Onan MJA Series Service Manual page 109

--
107
REVOLVING FIELD GENERATOR
TROUBLE SHOOTING CHART ll,MAGNECITER
Troubles are listed in advancing order, from no output voltage to a
rated but fluctuating output voltage. The .relationship between trouble
and cause is not always consistent from model to model, so the follow­
ing information must be used as a guide, npt an absolute rule.
: ­
,
Ie
:'
:.
NATURE OF
PROBABLE
CORRECTIVE
TROUBLE CAUSE
ACTION
Gener.ator will. not build up
Circuit breaker in "off" Reset and close breaker'
voltag,,!,.
or "tripped"po::;ition
...
Open in ci.rcuit iJreaker
Stop plant and check
breaker continuity
..
No AC power to Ma·gne­
citer
Check AC voltage at
E 1-E2 with the plant
ope rritinl£~ Voltage
should be five per cent
of the rate!: voltage, .
If ·not, ch(:ck contin­
uityfrom E 1-E2 back
to the generator
Contacts dirty
ill
Build- Stopplallt. Clean by
up Relay of 02SXINIA drawing bard surfaced
paper betweellcontacts
Partial loss ofnsidual
in ·Rotor
With plant .operating*,
place a jumper across
G 1 -G 2 until voHal£ebe­
gins [obuHd-up. Then
c
~~,
remove
,
_.
,~
Pair ofField Rectifiers
(either 1 &40r 2
&
3)open
Test reclifiers lind re­
place Hdefeetive
Both Field Rectifiers 2 T.est r.ectifiers and re-
i':,,··'"
''''
and 3 shorted plRce if defective
::-.":.. j". . ' - : ' : . ; .
. .QU!lWt voltage bUlld
up;:
.:6rcuit breaker opens
iJi about five seconds
" "':.c'­
Either Field RectifieJ'2
or 3 shorted
Test reetificrsallQ re­
place if defective
6utputvoltage slow to uu ild
Either Field Rectifier 1 'fe::;t Redifier and re-
up .and five pel' cent below
01''1 shorted place if defective
ratt.:d Noltage .afterbu.i1d up,
Voltage r . .,gulatioll poor .
.
~.
,. Be catltiuuswhen trouble shooting on
all
operating plant.