Standby not functioning properly

Hello everyone, I'm new to this forum and very excited that I found it.
So I've had my GMD40 a few months and the standby has been working normally(stone cold quiet) until my gig yesterday. In standby mode I can now here my guitar, although not as loud as when I switch it to "play" but I can here it none the less. I know this is not normal. Anyone else ever experienced this issue and/or have any idea what is causing this to happen? Thanks in advance!!

Hi Jose. This is an odd one.

The Standby in the GM series does not work like other amps. The TSC controls the output valves through a MOSFET in the cathode of each valve. If the MOSFET is on there is very little resistance in the cathode and the valve current can flow. If it is switched off the cathode has a high resistance which prevents any current flowing in the valve. This is not how most amps work in Standby. They usually remove the HT voltage to the valves which is a bad thing! No amp of that sort should be left in Standby mode for any length of time as it gradually kills the output valves by cathode poisoning. The valves will not "wear out" by being left on with the Master Volume turned down. It sounds as though something is odd in the TSC control of your output valves.

All I can suggest is to back up your patches and perform a factory reset of the software. If you don't have any custom voices defined then things are even simpler as the patches will go back to the factory supplied. This is covered in the manual. Try that first and see if it makes a difference.

I've just had a reply back from H&K as I asked them a question about your problem.  In the manual for the Triamp there is advice on performing a simple TSC reset to the system.  It isn't in our manuals but they have confirmed that this applies to the GM40D as well as the Triamp units.  Try this:

Triamp Manual wrote:Warning: If tubes are replaced by a different type (e.g. EL34 by KT88),it is recommended to reset the TSC module:

• Switch Power off, switch Standby in Play position
• Switch Power on
• Wait for at least three minutes.

Of course the idea of a valve replacement does not apply to us but it may just be helpful.

I should also have added earlier that the Standby in the GMs does not mute the amp entirely. This is by design not by a fault in order to preserve the output valves against damage as I described above. The sound level in Standby should be very low however and it sounds as though this is not your problem here which is why I never mentioned it.