Hello TEA,
I hope, you can help me with a thing that confuses me.
A few months ago I have bought a nice HP 3456A.
Here are some pictures of it:
Top view of the digital part:
![](https://i.imgur.com/1YHM2Cd.jpg)
Top view analogue part:
![](https://i.imgur.com/JfrRzP0.jpg)
Mains input, no RIFA surprises:
![](https://i.imgur.com/kEzRoyZ.jpg)
The power supply unit, top view:
![](https://i.imgur.com/yXouiRb.jpg)
El Capo:
![](https://i.imgur.com/5djaQMw.jpg)
The input amplifier:
![](https://i.imgur.com/Xwlzzi7.jpg)
Some input protection:
![](https://i.imgur.com/OABmiEN.jpg)
A fancy standoff party:
![](https://i.imgur.com/ej8nxz3.jpg)
A funny thingie, no idea what this is, looks like a wirewound resistor:
![](https://i.imgur.com/s9OvyPi.jpg)
Another HP special item:
![](https://i.imgur.com/gygZlOZ.jpg)
And this is the master of all this desaster, the reference:
![](https://i.imgur.com/AgwQfiC.jpg)
But now to my question, hopefully some 3456A experts are around.
The schematic for the oscillator crystal states the following thing:
Mains input 60Hz - 5.85MHz
Mains input 50Hz - 4.875MHz
![](https://i.imgur.com/D6fisib.png)
But when I'm looking at the crystal in my 3456A I found a 6MHz crystal:
![](https://i.imgur.com/ENOjrt4.jpg)
It looks geniune and untouched.
Can somebody explain this to me? I'm a bit confused.
![Confused :-//](https://www.eevblog.com/forum/Smileys/default/confused0024.gif)
I have ordered some 4.875MHz crystals from this .cz company
http://www.krystaly.cz/en/Can I replace the existing crystal with one of the 4.875MHz?
Thanks for your answers.
Mounty