A look at my brand-new Boss Katana 100 MkII guitar amp.

[Sonic Mountain]

That's a pretty comprehensive going over Doc!

My drummer just bought a Mk II... well a MkI but they ran out of stock and sent him a II instead. Interested to have a mess around with it this weekend.

[DrNomis_44]

Update:

Sorry to have to say this, but my Boss Katana amp decided to pack it in yesterday, and stopped working normally, here's what it is doing:

* Powers up normally.

* No sound from the speaker, even at full power and volume settings.

* I do get sound out of the Headphone/Recording Line Out socket on the back panel.

* Some of the channel buttons on the front panel do not respond when I press them.

* The GA-FC Footswitch seems to operate normally when plugged into the amp.


Here's what I have tried so far:

* Performed several Factory Resets, this only temporarily fixed the no-sound issue once and the amp reverted back to the no-sound fault condition after switch-off and then power up.

* Performed a few firmware re-updates, this did not fix it at all.

[fender3x]

Do you have the circuit diagram? Can you separate the pre- from power-amp parts? It sounds like you have a malfunction that may be after the pre- but is either in the power amp circuit board or after. I don't know what to make of the fact that it works briefly after a reset then cuts out. If this is a class-D amp, I wonder if there is some problem in the power-amp, but I don't have a clue as to how you'd diagnose it!

[DrNomis_44]

Do you have the circuit diagram? Can you separate the pre- from power-amp parts? It sounds like you have a malfunction that may be after the pre- but is either in the power amp circuit board or after. I don't know what to make of the fact that it works briefly after a reset then cuts out. If this is a class-D amp, I wonder if there is some problem in the power-amp, but I don't have a clue as to how you'd diagnose it!

I was actually pretty lucky, I managed to find a set of Service Notes for the Katana KTN-100 series of amps online from Scribed in PDF form, fortunately I managed to download a copy before Scribed deleted it, the Service Notes contained full schematics and PCB layouts so, it'll be very helpful, I also have a couple of oscilloscopes and signal generators too, last night the amp did seem to come good all on it's own for a short time, so, that suggests that most of the circuitry is working in a fashion, the amp has a muting circuit and also a muting signal line from the amp's CPU to the power amp IC, so, I'm thinking that maybe the amp's CPU is muting the power amp when it shouldn't be muting it for some reason, what makes me think that is that I do seem to get signal through the headphone/recording line-out socket on the back panel when there's no signal coming through the speaker.

The amp uses a dedicated power amp IC that's located on a big heatsink, it is soldered to a separate little PCB, looking at the schematic, I noticed that one of the connector pins is labeled CPU Mute or something like that, it's possible that the amp is suffering from some kind of CPU controller issue, maybe caused by bad supply filtering on the supply rail/s that power the CPU, my forte is in analog electronics, I'm not that great with complex digital circuitry, but I do know some digital electronics theory, hmmmmm....maybe once I get the amp put back together again, I could use my FNIRSI digital scope to check the noise-levels on all the amp's supply rails, I stripped the amp-chassis down to the bare chassis in order to clean-out some dirt, and insect detritus that had accumulated in the amp chassis, the Service Notes detail how the Katana is disassembled and put back together again, so I should be okay.

Fortunately, the amp uses an old-school linear power supply, rather than a more modern SMPS, so I don't have any high voltage caps to deal with, the highest voltage rated caps in the amp are a couple of 4700uF/63V can caps in the power supply, which would be the supply filter caps for the power amp IC.

[fender3x]

I understood just enough of that for it to be clear that I should never attempt such a thing. Will be interested in the eventual diagnosis and what you end up doing about it! Also my blood pressure spikes when I hear expressions like "big caps." Do you think you can repair the wayward circuit board--or will you be just popping in a new one?