Hi

I'm new to this site, normally over at DiyAudio.com

I have built a number of simple point to point SE Tube amplifiers over the years and acquired a little knowledge as I went along.

My son asked me if I could look at a guitar amplifier for his girlfriend's father.
I grudgingly agreed (I work on a principle of Never Volunteer) and asked him to find out the make, model and the fault.
I don't have the amp in my possession at this time or a circuit diagram.

The amp is a Peavey TNT 150 and the first thing I find its solid state not tube.
This presumably means circuit boards!!! this is outside my comfort zone and its not my amp.

I'm committed to doing something and therefore asking for your help, if the probable fault can be determined and it's a simple repair I may go ahead, if not I will have done my bit and everyone will be happy.

The symptoms.
When switched on the 'Compression LED' illuminates and the amp hums.
The hum then starts to pulse.
No bass output normally but intermittent distorted bass when moving the 'Gain Control'.
Loud thump when turning off.


From Peavey TNT 150 User Manual.
'The compression circuits eliminates audible power amp clipping, reduces distortion and protects the loudspeaker.
In use, the compression LED may occasionally illuminate, indicating that compressor is engaging to prevent distortion.  If the LED is continuously illuminated, Gain control or Low EQ settings should be reduced to prevent possible loudspeaker damage.'

Thanks in advance.
John