Re: 8753ES Source module schematic
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Hi Vladan¡ ? Pin 14 reads about 4.5 Ohms to ground. I have another Source module for comparison that reads a bout 1.5K. Now working on how to determine shorted part. Have eliminated the attenuator, Oscillator, and YIG, as it still reads ¡®shorted¡¯ with the board completely removed from the assembly. I suspect that Tantalum (looks like 10 uF) but there seems to be an electrolytic of 3.5 uF in that circuit also, but haven¡¯t confirmed. Anyway, it¡¯s late here so calling it a night. Thanks for your help so far; that Pin 14 pointer helped a lot. ? Tom. ?
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From: [email protected] <[email protected]> On Behalf Of pianovt via groups.io
Sent: Wednesday, November 24, 2021 9:56 PM
To: [email protected]
Subject: Re: [HP-Agilent-Keysight-equipment] 8753ES Source module schematic? I am looking at a source module as I write. I am not sure if 22V goes anywhere else in the instrument, but on the source it connects to pin 14 of P1 (that long brown AMP connector that attaches to the mother board). From there it goes through a filter and then to various places.
- One of those places is the DIP connector for the ribbon cable to the step attenuator. It's next to the 20W resistor. Be careful to not bend the resistor, it can lead to a board failure. Disconnect that ribbon and see if it's the attenuator that's drawing the current.
- The power supply filter I mentioned above consists of:
????????????? A small capacitor to ground (0.1uF, smt), it's on the bottom side of the board.
????????????? A series coil (toroid with many turns in a plastic base, near the middle of the 20W resistor). I doubt this coil is the problem.
????????????? A yellow 10uF SMT tantalum capacitor near the Q16 TO220 transistor with the heat sink. It's the SMT capacitor under the attenuator bracket, near the tip of the heat sink.
If the above are all OK, completely detach the circuit board from the rest and check the resistance from pin 14 on the AMP connector to ground.The circuit board has several sockets that bring power, etc. to the microcircuit housing below. WHen you detach the board from the housing, you are checking if the problem is with one of the microcircuits.
If none of this works, let me know and I will look closer.
Vladan
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