Page 1
Trouble shooting guide for
Detecto Mechanical Physicians Balance Beam Scales
Models: 475-485-4420-4520-495-437-438-439-337-339
Symptom:
Beam stays down when load applied to scale platform
Diagnostic:
2) Draft rod not connected in scale base,
Note: The draft rod is the connecting rod that is located inside the column.
Cannot balance (Calibrate Zero) using zero balance adjustment
1) Packing material in scale base
Solution #1: Packing material
1) Turn the scale on its side or lie across a chair or table so that the
bottom of the scale can be viewed.
2) Remove all packing materials such as cardboard from inside of the
scale base. The cardboard packing material will be wedged
between the lever assemblies and the scale base.
3) Set scale upright
4) Zero balance the scale (See instructions)
5) Check for scale proper operation
Note: A scale that is working properly will repeat the same readings both
with an applied load and also balance at zero without requiring
adjustment of the zero balance screw.
1
Page 2
Solution #2: Draft rod
1) Turn the scale on its side or lie across a chair or table so that the
bottom of the scale can be viewed.
2) Connect draft rod (See below)
3) Set scale upright
4) Zero balance the scale (See instructions)
5) Check for scale proper operation
Note: A scale that is working properly will repeat the same readings both
with an applied load and also balance at zero without requiring
adjustment of the zero balance screw.
.
*******************************************
Symptom:
weight is lighter than it should be.
Diagnostic:
Solution:
on a solid surface.
Weight readings are ok up to a point then are inaccurate; indicated
Inference or obstruction of lever system under scale base
Remove obstruction or if on carpet or padded floor set scale base
*******************************************
2
Page 3
Symptom:
Weight readings change when load is applied to different positions
on the scale platform:
Diagnostic:
2) Broken weld on lever
3) Broken/worn pivot on lever and/or bearing
Weight readings are inaccurate
1) Loose/Missing “S” hook and/or bearing
Solution #1:
Loose/Missing “S” Hook (Union Hanger)
Visual inspection of scale base:
Weighing platform should have an equal spacing from base, if it
tilts or leans to one corner indicates a possible missing “S” hook
(Union Hanger) and/or bearing
1) Turn the scale on its side or lie across a chair or table so
that the bottom of the scale can be viewed.
2) Disconnect draft rod
3) Install the bearing if required (See below)
4) Install the rounded end of the “S” hook onto the lever
5) Hook the flat end on the “S” hook onto the scale base
support bracket.
6) Connect the draft rod
7) Set scale upright
8) Zero balance the scale (See instructions)
9) Check scale for proper operation
Note: A scale that is working properly will repeat the same readings both
with an applied load and also balance at zero without requiring
adjustment of the zero balance screw.
.
3
Page 4
4
Page 5
5
Page 6
Solution #2: Broken weld on lever
for a broken weld or damaged pivot; Look for signs of a broken
weld (s) such as paint scraped off by the rod twisting inside the
weld. Usually this problem is not easy to see.
Replace lever assembly if damaged then check scale for proper
operation.
Note: A scale that is working properly will repeat the same readings both
with an applied load and also balance at zero without requiring
adjustment of the zero balance screw.
.
If all “S” hooks and bearings are in place then inspect the levers
6
Page 7
Solution #3:
Broken/worn pivot and/or bearing
Inspect the pivots and bearings for signs of wear or damage.
Replace any worn or damaged parts and check scale for proper
operation.
The lever pivots ride on the bearings
and union hangers. If the pivots or
bearings are worn or broken the scale
will not repeat or give accurate weights.
*******************************************
7
Page 8
Symptom:
Beam does not float.
Beam is not responsive or is sticky
Instead of floating to balance when weighing the beam sticks,
When nearing the balance point, the minor poise can be moved
several divisions with little or no response.
Weight readings are inaccurate
Diagnostic:
the trig loop causing it to drag and not float freely.
2) Shelf lever is tilted and not hanging correctly
1) Beam balance indicator is touching either the front or back of
Solution #1:
Note: A scale that is working properly will repeat the same readings both
with an applied load and also balance at zero without requiring
adjustment of the zero balance screw.
Balance beam touching the trig loop
1) Remove plastic beam covers, lift up then unsnap.
