Products > Test Equipment
Teardown - Hitachi V1065
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grumpydoc:

--- Quote ---From what I can see in the circuit description, it depends on the trigger circuit, not the CPU. I am a decent amount off, not just a few digits.
--- End quote ---
I've just had a look, not really paid attention to that part of the circuit before.

The trigger circuit is the logical place to start as you obviously want to clean up the input signal to a pulse train to count.

If you look the trigger pulses are fed from the top of R655 (waveform 4 top right of sheet 4 of the circuit diagram) to IC2170 which is an 74AS74 configured to give a /4 frequency division (bottom left of sheet 5). From there it is passed to IC2171, a 74LS393 dual 4-bit counter where a further /32 frequency division takes place. After that it is fed to the PC5 input of the CPU via input selector IC2161 (bottom left of sheet 8 now).

If your frequency counter is off I'd check the CPU clock frequency first - there isn't really much to go wrong, just a crystal, two caps and a resistor straight to the CPU but the CPU clock is the only reference for the frequency counter that I can see.
Flump:
thanks for the look inside grumpydock
lots of good info here.

I wonder if anyone knows if the scope test point on the front of it
can be adjusted as mine reads 1043 measured by the scope  and not 1k,
my multimeter reads 1042 so it is the test point reading high.
true:

--- Quote from: Flump on May 02, 2014, 01:46:11 am ---thanks for the look inside grumpydock
lots of good info here.

I wonder if anyone knows if the scope test point on the front of it
can be adjusted as mine reads 1043 measured by the scope  and not 1k,
my multimeter reads 1042 so it is the test point reading high.

--- End quote ---

It's not meant to be that accurate. If you want it to be, I'm sure you could solder something in to correct it...
rbm:
I hope that I can ask a question about the sister scope to the 1065, the V-695 (60MHz model).  They share a great deal in common.

I recently purchased one and just received it in the post.  The owner didn't disclose the broken selector switch (S1603 on the schematic); I assume it is broken because it does not select any of the functions reliably. 

My selector switch has no centre detent position (only up and down), and the up / down positions are not-momentary in operation (the switch remains).  From the above text "fairly normal centre biased toggle" and from the schematics, S1603 looks to be a DPDT centre detent, possibly momentary action.  Is this correct or should the up-down positions be non-momentary?

I'll have to tear into the scope to take a look at the front panel circuit.  However, from the pictures posted above, it appears that S1603 is not able to be serviced.  Will I need to desolder and replace this switch completely or can it be salvaged?

Thanks in advance for helping.
grumpydoc:

--- Quote ---My selector switch has no centre detent position (only up and down), and the up / down positions are not-momentary in operation (the switch remains).  From the above text "fairly normal centre biased toggle" and from the schematics, S1603 looks to be a DPDT centre detent, possibly momentary action.  Is this correct or should the up-down positions be non-momentary?
--- End quote ---

It's a centre-biased DPDT, open contacts in the centre position and not momentary action. From memory it has a mounting for the grey paddle switch which is the one feature that might be difficult if you try to replace it.

However, it is likely that the switch can be salvaged as it sounds exactly like the switch on the scope I took apart. You do need to remove the front panel switch and LED board which means taking out the PSU/HV board and the CPU board - after that there is enough room to wriggle it out. Take the grey plastic paddle off squirt some contact cleaner or IPA into the top of the switch, then work the switch a bit. It will probably start to come free and work correctly. Repeat if necessary and if the contacts are not working try to get some contact cleaner or deoxit or equivalent into the switch itself. Finish with some light oil into the top of the switch (especially if you used IPA to clean - many commercial contact cleaners have a light lubricating oil in them anyway).
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