotech, if so yes they are in Montreal.
The reason why I suspect it will fail again after repair is that it gets super hot, the room it's in is set at a good temperature but still the psu gets hot.

Anyway, I'm waiting for a quote for the repair right now.
Thanks for the help.

[matskull]

Hi there, I ended up buying a grs psu. I installed everything and I unplugged every strip from my console and plugged them one by one, everytime I checked the amperage.
Everything seemed normal and there was no short, the console was getting a perfect +16V.

I used the console for two weeks or so with no problem until tonight.
All of a sudden the lights on my console started to flash and we could hear a pulse noise. I checked the power supply and the +16V indicator light was flashing as well.

I took a reading of the positive rail output and the reading was going from +16V to +19V. I turned it off, unplugged the dc cable and turned the psu back on without the console and it was outputing a steady +16V.

Could a short in the console really cause more voltage to be drawn?
That psu is supposed to have an overvoltage protection and all that, I don't know what to think.

The company that built me the psu are out of the country until june and I don't have a job right now so I can't hire a tech.

Can anybody help me?

[davide.bonetti]

what Midas console are we talking about?

[matskull]

Originally Posted by davide.bonetti

what Midas console are we talking about?

It's a Midas TR from the 80s.

[Matt Syson]

Hi
Surely the people who assembled the supply have some form of responsibility especially as it is only a few months old??
'away until June' sounds a bit lame, they should be organising some form of 'backup'.
At least it should be possible to obtain another 'module' and wire it in although the fact it has failed is a bit suspicious and may well warrant a visit to find out WHY it has failed.
Matt S

[matskull]

Originally Posted by Matt Syson

Hi
Surely the people who assembled the supply have some form of responsibility especially as it is only a few months old??
'away until June' sounds a bit lame, they should be organising some form of 'backup'.
At least it should be possible to obtain another 'module' and wire it in although the fact it has failed is a bit suspicious and may well warrant a visit to find out WHY it has failed.
Matt S

Since I wrote my post here I got a reply from them.
After exchanging some emails they explained that the psu is getting into protection mode and that something in the console must have an intermittent problem. I won't explain what happens exactly but what they told me made sence.

I am investigating the problem, I've got an idea of which strip might be causing the problem but I'll have to do some test this week.

I thought too that it wasn't good business to not give any support for three weeks, I'm glad they answered my email after the initial automatic "out of office" reply.