blax300rs potential problem
T. Pratum (pratum@u.washington.edu)
Tue, 21 Jul 1998 16:58:54 -0700 (PDT)
We have had 2 blax300rs failures in the past 6 months, and one of our
electronics engineers has found the same problem in both cases- the
MSA1023 amplifier in the blmx001 failed due to a failure of the bias
resistors R16,17,and R9 (150 ohm 2 watt composition). Their resistance
appeared to have decreased over time (in at least one case down to 10
ohms). I have checked 2 other blax300rs units that were delivered at the
same time (approx June 1995) and found the same problem in each of them
(although the MSA1023 hadn't failed yet). I also checked 2 other blax300rs
units which were delivered earlier (in 1994) and found no such problems.
So, my warning is that if you have a blax300rs that was delivered in 1995
it might have some bad resistors in it which will eventually stress the
MSA1023 into failure. You can check them in-situ with an ohm meter after
opening the unit up- they are quite obvious and the 3 in parallel should
have a resistance of 50 ohms (approx.). If anyone is interested in any
further information, please let me know.
Tom Pratum
Dept of Chemistry
Box 351700
Univ of Washington
pratum@u.washington.edu
http://weber.u.washington.edu/~pratum