02-02-2016, 05:18 PM
(02-02-2016, 04:20 PM)pwdrive Wrote: All workie workie so far, the only waveform I had to hand for checking was the 'scopes Cal and the AC mains, the 'scopes Cal waveform is a bit shy of its target frequency, but by not a lot, inside it looks like two or three transistors for the Cal osc, there's a couple of presets close by, it's hard to say what one was labeled up as but the other is Cal, possibly one for set frequency and one for amplitude.
I really wouldn't worry about that.
The main purpose of the Cal output is to allow you to adjust the HF compensation on a x10 probe.
The voltage and frequency accuracy is secondary to this - good enough to check you're in the ballpark, but that's all.
Some 'scopes have a preset to allow you to find-tweak the voltage, but I've never seen one for frequency; you're at the mercy of the caps used in the astable multivibrator (usually 10% or worse IME).
Some really posh models will generate the cal signal more carefully - dividing down from a stable clock that is used elsewhere, but presumably not here...
Generally, it looks quite reasonable, but I'm surprised the EHT is only 2kV. You'll be OK with basic stuff, but low duty-rate signals will be hard to see. The Philips PM3215 uses 10kV IIRC.
I note from the manual that it has a Y-out on the back. This is incredibly useful (though many folk ignore it). If you didn't have the built-in frequency counter, that would be an obvious use. I connect mine to a powered 'speaker by default, and use it a lot for all sorts of work beyond the obvious...
They've replaced the Volts/Div rotaries with relays and programmable gain amplifiers under control from the rotary encoders and a microcontroller. Likewise for the Time/Div control. Assuming they used half-decent encoders, this ought to be more reliable in the long term - switches are the weak point most modern gear.
