Power Electronic Triac Failure - Miele CVA 2650 Technical Information

CVA 265x & CVA 266x
Technical Information
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Power Electronic TRIAC Failure

Some CVA coffee systems may experience a power electronic TRIAC failure.
Symptoms:
A machine that hangs during the last two minutes of descaling and has an
NTC fault stored in memory is most likely affected by this failure. Machines
that stay warm even after several hours of being in standby mode are also
likely to have this fault. Some machines will display no obvious symptoms.
Models affected:
CVA 4062, CVA 4066, CVA 2652, CVA 2662.
If a CVA 2650 or CVA2660 was upgraded with a heater conversion kit, this
behavior may be seen on these models.
Serial number ranges:
CVA 406X: 81485399 – 703004504*
CVA 26X2: 81483273 – 703004504*
*Be aware that you may encounter 9 digit serial numbers in the near future.
Nature of the problem:
TRIACS are solid-state devices used to switch AC line voltage on and off.
These devices are used in the CVA electronic to control the heaters. In this
scenario, when the TRIAC fails, it continues to pass one half of the AC sine
wave to either the coffee or steam heater continuously. This means that the
affected heater is being fed with 50% voltage as long as the machine is
plugged in and the main power switch is on.
Diagnosis:
The machine must be plugged in, main power switch on and in standby mode
(clock display visible only).
Remove the top panel; if the machine has been in standby mode for several
hours, neither of the heaters should be warm.
Check voltage on both heaters; there should be no AC or DC reading.
Use your clamp meter on the live line – if it indicates two or more amperes
flowing, the machine is faulty.
If any of these conditions are present, follow the repair procedure as noted
below.
Repair:
See the tables below for the specific part numbers.
Replace the power-control electronic.
Replace the NTC.
Replace the temperature limiter.
If the temperature fuse is open, you must also replace the heater, gaskets,
temperature fuse and elbows along with the above parts.
All replaced electronics must be returned to Princeton, Attention
Engineering Services, and marked with the serial number and incident
number. Additionally, you must use the word "TRIAC" somewhere in
the resolution notes.
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