amplifier works ok @low volume protects when volume turned up

This is a Carlsbro Marlin 8400 mixer amp
it is a name only amp it's made in thailand? made under carsbro licence
But it's going into protect when i increase the volume
when i turn it on the music from cd player can be played at low volume
When i turn the volume up it clicks & sound goes off
turn volume down & it comes back on
I have tested all transistors & all are good. replaced most of the smaller trannys
like 1306b / 3298b / tip 42 & 41
The outputs are 3 x 2sa1943 3 x 2sc5200 not replaced them
they test ok.. But can they fail when in use. & not take out the fuse?
I am testing it with a light bulb just in case...
but can't find the problem..anyone Got any Idea's
 
This is a Carlsbro Marlin 8400 mixer amp
it is a name only amp it's made in thailand? made under carsbro licence
But it's going into protect when i increase the volume
when i turn it on the music from cd player can be played at low volume
When i turn the volume up it clicks & sound goes off
turn volume down & it comes back on

I have tested all transistors & all are good. replaced most of the smaller trannys
like 1306b / 3298b / tip 42 & 41
The outputs are 3 x 2sa1943 3 x 2sc5200 not replaced them
they test ok.. But can they fail when in use. & not take out the fuse?
I am testing it with a light bulb just in case...
but can't find the problem..anyone Got any Idea's
Does it go into protect plugged straight into mains? No load attached?

What load are you actually driving?

Some details on cabinet(s) please.

Are there Piezos in the cabinets?
 

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The main input to the board is to the left of the large cap. down by the rectifier.
I'm not sure where to take Voltages from when the amp goes into protect to see if there is a drop..I have tested the output from transformer & all seems Fine..

I don't think there was ever a schematic for this amp?
 
The amp will come on when plugged in & play music from a cd player connected to line in on chan 1. it's the same on all channels 1 to 8
you here it click & the sound is there. If you turn the volume up just a little the music sounds good but it clicks & goes off. it's plugged into a 400 watt speaker. This speaker works fine on other amps..
 
Does it also go into protect if you turn up the volume with nothing playing?

If not, check all the bigger resistors near the output (and take a look at solder joints while you're at it). These symptoms would be typical if one or more had gone high, which can throw output stage DC offset out of whack under load.

You have verified that the speaker measures something sensible like >3.2 ohms at the amplifier end of the cable, and accidental shorts are out, right?

If it does go into protect if you turn up the volume with nothing playing, you have a problem with DC from a previous stage being amplified, or maybe an oscillation problem, both possibly bad caps.
 
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OK. tested with no load & it's not going into protect
You here it click. then i turn the levels up & master volumes..NO tripping
Checked all resistors large and small all ok
I have renewed all the transistors in the out put..apart from the 3 x 1943 & 3 x 5200
These check out fine..But could one of them fail under load?
or should i look for anything faulty in the mixer front control panel