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Tandon TM100-1 Compliance Adjustment

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Tandon TM100-1 upper arm and screws (manual figure 5-14)
Tandon's Figure 5-14: the upper arm of a single-sided drive and its two upper arm screws on the carriage assembly. The compliance adjustment is made by loosening these screws and moving the arm.

The Tandon TM100-1 has one read/write head, below the diskette. Its logic board has only one head connector, P6, which Tandon's board drawing labels the lower head.[1][2] Where the double-sided Tandon TM100-2 has an upper head on a gimballed flexure, the TM100-1 has an upper arm carrying a felt pad.[3][4] Tandon calls the head output at its maximum, with the pressure of the felt pad centred over the read/write gap, the compliance. Its manual gives a check and an adjustment for single-sided drives, made by moving the upper arm; for double-sided drives it says the compliance must be checked and adjusted at the factory.[5]

Tandon's tables call for the compliance check after the upper arm assembly or the head module assembly has been replaced on a single-sided drive, and send a drive that fails the head output check to the compliance check.[6][7] A felt pad that is damaged or worn cannot be cured by adjustment: Tandon replaces the whole upper arm assembly.[7]

Symptoms

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  • The head output check fails: with certified media, the read signal at track 39 is below 200 mV peak-to-peak. Tandon's troubleshooting table gives three causes: defective media, a drive that cannot read, and misadjusted compliance.[8][7]
  • The compliance check fails: pressing on the upper arm with 15 g raises the output by more than 10 %. Tandon lists a defective diskette and a damaged or worn head load pad as the causes.[5][7]
  • With a diskette inserted, the felt pad does not clear the disk when the front door is opened, or the head arm does not rise when the door opens.[4][9]

A low signal is not always the head or the pad. Tandon notes that inferior or defective media can give about 100 mV peak-to-peak on a good drive.[8] Tandon's troubleshooting table gives other causes for a drive that will not read: the radial alignment, the index burst and the Track 0 switch adjustment, the read electronics on the logic board, and the head itself.[7] For those checks see Tandon TM100-1#Alignment and adjustment, Tandon TM100-2 Head Alignment and Tandon TM100-2 Track 0 Switch Repair. Spindle speed has its own entry in the table and is set the same way on both drives; see Tandon TM100-2 Spindle Speed Adjustment.[7][10] See also the 5150 troubleshooting guide.

Tools and parts

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  • A dual-channel oscilloscope; Tandon names the Hewlett Packard 1740A or equivalent.[11]
  • An exerciser (Tandon names the AVA Model 103C) or software that can step the drive to any track, select the head and write a 1F pattern (all zeros in FM) or a 2F pattern (all ones in FM).[11]
  • A certified output diskette without a write-protect tab; Tandon names the Dysan 104/2D or equivalent.[11]
  • A gram gauge able to apply 15 g.[5]
  • A 5/64-inch Allen wrench for the two upper arm screws.[4]
  • A replacement upper arm, Tandon part number 171103-001, if the pad is worn or the compliance cannot be adjusted. Tandon's spares list has no separate part number for the felt pad.[12]

Procedure

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Preparation

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Tandon TM100 logic board test points (manual figure 5-1)
Tandon's Figure 5-1: the logic board test points. TP1 and TP2 are in the upper middle of the board, TP10 at the upper right and TP7 at the lower left beside the terminator socket.
  1. Check the supply at the drive: +12 V within ± 0.6 V and +5 V within ± 0.25 V. Tandon asks for the supply voltages to be checked before any fault-finding.[10][13]
  2. Connect the drive to the exerciser or host computer and to its power supply.[14]
  3. Remove the two screws that attach the logic board to the guide rails, lift the board out and lay it on the drive. Tandon's note says this lets you reach the drive to move the head.[5][15]
  4. Set up the oscilloscope as in the table below for the check being made. Both checks read Test Points 1 and 2 differentially, with channel B inverted and added to channel A.[5][8]
Tandon's oscilloscope set-up
Setting Head output check (5.11) Compliance check (5.13)
Channel A Test Point 1 Test Point 1
Channel B Test Point 2 Test Point 2
Ground Test Point 10 Test Point 10
Mode A plus B, B inverted A plus B, B inverted
Vertical 50 mV per division 100 mV per division
Time base 20 ms per division 10 µs per division
External trigger Test Point 7 Test Point 7, positive edge
Track and pattern Track 39, 2F (all ones) Track 34, 1F (all zeros)

