Technical Service Bulletins; Some Cvas May Experience A Power Electronic Triac Failure - Miele CVA 4062 Technical Information

CVA 4062/CVA 4066/CVA 4068 Coffee Systems
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Technical Service Bulletins

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Some CVAs 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 CVA 2660 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 the heater
continuously (either the coffee or steam heater). 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.
1. Replace the power-control electronic.
2. Replace the NTC.
3. 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.
Technical Information
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