WHERE IS MY BLUE LIGHT!

So I just changed all tubes and I put chassis back together and NO blue light. I figured maybe they are disengaged with chassis removied but NOPE.

Can someone help as to what may have happened?! Fuse?!

Take the right side off, facing the amp, and follow the lead down to the clip. Make sure it's connected snugly, and that the wire looks ok. First thing I'd check.

Hi SOS. Bishop is right there, the cable is on the right as you look at it and can easily be pulled or nipped when refitting the top and ends. Also take the whole lid off again and check that you have the LED PCB along the top of the front panel the right way up and seated correctly with its locating clips fitted right. If you have squeezed this PCB too hard with the lid you may have cracked it or somehow damaged a track. It's effectively a loop with each LED in series so a single break anywhere will take out all of them.

If that doesn't turn up anything then see if you can get your hands on a meter or any other way of measuring voltage. I would start at the two pads where the leads are connected. With the LEDs out of action you should get about -22V there as that is the supply it is fed from down below. The voltage is fed up through a resistor in the lower chamber to limit the current to the LEDs so that will prevent damage of any sort. With the LEDs drawing no current the resistor is dropping no voltage so you should see the whole -22V. Measure the voltage there to be prove the cables are ok and feeding the voltage up to the PCB. If not then you have a fault with the plug/socket below or in one of the two wires. Then just keep the probe in place on one end and work your way along the PCB from the other one following the live track to each LED. When you lose voltage you have the section with the break in it. (Of course that assumes you have a meter available.)

I hate to hijack a thread, but my question is tangentially related. Does H&K, or a third party, sell replacement LED kits for these amps; like, if the OP broke his, could he get a replacement? Further, in my own case, is it possible to get such a kit in other colors? I saw another H&K amp head line with a red LED front and thought it looked badass. I would love to get a red or purple kit for my GM Deluxe 40!

It's a pretty easy job to get at the LED strip. You just have to remove the top cover and it's there in front of you. It has very little on it except the diodes themselves. They are surface mount devices on a PCB that is just a two track strip. If you are capable of soldering these tiny SM devices then you can easily change them out with similarly specd types of other colours. As far as I know there is no simple replacement strip on the market but I could be wrong on that.

You shouldn't remove the valve cover without knowing the simple procedure to do so without voiding your warranty. And when refitting it it is important to be careful with correctly seating the LED strip under it as it is easy to pinch the wires feeding it from the bottom cavity.