Replaced at power supply.New problems for the brains!!

[Housedarest]

Hi guys!! Hope you can help. I have replace the at power supply in my d8b after failure which left the desk error 43.

I'v installed the replacement psu. The console side now immediately receives power as soon as the mains is switched on and awaits me to switch on the pc side. It boots fine and works fine as far as I can tell. When I shut down after the pc has gone the console illuminates all pot lights and meters until ac power is switched off.

The at supply I got has all the same specs. But does not have identical mounting points and an extra floppy power / hd connector. I attached the wires one by one as I removed the old unit. The only thing I noticed that was different was there was no earth connector coming out of the black switch wire form the at psu. I assumed that the power supply was earthed differently and had it required it, it would have been there. This I have thought might be the source of the issue. My other guesse is the old psu has damaged something.

Any help would be appreciated, there's not many people around to ask about this thing anymore.

Big thanks

Sam

[TerryO]

I'm not absolutely clear what you have been doing with the power supplies. Maybe it would help to describe the power supply arrangements of the D8B. There are actually 3 power supplies in the Rack Unit.

(1) A regular AT power supply that powers the computer (CPU) - it also supplies 12 volts to the console where it is used by the fader drive motors. (This appears to be the one you have replaced).

(2) A switched mode 5 volt high current power supply for the console digital electronics, leds and etc.

(3) A linear power supply providing + and - 16 volts for console analog circuitry plus 48 volt phantom power.

All 3 power supplies are switched on (and off) by the Rack Unit panel switch. There is a printed circuit board in the rack unit that takes care of all the necessary push-on connectors. If you are switching the AT power supply independently of the other supplies then the 5 volt supply will maintain current to the console (keeping leds etc on) until it too is switched off. As for the earthing wire (or lack of it), there should be an earth lead coming from the AT supply and attached to the rack mount chassis with some other earthing connections. Apart from safety considerations, in audio equipment there should generally be one primary earthing location to avoid undesirable effects. It is usual for the housing of computer power supplies to be connected to earth internally. It is therefore likely that the rack unit and consequently the whole system is earthed by having the AT supply screwed to it - not the best arrangement in these circumstances.

Hope this helps.

Terry.

[Housedarest]

Hi terry, thanks for the reply.

Sorry I have not been clear. You are correct in thinking it was the first on your list that was changed.

It appears that the 5 volt supply is receiving power regardless of position of the switch on the main rack unit. There was only one switch on the new AT power supply that had 4 wires, white blue, brown, black. The power supply I removed from the desk had an extra wire which was the earth. I swapped the clips from the old wires and soldered them to the new. One by one.

I read in another post there was away of achieving this effect (the console receives power regardless) by doing something with the black wire. I'm going to double check my connectors and add the earth in the meantime.

Hope this helps.....

Thanks again

[TerryO]

OK. It would appear that the AT supply that you are using is (was) fitted with the normal power switch. You've removed this and replaced it with the push-on (spade) connectors of the original PSU. I think I have an explanation why you're having a problem. The Mackie (Sparkle) power supply uses Black/White as the power (source) connections and Brown/Blue as the return connections to the AT supply. Your replacement power supply is almost certainly using the reverse of this arrangement. This is a quote from a PC power supply reference site:

"The four or five wires are usually color-coded as follows:

•Brown and blue—These wires are the live and neutral feed wires from the 120 V power cord to the power supply. These are always hot when the power supply is plugged in.
•Black and white—These wires carry the AC feed from the switch back to the power supply. These leads should be hot only when the power supply is plugged in and the switch is turned on.
•Green or green with a yellow stripe—This is the ground lead. It should be connected to the PC case and should help ground the power supply to the case."

Looking at the printed circuit layout it would explain the behavior of your system. You'll have to re-arrange your coonections to satisfy what appears to be Mackie's non standard arrangement. You'll also have to open the AT supply and connect a lead to the earth terminal of the power connector (be careful in there). Whether you should disconnect the internal earth connection of the AT supply is difficult to say.

HTH.

Terry.