Yaesu FT-901DM Maintenance Service Manual page 75

SERVICING
MOSFET CHANGES
Because of a potential parts availability problem,
many of the 3SK40M MOSFET components were
changed to 3SK51-03 types. There is no reason to
make this change in the field, unless the 3SK40M
types are not available in your parts inventory.
For replacement MOSFET servicing, please refer
to the chart below.
CODE
© Replacement with this type OK without further
change.
A When changing to this type, make resistor change
at right.
x Do not replace with this type.
Example:
PART 3SK40M 3SK40L 3SKS51-03 Change for
(R/B)
Qo x Riz6: 390-270
This means: when replacing Qioe. it may be re-
placed with type 3SK40M with no further changes;
a 3SK40L(R/B) may be used by changing Rize
from 390 ohms to 270 ohms; type 3SK51-03
should not be used.
RF PROCESSOR/XTAL UNIT TRANSISTOR
MODIFICATION
On the NB UNIT, transistor Q202 should bear a lot
number . . . 7J. 7K, 7L, or earlier. If the transistor
bears a lot number 8A, 8B, 8C, or later, the
transistor should be changed from type 2SC1815Y
to type 2SC372Y.
The same consideration applies to transistors
Qi301 —Qi310 on the XTAL UNIT.
The new 2SC1815Y transistors exhibit higher noise
than Yaesu specifications will allow, hence the
change to the 2SC372Y.
PART | 3SK40M |3SK40L | 3SK51-03
(R/B)
Quoi | © Rios 39K + 47K
Qro6 ° 4 x [Rize 390 +270
Qi07 ° | x |Rizs 390 + 270
Q209 ° °.
| Qzio ° °
Qaiz o | © |(3SK41M OK)
[Ost o | & 'Rqaos 560 > 1K
| Qao2 & (Rais 560 > 1K
Qso3 ° a |Razs 560 > 1.8K |
| Qaos | & [Rasa 560 > 1.8K
Qoor E 4 Roos 56 > 1.8K
[Qi209) 2 | 4 [Riase 470K + 680K
Q2809 ° °
Q2901 ° b]
3-20
2SC1815Y
8A ——]|— Lot number