broken boogie - help!!

[johnnyvanallan]

help!!
i have bought an american (110v) express 5.25 1x12 and i am living in malaysia (240v)
i am sticking the amp through a 300w (twice recommended) step down transformer, into a voltage regulator (ensures a steady 240v) and then into the mains. i flick the power and the fuse blows. i have bought 5 replacement 1a slo blo fuses (same as was supplied) and the same has happened with all 5. the channel 1 light briefly lights up, prior to the fuse blowing, but nothing else does.

john

 

[tmac]

Hi John! If you are sure the amp is receiving the correct voltage, maybe a damaged tube is to blame? I would try to start it up without any tubes.

Is this an amp that you have recently received and have not yet gotten to work? New or used?

If the amp blows the fuse without any tubes I guess a technician should probably be contacted, if you are not yourself experienced with tube amp repairs. It is quite dangerous to poke around inside the amp chassis.

Good luck, I hope you will be able to enjoy your amp soon! I have a USA Express 5:25 in Norway (240V). I'm using a 100W step-down transformer but I am going to change to one with 300W capacity since I don't trust the current one to last at a loud volume.

 

[soundchaser59]

help!!
i have bought an american (110v) express 5.25 1x12 and i am living in malaysia (240v)
i am sticking the amp through a 300w (twice recommended) step down transformer, into a voltage regulator (ensures a steady 240v) and then into the mains. i flick the power and the fuse blows. i have bought 5 replacement 1a slo blo fuses (same as was supplied) and the same has happened with all 5. the channel 1 light briefly lights up, prior to the fuse blowing, but nothing else does.

john

The way I read this and understand what you wrote, it sounds like you are supplying a steady 240 volts to an amp that is rigged to run on 110? If that is correct, then naturally the fuse would blow. I hope that is the only thing that blew.

If the amp needs 110 volts to run, then you need a transformer/regulator that puts out a steady 110, not 240.

And I haven't looked at my own amp, but are you sure that 300 watts of power supply is enough to run the amp? Most of the guitar amps I've had in the past, at least the biggest ones, seem to draw 500w or more from the outlet. I'd be surprised if the Express is not drawing more than 300w, but I guess its possible.

 

[tmac]

And I haven't looked at my own amp, but are you sure that 300 watts of power supply is enough to run the amp? Most of the guitar amps I've had in the past, at least the biggest ones, seem to draw 500w or more from the outlet. I'd be surprised if the Express is not drawing more than 300w, but I guess its possible.

The 120V version of the amp only uses a 1A slow blow fuse, so it does not draw more than around 120W. I currently use it successfully through a 100W step-down transformer, although I am going to change to a 300W model to make the sure it holds up if I crank the amp for more than a few seconds, and to make sure there is no significant voltage sag and the likes coming from the step-down transformer.

 

[J.J]

Just for reference, I put a watt meter on mine and it draws 57watts when on (not standby) and played at low levels.

 

[tmac]

Just for reference, I put a watt meter on mine and it draws 57watts when on (not standby) and played at low levels.

Very interesting, so I just did the same on my amp (also 5:25). I got the following results the the power usage while silent:

Push-pull mode: 53W
Single-ended mode: 49W

Some other time I am going to check the power usage while playing loudly, to see how high it goes.

 

[tmac]

To complete the picture, here are my measurements while playing loudly, i.e. master at 100%, gain at 75% on the clean channel:

Remember that these are quite inaccurate figure...

25W mode: around 75W
5W mode: somewhere around 55W

- Torquil