JAN philips 5751, V1 powerball, noise...

[MDV]

High pitched whistle, not very loud, but loud enough to be obvious.

Problem?

[Dmoney]

sounds horrible.
the test is to tap it with a pencil or something, gently, and see if you can hear the noise of the tap coming through the speakers.

[MDV]

Good plan. Ta.

[Twinfan]

Sounds like a microphonic valve to me...

[MDV]

That was my guess.

Its really not that loud though. Its not like the amps shrieking at me like microphonic pickups or anything.

But will test it - Hadnt thought of tapping it, for some reason.

[Dmoney]

i had the same issue not so long back and totally forgot about tapping it.
it didnt sound 'microphonic' to me either, just more noisey and i guess pretty much how you describe it.
i had the issue with my uberschall right out the box, but guitarguitar sent me a new tube for free.

not like some practice room amps ive used that sqeaul all the time, or just feedback a lot and thud and ting really loudly out the cab if you flick the head with your finger.

[MDV]

Oh, lets say it is microphonic.

Since its queit enough for the noise itself to be a problem and I can easily put up with it, will leaving it there cause any other problems with the amp?

May as well leave it in than change it if its not causing me any real problem and isnt going to harm the amp/other valves - no point using up my jan 5751s faster than I need to.

[Twinfan]

Won't do any harm leaving it in, but it may be worse at gig volume????

[MDV]

I can test that later too. Havent had it much above fun-volume-on-a-stereo (maybe 90db at 1m) in ages, being that I'm not gigging at the moment, but it would be nice to know if it does or not.

[Twinfan]

I'd make sure you have a spare with you.........

[MDV]

Word.