Backspace

SYMPTOM

POSSIBLE CAUSE

REMEDY

REMARKS

1. Machine will not backspace

1. Not enough backspace rack motion (9-4)

a) Adjust clearance between cam  follower (10-5) and backspace latch (10-7).

b) Intermediate lever broken or maladjusted (11-1)

Adjust latch clearance for minimum clearance - no binds (10-8)

2. Carrier binding on dust cover (12-1)

Check and adjust covers and cover latches.

Some dust covers may have to be formed.

3. Card holder binding on platen (13-1)

Adjust card holder.

Check with four copies of paper in machine and multiple copy lever in #1 position.

4. Tab overthrow stop (9-5) hitting tab rack (14-10).

Adjust tab overthrow stop for clearance between the tab trigger and tab overthrow stop.

To adjust:

1. Machine off.

2. Depress tab keybutton and latch out tab lever (9-6).

3. Adjust .005" clearance between overthrow stop (9-5) and tab trigger (9-7).

5. Cords off pulley

Check and replace cords on all pulleys.

6. Binds in backspace rack or teeth on rack missing.

Observe all teeth on rack (9-4)

Move backspace rack back and forth manually using the intermediate lever (11-1) to check for binds.

7. Return spring for backspace rack broken or missing (7-9)

Replace or repair spring (7-9)

8. Binds in backspace pawl (15-11)

Check ease of movement of back space pawl with spring hook (15-11)

9. Spring missing on back space pawl (15-11)

Check and replace or repair

If spring is missing or damaged, pawl will not be held into rack.

10. Not enough pawl bite on backspace rack.

a) Check backspace pawl spring

Pull backspace pawl (15-11) to rear with spring hook, release pawl and it should snap back into rack.

b) Adjust clearance between escapement torque bar (16-4) and backspace pawl (15-11).

Clearance adjusted by bristol screw (16-5).

c) Adjust clearance between escapement torque bar (16-4) and pawl mounting stud (15-12).

Adjust pawl mounting stud for .001" clearance between stud and escapement torque bar. The pawl mounting stud is an eccentric screw.

After the last two adjustments are made, check and adjust the following:

1. Adjust escapement link (23-14) for .010" clearance between trigger (22-11) and escapement torque bar (22-13).

*Before adjusting escapement trigger - check trigger upstop (22-12) and spacebar latch screw (21-6) to insure they are not restricting the escapement trigger (22-11).

11. Mainspring tension too tight.

Mainspring tension is adjusted by rotating spring cage (17-1)

Mainspring tension should be approximately 6 turns.

12. Backspace keylever pawl overlap.

Adjust the overlap of the backspace pawl (18-10) with the backspace interposer (19-2) using the key lever guide (19-5).

Overlap approximately .040"

13. Backspace keylever pawl clearance

Adjust "U" shaped slot in keylever for clearance between keylever pawl (18-10) and backspace interposer (19-2).

Clearance approximately .020"

14. Backspace latch (10-7) not under cam follower (10-5).

a) Adjust bristol screw (21-7) so latch will move freely under cam follower, when keybutton is depressed.

b) Adjust bristol screw (20-1) until latch moves to rear beyond cam follower approx. .010"

Backspace interposer (19-2) pushes the backspace latch (10-7) under the cam follower (10-5).

15. Backspace interposer binding (19-2).

Check and adjust for binds.

Check spring on interposer.

16. Clutch release arm (20-2) not releasing cam (3B-5).

Adjust cams (3B-5) left or right. Arm may be binding on cam.

Function cams adjust left and right until clutch release arms have equal bite on both cams.

17. Backspace pawl binding on tab lever (9-6).

Form extension on escapement bracket to eliminate binds and to adjust clearance between backspace pawl (15-11) and tab lever (9-6).

Use spring hook - push backspace pawl left and right to check for bind.

Machine will not backspace.

(Selectric II typewriter dual pitch)

In addition to previous adjustments.

1. Not enough carrier motion from driver (24-16).

Adjust backspace latch (26-20) and form extension (26-21) alternately until both are correct.

Be sure driver does not contact ratchet at rest position.

Clearance between backspace latch (26-20) and cam follower (26-22) approximately  .005".

Clearance between backspace driver (24-16) and ratchet (24-17) approximately .030".

2. Pitch cam cable broken or damaged (25-18)

Replace or repair

If cable is broken:

1. Replace cable

2. Place machine in 12 pitch position.

3. Depress backspace keybutton.

4. Rotate machine with turning wheel until backspace driver just contacts backspace ratchet.

5. Loosen sheath and adjust until mark (27-24) lines up with stud (27-23).

3. Backspace bellcrank stud broken.

Stud and screw available for replacement.

4. Worn teeth on backspace driver or ratchet.

Replace driver (24-16) or and ratchet (24-17)

Machine will not repeat backspace

1. Backspace repeat stop (28-25)

Adjust repeat stop (28-25) by forming extension (28-26).

Adjust repeat stop (28-25) by forming extension (28-26) for a single function operation.

2. Keylever pawl overlap (18-10)

Adjust keylever guide for overlap of the backspace pawl (18-10) with the backspace interposer (19-2).

Overlap approx. .040".

3. Keylever pawl clearance (18-10)

Adjust "U" shaped slot in keylever for clearance between keylever pawl (18-10) and backspace interposer (19-2).

