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465/Repairs: Difference between revisions
→CRT Circuit Troubles
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==CRT Circuit Troubles== | ==CRT Circuit Troubles== | ||
<nowiki>The 465 "Family" of scopes has been known to have issues with "no display" or a "shrunken" screen trace. This includes 465,465B,466,468 and 475 scopes. The schematic for each series is almost identical but each one uses different and component ID numbers in their schematic. | |||
1. This may be attributed to a failure of the HV transformer and/or the HV Multiplier. | 1. This may be attributed to a failure of the HV transformer and/or the HV Multiplier. | ||
a. These parts are generally shared across the entire family of instruments. | a. These parts are generally shared across the entire family of instruments. | ||
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c. The HV Multiplier has likely shorted to ground and is demanding more current and voltage from T4015 than the transformer is able to deliver. | c. The HV Multiplier has likely shorted to ground and is demanding more current and voltage from T4015 than the transformer is able to deliver. | ||
d. You will find several other voltages are off as well throughout the circuit. | d. You will find several other voltages are off as well throughout the circuit. | ||
10. Locate Service Jumper W4032 and with the scope turned off, carefully | 10. Locate Service Jumper W4032 and with the scope turned off, carefully de-solder and lift one end of this jumper from the circuit board. This isolates the HV Multiplier from the ground. | ||
a. Turn the scope power "on", if everything else is OK, you should see a trace which should be dim, but still visible. Dim room lighting helps spot the trace. | a. Turn the scope power "on", if everything else is OK, you should see a trace which should be dim, but still visible. Dim room lighting helps spot the trace. | ||
b. You should be able to fully control the trace position and other characteristics, however, it will be quite dim and somewhat unstable. | b. You should be able to fully control the trace position and other characteristics, however, it will be quite dim and somewhat unstable. | ||
c. The beam finder will cause the trace to contract about 10-15% below its previous size. | c. The beam finder will cause the trace to contract about 10-15% below its previous size. | ||
11. Re-Test all voltages in the CRT circuit and confirm that they generally agree with the schematic. | 11. Re-Test all voltages in the CRT circuit and confirm that they generally agree with the schematic. | ||
12. Retest for the same | 12. Retest for the same wave forms (Step 6 and 8) as before, these should be more close to the ones in the diagrams. | ||
13. Locate a known good HV Multiplier and replace as needed. | 13. Locate a known good HV Multiplier and replace as needed. | ||
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