Noise pb with brand new HT-20r Mk II

HT-1R MkII, HT-5R MkII and HT-20R MkII Head and Combos.
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hbbk
Posts: 2
Joined: Sat Jul 27, 2019 3:51 pm

Mon Jul 29, 2019 11:37 am

Hi blackstarists

I bought a brand new HT-20r Mk II in march and after few weeks I'v got a strange mechanical noise.
This noise seems to be related to one of the tube spring and occur only around certain notes (around C - B, C# - and harmonics G...), this was at the beginning, in the meantime I opened the amp and moved the spring and now the center note is a D....
Here is a little video (you need to push up the treble to listen to the spring noise) - as you can ear the noise disappear when I touch the tube (and when I remove the spring too)
https://youtu.be/SJEVXW7IO7s

Any help is welcome, should have to give the amp (still under guarantee) to the shop I bought it (I'm from france) or is there anything easy I can do ? (completely removing the spring seems to solve the pb but I suspect this piece is not here for nothing ?)

Except this (little but really annoying) problem this is a fantastic amp ;-)

very best

hbbk
Posts: 2
Joined: Sat Jul 27, 2019 3:51 pm

Sun Aug 04, 2019 9:00 pm

[Edit after few hours]
In fact what is written below is false: after few hours I tried again and the noise is back (even with the spring removed), I suspect that this is due to the fact that valves warmed up... so next step is that I'll have to change the valve (and learn to deal w/ bias ;-))

[first v of message]
----
Answering to myself in case it can help later.

- I checked microphony on tubes, nope (all tubes seems to be ok)
- Tried to make spring and tube stop to vibrate by inserting various stuff on or around them, nope
- The only thing that worked is to completely remove the valve spring fixation... Now no more parasite noise, the amp sound great again !
I suppose I'll have to really care about vibrations now, I'll have to check regularly that the tube is not moving

But that's really a pity for such a so expensive amp, I suspect this is a design problem or maybe a specific defect on that particular amp... I love it, use it daily and don't want it to be away for week to the after sales service. If a blackstar official is around here maybe he could contact me to see what could be possible

cheers

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