ML 380S Preamp power supply fuses blown.

[cooky1257]

Here I am almost ready to finally install my newly acquired Mark Levinson 380S/333 pre/power when manoeuvring the kit into its shelving unit there was a low crackle coming from the slightly dislodged power plug/at its G-Sub socket and the pre amp went dead. On checking the 2x T 250v 250mA slow blow fuses, both had gone. My question is, is this a particularly delicate bit of kit or would the mains plug doing what it did be likely to blow these fuses?
Dont mean to sound daft like ;-)

 

[philiphifi]

hi - i have ML gear (cd and dac). They are reliable and i have not had any issues with them but i have to be careful when using them. The cd tray does get jammed if i am not careful. Is yours a UK version?

 

[Arkless Electronics]

Here I am almost ready to finally install my newly acquired Mark Levinson 380S/333 pre/power when manoeuvring the kit into its shelving unit there was a low crackle coming from the slightly dislodged power plug/at its G-Sub socket and the pre amp went dead. On checking the 2x T 250v 250mA slow blow fuses, both had gone. My question is, is this a particularly delicate bit of kit or would the mains plug doing what it did be likely to blow these fuses?
Dont mean to sound daft like ;-)

I wouldn't expect that to blow any fuses... obviously it has though! My first thought is that maybe it has an over sized transformer and either no soft start protection or the rapidity of the mains going on and off as the plug was joggled was too fast for the soft start to react to. I'm hoping it doesn't have an SMPS rather than a transformer as that would be MUCH more difficult and expensive to repair if it's blown...

I'd replace the fuses and try it with no power amp connected first. Obviously if the fuses blow again with the mains plug properly in place then it is damaged. If it powers up then it would be best to try it by checking tho output on a 'scope if you have one or by using with an integrated/passive pre/headphone amp with vol control at first just in case it has a huge DC offset or is giving 4V of mains hum out due to any further damage.

 

[cooky1257]

Ah, Thanks all, OK, I've ordered some replacement fuses so will post an update as and when.
@Jez its got a toroidal tranny no SMPS-thing has been working fine thus far. Will follow your advice.

 

[Arkless Electronics]

Ah, Thanks all, OK, I've ordered some replacement fuses so will post an update as and when.
@Jez its got a toroidal tranny no SMPS-thing has been working fine thus far. Will follow your advice.

Toroidal bad for switch on surges so it figures

 

[martin clark]

The other thing that can do this would possibly be a blown bridge rectifier on the output side of the transformer. Usu cheap and easy to fix, but not so easy to detect..!

 

[337alant]

You may have had a loose fitting plug or connection which has arced whilst maneuvering into the cabinet, could be enough to blow a fuse?.
If it was inrush current then it would have blown as soon as you powered it up.
Try another mains lead that has a tight fit


Alan

 

[Arkless Electronics]

You may have had a loose fitting plug or connection which has arced whilst maneuvering into the cabinet, could be enough to blow a fuse?.
If it was inrush current then it would have blown as soon as you powered it up.
Try another mains lead that has a tight fit


Alan

The inrush current stresses the fuse like work hardening and they can eventually go for no apparent reason when you switch on one day... if this was repeatedly switching it on and off several times a second....

 

[cooky1257]

Thanks for all the contributions/ advice. Top marks to RS who got fuses to me next day with free delivery. I ve just fitted them and bingo pre is back in business. Result.

 

[cooky1257]

A peek inside( central cover over section from tranny to top removed) to see what £6k buys you.....

Lots of these orange components.