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I've been quoted $700, guaranteed good, from a dealer recently. Even if one channel is zapped, $103 is good.
If it's totally dead, it's usually a bad eeprom. We can fix that. Otherwise, it's unfixable.
I often use the TDR channel as a pulse generator/trigger, and sample off the other one.
I'm just
What's the setup? Pulse generator driving laser diode and triggering the scope?
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I have a little dead-bug gizmo that I use for testing photodiodes--it's a TO-18 can diode laser, 750 nm, 5 mW. Running it from a Tek SD-24 TDR pulse via a Mini Circuits 3 GHz amp, I get edges just under 200 ps.
So the testing setup is
Ch1 TDR -> amp -> diode -> fibre -> PD-> hardline -> SD22 50-ohm input.
I can do the same thing with a flashlight or a small LED, and look for response changes on the spectrum analyzer, but that's much slower and not nearly as much fun. I'm especially interested in the effects of large reverse bias and electrostatic fields on the plastic case--my guess is that cranking up the bias and depleting the very top of the epi will be a win for noise cancelling, but we'll see.
Cheers
Phil Hobbs
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A dozen! Hey, leave some for the rest of us!
Eh, no matter I s'pose. I'm not doing anything fast right now.
-- Cheers, James Arthur
76xx are a different animal. "Cooking" 60Hz PSU. No provision for illuminations on plugins.
The 7904A has a more refined pushbutton at top left.
I have both sorts. Two 7904s and a 7904A (guess which is my personal one). 7904s, at least every one I've used, seem to startup from cold with a couple of false trips, click, click, settle down. The A version comes right up. The A version has a (noisy-ish) fan, unlike the fanless earlier
7904s. Also, the A versions have a separate HV generator, driven from the main PSU, up a pair of 50 ohm cables, which lives "upstairs" in the (detachable) display unit.Running a spectrum analyzer plugin in an A series shows up some PSU interference, pips about 90dB down, at carrier */- 20 kHz. Happens with both 7704A and 7904A. Plain old 7904s don't show it.
Of the 100s of 7904s I've used, none must have been 'A' models.
Obviously I haven't (used an 'A' model) since I've never seen a 7904 that splits in half. I've had a few 7704As (mostly the DPO version used in their SPS systems).
LIkely no switchers at all. They probably figured 90dB was good 'nuff. ;-)
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