Amplifier power problem, please help.

[loganbiffy]

Hi folks, was at band practice tonight and i the middle of a song my amp power cuts off.

So i change the fuse in the plug and it still doesn't work.
Opened it up and doesn't seem to be any obvious issues like anything being burnt out or such.

Any ideas guys? Cheers.

[Jeid]

What kind of amp is it? Any noise or anything?

Could be the amp fuse rather than the power lead fuse.

[loganbiffy]

What kind of amp is it? Any noise or anything?

Could be the amp fuse rather than the power lead fuse.

Its a Laney 120 World series from the 80's, The amp fuse that is just below the power supply input? It looked ok too but i ain't entirely sure how to tell if its knackered or not.

[The Pepsi Challenge]

Valves probably.

[Jeid]

It's not a valve amp I think...

[loganbiffy]

It isn't a valve amp, you are correct Jeid. Just an old transistor amp.

Laney World Seried 120tr.

[Chobbersjnr]

the fuse that's inside the amp should be see through???? if so you'll be able to see if the wire is broken inside the fuse.....

Is there a slo-blo fuse that screws out of the back of the amp???? could be that

use a multi meter to check also.

If it don't power up after you've check out the fuses it may be something nastier like the transformer packing in......................not nice.
Did it pack in instantly??? was there a burning smell???

[loganbiffy]

the fuse that's inside the amp should be see through???? if so you'll be able to see if the wire is broken inside the fuse.....

Is there a slo-blo fuse that screws out of the back of the amp???? could be that

use a multi meter to check also.

If it don't power up after you've check out the fuses it may be something nastier like the transformer packing in......................not nice.
Did it pack in instantly??? was there a burning smell???

Yeh it just cut off in the middle of a song.
No burning smell or anything like that, just died.
Fuses are ok, seems to be something to do with the power, prob the transformer, expensve to fix?

[Chobbersjnr]

expensve to fix?

it can be.......

we got damaged about £70 for a fender tremolux replacement transformer

[theweemidget]

£70 for a fender transformer that is not too bad i've seen crazier prices for transformers mate. The amp just dieing hmmmmm no smells fuse ok, check the fuse in the plug as well. It may not be the case of your transformer usually they are robust and a transformer you would smell. The amp just cutting out is a good sign with no smoke or anything. I would not go by looking at fuses as chobbers said check with a DMM for continuety. Your amp is fairly old it could be an issue in the power supply with capacitors drying out. did you hear any ghost noting that means the note sounds out of tune and double. I will check the schematic for the amp to see what i can find, dahhhh bloomin transistor amps you should stick with valve amps lol. Also if the thing is completely dead it might be power transistors, but i would book the whole thing in for a service anyway

[loganbiffy]

£70 for a fender transformer that is not too bad i've seen crazier prices for transformers mate. The amp just dieing hmmmmm no smells fuse ok, check the fuse in the plug as well. It may not be the case of your transformer usually they are robust and a transformer you would smell. The amp just cutting out is a good sign with no smoke or anything. I would not go by looking at fuses as chobbers said check with a DMM for continuety. Your amp is fairly old it could be an issue in the power supply with capacitors drying out. did you hear any ghost noting that means the note sounds out of tune and double. I will check the schematic for the amp to see what i can find, dahhhh bloomin transistor amps you should stick with valve amps lol. Also if the thing is completely dead it might be power transistors, but i would book the whole thing in for a service anyway

Its def not any of the fuses, al have been checked with a digital multimeter.
whats the deal with power transistors?
Don't really know much about them.
Also i prefer transistor amps to valve amps, they give me the sound im looking for.
Cheers.

[Deemac]

I'm no expert with amps but sometimes the simplest of things can be overlooked!!

Have you checked the cable/connection from the output of the amp stage to the back of the speaker?

[Chobbersjnr]

my amp power cuts off..

I'm no expert with amps but sometimes the simplest of things can be overlooked!!

Have you checked the cable/connection from the output of the amp stage to the back of the speaker?

1st quote says it all. If the speaker wasn't connected to the amp, the power would still run but without sound.......

[theweemidget]

i had a problem with my hifi amp it was being a bit funny turned it on and turned it off again wouldn't turn on. plugged my dmm into the live and neutral of the power cable getting approx 240V, checked fuses on amp etc all was fine, then the amp started working again and 2 weeks later same deal so i took a plastic screw driver and ran the tip up the power socket on the amp and had no bother since.

Fair play bout transistor amps, i don't like em persoanally other than H/H and well the old laney amps cause they had h/h hardware in em and plus it's easier to work on a valve amp if something goes wrong.

Power transistors are those thing in the heatsink onthe back, power transistors provide the power for the amp a transformer just changes the voltage. just get your amp serviced, I service mine every 6 months

[stratman]

Have you tried another mains lead that you know works?

[loganbiffy]

Have you tried another mains lead that you know works?

Yeah ive tried another lead, i know the original one works anyway cause i tried it on my mates laney.

[BigKev]

If there is no sign of life at all from the amp (pwr lights, noise etc.) and you have checked the following:

The leads pins and fuse,
The socket! (it can happen)
The amp socket pins
The internal amp fuse
Have given it a kick

then its probably time to check the power board, that means a service if you really like your amp! and it would cost you money too!!

If it has been opened before or you wouldnt mind busting the warranty (1980s hmm..) there is the option of getting a friend to check it for you before you spend the money on a service.

By the term "friend" i refer to a qualified instrument or electricial of course!

Its a very bad idea to do it yourself, for a number of reasons. . . . .

[loganbiffy]

If there is no sign of life at all from the amp (pwr lights, noise etc.) and you have checked the following:

The leads pins and fuse,
The socket! (it can happen)
The amp socket pins
The internal amp fuse
Have given it a kick

then its probably time to check the power board, that means a service if you really like your amp! and it would cost you money too!!

If it has been opened before or you wouldnt mind busting the warranty (1980s hmm..) there is the option of getting a friend to check it for you before you spend the money on a service.

By the term "friend" i refer to a qualified instrument or electricial of course!

Its a very bad idea to do it yourself, for a number of reasons. . . . .

Yes there is just no power getting through at all. It is open, i have the head here just now.

There is no readings coming from the power input or power switch connections when tested with a multimeter.

[theweemidget]

ok like big kev said yeah get someone who knows what they are doing to fix it is a good idea i only do my own amplifiers because i know what i am doing with them. and you may need more than a multimeter at this stage you need to know the places where the faults are likely to occur i e the power supply. maybe 1 of the zener diodes or something shorted. or it could even be something as simple as a dry solder joint. amplifiers are funny things and usually there are signs when they are about to conk so to speak just some are more obvious than others. best advice if you love that amp get it serviced properly cause i have seen some major hack jobs done over the years and it's not funny it can be bloomin dangerous not only to the amplifier but to your safety.

[loganbiffy]

ok like big kev said yeah get someone who knows what they are doing to fix it is a good idea i only do my own amplifiers because i know what i am doing with them. and you may need more than a multimeter at this stage you need to know the places where the faults are likely to occur i e the power supply. maybe 1 of the zener diodes or something shorted. or it could even be something as simple as a dry solder joint. amplifiers are funny things and usually there are signs when they are about to conk so to speak just some are more obvious than others. best advice if you love that amp get it serviced properly cause i have seen some major hack jobs done over the years and it's not funny it can be bloomin dangerous not only to the amplifier but to your safety.

Yeh its an idea but i have no idea where to get it serviced, i dont know anyone who does it up this way.