Emu XL-7 & MP-7 User's Group

Hi,

I'm not an expert when it comes to switching power supplies, so I'm just relating some information I gathered during the course of the repair. So I'm not exactly 100% sure about all the details but below are some of the things I picked up.

Before I say anything else, I must wholeheartedly recommend a Mr. Lazaros Papazoglou of Olympus Electronics, Wirral, UK. He did a great job at a superb price, and he was fast, a total pro. He specializes in repairing power supplies of all types.

info@... 


The resistor in this case is a large resistor R7. This had failed and was too discoloured to identify. This is 120KOhm. I am not exactly sure of the power rating of this one, although there is speculation that the one in the Powdec PSU is under specified and should be 5 or 7 watts, it certainly appears to diisipate quite a bit of heat.

Luckily we had another, working XL-7, so I could have a look at the PSU in that. In the working XL-7, that resistor R7 is again, very discoloured. Like it's had a good roasting. So no doubt, that will fail sooner or later too.

The controller chip in question, as far as I know, is the PWM controller, which is a UC3842. This is a current part and can still be obtained easily, so I am told. I can't be more specific on that, I don't know exactly where that chip is or whether it is surface-mount or not. You are welcome to get in touch and send me some pics of the PSU and i'll have a look.

It is said that that part of the circuit (PWM controller) is under  greatest stress when you power on the machine. So I try to keep mine on 24/7 these days :)  When the PSU fails in this way, all you notice is that it won't power on. It won't become intermittent, just stone dead :( 

Regarding the rear panel hard power switch, I can tell you that the machine described above, the one that failed, was always switched on using the rear panel switch so I don't know if that makes a big difference or not?

Oh well, at least they can be fixed :)

Cheers,
Matt

--- In xl7@yahoogroups.com, "ackack1020" <sackley85@...> wrote:
>
> Please elaborate on the resistor and controller chip. I'm always scared of the PSU going out, and I'm sure this info would help a good amount of other CS users...
> 
> Also, I've said it before, but I'm finding that using the hard power switch (rather than the soft front panel one) keeps the unit working well. Actually, at this point, I just switch all my kit on/off with one surge protector.
> 
> -Sack
> 
> --- In xl7@yahoogroups.com, "retroillumination" <retroillumination@> wrote:
> >
> > Hi,
> > 
> > Some time ago I was looking for a replacement. Powdec say that the Command Station PSU was a one-off design made to Emu's specifications. That probably explains why there aren't many around now.
> > 
> > That's not to say that another PSU could not be made to work in its place. If it has the correct voltages present, and can supply enough current at those voltages, and do all that without having to dissipate too much heat, there's no reason why it shouldn't work.
> > 
> > But in the end it turned out that the old PSU had a fault which could be fixed relatively easily and cheaply, by replacing a dead resitor and a controller chip. Do you still have the old PSU?
> > 
> > 
> > --- In xl7@yahoogroups.com, "intrepidpete" <peteflagg@> wrote:
> > >
> > > Anyone replace the PSU power supply in a Command Station or Proteus 2500 in the last couple of years? If so, where did you order the PSU?
> > > 
> > > I can find the old powdec/powergatellc/powersupplyemporium PTE43-XX-C 10-pin 43-watt PSU in cage listed here: http://www.powdec.com.tw/pages/pte43.htm
> > > but there does not appear to be any way to actually order one. Part not made any longer? No other supplier?
> > >
> >
>