arc vt150se


i have a pair of arc vt150se mono blocks with a arc ls26 preamp.on of the mono block is giving some sort of cracking noise when it is on after 5 minutes and continuing till the amplifier is set off.any suggestions what the cause could be?
Have you tried switching the tubes yet[one set at a time]?Could simply be a bad tube or dirty tube socket.You can clean the sockets with Deoxit and a pipe cleaner,be sure to unplug them the night before so they can discharge.Also you can try wiggling the speaker cables and interconnects to check for a bad connection.If there is an internal part beginning to fail,these remedies of course won't work and it's time for the repair shop.Not a good idea to poke around inside,the voltage can be lethal.
>> Not a good idea to poke around inside,the voltage can be lethal. <<

High voltage will not hurt you, high amperage will drop you dead...

What about when there is no preamp connected to it?
Will it still emit that crackling noise ?
There might be a faint hum when nothing's connected but it will be a safe thing to try
Wonderful amps.

You should try to isolate the problem. Remove the Pre amp to make sure it's not that. Then cables and finally tubes. It could be a dry joint or anything. I wouldn't poke around inside though. Death awaits you if you don't know what you are doing. A lot of stored power in the power supply.

If this fails to find the problem send it back to ARC. It could probably do with a service anyway. Some new coupling caps would bring huge sonic joy I am sure after many years of hot use. One of my favourite amps of all time. Epic on a Magnepan or ML CLS