1st post and of course...I NEED HELP...amp keeps blowing main fuse

[joeblizow]

got a rb 980bx and it keeps blowing the main fuse in the back
ac t4A FUSE Im assuming 250volt (thats what i used) not sure if need slow blow or fast is the correct one

everytime I put in a fuse and turn on "pop"
and I did search the forum before posting and it said not to keep inserting fuses...

just wondering if anyone may have any new solutions or input on this issue
thanks

[srb]

Is yours a 120V or 240V unit? This Rotel Fuse Chart http://bwgroup-support.com/rotelfuses.html, which is for 120V units, lists an 8A fuse for the RB-980BX, but apparently your rear panel fuse holder is labeled "T4A", hence my question on 120V vs 240V.

The "T" is for time-delay or slow-blow which is what you should be using and most fuses for 120V equipment are rated for 250V.

If there were a short in the speaker output circuit, one might expect the internal rail fuses to blow rather than the main AC fuse, but it still couldn't hurt to check that there isn't a short in either the speaker cables or speakers themselves. Disconnect the speaker cables from the amp and try to power it on with a new fuse. If it still continues to blow (and the fuse amperage rating is correct) then something internal in the amp has shorted out and would need qualified service.

Steve

[joeblizow]

actually says 230v

[srb]

Okay, so you're presumably not located in the U.S. and have a 230V unit which would have a 4A fuse instead of the 8A fuse that 120V units would use.

Have you tried to power up the unit with no speaker cables connected?

Steve

[joeblizow]

i am in US but they were bought overseas.....and yes i have tried to power up with nothing connected....ive tried 4a fuses first then 8a because it said 8a on fuse chart which was obviously wrong

[joeblizow]

Should i try a 125v fuse
4A slow 125v

[srb]

A fuse is usually rated at a higher voltage than it will be used at. A 250V rating is more or less standard on 120V circuits. Using a higher voltage rated fuse just means that it is operating with a higher safety margin.

As long as the voltage rating is at least met or exceeded, the important specs are the amperage rating and the response time (fast-blow or slow-blow). If a circuit calls for a 4A slow-blow fuse, using one with a voltage rating of even 600V is fine.

If a device is designed to operate at 230V and the proper fuse is 4A, the corresponding version that is built for 120V would use an ~ 8A fuse, as corroborated by the Rotel 120V fuse chart.

As this story unfolds, you apparently have an amplifier that is designed to run on 230V (and most likely at 50Hz frequency, depending on the country of origin). That amplifier will not operate properly when plugged into a 120V/60Hz outlet. Although I wouldn't necessarily expect the fuse to blow (like I would if a 120V amplifier was plugged into a 230V outlet), the secondary windings of the transformer would not supply enough voltage to the amplifier circuit.

Normally either an external step-up transformer is needed between the wall outlet and the amplifier, or the amplifier needs to have its internal transformer rewired (if the transformer was equipped with two 115V primary windings that were wired in series) or replaced altogether with a new transformer.

Is this the first time that this amplifier has been powered up on U.S. 120V power? I believe that the RB-980BX has a 2-conductor captive power cord. The plug that was used abroad would have likely been different than the U.S. standard NEMA-1 type, and if the plug was replaced, it may have had the neutral and hot leads reversed perhaps explaining why the fuse blows.

In any case, if the amplifier has not been rewired for 120V use or an external step-up transformer is not used, then the amplifier will not work properly.

Steve

[joeblizow]

i actually have 2 of the same amps....one of them works fine
so I dont know if outlet would be the issue?