A1 Control/Display Pwb Problems; Verifying Microcontroller Faults - ConMed Hyfrecator 2000 Service Manual

2000
The best method to use on the Hyfrecator® 2000 cannot be prescribed, since it depends upon the
technician's skill, understanding of and experience with the unit. However, if your service organization has
service responsibility for about twenty or more Hyfrecator® 2000's, it may be effective to stock at least one
set of spare PWBs to allow for rapid turnaround, and perhaps one known-good Hyfrecator® 2000 to use in
confirming a suspected bad PWB and for troubleshooting to the component level after the repaired unit is
returned to service.
A stock of replacement spare components most likely to fail will also minimize downtime. Recommended
spares are denoted by an asterisk (*) in the parts lists appearing in Section 5.

4.4.7 A1 Control/Display PWB Problems

This PWB is the more complex of the two in the system and thus the most difficult to troubleshoot.
Additionally, it lies midway between system input signals which originate on the A2 Power PWB and the
HV power supply, RF PA and tone generator control signals used by the A2 PWB. Thus, some faults on the
A1 PWB can produce the same symptoms as other faults on the A2 PWB.
If the symptoms involve a Fault Code, refer to the Appendix and Section 4.4.1 for fault isolation guidance.
If the symptoms do not include a Fault Code, and the POST display appears normally, then the problem is
most likely on the A2 PWB. This is most easily confirmed by moving the A1 PWB to a properly
functioning spare Hyfrecator® 2000 and verifying that the symptoms have disappeared.
NOTE: Since Calibration data which is affected by A2 performance is stored in A1U3 and A1U4 EPROMs,
this board swap may produce a Fault Code either during POST or during activation. In this case, simply
enter Service Pseudo Run (Section 4.4.4) rather than recalibrate with the new A2.
Some intermittent problems may be traced to bad connections at either end of the 16-conductor ribbon
cable between A2 and A1. Although it may be possible to repair such failures, it is difficult to perform a
reliable insulation displacement connection without the proper tool. It is preferred to simply replace the
faulty harness assembly.

4.4.7.1 Verifying Microcontroller Faults

The most straightforward method of confirming that one of the microcontrollers, U1 or U2, is defective is
to replace it. However, these components are costly and available only from the factory, and desoldering may
damage a possibly good microcontroller or the PWB. Thus, it is worth taking some time to verify that the a
microcontroller is defective before pursuing replacement.
Some Fault Codes are specific to internal microcontroller processes. However, these processes rely on the
presence of clean +5V power of the correct voltage (+4.5 to + 5.5V) on VDD (pin 20) and MCLR (pin
1), and good ground on pins 8 and 19. Use both an oscilloscope and a multimeter to verify these signals
directly on the microcontroller pins.
A 4 MHz clock must also be present on each microcontroller and operating within 20 kHz of 4.00 MHz.
This may be checked with an oscilloscope probe with a 10K 1/4W series isolation resistor at the tip on pin
10; loading pin 9 with this probe may cause the oscillator to stop. Oscillator failure may be caused by either
the microcontroller or the resonator. A resonator failure may be confirmed by exchanging Y1 and Y2 or by
"shot-gunning" a new resonator.
If +5 V power and the clock are functioning correctly, then proceed with microcontroller replacement.
38