Repair of smps SOUNDCRAFT PSM300 HELP needed

MicrosiM

MicrosiM

Administrator
Staff member
Resonant said:
Found it!!

Diode on the 48V side was shorting out.
Both +17V and -17V are running

Of to the shop to get new diode and soldering iron since mine just decided to stop working to.

You are the man! I would get you so drunk if you were here right now

Thank you :w)
Click to expand...


:)

That sound cool, really

Thats the PHANTOM Power diode!

I am glad that you have just fixed it !

GOOD LUCK :D
 
A

a1rstudios

New member
Hi At last i have seen someone with the same problem, I have the same SMPS for soundcraft ghost and i noticed the main fuse blown i have average knowledge of electronics so i thought id give it a shot. I notice the 2 large caps on the input side where swollen so i got 2 replacements hoping that would solve the problem. Once pluged in (Not connected to the Desk) the relay went mad clicking and blew one of the new caps open circuit. At that point i knew i was out of my depth as i dont have a scope only studio tools DMM soldering iron etc. I have checked all the diodes with the DMM and metered out a few caps on the output. I am wondering where is this Diode you found on the 48v maybe by luck we have the same fault. I am on a tight budget and have had to put all my recording on hold so any help would be greatfully appreciated.

Thanks
 
R

Resonant

New member
Hi there

The diode was the very first one after the transformer.
DSC_1677.jpg

That relay going mad is do to the voltage drop, probably because you have a short somewhere, most likely the mosfets. Check those

As for the capacitors I have no idea. The new ones might have blown do to the relay opening and closing.
This causes the on capacitor to charge and discharge by shorting in out.
 
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a1rstudios

New member
Hi Thanks for the reply. I have ordered 4 new mosfet's and 2 of the large 470uf 200V Caps Hopefully that's the cure. The picture you have Shows a Transistor on a heat sink is the diode in front of that ?
I am going to use a light bulb when testing, I am wondering is it ok to run this PSU without it connected to the Mixing console as i do not want to damage any components in that

Cheers
 
MicrosiM

MicrosiM

Administrator
Staff member
a1rstudios said:
Hi Thanks for the reply. I have ordered 4 new mosfet's and 2 of the large 470uf 200V Caps Hopefully that's the cure. The picture you have Shows a Transistor on a heat sink is the diode in front of that ?
I am going to use a light bulb when testing, I am wondering is it ok to run this PSU without it connected to the Mixing console as i do not want to damage any components in that

Cheers
Click to expand...


Connecting the PSU to the console at any stage of the repair will damage the console without any previous warning. :x:

You must disconnect the console from the PSU. try to follow (Resonant) into his repair.

Me & Resonant will try to help out


Regards
 
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a1rstudios

New member
Hi MicrosiM I have the supply Disconnected from the Desk since it first blew the Fuse so i will keep it that way until It is fixed, I was just curious did it require a load to be on it for the PSU to work properly.
Resonant I checked out that diode with DMM between both outer legs to the centre leg and both conduct one direction only no short or open circuit. I Have the mosfet's and caps on order so I hope to have them within a few Days.

I will keep you informed Thanks
 
A

a1rstudios

New member
Hi, I have fitted the 2 mosfets and the 470uf 200V Capacitor. I have only Just noticed that I have only a 60w Bulb in the Limiter as I am in Ireland we have only energy saving bulbs so I cant get a 100w. Could I put a 40w in series with the 60w to get to 100w. Anyway I tested the supply and the fan spins at a slower speed the 60 watt bulb is full bright to dim cycling every second. the 48v phantom power green LED is cycling bright to dim at the same rate. The 17v rails have no LED lit so I am just wondering is this because of the 60w bulb.

Sorry for the Delay had to wait a while for the parts, I have a second set of mosfets also on the ready
 
R

Resonant

New member
To get 100W you need to put the 40W and 60W in parallel.

