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evildmp
Topic Author
Posts: 12
Joined: Sat Sep 16, 2006 11:05 am

Replacement UK PSU for M1000

Thu Dec 31, 2009 3:27 pm

The PSU for my M100 stopped working.

A multi-voltage PSU I've tried as a replacement works OK for a day or so, then after a while the display starts flickering on and off, and there's a nasty hum from the audio output, until it's unplugged and allowed to cool down again.

I don't know if it's the PSU or the Soundbridge which is faulty, hopefully it's just the former.

Will the M1000 work with any PSU that can meet the specs of the original unit?
 
S80_UK
Posts: 1035
Joined: Wed Oct 25, 2006 3:11 am
Location: Cambridgeshire, UK

Fri Jan 01, 2010 4:24 am

Hi,

Please use the search facility on the forum - this topic has been covered a great many times. (I have lost count how many times I have written this...)

From your description it sounds as though your replacement supply does not have a regulated output. It is essential that it does. Otherwise you will most likely damage your SoundBridge. For an M1000 (connectors under the end-caps) this must be 9 volts regulated at a current of at least 1.3 amps (more current capability is OK, but not more voltage). For an M1001 with connections at the back (and M1001s that say M1000 on the front!) this must be 5 volts regulated, at a current of at least 1.5 amps, but again more current capability is OK, more voltage is not.

If you are unclear on whether your supply has a regulated output then do not guess. Use a voltmeter to measure it. If it is supposed to be 9 volts, then if the meter says 8.8, 9.1, or even 9.4, then you can assume that it is regulated. If the meter says 11, or 12 or more then it is not regulated and it must not be used.
Roku M1000, M1001, M2000, R1000, Roberts WM-201, Stream 83i
 
evildmp
Topic Author
Posts: 12
Joined: Sat Sep 16, 2006 11:05 am

Fri Jan 01, 2010 11:52 am

S80_UK wrote:
From your description it sounds as though your replacement supply does not have a regulated output.

If you are unclear on whether your supply has a regulated output then do not guess. Use a voltmeter to measure it. If it is supposed to be 9 volts, then if the meter says 8.8, 9.1, or even 9.4, then you can assume that it is regulated. If the meter says 11, or 12 or more then it is not regulated and it must not be used.


Thanks. Without load, it reads a steady 9.38 volts. I haven't gone to the trouble of working out the on-load output.

I don't know if it's regulated; it's an adjustable PSU with a wide range of voltages (1.5-12V) and says "IC UNIVERSAL REGULATOR" on it - whatever that means. It's rated at 3.6VA, so that should be OK at 9V.
 
skydreamer
Posts: 6
Joined: Sat Mar 10, 2007 9:25 am

Mon Jan 11, 2010 3:49 am

3.6VA is too small, this will give you only 400 mA (0.4A) at 9 Volts. You need a bigger PS, Maplin is your friend if you live in UK/Ireland.
 
S80_UK
Posts: 1035
Joined: Wed Oct 25, 2006 3:11 am
Location: Cambridgeshire, UK

Mon Jan 11, 2010 3:55 am

skydreamer wrote:
3.6VA is too small, this will give you only 400 mA (0.4A) at 9 Volts. You need a bigger PS, Maplin is your friend if you live in UK/Ireland.

Correct! As above, you need at least 1.3 to 1.5 amps to have a good margin. More current capability is better. For supplies rated in VA (literally VA = volts times amps) then that means at least 12VA. Personally I would look for a supply that can deliver 9 volts at about 2 amps (18VA). The supply will be less stressed, will run cooler and will last a lot longer.
Roku M1000, M1001, M2000, R1000, Roberts WM-201, Stream 83i
 
evildmp
Topic Author
Posts: 12
Joined: Sat Sep 16, 2006 11:05 am

Mon Jan 11, 2010 1:07 pm

S80_UK wrote:
skydreamer wrote:
3.6VA is too small, this will give you only 400 mA (0.4A) at 9 Volts.

Correct! As above, you need at least 1.3 to 1.5 amps to have a good margin. More current capability is better. For supplies rated in VA (literally VA = volts times amps) then that means at least 12VA. Personally I would look for a supply that can deliver 9 volts at about 2 amps (18VA). The supply will be less stressed, will run cooler and will last a lot longer.


<Bangs head>. Not sure how I managed my calculation. Maybe I shouldn't have been trying to do it at 10.30 on Christmas Eve. Anyway, yes, no wonder that PSU and the Soundbridge didn't get on too well.

In the meantime, I've substituted one that has worked faultlessly so far, so now I am pretty sure the fault was not with the Soundbridge.

Last question: how could they make the original Roku PSU so small, when others are so huge?
 
S80_UK
Posts: 1035
Joined: Wed Oct 25, 2006 3:11 am
Location: Cambridgeshire, UK

Tue Jan 12, 2010 9:55 am

evildmp wrote:
Last question: how could they make the original Roku PSU so small, when others are so huge?

Answer - by breaking the rules... :?

If you take one apart, you will see that some components are far too close together for good thermal management. In one supply that I examined recently, the main reservoir capacitor was neatly laid down directly over and in contact with a small heat sink for the main power switch device with only two layers of thin plastic between. Even with a rating of 105 deg C, this capacitor will dry out and lose capacitance relatively quickly causing the supply to fail. In a larger supply with enough room to keep the hot bits away from the cool bits this process will take a great deal longer, and ideally the power supply would last as long as the product remains useful.
Roku M1000, M1001, M2000, R1000, Roberts WM-201, Stream 83i

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