Allen and heath power supply..

[tony6]

Hi everyone, hope you are all having a good day?

Can anyone help me.??

I have just picked up an Allen and Heath system 8 248 mixing desk.. It has no power supply for it. It has been sitting somewhere for a few years and I have no idea if it works, and if all the functions are still ok? I would love to get it up and running, and use it at a later stage.

Can anyone offer me any support and advice on how to obtain a power supply or even make one? There is a guy in Devon that re-makes these PSU's but they cost £165.00. I don’t mind buying one, but it would be pointless if the desk is not in any good working order..

I don’t mind putting one together myself, but all the help I could get would be much appreciated.

Has anyone made a psu, do you have part no.? Diagrams? I know it's a lot to ask, but I don’t want to see it just sitting there..

Many thanks
Ant

[enoughstatic]

Allen & Heath power supply source

Hey there. I own a Sytem 8 1616 Allen & Heath mixer. I built myself a nice reliable power supply (i've be designing, building, fixing music gear for about 17 years).

If you are interested in having me build you one (I'm going to start selling them world-wide), let me know.

Details for the power supply are at http://www.wireaudiorepair.com/mps8p/

Eric

[Enzo]

Hi, welcome to the forum.

If I might offer an observation, if you plan to ask high dollars for your product, you might tighten up the execution a bit. If I were in the market, I might expect the fan to be straight, and the vent holes for the fan and makeup air to be punched to a pattern and not drilled just more or less in a pattern. Those holes ought to be confined to within the dimensions of the fan. Frankly I'd really expect a grille over the thing and a full hole for the fan. Restricting the air flow like that is the same as using a smaller fan.

I'd like the legends to be silk screened or otherwise printed. I highly recommend adding legends for fuse values.

Speaking for no one by myself, I would REALLY prefer it in a rack mountable chassis.

Those larger filter caps need to be supported somehow - clamps, glue, something.

And the output cable, while relieved of strain at the entry point, really needs to be supported inside the box, rather than hanging by its wires.

Personally I like to see my components all aligned - parallel or perpendicular. I am perhaps being anal about it, but I like to make all my resistors read the same direction as with my caps. Those two resistors wrapped around each other are ugly - 10ks? I'd look for a 5k resistor or mount the two on terminal strips.

The exterior shots show output fuse holders, but I don't spot them in the interior shots. Are the LEDs driven from the load side of the output fuses?

ANd nit picky, the mains cord should have the ground wire longer than the other two so that if the cord ever pulls out, the ground wire will be the last one to snap off.

Did you consider an IEC connector and detachable mains cord? Especially if you plan to export these? Are the primaries on those transformers dual?

I won't get into the approvals and safety issues.

I am not picking on you, I hope you find the market you seek. But when someone shells out $900 for something they expect more than just it works.

[Mark Black]

If I were in that predicament I would look for an existing power supply for almost any large-format console and modify the plug for the board end to work with the A & H. Most analogue consoles have very similar voltage and power requirements: +/- 15 to 18V at a few amps and +48V at less than an amp. Some use another set of voltages for LED drive or console lights and those could be ignored if not needed.

Maybe something like this:
http://cgi.ebay.com/NEW-NOS-Mackie-2...=1218551984161

A Soundcraft would be nice, but they tend to go for more money.

Some research into the actual requirements of the console would be helpful, but reading between the lines of the above-mentioned "replica" power supply I see TO-220 voltage regulators which probably means only 1.5A to maybe a maximum of 3A per rail...

Then again for a quick & dirty way to just test the major console functions you could use a couple of car batteries hooked up to give you +/- 12V with center common and kluge a hookup to the board with wires soldered right to where the ones from the power supply plug in the board go to their respective points. I'm kinda cautious, so probably would incorporate some in-line fuses (at about 2A) just in case things are really wrong in the console. I would also run the +/- voltages through a double-pole switch so both rails could be connected at the same time. The voltages won't be exactly right & therefore less headroom, and the +48V phantom won't be there, but at least you could get an idea of whether the major functions all work. The batteries should give you plenty of time to find out.

One caveat: car batteries have a LOT of energy and can cause major mayhem if care is not used. A guy I used to work for accidentally got his metal watch band between the positive terminal of his battery and the car frame - the result was a red-hot watch band and the damage required skin grafts.

[Enzo]

Amen. I do not wear wrist watches, rings, bracelets. AMps are bad enough, but I also work on video display monitors, where there are thousands of volts just waiting to leap over to your personal metal.

