HF oscillation or DC trip @ power amplifier

[fgchong]

I am using Reference 10 for about 2 years and lately I have this HF oscillation or DC trip @ one of the channel of the Goldmund power-amplifier (either the Telos 250 or 1000+). Fault intermittent i.e. resumed to normal when I reset the power amplifier. This has being going on for a couple of times and each time it trip, the speaker cut off with exploding sound (I am using Alexia).

Send the set to the local agent but their technician could not locate the root of the problem as the fault did not occurred even running for almost 500 hours.

Just wonder any members here have the similar experience to share.

Thank You

[TOGA]

I have similar experience.
My suggestion.
1. Can it be related to bad tubes ? Tubes is likely to have slight DC offset higher than SS gears and when tubes gone bad it can get worse I dunno.

2. Moon amplifier shut down in a similar way when I try to play my old Sony CDP X77ES on RCA, but it didnt
Happen when run XLR,also this happened when I liked to have some fun connecting my first ever surr processor
The Yamaha DSP-1 to my current system, the amplifier shut down. This means sometimes the DC leak is from source and can reach power amp. Old source with bad capacitors can do this.

Toga.

[fgchong]

Toga,

Appreciate your information. The trip occurred with any of my 3 sources, that should rule them out. Not sure when bad tubes will cause this, will monitor the situation and hopeful the fault can be permanent.

[TOGA]

Can you try one channel at a time ?
In case a faulty leak comes from one exact channel.
Is it likely to be caused by power supply 6550 tube ?
Toga

[microstrip]

The REF10 is capacitor coupled, it should not be a DC problem.

Probably a faulty tube that starts oscillating at ultrasonic frequencies.
The best way to diagnose is connecting an oscilloscope to the output of the amplifier and slightly tapping the tubes with a pencil (including power supply) - sometimes it triggers the oscillation.

You can also swap all the tubes between channels and see if the problem moves to the other channel.

It can also be due to RF pickup - do you use un-screened cables?

[fgchong]

Appreciate all the information. I am using a 10m pair PAD XLR cable between the Reference 10 and Telos 1000+. Will first try out my other pair of balance cable this evening before replacing the power tubes.