2) Loosen the two screws that hold the beam yoke bracket to
the column
3) Move the beam yoke bracket so that the beam balance
indictor is located in the center of the trig loop.
4) Tighten the two screws that hold the beam yoke bracket to
the column
5) Replace plastic beam covers
6) Zero balance the scale (See instructions)
7) Check scale for proper operation
Balance indicator should be located such that it does not touch either
side of the trig loop.
8
Page 9
Solution #2:
Shelf lever
Check shelf lever for proper assembly and that it is hanging
straight from its supports. The shelf lever is located inside the
beam assembly in the “T” area of the column assembly. If it is
hanging at an angle from the supports, grasp the shelf lever and
gently shake it, Zero balance the beam and test the scale for proper
operation.
Note: A scale that is working properly will repeat the same readings both
with an applied load and also balance at zero without requiring
adjustment of the zero balance screw.
Shelf Lever
9
Page 10
Shelf Lever
Beam
Yoke
Bracket
Note: It is important that the shelf lever hangs straight from the supports.
*******************************************
10
Page 11
Zero Balance instructions
11
Page 12
Calibration Procedure
Detecto Mechanical Physicians Balance Beam Scales
Models: 475-485-4420-4520-495-437-438-439-337-339
Tools required:
Screwdrivers: One straight blade and one Phillips.
Test weights: one totaling 50 lbs, one totaling 250 lbs.
Calibration procedure:
1. Begin by moving both the sliding poises to the 0 position.
2. Observe if the balance indictor is in the center of the trig loop
(Arrow pointer on the right end of the beam is in the center of the opening)
If not, adjust the zero adjusting screw located at the left end of the beam till
balanced.
3. Scale balanced at 0
4. Place a 50 lb test weight on the scale
5. Move the upper sliding poise to the 50 lb mark
6. Observe if the balance indictor is in the center of the trig loop.
7. A correct reading will be the balance indicator in the center of the trig loop with
50 lb weight on the scale, small poise is at the 50lb mark and the large poise at 0.
8. If not alter the amount of weight inside the small sliding poise.
• If the arrow is DOWN, this indicates that the small poise is too heavy
therefore requiring the removal of a small amount of weight from the
small poise.
• If the arrow is UP, then the small poise is too light therefore you must
add weight to the small poise. Lay the additional weight on top the
poise till balance is achieved, then open the poise and place the
additional weight inside the poise. Check for balance indication.
Note: The poises are held together by small Phillips screws along the back.
Remove the Phillips screws in order to gain access to the inside of the poise.
9. Remove the test weight, and slide the small poise back to 0.
10. Observe if the balance indictor is in the center of the trig loop.
11. A correct reading will be the balance indicator in the center of the trig loop with
both the small and large poises at 0lbs and no load applied to the scale platform.
12. If not, adjust the zero adjusting screw located on the left hand side of the balance
beam till balanced.
Repeat steps 3 -12 till the scale balances both at 0lbs and 50 lbs.
13. With the scale balanced at both at 0lbs and 50lbs test the large sliding poise with a
total weight of 250lbs.
14. Apply the 250lb test weight to the scale platform.
15. Move the lower sliding poise over to 250 lb mark while ensuring that the small
sliding poise is at 0.
16. A correct reading will be the balance indicator in the center of the trig loop with
250 lb weight on the scale, large poise is at 250lbs and small poise at 0.
17. If not alter the amount of weight inside the large sliding poise.
12
Page 13
• If the arrow is DOWN, this indicates that the large poise is too heavy
therefore requiring the removal of a small amount of weight from the
large poise.
• If the arrow is UP, then the large poise is too light therefore you must
add weight to the large poise. Lay the additional weight on top the
poise till balance is achieved, then open the poise and place the
additional weight inside the poise. Check for balance indication.
Note: The poises are held together by small Phillips screws along the back.
Remove the Phillips screws in order to gain access to the inside of the poise.
18. Repeat the above steps till the scale repeats at 0lbs, 50lbs and 250lbs.
Note: This may require adjusting 0, 50lbs and 250lbs till all points repeat.
19. Once complete, test the scale operation at various weights to confirm operation.
13
Page 14
15
Page 15
16
Page 16
17
Page 17
18
Loading...