[enoughstatic]

Enzo,
Thanks for replying. I always appreciate and respect feedback and constructive criticism.

The Fan appears to be straight to me. As far as the holes go--yes, you are right. There is enough air in this case, but ideally (and aesthetically!) it should be improved. Adding a grill and of course, cutting out a hole to match the fan airway would be the right thing to do.

Legends for fuse values would make sense, otherwise how would someone know the type/value?--good point.

A friend of mine just set up a screen printing outfit in their home, so I'm definitely interested in that for both looks and being informative.

Rack mountable: Yeah, I know. I should consider that, but this is a replacement for the MPS8P strictly. Unfortunately, I don't have the money to buy in bulk (often times, qty's of 10+ or even 25+) for many of the parts to make this even affordable. Perhaps I could make a rack mountable version for the original rack-mount units themselves.

Filter caps were glued a couple days after those pictures were taken. I never leave large components free to break off. I think I should have waited to take a picture until I was completely done with a final power supply unit... but again, this is a non-prototype unit!

Extra strain relief is a good idea. However, not too big a deal, as most of these units are almost always going to be a semi-permanent installment, so the single chassis strain relief is good enough.

As far as components being all aligned: this is a subjective matter. Like the old beautiful HiWatt amplifiers--they are built very "military" like. I am more than capable and willing to, but again prototype: need I say more?

Resistors reading the same direction... I know... I used to do that for many years, but as that idia is strictly for looks, not a big deal. it makes servicing perhaps a little easier--for some, I suppose. You must have worked in manufacturing, too (in some way or another)?

The two 10k resistor are ugly? Yes, 2 10k's in parallel equal a singl 5k resistor--again, oops--this is a prototype. Perhaps I should have made that clear before posting. My fault.

The LEDs are indeed driven from the load side of the fuse. Otherwise, what would be the point? Right?

I agree about the mains cord. I thought about that before installing it. However, not having fancy cutting tools (as the fan holes are a good example of that I suppose), I don't have the will to sit there and file the chassis for an IEC cut out. But perhaps it would be worth it... I'll try it on the next and see how much more time it takes and if I can get it to look good by hand.

True about the earth ground wire being slightly shorter than the live and neutral, but that strain relief is nice and tight and if someone really pulled that thing hard... well, they're more likely to pull the whole casing rather than the cabling out of the chassis.

The primary of both transformers are dual, so yes, it could easily be converted.

Approvals and safety issues. This unit runs cooler than the original design. My capacitors are not subjected to marginally high voltages. The mains fuse is intact to act upon overload and well as the DC output fuses.

Linear power supplies are straight forward, as far as any safety issues that I know of, I can't see any that I haven't already addressed at this point, but of course, I am open to suggestion.

If someone shells out $900, they should expect "more than it works". How about, it will work for longer than your mixer will be in service... or it can be serviced and maintained easily, if need be.

[Enzo]

OK, as long as you understand this is constructive criticism.

The power cord ground wire should be longer than the other wires and mounted to its own screw to the chassis for code reasons. When the code guys come calling, you can't just tell them, "Oh my strain relief is nice and tight." With a captive cord, cords are often secured, either tie wrapped to something, or even taped or tied to something. The power supply could be sitting on something and get knocked off. That will bring it up short on its cord, which need to pull away with the ground parting last.

Screen printing is fine, but you can also go to any Staples or Office Max or even the office supplies section of a department store and find label makers. No not the old DYmo Labels. These are small devices that basically print a nice label on some tape for transfer to a flat surface. I think Brother makes a whole selection of them. If aligned with the edges of your unit, they will look nice and neat and simply done. Kind of old school these days, but you can buy sheets of small dry transfer letters and apply nice neat lettering to a flat surface by rubbing those down. Or a small sheet of clear plexi would protect a nice label made on your printer.

If someone shells out $900, they should expect "more than it works". How about, it will work for longer than your mixer will be in service... or it can be serviced and maintained easily, if need be.

What I meant was, when someone pays a large amount of money, they expect it to look like it was worth the amount. If my car were running perfrectly but the body was all dented in and scraped up, you might not look as kindly towards purchasing it from me as you would if it looked nice. A customer will be turned off if it looks like something someone threw together in their basement. What about the interior photos inspires confidence that it will be reliable and easily serviced? What about the interior photos should inspire me - a service guy - that it will be convenient to service?