Clearance is approximately .020".

4. Backspace latch height (10-7)

Adjust bristol screw (21-7) so latch (10-7) will move freely under cam follower (10-5) when keybutton is depressed.

Backspace interposer (19-2) pushes the backspace latch (10-7) under the cam follower (10-5).

5. Backspace interposer restoring bail (29-26)

Adjust restoring bail (29-26) by forming lugs (29-27) until the interposers restore approx. .020" beyond the latch plate (30-28).

Lug (29-27) on right side is for carrier return and index interposer restoring. Lug on left side is for spacebar and backspace interposer restoring.

6. Worn pawl (5-3) on back space cam (3B-5).

Replace pawl (5-3)

Also check spring. When replacing pawl the pin goes in small window of cam wheel.

7. Broken or damaged spring on cam pawl.

Repair or replace

Machine continue to backspace against margin.

1. Backspace interposer latch binding or worn (33-34)

a) Lubricate

b) Replace worn latch

Replacement latch, screw and nut available.

2. Worn latch plate (30-28)

Replace

If latch plate is worn - remove plate and rotate it 180° - reinstall and adjust.

3. Interposer restoring bail (29-26)

Adjust restoring bail (29-26) by forming lugs (29-27) until the interposers restore  .020" beyond the latch plate (30-28).

Lug (29-27) on right side is for carrier return and index interposer restoring. Lug on left side is for spacebar and backspace interposer restoring.

4. Binds in clutch release

arm (20-2).

Lubricate and release binds.

Adjust cams (3B-5) left or right,

arm may be binding on cam.

5. Not enough clutch release arm bite (20-2).

Adjust cams (3B-5) left or right for more bite.

Not enough bite will cause cam to repeat.

6. Too much mainspring tension (17-1)

Check number of rotations on mainspring. Mainspring should be rotated approx. 6 turns.

Too much mainspring tension puts a load on restoring system (29-26).

Machine backspaces intermittingly.

1. Keybutton binding on machine cover.

Adjust machine cover or form keybutton stem.

2. Backspace interposer binding (19-2).

Check and adjust for binds.

3. Carrier binding on dust cover (12-1).

Adjust dust covers latch or form dust covers.

Also check for objects under carrier binding on dust cover.

4. Card holder binding on platen.

Adjust card holder.

5. Carrier cords off pulleys

Install cords on pulleys - check pulley in back center frame of machine.

Check cord tension on tension pulley (19B-29).

6. Binds in pinion gears.

Adjust tab pinion gear (31-30) and carrier return pinion gear (31-31) for approximately  .005" backlash with escapement cord drum (31-32)

7. Backspace latch height (10-7).

Adjust bristol screw (21-7) so latch (10-7) will move freely under cam follower (10-5) when keybutton is depressed.

Backspace interposer (19-2) pushes the backspace latch (10-7) under the cam follower (10-5).

8. Backspace rack motion (9-4).

a) Adjust clearance between cam follower (10-5) and backspace latch (10-7).

Adjust latch clearance with adjusting screw for minimum clearance without failure (10-8).

b) Intermediate lever loose, broken or maladjusted (11-1)

9. Clutch release arm (20-2) binding against backspace cam (3B-5).

Adjust function cams left or right.

10. Keylever pawl overlap (18-10)

Adjust the keylever guide (19-5) for overlap of the backspace pawl (18-10) with the backspace interposer (19-2).

Overlap approx.  .040".

11. Keylever pawl clearance (18-10).

Adjust "U" shaped slot in keylever for clearance between keylever pawl (18-10) and backspace interposer (19-2).

Clearance is approx. .020".

12. Binds in carrier shoe.

Loosen locking nut and adjust screw (32-33) for shoe clearance minimum clearance - no binds.

Position carrier at different points along writing line and check clearance.

13. No lubrication

Lubricate machine.

Express backspace keybutton will not move

carrier.

1. Shoe clearance (34-36)

Adjust bellcrank (33-40) by forming, to get shoe clearance

2. Shoe overlap (34-36)

Adjust shoe bracket by forming at arrow 36.

3. Keylever pawl (33-39) on wrong side of bellcrank (33-40).

Correct pawl position and go to adjustment 1.

Carrier jams at left margin after express backspace.

1. Shoe clearance (34-36)

Adjust bellcrank (33-40) by forming to get shoe clearance.

2. Restoring spring missing or damaged on express shoe.

Repair or replace spring.

Express backspace operates intermittently

1. Oil on carrier return spring. (31-31)

Clean oil off spring with cleaning solution.

Carrier return spring should never be oiled.

2. Shoe clearance (34-36)

Adjust bellcrank (33-40) by forming to get shoe clearance.

3. Shoe overlap (34-36)

Adjust shoe bracket by forming at arrow 36.

4. Shoe restoring spring damaged.

Repair or replace spring.

Machine indexes as well as backspaces.

(Selectric II typewriter)

1. Index interlock (Paddle) broken or maladjusted (33A-35)

Replace or adjust paddle - when backspace keybutton is depressed the interlock lug (33A-36) is pushed to rear for index operation.

Check paddle clips - they hold the paddle shaft in place (33A-35). Not enough bite will cause cam to repeat.

2. Not enough clutch release arm bite (20-2).

Adjust cam (3B-5) left or right for more bite.

Not enough bite will cause cam to repeat.