Power Valve Repair

The latest saga involves the Exhaust Power Valve. When I rebuilt the bike I checked the servo motor and it was fine, the control unit being more time consuming to test, was refitted, assumed ok. The valve operates at 7,600 RPM, and as the bike was being run in, I wasn't able to verify it worked. So, with a few hundred miles on the clock I checked to see if the valve worked...blipping the throttle to about 8000 RPM, there was no movement. I stripped the bike down and checked the wiring, it was ok, so I refitted a spare control unit and servo....still dead. Checking the motor once more I found the one I'd fitted to be ok, and my spare to be dead, so the control units were suspected to be the fault....I tested the two I had, and both were out of spec, and they even differed from each other.  I knew a new unit was £300. I phone call to Robinsons confirmed they had one in stock, and let me have it for £100 inc postage, a much appreciated gesture, especially as I was not 100% sure this was the problem. Anyway, with the control unit fitted, it now works perfectly!