133
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P6046: Difference between revisions
repair issues
(amplifier.cd link) |
(repair issues) |
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housings in place. | housings in place. | ||
The input FETs must be a matched pair. A possible replacement is the 2N4416A. | The input FETs must be a matched pair. A possible replacement is the 2N4416A in a metal | ||
TO-72 package with the substrate pin provided as in the factory part 153-0559-00. It is | |||
pretty expensive; currently (2014) it's about $6 US dollars each. | |||
Another much cheaper replacement is the 2N3819 in a plastic TO-92 package. | |||
The matching criteria should be Idss. | The matching criteria should be Idss. | ||
If the "DRAIN VOLTS" adjustment step (R125) fails, check and replace R124. It is a 270K, | |||
1/10W carbon composition resistor and it will eventually drift high so the 10.5V drain voltage | |||
can not be reached. The calibration section is not clear about the settings for this | |||
measurement, but the schematic diagram shows the voltage measured with 200 mV/DIV set | |||
on the amplifier. | |||
==Calibration== | ==Calibration== | ||