I wonder if you’ve misidentified some components.

The two “yellow caps” located between the big capacitors are not actually capacitors.  They are varistors (or MOV for metal oxide varistor).  These have high resistance, but as voltage rises their resistance drops.  In the event of a voltage spike, these shunt excess voltage away from the circuit, acting as protection devices.  If they are dead then it is very possible your device suffered a voltage surge.  If so then this is recoverable, but there may be multiple component failures.

You said that you replaced 2 pairs of transistors.  The first pair are transistors and you need matching components (part number K13A60D).  The second pair are not transistors - they are dual diodes (part number SBR10100).

When you say it ‘blew again’, how fast was that?  Was it right away, or only after trying to play some music?

The first two transistors you mention are part of the 36V circuit.  When the device is idle (or even playing at very low volume), the amplifier is run off of a 14V supply that comes from the central transformer (which is driven by the PWM).  Once the volume is turned up, then the 36V circuit comes on.  That is where these two transistors come into play.  They are switched via signals that come from the mainboard, through the riser board, then out the small plug in connector on the end of the riser board.  Since this is part of the 36V circuit, you should be able to get the device working (albeit perhaps without any audio being produced), even if these are damaged.

You need to know if the PWM and transistors are actually working or not.  If you use a multimeter in diode test mode, you can look between each pair of pins (eg 1-2/1-3/2-3/2-1/3-1/3-2).  You need to test all pin combinations in both directions.  You want to see either an open circuit, or a small voltage like 0.6V.  If you get any shorts then the device is bad.

Ideally, if you can get it running with the dim bulb, then you can check the back side for the various bias voltages.  There are test points marked for GND, 5V, 3.3V, 14V, and GND36/36V (the 36V points may measure 15V and that’s ok).  You don’t need the riser board or main board connected to test these voltages.

Allright, thanks for the clarification! Sorry for my lack of terminology, I have never gotten any electronics classes but I am quite up to speed through what I learned myself. I never got the device to play music. In the state it’s now, the dim light bulb goes out but no white light and no bias voltages nor any voltages on the secondary side, so I suppose the PWM is not switching. What do the transistors (K13A60D) do in the circuit? As these heat up quickly. 

The PWM is good for sure as I just replaced it again. Before, the light bulb would stay on full brightness, after replacing the PWM the light goes out after a second. I suppose i will take more measurements according to previous posts in this forum and lead my way back to the problem.

One more thing: I replaced the transistors with a part labeled MBRF 10L100CT, is this similar enough to the K13A60D? I ordered these a while back when I had even less of an idea of what I was doing with this amp  -Edit: Wait, I think these are just two different components. I probably messed up while ordering back then.

As I cannot find a retailer selling the K13A60D, I am looking for an equivalent n-channel mosfet. I came across this one ;NTP360N80S3Z. The only main difference is the avalanche current, which is 2A instead of the 13A of the K13A60D. Would this matter? My guess is yes, but I would like another opinion by more specialized people in this forum. Also the turn-on/off times differ a little. They all seem to be shorter on the equivalent mosfet.

I replaced the mosfets and now I am having the bias voltages. The 3.3V and 5V is correct, but the normally 15V shows up as 13.5V on my board. Still no status light and there is a ticking sound on startup which repeats about 6 times with an interval of about a second. I am out of options at this moment. It seems like the voltages coming out of the transformer might be a bit lower than usual? The 3.3v and 5V might be correct due to the regulator, but the 15V is not there as I think it comes straight from the transformer. Also the 5V_sw pad shows about 0.2 volts.

Bob’s my uncle! Got it working, you will never believe what the problem was.

There were two small spiders/bugs stuck inside the shielded compartment of the main board. They must have caused a small short preventing the amp form booting as all the voltages were there. Got it set up in the app right now. The amp is connected to WiFi and is now slowly blinking orange. I guess that is because I have not selected anything for it to play. Will test the sound soon. Now the challenge of putting everything back in the case. Very happy with my progress so far as I learned so much with this amp. I was a total newby before. Thanks for the help to whoever was involved in this forum.

Couldn’t agree more! Never suspected the riser and main board to be faulty as the power supply gave me most troubles. 

Got it to play music yesterday. Sounded great after such a journey.

One thing, it was not very consistent. On high volumes, it sounded great but down low there was some cracking. 

Booting it up today, I only get a slow flashing orange LED and sometime a very dim white light. I am getting 15V on the 36 pad and 36V when I play some music through the app. That all works fine.

I started digging deeper (on the secondary side only, assuming the primary works perfect) and found that on only one of the two shottky diodes, the middle pin is getting 15/36V. The most outer one (diode, not pin)  is getting voltage while the more inner one is not getting anything. What are these middle pins connected to? As I do not find an immediate link probing my DMM. The two outer pins are ground I assumed.