Cystern inlet valve

[joesoap13]

Hi guys, appreciate a bit of advice please.
My upstairs toilet cystern, for some reason, the last year or so has been making a noise, vibration, when just at the end of filling.
Just a few seconds till it finally stops water coming in ?
I know it’s the inlet valve diaphragm, BUT, I have changed it 5 times for new ones, but to no avail.
After the first couple of quiet fills it reverts back to making the noise.
Luckily , it’s only used once a day, so not really something that drives me mad.
However, I would like to fix it.
Tried reversing diaphragms, same result.
Apart from replacing the entire valve, any advice would be appreciated.
I don’t have a isolation valve on the inlet flexi hose to reduce the pressure to the cystern, but turning the sink tap on at the same time as it’s filling doesn’t help, so probably no point putting one in ?
Why it is quiet for the first couple of flushes, then starts again, even just taking it out and putting it back in , has me stumped.
Cheers

 

[kidgreen61]

Probably just one of those things, just bite the bullet and change the whole valve, they're not expensive.

 

[joesoap13]

Reckon you are probably right.
Just tried turning the stopcock down to the whole house, still the same.
Cheers

 

[Exedon]

As above change the inlet valve we use the brass shanked fluidmaster,
Just to be clear turning down the stop tap or isolation valve don't reduce pressure at all just volume.

 

[joesoap13]

Cheers exedon, realised that when I posted , flow rate.
What’s the cone I read on posts?
Is it where the diaphragm hits against to stop inlet ?

It’s the ball type.
Changed downstairs to dual flush few years ago, but it packed altogether.
Cheers