If you like blue LEDs on your amps, heaps of features then you are in for a treat. H&K amps look smart and sound fantastic and offer a lot of tonal options. Price wise they are also very competitive and come with nice accessories so it is easy to see the appeal.
In the UK I only see a few H&K amps a year and the faults are usually routine service items like pots, jacks and valves. For those that use them, they always seem to like them and it is easy to see why great sound, lots of features and often very portable.
Build quality is excellent but they do like to cram a lot of parts into a small box resulting in difficulty maintaining and possible overheating. The small amps are easy to pull off a speaker cabinet and this is a common cause of people asking for my help with these amps.
Hughes & Kettner Tubesmeister and Grandmeister Repair
These amps are pretty similar Tubemeister 18, Tubemeister 40 and Grandmeister 36 they are essentially lunchbox style amps with blue illuminated front panel and loasds of useful controls. Aside from routine maintenance like valves, pots and jacks I have seen quite a few with issues on the TSC bias controller.
This device constantly monitors the bias current and adjusts it making the amp self maintaining. The issue I have come across is that with valve failure the mosfet transistors that control the bias current blow causing strange symptoms. Including:
- amp may develop a slight hum when in play mode. H&K amps are normally pretty noiseless so this is obvious and very intrusive. You could finish the gig but you could not record.
- amp may produce sound in both standby and play mode. This is because the standby switch adjusts the bias turning the power valves off but because the controller has gone a little crazy it does not turn the valves off properly.
- The red LEDs on the rear of the amp may indicate excessive current or flash as though the valves are bad. But if you have replaced the power valves you do not expect to see this. In the event of a failure of the TSC you are very likely to see this.
- Control Grid voltage might be a little low
If you would like help getting your Hughes and Kettner amp working again please get in touch as with the smaller models a remote repair anywhere in the UK will be possible