| Products > Test Equipment |
| HP 8594E Spectrum Analyzer. At last I own a decent Spec An. |
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| 0culus:
--- Quote from: MarkL on January 22, 2019, 09:52:23 pm --- --- Quote from: 0culus on January 22, 2019, 08:30:54 pm ---Oh yeah, I'm sure you know this, but many SAs (including this one) cannot tolerate any DC level on the RF input. DC blocks are your friend to ensure the signal is AC coupled and prevent an expensive repair. --- End quote --- In general that's very sage advice. But on the 8594E (and 94L/95E/96E), the attenuator has a built-in DC block which is always in-line by default. It is rated 50V, and also limits the lower range to 100kHz when in-line. You can see the DC block in the block diagram in the Assembly Level Repair manual, and it also appears in the specifications in the Calibration Guide for those models. They all have warnings on the front panel of "0VDC MAX", but that is only true if you manually change the coupling to DC in the AMPLITUDE menu (3rd page). --- End quote --- Interesting! Learn something new every day. :-+ |
| Bicurico:
I am reading this thread out of interest... Could someone explain what the "OVEN COLD" and "REF UNLOCKED" mean? Well I know they mean that the oven of the OCXO is still cold and that the reference signal is not locked - but is it a fault or did the machines in the pictures just not warm up enough? Is this a sign to keep your fingers from similar offers on eBay or does it mean the seller doesn't know much about the device and did not test it properly, considering that it works because something is happening on the screen? Thanks, Vitor |
| MarkL:
--- Quote from: Bud on January 22, 2019, 06:35:27 pm ---... Battery replacement procedure can be found in this forum somewhere, involves taking a board out and swapping the battery while relying on the charge hold by the memory capacitor. ... --- End quote --- It's in the Assembly Level Repair chpt. 7, under a section called "A16A1BT1 Battery". But backup the constants first, just in case! |
| MarkL:
--- Quote from: Bicurico on January 22, 2019, 10:07:42 pm ---Could someone explain what the "OVEN COLD" and "REF UNLOCKED" mean? ... --- End quote --- Almost every time REF UNLOCKED is because the block jumper from "REF OUTPUT" to "REF INPUT" on the back is missing (as is the case in one of those listings). It seems that people like to pull them off and sell them separately for a ridiculous price. The SA will still run without it, but with meaningless frequency readings. EDIT: Fixed ambiguity. |
| TerraHertz:
--- Quote from: Bicurico on January 22, 2019, 10:07:42 pm ---I am reading this thread out of interest... Could someone explain what the "OVEN COLD" and "REF UNLOCKED" mean? --- End quote --- As explained by MarkL above, the "oven cold" (probably) means the seller didn't leave the unit running long enough before taking the photo. And "ref unlocked" typically means there's no freq reference to lock to. In the first link I gave, because some fool has swiped the jumper from the back of the machine. You can see that in the seller's pics of the machine rear. Given that seller's price grasping on a badly damaged unit, it was probably him. On the one I bought the jumper is in place, and the screen says "ref uncal" which is (probably) just because the crystal oven is cold. --- Quote from: Bud on January 22, 2019, 06:43:39 pm ---Also keep in mind the close to the carrier phase noise of the device is about 80 dBc/Hz if i remember correctly, so you can't measure external signal near phase noise better than that, the analyzer will dsplay its own phase noise. --- End quote --- :D And once I have this thing to play with, I will be able to teach myself what the hell that all means. (I get it a *little* bit.) Is the unit's Option 140 "Narrow bandwidth and precision freq ref" relevant to that? |
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