HT5-R Amp switched on => cracks-sparks-...sounds

[MVa]

Hi,
some issue popped-up after leaving the HT5-R a full night powered-on...
The amp produces a cracks-sparks-...sound after 10-15 seconds and keeps on ding this way. Changing volume, gain,clean/dist. doesn't change anything to it.
Any idea where-what to look for?

(a sound sample can be provided)

Thanks for your reply!

MVa

[thephantum]

Most likely a bad power tube,, but it could be a number of other things too. I would try putting a new 12BH7 in and see if the problem stops. If so have the amp biased. If not, then it needs to go on a bench to get diagnosed.

[MVa]

Thanks for your feedback!
so, I will visit my local guitar/amp handyman in the upcoming days....
MVa