This is a follow-up on our failed A2 Power Supply
on a MAT 252. Thanks to those ISOGEOCHEM readers
who responded with helpful suggestions.
The transformer failed due to a shorted
transistor on the motor control board for the
bellows (Q1 BD675 or Q2 BD676). The power
supplies, which are used on MAT 252 and Delta
S/Plus mass spectrometers are no longer supported
by ThermoFisher. Consequently neither the power
supply nor the transformer is available through ThermoFisher.
There are a few companies that repair these power
supply in Europe. The most helpful over email was MasCom
Analysengeräte Service GmbH
DE 28279 Bremen
Fon: 0049 (0) 421 5729711
Fax: 0049 (0) 421 571032
Juergen Dunkhorst (MasCom) indicated that the
transformer could be purchased for about 200 Euro
with a delivery time of two weeks. Installation
and testing was estimated at 2-3 hours labor at 108 Euro/hour.
We have an electronics shop in our School and
they offered to repair the power supply for about
the same cost. Their approach was to purchase 5
separate transformers to replace the single
failed transformer that feeds 5 separate 15V and
24V circuits. I used our electronics shop because
I did not know what caused the failure and did
not want to send a repaired unit back to Germany if it failed again.
The new transformers were purchased from Digi-Key
(Signal Transformer brand, part number DST-6-36 -
36VCT @ 0.55A for series and 16V @ 1.1 A for
parallel secondary RMS Rating) and mounted on a
printed circuit board. Five separate transformers
easily fit in the power supply.
After approximately 1 month of downtime the
instrument is again collecting data and the bellows operating.
There is a warning sign for this type of failure.
The LED on the front of the A2 Power Supply is
connected to the circuit feeding power to the
motor control board. If you have problems with
your bellows, look quickly at the LED to see if
it is bright or dull. A dull LED on this power
supply indicates an excessive load on the
circuit. Apparently the transformer can handle an
excessive load for a short while, but not long.
If the LED dims and the bellows do not work,
quickly turn off the power to the power supply
and then check the motor control board. It is
likely that either Q1 or Q2 have failed.
Hope this helps.