Karaoke AMP loss of sound problem

[Calgacus]

Hi

Myself and my Wife do Karaoke Gigs in our local towns

Our Favourite AMP has been playing up recently

Make/Model :Leem PM401d

Description
Al of a sudden during a gig all sound will go to a very low level
no warning that this is about to happen. The AMP still has power
during this event and the only way to correct it is to power cycle
the AMP. I have eliminated all the speakers and cables and suspect
something is not quite right inside the AMP. Possibly heat related

As i feel it happens more often as the warmer weather is coming in now.

I have a basic electronics knowledge but am handy with my multi meter
and soldering iron.

Does this sound like a common problem in amps and if so where should i start looking

I opened it up a few months ago but could not see anything obvious..no swollen caps

or signs of components overheating

Any help greatly appreciated

We will be using it tonight so will update if it plays up again

Thanks


Calgacus

 

[davenn]

hi there
welcome to the forums

OK ... when it fails does it ever recover some minutes or whatever later ?
or only recovers after unit is switched off and cools down ?

if the later is the case, how long does it need to stay off for ... ie. can you switch it off and back on straight away and it will work ?

cheers
Dave

 

[Jagtech]

Is it, by chance, sensitive to bumps or vibrations? Due to the environment these amps are usually exposed to (moving, bumping around, temp changes, etc) one night suspect loose or cracked solder connections on the PC boards.
Just a thought.....

 

[Calgacus]

Hi

Thanks for replies

As its in use when it looses the sound, i don't have time to wait to see if it recovers
it's always shut down for couple seconds then works straight away again every time.

I have also never been able to duplicate the fault at home it works flawlessly at home
even on for hours at at time..my only guess to this is perhaps because the music can't be played as loud at home thus not driving the amp very hard(my first reason for thinking overheating)

It is also not exposed to any bumps etc...its in a flight case with plenty ventilation. this obviously doesn't rule out dry joints.

I will look at that soon as the Venue is now closed for 4 weeks for refurbishments

It was in use for 5 hours last night and because it was busy my wife tried to limit any
interruptions from it by power cycling it once every hour or so which seemed to make a difference as it did not cut out once

Thanks again

 

[duke37]

If it comes back on immediately, I would think it is not a tempeature problem unless it is a dry jount which will cool very quickly

Is there an overcurrent circuit wiich resets when the power is turned off?

 

[Calgacus]

Hi Duke...i am not sure if it has overcurrent circuit

I am going to open it up this week and look for dry joints, i will post some pics of the boards inside

Thanks