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Teardown - Hitachi V1065
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Miti:
About the frequency counter on the Hitachi scopes.
I have a 1585 and I'm frustrated by the frequency counter accuracy too. This model has a PEF-875 board and there's the uC and the frequency counter. I applied 1MHz from a Ublox GPS module and it reads 998.1KHz. If I touch one of the pins of X4101, the blue resonator in the picture, with an oscilloscope probe connected to a reasonably accurate frequency counter, the reading goes up to 999.6KHz and the frequency counter reads 12.006MHz. As you can see in the picture, there's a place for crystal oscillator but they decided to use a ceramic resonator. Really Hitachi? The PEF-875 board seems to have two 32 pins headers soldered to the one beneath so would be pretty hard to remove it and I may damage some pads. Again, really Hitachi?
I, being a bit of a precision nut, intend to desolder the resonator from the top and install a crystal that has much tighter tolerance and stability than a ceramic resonator. By my calculation, the crystal must have a load capacitance of 21.5pF so I don't need to change the two 33pF load capacitors shown in the schematic. A 20pF CL crystal should do it.
I'll let you know how it goes.
Miti:
The resonator is out, ready to receive the crystal.
Miti:
All done, the crystal is in and check this out...bang on.
Why did I do it? Do I need this accuracy? Of course not, it is called OCD ... Oscilloscope Compulsive Disorder    :-DD
rbm:
Interesting upgrade.  I have a V-695. I have to see if I can do this modification, or even if it is necessary to do it.  You modified X4101 on the PEF-875 board from a 12MHz resonator to a 12.000 MHz CL crystal if I understood correctly.

I'm not sure of the exact differences in the frequency display hardware between your V-1585 and my V-695.  If my V-695 scope is equipped with a PEF-782 board, would I consider doing this modification to X3101, which is also a 12.000 MHz crystal?
bitseeker:
Nicely done, Miti. Why did you do it? Because you could. And it looks cool. Sounds good to me.
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