Your unit may well work perfectly and reliably, I am not suggesting otherwise, but does it LOOK that way to potential customers?

If the fan is straight, my apology, it must be perspective in the photos. There is one shot from either side and in both the fan looks like it is sloping away. I guess it can't slope both ways. But the holes are awful, and the different length mounting screws are obvious.

There are some tools that would help you make IEC connector holes or larger holes like for a fan. One is a nibbler tool, and the other is my reliable old friend the Dremel.

My nibbler looks different, but here is one:


It makes nice square little bites out of sheet metal. I start with a couple drilled holes near my corners, then nibble away the surrounding material. Doesn;t take all that long to make a nice square hole.

And the Dremel has any number of cutting tools available - cutof wheel, saw blades, milling heads.

And for the record, no, I have not worked in manufacturing. But I have run a profesional service bench the last 35 years or so. And I appreciate neat, well laid out products that don;t get in the way of themselves when service is needed. WHen I see parts all aiming the same direction, I see attention to detail. I can deal with anything, but I much prefer a circuit board where all the ICs point the same way instead of having to wonder which end is up every time you move to another chip. Or transistor, or resistor, etc. I used to open those little Gorilla practice amps and see parts sticking up every which way from the pc board. SOme down tight, some sticking up, it was a mess. I compared that to a nice Peavey practice amp that was well made with parts in a row. Can I repair either? Of course, but it is so much nicer to work on the Peavey.


Yes, power supplies are simple. The safety issues I refer to are the ones like the power cord. There are things like how far apart certain thing are supposed to be. How long a piece of wire can be without support, stuff like that. I wasn;t too concerned over the circuit itself. But while you focus on it running cooler than the original and whatnot, someone else might be more interested in what order the fuse and mains switch are wired. (WHich look fine)

I remember a product I was a technical rep for a long while back - a piece of amusement equipmet. We made it in a manner we felt safe and secure, but we installed a unit somewhere in greater Detroit, and the electrical inspector dropped by and told us this gear could not be powered up during business hours without certain wiring be enclosed in conduit. No, I don;t expect the electrical inspector to look at you funny, but you never know when odd challenges might erupt.

I would just recommend concern for details when selling such a product. You sell across state lines, you are in interstate commerce, not to mention when you sell outside the USA. You get the RoHS thing covered?

[Steve Conner]

If I shelled out $865 and that heap of junk arrived in the post, I think I'd die of shock. Maybe even electric shock.

[Iain]

Hello Tony
I saw your post,I also own an allen & heath 24:16:2 system 8 desk and have been trying to find another 24 track (to link together) for years, just finding lots of 16 track ones. Would you be intrested in selling your desk to me? (hope this is'nt sounding a bit blunt,but i've just come out of my little studio thinking, "There must be another one somewere")
All the best,Iain

[matthewhorton]

Can anyone offer me any support and advice on how to obtain a power supply or even make one? There is a guy in Devon that re-makes these PSU's but they cost £165.00.

Hi Ant,

Im in a similar situation to you. Please could you give me contact details for the technician in Devon? It would be very much appreciated.

Many thanks,
Matthew Horton

[Iain]

The technicion I suspect is orchid-electronics.co.uk. Exeter based manufacturer of splitter units. I can't remeber his name,but he,s very good. knows about system 8 desk's and recomended by allen & heath. there's a phone no. on his webb site I think
good luck!
Iain

[oc disorder]

On the Allen & Heath site they have the schematics for the system 8 MK 1, 2 and 3 but not the PSU !
http://www.allen-heath.com/veterans/...product=System 8
However in another mixer there is this MPS8.PDF (attached) which seems to match the pins for the System 8 MK 1 .
Its basically a + and - 15 volt supply with a 48volt phantom supply.
Seems like its not a huge task to make one.

[jrfrond]

I am with Mark Black on this one. Just about any analog console supply could be adapted to the System 8 console. You have +/-15V and +48V for phantom power. Every console supply has these. Why reinvent the wheel?

Looking at the schematic, the only thing you need to be concerned about is current rating, or more accurately, wattage of the supply, as each mic pre sports differential input transistors in parallel pairs, not the usual two-transistor configuration. Most likely, any PSU made for an 8-buss mixer would work. See if you can find a PSU for a Mackie 8-buss, Behringer MX9000, Soundcraft Ghost, etc. They should all work just fine.