Hi hero
Just to thank you for your help, I got a couple of 2n3958 for just 5 gbp (ok, I paid more for the delivery then the pieces!), anyway it was worth, I spend just some time to bias it like the old one , now look like my scope is working.
So thanks for your help it was very appreciate. (by the way I try to match two fets but It didn't work, ok I don't have so many tipeso I tried just with j112, j310, but I think they have charatteristic totally different then this one, and last my limits in elestronics are pretty evidents ;-)).