Hammond Organ L-100 Series, Service Manual

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If the generator turns and the tubes light, but no sound can be
obtained with all controls in playing position, the most likely source
of trouble is the amplifier.
In most respects this is a conventional amplifier circuit, and
the schematic diagrams,
Figure 5–2 Interactive L-100 Series
Schematic , will enable the technician to locate the problem.
4–7–11 KEY DOES NOT PLAY OR HARMONIC IS MISSING
This may mean a dirty key contact, a broken connection, or a dead
note in the generator. The steps below will serve to isolate the
trouble.
NOTE 4–7–A
The following checks must be performed with the DRAWBARS tab
depressed.
a. Ordinarily only one of the several frequencies used on the
key will be missing. This can be determined by holding the
key and operating each drawbar for that manual, observing
on which drawbar the key fails to play. Reference to the
manual wiring chart,
Figure 1–8 , will tell which frequency
number is missing.
b. See whether the same frequency is miss ing where it is used
on other keys of the same manual. The wiring chart will
tell with what other key and what other drawbar you should
get the same frequency. If it is missing on one key but not
on others, a key contact is probably dirty. In some cases it
may be cleared by striking the key 15 or 20 times in a rapid
staccato manner to loosen the dirt.
c. If this procedure is not effective, adjustment of the busbar
shifter for that manual will clear it. (See Paragraph 1–5
Manuals .) This will slide the busbars endwise so they
present a clean contact surface. In extreme cases, it may
be necessary to hold down the faulty key while making the
adjustment.
d. If the frequency is missing on all keys of one manual but not
on the other manual, look for a break in the cable connecting
one manual to the other.
e. If the frequency is missing on both manuals, check the
manual-to-generator cable or the generator itself.
f. The output of any single frequency on the tone generator
may be checked by pulling out any drawbar and connecting
a clip lead from the back end of the drawbar to the generator
terminal in question. See
Figure 1–7 for location of all
generator terminals. If the generator is all right, the note will
play loudly.
CAUTION
Never test the tone generator with an outside source of current such
as a continuity meter, as serious damage may result to the sensitive
filter transformers and permanent magnets. By the above method, all
necessary tests of the tone generator may be made with the current
supplied by the generator itself.
g. If it fails to play, try touching the clip to the input side of the
filter coil (not the grounded tap) and the input side of the
filter condenser (
Figure 1–7 ) in order to check these parts.
Disconnect the condenser to eliminate the possibility of
a grounded transformer. If the signal is still missing at the
magnet coil terminal, it means that the tone wheel is not
turning, the coil is defective, or the magnet is not properly
adjusted.
h. If the tone wheel is not turning, the frequency of the other
wheel on the same shaft will also be missing (with the
exception of a few wheels which are alone). On the generator
magnet location drawing (
Figure 1–6 ), the two frequencies
whose numbers are connected by a dotted line are on the
same shaft.
Another way to check the wheel is to remove the dampening
pad under the generator (it is held by the two long channels
which form the generator frame) and feel the wheel with your
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