Pro Sound Amp trips-out on startup

[colslo]

Hi.

We are experiencing some problems with our Pro Sound 1000 amp. When the amp is turned on there is a tendency for it to IMMEDIATLY blow the small glass fuse in the mains ac input on the amp. We start power up with the Behringer mixer off and EVERYTHING turned down to Zero. When it happened first time we took it back to Maplins & they just exchanged it. The second time they showed me the fuse holder & gave me some replacement fuses, saying it must be caused by our other equipment! We started using a anti power surge extension lead with a safety earth trip plug and the amp has actually tripped the earth trip plug a couple of times.

Has anyone any ideas why this should happen? Is it possibly us, or a faulty batch of amps.

Thanks for any advice.(a newbie)

Colin

[ChrisD]

If the amp is blowing a fuse instantly on start up and has no other pieces of equipment attached, then there is some kind of low resistance path between live and neutral. If it is blowing fuses without kit attached, take it back to the Maplin store, and get them to plug it in and show you how to use it. Then when it blows the fuse, ask for a replacement amp. If it doesn't blow with no kit attached, turn it off, plug some speakers in, and turn it on again. If all is well, turn it all off, add an input source (minidisk, cd player etc). If that works, then play something through the amp to the speakers. Then try adding your standard Behringer mixer and see if that blows the fuse.

 

On reflection of the above advice and after reading your post again, the fact that it's tripping an earth trip (RCD or similar), it suggests there's a low impedance route between live and earth - (i.e. something shorting between the mains power coming into the amp and the case of the amp). This is a little more worrying than a live-neutral short and so I would be tempted just to take it back to Maplin and ask for a refund. I don't know about your local Maplin but at mine some of the staff know what they're talking about, whereas others don't. If they don't want to refund your money, ask them to test it for you. I imagine it's under warranty.

 

Hope that helps, and good luck.

[colslo]

Thanks for thast Chris.

I will give it a go.

Colin

[james jag]

at the risk of sounding high and mighty, stop buy things like that from maplins

 

and also does sound like a manufacturing fault, if it keeps happing when it is pluged strait in and turned on, also a surge protection adaptor will not stop you blowing fuse's and what happing is and over current problem in the power circuit, maybe a low impedance on the output, do you have speakers connected when powering up ?

[themadhippy]

We start power up with the Behringer mixer off

whilst proberly not the cause of the problem,its normal to power up source-desk-amps,power down in reverse,stops those annoying pops and thumps that can damage your speakers

[Mixermend]

Do check that you are using the correct type of fuse.

The fuse value (in amps) is obviously important - but so is the blowing characteristic of the fuse.

On a power amplifier - especially a high power one, probably fitted with a toroidal mains transformer - the fuse should be of the surge resisting, or time lag type.

The correct type and value should be marked near to the fuse holder:

 

F = fast blow

T = time lag (or surge resisting).

 

Make sure that you fit the correct type!

[colslo]

Hi Guys, Thanks for all inputs.

In answer to James, I had the speakers & Mixer pre connected, albeit that ALL levels were turned to zero on all the gear. It trips about 10% of the time. The replacement fuses came from Maplins, but that’s a good point about using the correct fuse, which I will check out. My main concerns are, is it the amp that’s faulty or can these symptoms be caused by a fault in my other gear. The speakers seem ok, (Pro sound 200WRMS) but as I’m a newbie I don’t know how to test them, apart from listening.

Thanks for the “source-desk-amps” power up advice. I was never quite sure. We may have got that the wrong way around, but EVERYTHING was always Zeroed.

Thanks again.

Colin

[Bobbsy]

Two points on this...

 

First off, I've known a couple of people with Maplins Prosound amps and both of them had problems with them tripping. One had the switch-on problem like yours; the other had lots of heat-related trips in use. Both eventually gave up and bought better quality gear.

 

Second, just to reinforce what was said earlier, the normal switch-on order for gear would be outboard and sources first, then your mixer, then any processing between the mixer and the amps, then amps last. Doing it this way avoids sending any switch-on bumps "down the line".

 

Bob

[colslo]

Cheers for that bob.

Looks like you get what you pay for.

I guess I will have to look out for a good second hand amp.

Cheers

Colin