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576/Repairs: Difference between revisions
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Horizontal control range insufficient to center. | Horizontal control range insufficient to center. | ||
Q669 was bad, but installed a matched pair of 2N3906 PNP. | Q669 was bad, but installed a matched pair of 2N3906 PNP. | ||
Tek recommended replacement was 2N4250. | Tek recommended replacement was [[2N4250]]. | ||
40V Vce 250mV @ 500 μA, iC 10mA 200mW F 50MHz TO106 (NLA EOL 02/17). | 40V Vce 250mV @ 500 μA, iC 10mA 200mW F 50MHz TO106 (NLA EOL 02/17). | ||
2N3906 seems to work just fine. | [[2N3906]] seems to work just fine. | ||
==Symptom: Noisy signal 12.5 rails +/- as well as slightly low +12.5 and -12.5 Rail voltages== | ==Symptom: Noisy signal 12.5 rails +/- as well as slightly low +12.5 and -12.5 Rail voltages== | ||
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==Symptom: 1-2-5 Horizontal Balance will not calibrate== | ==Symptom: 1-2-5 Horizontal Balance will not calibrate== | ||
Unable to balance 1-2-5 Horizontal Balance within limits of trimmers R 650 – R645. | Unable to balance 1-2-5 Horizontal Balance within limits of trimmers R 650 – R645. | ||
Found that Q631A-B ( | Found that Q631A-B (dual) and Q633A-B (dual) had been replaced with pairs of badly matched single components. | ||
Found two NOS Q631 and Q633 and installed these. | Found two NOS Q631 and Q633 and installed these. | ||
Followed | Followed calibration procedure per 070-0905-01 Sec. 5. | ||
Display is now balanced in the 1-2-5 ranges in both Horizontal and Vertical axis. | Display is now balanced in the 1-2-5 ranges in both Horizontal and Vertical axis. | ||
Display is rock solid and dot/traces do not "jump around" when switching HORIZONTAL ranges. | Display is rock solid and dot/traces do not "jump around" when switching HORIZONTAL ranges. | ||
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==Defects found without any noted symptoms== | ==Defects found without any noted symptoms== | ||
Found D507-D708 9V Zener VR TC shorted (continuity both directions) on both Step Gen and Display Board | Found D507-D708 9V Zener VR TC shorted (continuity both directions) on both Step Gen and Display Board. | ||
Tek's recommended replacement is a [[1N936]], available at [https://www.mouser.com Mouser Electronics]. | |||
Found shorted D83 - 1N4152. | Found shorted D83 - 1N4152. | ||
Replaced Symptoms not noted, but seems to have less distortion in the display. | Replaced Symptoms not noted, but seems to have less distortion in the display. | ||
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Preemptive strike: | Preemptive strike: | ||
Replaced K101 K102 and K103 | Replaced K101 K102 and K103 relays. | ||
No symptoms or malfunctions noted. | |||