Marshall Valvestate 8080 intermittent volume dips

[cosrjc]

Hi - My Valvestate 8080 has a problem on the Boost Channel. The volume is often low, but also swells and fades down over 3-4 seconds - bit like a very slow trem. The problem is intermittent - happens 50% of the time on average. The valve seems fine (eg it works on clean and crunch) any advice before replace it? I have a volt-meter and soldering iron at the ready, but don't have a huge amount of experience!

tx - cos

[Jerry]

I'd would suggest pulling the chassis and looking at the solder side of the circuit board for bad solder joints or possibly a pot that took a hit and the back casing has been knocked loose. It sounds like the clean channel works fine, doesn't lose volume.

[cosrjc]

many thanks - will work my way round the connections - poor thing's been gigged regularly for past 4 years so plenty of knocks... cos