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                           BULLETIN
    FSB-113 - RAM CONTAMINATION PROBLEM WITH WHADCP PIO BOARD
                    DATE/REV:  01SEP97 / 0
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ABSTRACT: Some Workhorse ADCP PIO boards have transistors that
can emit a high magnetic field capable of contaminating RAM.

INSTRUMENT/PROGRAM AFFECTED:  Several Workhorse ADCP systems
that shipped between 01MAR97 and 01JUN97.

DESCRIPTION: In March 1997, we began to receive a transistor from
a manufacturer that can emit a very high magnetic field. This
field can contaminate the RAM-based operating system on the
Workhorse ADCPs manufactured between 01MAR97 and 01JUN97. How- 
ever, not all systems are affected.

Some reported symptoms of this problem include (1) Multiple
deployments, and (2) Deployments that stop early. However, it is
possible for any type of symptom to occur because this problem
affects the RAM-based operating system. If RAM is contaminated,
anything can (and of course will :-) happen.

We have tried to develop a bench test to help identify those
systems that have this "bad" transistor. However, the transient
nature of this magnetic field makes it difficult to simulate and
repeat the problem in all affected systems.

When this problem was first discovered, we thought we "caught"
all affected systems before they shipped. This is not the case.
The good news is, we have a fix for the problem. The bad news is,
you have to visually inspect the PIO board to see if the fix was
installed in your system.

SOLUTION/ACTION:

If you believe your system was shipped between 01MAR97 and
01JUN97, you will need to inspect the PIO board to see if the fix
was installed.  Proceed as follows:

1. Remove the transducer head as described in the manual.
2. Locate the PIO Board (Fig. B-4 in manual).
3. Locate transistors Q9 and Q10 (Fig. B-5 in manual, bottom).
4. Verify the "gate" on these transistors (top-most leg of the
   transistor when viewing Fig. B-5) is "standing up" off the
   board, and has a 10-ohm resistor soldered between the gate and
   the PIO board.
5. If you do NOT have a resistor installed for each of the
   transistors (Q9 and Q10), contact RDI. We can then determine
   if you can install these resistors "in the field," or if it
   would be better for us to send you a replacement PIO board.

We apologize for any inconvenience this may cause.
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