Head output check

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  1. Insert a certified diskette without a write-protect tab.[8]
  2. Seek to track 39.[8]
  3. Write a 2F pattern on head 0.[8]
  4. Check that the amplitude is 200 mV peak-to-peak or more.[8] Tandon's steps 6 and 7 repeat the test on head 1, which the TM100-1 does not have.

Tandon suggests establishing a nominal amplitude for the diskette on a known working drive. Amplitudes above 200 mV peak-to-peak are acceptable in all cases.[8]

Compliance check

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  1. Apply power to the drive and select it.[5]
  2. Insert a diskette without a write-protect tab.[5]
  3. Write a 1F pattern on track 34.[5]
  4. Note the output voltage on the oscilloscope.[5]
  5. With the gram gauge, carefully apply 15 g of pressure to the upper arm.[5]
  6. If the output rises by more than 10 %, adjust the compliance.[5]

Tandon's note likens 15 g to the weight of a quarter, but a current US quarter weighs 5.67 g, so use the gauge.[5][16]

Compliance adjustment

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The adjustment uses the same set-up as the check, with the oscilloscope showing the output while the arm is moved.[5]

  1. Loosen the two screws that attach the upper arm to the carriage assembly a quarter turn anticlockwise with the Allen wrench (Figure 5-14).[5]
  2. While watching the output, move the upper arm around the axis of the head until the output amplitude is at its highest.[5]
  3. Hold the arm in that position and tighten the two screws clockwise.[5]
  4. Repeat the compliance check.[5]
  5. If the compliance cannot be adjusted, replace the upper arm.[5]

Replacing the upper arm

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Tandon TM100-1 upper arm parts (manual figure 6-25)
Tandon's Figure 6-25: the upper arm assembly, spring, spring retainer, two mounting screws and two washers above the carriage.

Removal:[4]

  1. Remove the logic board: unplug all its connectors, noting where each goes, remove the two mounting screws, slide the board about half an inch towards the back of the drive and lift it out.[15]
  2. Close the front door.[4]
  3. With the 5/64-inch Allen wrench, remove the two screws that attach the upper arm and spring retainer to the carriage assembly.[4]
  4. Carefully lift off the spring retainer and the spring.[4]
  5. Remove the upper arm assembly.[4]
Tandon TM100-1 felt pad on upper arm (manual figure 6-26)
Tandon's Figure 6-26: the felt pad on the end of the upper arm, which is lined up with the head when the arm is fitted.

Replacement:[4]

  1. Place the new upper arm on the head carriage, lining up the screw holes.[4]
  2. Carefully refit the spring and spring retainer with the spring seated at both ends, and line up the screw holes.[4]
  3. Refit the two screws without tightening them fully.[4]
  4. Line the felt pad up with the head by eye.[4]
  5. Tighten the two screws.[4]
  6. Insert a diskette and check by eye that the felt pad clears the disk when the front door is opened.[4]
  7. Refit the logic board: check its option configuration, fit the two screws that hold it to the rails, and plug every connector back into its own place.[15]
  8. Make the head output check and the compliance check.[4][6]

Testing

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  • Head output at track 39 is 200 mV peak-to-peak or more on certified media.[8]
  • Pressing 15 g on the upper arm raises the output at track 34 by no more than 10 %.[5]
  • The front latch opens and closes, the head arm rises when the door is opened, and the felt pad clears an inserted diskette.[9][4]
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References

