I can't help you specifically with the Expobar, but yes, I would say that evidence of a burn like that indicates an unexpectedly large current flow, and it's likely that just dropping another control board in will simply toast the new board as well.
I would suggest that there's been a short-circuit somewhere in the path, either due to problematic wiring (less likely), or failure of a major component (more likely), causing it to short.
I don't know whether you've seen a schematic for your machine, I think most consumer HXs are pretty standard in how they're designed. If you ignore the extra temperature management bits and brew boiler element of the brewtus, for which there's a schematic at:
The brewtus compendium
Then I think you have a reasonable generic wiring diagram for an HX
The control board relay drives:
1. The Heater (via the pressurestat and over-temp protection thermostat)
2. The Pump
3. The autofill solenoid
4. The steam boiler neon
I'd be looking to apply general electrical fault-finding principles to check that each of these components is not the culprit. First step would be to disconnect the wiring from each one at a time, and check for short-circuit across the terminals using an resistance meter. For the pressurestat, you'd expect a short across the common and the other wired connection, with no pressure applied from the cold boiler. The pressurestat overall state is harder to check because it needs pressure to switch it and you'll only get that with heat in the boiler.
I'd also be looking for further evidence of burned wiring or connectors throughout these areas of the circuit that might localise the fault.
Given that the pump still works from the brew switch, it would seem that the pump itself is OK.
Whilst it's possible to do all this yourself, it very much depends on your ability, and how far you're prepared to go with it. If you've been dealing with Chris, then I would continue to do so, as it seems like this is your best (and safest) bet to getting it resolved.
[Disclaimer: Advice offered in good faith. I will not be held responsible for loss or damage caused by any of the above]