IC-151 is positioned under a shield, as I recall (it's been awhile since I opened my radio). In such case, one has to find a runner or part interconnection node in order to probe the inputs and output for signal in/bigger signal out. Since this IC works for all HF bands, I'd recommend doing the check on 160 or 80 to enable seeing a useful signal image on the o'scope instead of just a blur.
While being "100% duty cycle" powered up, dissipating 250mA will make IC-151 a bit warm when using the "fat finger test", but this is not outside of the device's operating parameters. As I said in my other reply, one can butcher the wiring on the pc board to only have the 8VDC line be a switched input to the device, only present when PTT is depressed/enabled. I don't believe this is going to have an increased "ruggedness payback", nor will trying to use a heatsink glued to the top of the device's PLASTIC case. That's an exercise in futility. Some hams will micro-solder "heat radiating wires to the IC's ground pins in attempting heat sinking. The small SOIC ground tabs of IC-151 don't allow for much radiant heat to escape. (Kinda like trying to run 20A through a #20 wire and removing the wire's getting blistering hot with a heat sink...another exercise in futility.)
Since Icom itself points a finger to static conduction onto the runners of IC-151 as the source of its early demise, one can do the PIN diode additions to the pads that already exist on the home board of IC-151. This begs the question of why they weren't there in the first place if the pads for them were!!!
There is another way to prevent this static invasion syndrome. Use an antenna whose feedpoint is already at DC ground to not let antenna static build up when storms are brewing. A good balun across the feedpoint of a dipole or beam will do this, as well as RF matched feed systems like a hairpin match or Gamma match. My Cushcraft R5 vertical uses a DC ground matching box at its feedpoint, too.
When I'm deploying a new dipole or other such doublet, I use an old trick... I solder a 2W non-inductive 100K carbon comp resistor across the feedpoint / center insulator of the new antenna if I'm not employing a balun. I cover the resistor in heatshrink tubing to protect it from long term UV. It is simply soldered to each side of the center insulator, one side to the center conductor of the coax and the other to the shield side.
100K does nothing to your match and is "in-parallel" to the feedpoint. It also uses a tiny amount of your RF power applied to the feedpoint. The great thing it does, though, is two-fold. First, when electrical storms are brewing 100K equalizes the Voltage potential between both sides of the dipole connection on a continuous basis. This keeps the Voltage applied to your radio's coax input to a low level, much less than what it would take to blow a P-N junction inside of a semiconductor. This Voltage equalization across the antenna's two halves also reduces the propensity of a lightning strike. You cannot eliminate every strike, but a vastly reduced DC Voltage impressed by Mother Nature across your antenna's feedpoint reduces its "attractiveness" (pun intended) to violent static discharge to a cloud.
The 2nd benefit is that you have a "quick and dirty way" to do a crude health check of your coaxial cable's run to the feedpoint of your antenna. Put a VOM in DC resistance mode across your PL-259 in the shack. If it measures near 100K, you're good. If you get an open, you have a break somewhere in your coax run. If you have a measurement of zero Ohms or just something way lower than 100k Ohms, say up to 10k or so, you have a deterioration or some kind of shorting problem.
You get all of this plus IC-151 static protection at the same time. --30--