Possible Causes of Tube Amp Whistling?

[Steady339]

I have a whistle in one of my Manley 35 Watt Monoblock tube power amps.

Having difficulty trouble-shooting the annoying whistling.

Problem started after a power tube red plated and came back from the local repair shop that replaced a burned 10 ohm resistor.

The problem is not upstream in my preamp.

Don't have this issue with the other mono amp.

I have tried swopping out all tubes, but the annoying whistling persists.

The whistling sounds like some multiple of line voltage.

Please advise.

Roger

[jdandy]

Roger.......You may have an issue with a power supply filter capacitor. Speak to your tech about it. Don't mess with the power supply parts yourself. There are high voltages present and it is unsafe unless you have the schematic and are experienced.

[Steady339]

Dan, Thanks for your reply. Looks like another trip to the repair shop is in order.
I love the sound of this amp when it is working properly.

Roger

[AudioGremlin]

Why not contact Manley direct, their tech department are very helpful. Also they will supply schematics to owners upon request. I'm sure a Manley appointed tech wouldn't take long to diagnose and repair

[Steady339]

Audiogremlin, Thanks for your reply. I will phone Manley about the problem and see what they advise.

Roger

[Steady339]

This sounds strange, but I happened to touch the output transformer and this quieted the whistle.

I now remember tightening the transformer screws when the amp came home.

I loosened the output transformer screws and the whistle/ringing is now reduced. What is going on here?


Roger