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  1. ↑ Tandon, TM100 manual (1983), Figure 5-1 "Logic Circuit Board with Test Points", p. 5-2: test point positions and the J3 head connectors, P5 upper head and P6 lower head.
  2. ↑ Minuszerodegrees.net, "Tandon TM-100 - Single versus double sided" (annotated photograph), hosted as File:Tandon TM100 single-sided logic board (minuszerodegrees).jpg: a single-sided logic board has only plug 6.
  3. ↑ Tandon, TM100 manual (1983), section 4, "Read/Write Head Assembly", p. 4-7: the lower head is fixed to the carriage and the upper head is mounted on a gimballed flexure.
  4. ↑ 4.00 4.01 4.02 4.03 4.04 4.05 4.06 4.07 4.08 4.09 4.10 4.11 4.12 4.13 4.14 4.15 4.16 Tandon, TM100 manual (1983), section 6.4, "Upper Arm Assembly (Single-Sided Drives Only)", removal and replacement, p. 6-27, with Figures 6-24 "Upper Arm Screws", 6-25 "Upper Arm Parts" and 6-26 "Felt Pad on Upper Arm", pp. 6-28 and 6-29.
  5. ↑ 5.00 5.01 5.02 5.03 5.04 5.05 5.06 5.07 5.08 5.09 5.10 5.11 5.12 5.13 5.14 5.15 5.16 5.17 5.18 Tandon Corporation, OEM Operating and Service Manual, TM100-1, TM100-2 Disk Drives, 48 Tracks Per Inch, 179022-001 Rev. B (1983), section 5.13 "Compliance Check and Adjustment (Single-Sided Drives)", p. 5-15, with Figure 5-14 "Upper Arm and Screws", p. 5-16: definition of compliance, factory adjustment on double-sided drives, the check (15 g, more than 10 %) and the adjustment. Hosted as File:Tandon TM100-1 TM100-2 48TPI Operating and Service Manuals 1983.pdf.
  6. ↑ 6.0 6.1 Tandon, TM100 manual (1983), Table 6-2 "Guide to Checks and Adjustments", p. 6-6: head output and compliance checks after replacing the upper arm assembly; compliance check (single-sided drives only) after replacing the head module assembly.
  7. ↑ 7.0 7.1 7.2 7.3 7.4 7.5 Tandon, TM100 manual (1983), Table 6-1 "Troubleshooting Guide", pp. 6-3 to 6-5: "Will not read", "Fails head output check" and "Fails compliance check and adjustment".
  8. ↑ 8.0 8.1 8.2 8.3 8.4 8.5 8.6 8.7 8.8 Tandon, TM100 manual (1983), section 5.11 "Head Output Check", pp. 5-13 and 5-14: 200 mV peak-to-peak or more with certified media, about 100 mV with inferior media, oscilloscope set-up, track 39, 2F pattern.
  9. ↑ 9.0 9.1 Tandon, TM100 manual (1983), section 5.1 "Visual Inspection", p. 5-1: the front latch opens and closes and the head arm raises when the door is opened.
  10. ↑ 10.0 10.1 Tandon, TM100 manual (1983), section 5.5 "Drive Motor Speed Check and Adjustment", pp. 5-3 to 5-5: +12 V ± 0.6 V and +5 V ± 0.25 V; one speed check and adjustment for both drives.
  11. ↑ 11.0 11.1 11.2 Tandon, TM100 manual (1983), section 5.2 "Equipment Required", pp. 5-1 and 5-2.
  12. ↑ Tandon, TM100 manual (1983), Appendix A "Recommended Spares and Major Assemblies", p. A-1: 171103-001 Upper Arm.
  13. ↑ Tandon, TM100 manual (1983), section 6.1 "Symptom Diagnostic Techniques" and the note in section 6.3, p. 6-1: check the power supply voltages before using the troubleshooting guide.
  14. ↑ Tandon, TM100 manual (1983), section 5.3 "Power/Drive Select Check", pp. 5-2 and 5-3: connect the interface cable from the exerciser and apply power.
  15. ↑ 15.0 15.1 15.2 Tandon, TM100 manual (1983), section 6.4, "Logic Circuit Board" removal and replacement, pp. 6-7 to 6-9, with Figure 6-2 "Logic Circuit Board Mounting".
  16. ↑ Wikipedia, "Quarter (United States coin)": mass 5.670 g (6.25 g for the 90 % silver coins of 1932 to 1964).


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