My 1653 has suddenly started giving inaccurate results when testing rcds. On a ramp test, it indicates that its giving 33mA and not tripping the RCD, but another tester the same RCD is tripping at 24mA, which is about normal for a 30mA. Fluke are quoting a fixed repair cost of ÂŁ216 + VAT, to change the board. Test 4 less are not aptly named as they want ÂŁ240 + vat as a fixed repair cost! The tester is 6 years old and this is the first problem I've ever had ( apart from a fair bit of operator error in the early days!). Has anyone any suggestions as to what this problem may be or how it can be rectified without a board change?