Left-Zero Feature; Diagnosis Of "Heavy" Or Stiff Keyboards - IBM 29 Card Punch Field Engineering Maintenance Manual

. Punch clutch spring (broken, dry or gummy, orloss of
tension)
. Punch clutch armature (broken or worn)
. Punch clutch detent pivot stud (worn or loose)
. Punch clutch overthrow (too muchortoolittle)
. Relays (high resistance shorts or hold points burned or
welded)
7. High-speed cam contacts (binding roller, strap tension,
or loose contact pile-up)
8. Interposer bail contacts (strap tension, air gap, or
contact condition).
Anintermittently failing machine should not be returned to
the customerwithout investigating every suspected cause of
the failure.
1.7.1 Left-Zero Feature
1.7.1.1 Left-Zero Overflow/Iincorrect Punchout
Incorrect punchout of left-zero information occurs if the
operator keys-in more digits than the field can contain.
Reed-relay machines continue shifting the bits in the
registers; the first digits keyed-in are lost. Wire-contact relay
machines accumulate the overflow of bits in the first
register. |
Examples: In a reed-relay machine with a five-position field
programmed, the operator keys-in 1, 2, 3, 4, 5, 6. The
machine punches out 2, 3, 4, 5, 6 when theleft-zero keyis
pressed. In a wire-contact relay machine with a five-position
field programmed, the operator keys-in 1, 2,3, 4,5, 6. The
machine punches 3, 3, 4, 5, 6 when the left-zero Key is
pressed.
1.7.1.2 Intermittent Loss of Bits
Common causes for loss of information during read-in or
read-out operationsare:
1. Keyboard latch or bail contact adjustments
2. Keyboard restore bail contact adjustment
3. Error reset contact or backspace switch intermittently
breaking contact
4. Loose slip-on connectors to punch interposer magnet
unit
5. Loose connectors in 0-volt or 48-volt net to LZ relays
6. Punch CBsout of adjustment.
1.7.2 Diagnosis of "Heavy" or Stiff Keyboards
To isolate the source of trouble when a keyboard feels
"heavy" or stiff, make the following checks.
1.7.2.1 Key Pressure
Key pressure can be affected by lubrication, by interference
between the keystem and the cover, or by sluggish interlock
disks.
Lubrication: Check to be sure that the proper lubricant is
used in the correct places. Refer to "Chapter 3."
Interference: Check to be sure that the keybuttons are
centered within the holes in the cover face.
Interlock Disks: Check for dirty, magnetized, or oily
interlock disks.
1. With the machine on, press the P-key.
2. Using a gram gage, operate the P-key; 55 to 65 grams
should be read. Note the actual pressure required to
operate the key.
. Press the Q-key.
4. Using the gram gage, operate the P-key again. The
pressure required should not exceed 10 grams more than
the reading noted in step 2.
5. If step 4 failed to meet the requirements specified,
removethe interlock disks.
a. Wash the disks and the race in IBM cleaning fluid to
removeall traces of oil or dirt.
b. Test for magnetism by sliding the disks down an
inclined steel surface; replace all sticking disks.
1.7.2.2 Keyboard Cycle Time
To check for slow keyboard restore:
1. Open keyboard base and place machine in numeric shift
by inserting a card between the numeric keystem
contacts.
2. Feed a card to column1.
3. Short latch contact 6 and time the punching of 80
columns. Timing should be approximately 4.5 seconds.
4. If the time exceeds 7 seconds, repeat the punching
operation with one thickness of card inserted between
the keyboard restore magnet armature and thecore.
5. If an increase in speed of the punching operation occurs,
adjust the armature-to-core clearance to 0.005 inch. (No
increase in speed indicates a slow machinecycle.)
Note: Keyboard restore magnet coils are connected in
parallel. A short or open in either coil upsets the balance of
the circuit. Symptoms include slow keyboard cycles,
double punching, or extra spaces.
1.7.2.3 Machine Cycle Time
To check machinecycle timing:
1. Install an 80-column auto-dup program card on the
program drum.
2. With the machinein alphabetic shift, time the automatic
duplication of 80 columns (using blank cards). Timing
should be 4 to 4.5 seconds.
3. If timing exceeds the limit, slow action is due to the
punch clutch, the friction clutch, or the escapement
mechanisms.
29 FEMM (4/69) 1-11