I haven't got much experience with fixing smps, but to me it sounds like it could be the same problem as on mine. Only yours might have a short on one of the 17V sides.

Maybe disconnect the transformer from the 17V circuits(both of them) and see what happens.

Although I'm not sure this is good practice.. leaving loose switching inductors can cause massive EM waves.
But this was how I found out it was the 48V circuit on mine

I anyone reads this and knows better please advise
 
A

a1rstudios

New member
I have checked the 2 Diodes on the +/- 17v similar to the one you found but they are ok.I am unsure about disconnecting the transformer yet hopefully someone will confim can i do it. Is it possible that because i am using a 60w bulb that maybe the smps is working but not getting enough power to switch the 17v leds lamp is pulsing
thanks
Resonant said:
To get 100W you need to put the 40W and 60W in parallel.

I haven't got much experience with fixing smps, but to me it sounds like it could be the same problem as on mine. Only yours might have a short on one of the 17V sides.

Maybe disconnect the transformer from the 17V circuits(both of them) and see what happens.

Although I'm not sure this is good practice.. leaving loose switching inductors can cause massive EM waves.
But this was how I found out it was the 48V circuit on mine

I anyone reads this and knows better please advise
Click to expand...
 
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a1rstudios

New member
Thanks MicrosiM i will get the 60w and 40w in parallel and try that. Amazing I can get a simple 100w bulb here in Ireland.
 
A

a1rstudios

New member
Thanks I will try the 100w bulb and from there on i will try disconnecting the transformer, but as Resonant say's

"Maybe disconnect the transformer from the 17V circuits(both of them) and see what happens.
Although I'm not sure this is good practice.. leaving loose switching inductors can cause massive EM waves.
But this was how I found out it was the 48V circuit on mine
I anyone reads this and knows better please advise"

Is this ok to try.
 
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a1rstudios

New member
Hi I tried the 100w bulb (60w and 40w in parallel) both bulbs glow slightly fans runs maybe bit slower then usual I have 3 green leds 48v +17 and -17. Using a DMM im getting + & - 17v and 48v at the 3 wires going to the output. Has the replacement mosfets and caps fixed it? I am still relying on the bulbs and i will wait for your opinions before removing 100w.

Thanks
 
A

a1rstudios

New member
Hi I hope i can get advice on this. I took the bulb off and connected the power supply to 220v mains. I have the 3 LEDS 48v +17v, -17v the fan is at full speed only problem is that there is a high freq Ticking like as if there was something catching the fan(But there isnt) I bought the Power Mosfets of Ebay is there any chance they are poor quality causing this noise.
I am stuck here i thought i had this sorted with the replacement parts. I don't remember the SMPS making this noise in the past maybe it did apart from this it seems ok i ran it for 2 mins

Any help or advice would be greatly appriciated as i am out of my depth with only a DMM and soldering Iron and dont want to fry the console.
 
MicrosiM

MicrosiM

Administrator
Staff member
a1rstudios said:
Hi I hope i can get advice on this. I took the bulb off and connected the power supply to 220v mains. I have the 3 LEDS 48v +17v, -17v the fan is at full speed only problem is that there is a high freq Ticking like as if there was something catching the fan(But there isnt) I bought the Power Mosfets of Ebay is there any chance they are poor quality causing this noise.
I am stuck here i thought i had this sorted with the replacement parts. I don't remember the SMPS making this noise in the past maybe it did apart from this it seems ok i ran it for 2 mins

Any help or advice would be greatly appriciated as i am out of my depth with only a DMM and soldering Iron and dont want to fry the console.
Click to expand...

Showing small video showing the problem will help.
 
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a1rstudios

New member
I will do a video and upload. The second time I tried the SMPS without the bulb the relay started switching so had to power down. I Think I may have trouble doing the video without the bulb but as I have a second set of mosfets I will try it. I am wondering is the auto ranger causing the problem as I have all voltages at the outputs with the bulb.

Thanks for the reply i will upload video in the morning
 
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