[amblin]

 Hi everyone

My MPS2 was fine since I brought it new quite afew years ago but today it developed a habit of blowing up the fuse (1A /250V as indicated) whenever I plug in the power cable... I already tried unplugging everything from the unit but it'll simply blow the fuse as soon as I plug in the power cable.....  EVEN if I leave the unit's power switch on OFF position... Maybe something went bonkers in the power switch so there's a short circuit?



Visually I can see no damage on the PCB or parts but... Any ideas for a quick fix?

[James Tanner]

Hi amblin

Give Mike an email - mpickett@bryston.com

Power supplies are not something you want to play around with.

james

[amblin]

Thanks a lot , i'll contact him right away.   

I'm the kind of person who blindly believe in miracles.. But sadly after a dozen of them died in a flash I choose to suppress my stupidity..

[Wim J]

Did you replace the fuse with the same type of fuse? There are fast and slow fuse types. The MPS2 uses a slow type. The original one is a slow blow type and if you replaced it sometime with a fast blow then you could have this problem.
On your blown fuses there should not be a letter 'F', a letter 'L' (or T) would be perfect.

[amblin]

  holy cow! Mate this might be the exact problem! The electrician corner shop bulk selling them at 5c each never asked me anything about L or F.

 I just checked the fuses I just brought and it says ' F 1A250V' ! I can almost hear my physics teacher crying..

Now I believe in miracles again, you're my angel 

[Wim J]

holy cow! Mate this might be the exact problem! The electrician corner shop bulk selling them at 5c each never asked me anything about L or F.

 I just checked the fuses I just brought and it says ' F 1A250V' ! I can almost hear my physics teacher crying..

Now I believe in miracles again, you're my angel 

 

[amblin]

Hmmmm I wonder what exactly does all the letters mean on a fuse? Because a friend just gave me some marked 'T1A250V' instead of the 'T1AL250V' marked on the PCB ...and these still got blown in a flash...

So the fuse must be exactly the same? What's the 'L' in the name? Maybe that's the one making all the difference? I brought some T1AL250VP off the web...now there's an extra 'P'..why?

[srb]

The "L" following the "A" of the Amperage rating usually refers to the Breaking Capacity

L = Low (glass)
H = High (ceramic)
E = Enhanced (glass)

I believe the "P" at the end refers to Lead-free construction

Steve

[amblin]

Ah..thanks Steve !, finally I know what I'm looking at..

 But how about those without the 'L' such as T1A250V because I've seen examples without the L on the metal cap.. Could this be the reason why they're blown? I'm still waiting for those T1AL fuses to arrive and resisting the temptation to insert a brass bar into the slot and see if it's something gone bad in the MPS2 itself...

[srb]

But how about those without the 'L' such as T1A250V because I've seen examples without the L on the metal cap.. Could this be the reason why they're blown? I'm still waiting for those T1AL fuses to arrive and resisting the temptation to insert a brass bar into the slot and see if it's something gone bad in the MPS2 itself...

I've not seen any "E" Enhanced (glass) in person, so you can probably be fairly certain that the majority of the time if it's a glass body, it's an "L" and if it's a ceramic body, it's an "H".

I don't think that particular marking is mandatory as is the Type, Voltage and Amperage.  They would likely blow of course if they were the "F" fast-blow type when the "T" time-delay type was specified.

Steve

[amblin]

Thanks for the info, now the problem is I already tried several T1A250V time lag type and it blew those as well.. Visually I can spot no damage on the caps and other obvious parts but since it blew the fuses the exact moment I connected the power cable, maybe there's a short circuit somewhere?

[srb]

I guess I would be surprised if the fuses you've ordered with the additional "L" code prove any different, but I have been wrong once or twice in the past. 

I assume they're blowing even without any load components connected to the MPS-2?  If so, that really does seem like there's an internal short of some kind.  I guess we'll learn more shortly.

Good luck.

Steve

[amblin]

Yeah, without any load and blew them in a flash the exact moment I connect the power cable .

But on the package of those new schurter T1A250V fuses my friend gave me I just spotted a tiny tiny 'F1T' marking under the type section,  after some digging in piles of German/French PDF files it seem to indicate its a rather specialFAST ACT ,TIME LAG fuse, despite the fact that the metal cap on the fuse itself is clearly marked 'T1A250V'  so maybe they're the wrong fast type as well? Why they're making things so complicated....

I'm looking for the SLOW ACT, TIME LAG T1AL250V fuse, am I correct? What really worries me is that it blown the fuses without any load and the switch is on OFF position...

[srb]

I've never seen an electronic fuse with both Fast and Slow designations or opening characteristics ....

The slow-blow fuses have a "T" marking and are referred to, depending on the manufacturer as

Slow-Blow
Slow-Blo® (registered trademark of Littelfuse)
Time-Lag
Time-Delay

Normally interchangeable, I have read references to small differences in time curves between US and IEC International specs

Here is a typical chart of the Min and Max opening times depending on the percentage of amperage rating for the Littlefuse 218 Series, 5×20 mm, Time-Lag (Slo-Blo®) Fuse

 

Yeah, without any load and blew them in a flash the exact moment I connect the power cable.
What really worries me is that it blown the fuses without any load and the switch is on OFF position ...

Maybe even a short in the power switch?  (Seems like if there were a short in the power cord or IEC connector it might trip the house circuit breaker without blowing the internal fuse).

Steve

[amblin]

Thanks for all the info Steve , much appretiated!

And yeah..I was hoping maybe it's the switch or even the socket contacts because the parts inside seem pretty simple and rock solid..

Already called the local AD and the repair\checking will take min. 2weeks..  I find it very difficult to face the void in space after it's gone... Now where's my Atari and joysticks ..

[amblin]

Guess it's not the fuse after all , just took it to a electrician shop and after some quick tests the guy told me there's definitely a short circuit but he was unable to determine exactly which part went bad because I won't allow him to remove anything from the unit and check the underside.

I'll take it to the AD, thanks everyone for the help!