[time-nuts] HP E1938A schematics.

[Rob040 .]

Hi,

I've made some new schematics of the HP E1938 oscillator/controller module. I derived them from the HP schematics that I found on Brooks' site.
The aim was to have more clear versions for service/repair. They should reflect the situation as they left the factory, what isn't on the PCB isn't present in the drawings (not sure about the content of the oscillator 'puck'). It's the version with the 20P connector on the component side.
I made a One DAC and Two DAC version and made a separate sheet for the power supply, otherwise I wouldn't fit on one sheet (format is A2).
Please feel free to use it, you can find the package attached to this mail.

Because I didn't open the oscillator module, I'm not sure about the following things:

- In the voltage reference section: C65 (100nF) is in parallel with a 0 ohm resistor (R74), so I expect C65 is not present on the PCB. Is "No load" in this case the same as "Not mounted"?

- In the input of the amplifier section: R28 (0 ohm) is in parallel with potmeter (R77) of 50 ohm. No clue which of both is present.

- The capacitance mention on the label of the 'puck', where is it placed in the circuit? Is it one of the C2/C3 which has a fixed value of 100pF in the schematic? Or is it in parallel with CR1 (the BB512)? Or is it like I drew in the oscillator part (bridge section)?

- Type of U5 (Vref IC) is still unknown, anyone knows which type it is?

Best regards,

Rob Tromp


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