Power on noise

[bartman]

Hey friends,
I have two Tone King amps that have the same symptoms...
Upon power up there is an audible in-rush of noise, then a 'crackling' noise.
It subsides within a minute or two.
Power is clean,  mains supply runs through a Tripp-Lite iso-bar ultra.
Power tubes?

[bartman]

It seems quite odd that both these share the same symptoms.
Is it a design flaw ?
Cheap filter caps?
They are a Royalist Mk Ii and a Falcon Grande, both purchased new by myself...


Sorry,  Royalist Mk III.

[tubeswell]

Noise like that is most likely filter caps - which are e-caps (including e-caps used for filtering bias supplies if your amps are fixed bias - can’t tell without schematic )

[bartman]

Thank you for your reply.
I wasn't sure where to start. I understand vacuum tube theory and safety protocol, new to hands-on troubleshooting (retired electrician).
I don't have a schematic (yeah I know, first rule!)
I will pull the chassis on the Royalist first. It's only a year old. Imagine that!?!
Thanks again!

[tubeswell]

A bit of static discharge noise from filter caps is quite common in tube amps. A ~200k bleeder resistor in parallel with the reservoir cap can reduce this. Not all amp makers include these.

However, if these are EL84* output tubes, you might get some power tube crackle after 12 months if you’ve used the amp constantly. (Don’t know what’s in these amps - see if you can find a schematic next time - otherwise it’s just making stabs in the dark)

*i.e., little bottles wear out faster

[bartman]

Hey everyone,


Just an update on the Royalist.
All the issues came from the preamp tubes,  V1 and V2 ( both JJ ECC83S). Been burning for about an hour,  no issues.
I forgot KISS !


I do have a question: Should the preamp tubes get filament/heater power in standby?
I don't observe any...


Thanks,
Please be safe this weekend...


Take care,
Bart

[bartman]

I also want to clarify/update the symptoms:
There was not a "current in-rush" sound.
It was a LOUD crackling upon switching from standby to run.
I apologize for the misinformation.
Thanks again,
Bart

[pdf64]

... It was a LOUD crackling upon switching from standby to run...

...  All the issues came from the preamp tubes,  V1 and V2 ( both JJ ECC83S). Been burning for about an hour,  no issues.

That's strange, those symptoms are much more characteristic of output / rectifier valves.

... Should the preamp tubes get filament/heater power in standby?
I don't observe any...

That's strange.
12A_7 valve heaters don't get their valve's glass envelope anywhere near as hot as output or rectifier valves. But after a couple of minutes on standby, they should be noticeably warmer than they were before the power was switched on.

Even if no schematic is available, it's helpful to provide something, anything regarding the amps in question https://www.toneking.com/shop/amps/royalist-mkiii-combo/
https://www.toneking.com/shop/amps/falcon-grande/#brownback

It's worth noting that despite the misapprehension amp builders / designers / handbook authors are under, there's absolutely no technical benefit, and often significant technical downsides, of using standby in amps with GZ34, 5AR4, EZ81 rectifiers.

[Jennings]

All the issues came from the preamp tubes,  V1 and V2 ( both JJ ECC83S).

Sounds like it's probably a bit of dirt/dust/crud in building up round the pins of those tubes or in the sockets...give the sockets a good clean out and ensure the contacts are snug / tight.