Products > Test Equipment
Fool for the 8656A Sig Gen
jrharley:
themadhippy!
Thanks for the tip!
I'm just now getting into looking at this component, so this is great! Good to know there's some options.
This guy is a good bit snazzier than the HP part, which is pretty "opaque" as far as construction goes. This one's form factor doesn't allow much room for a lot of arrangement possibilities, so I'm guessing they're all in parallel? I'll run it down, I presume digi-key US can supply too.
Thanks again so much for the link and information, it's a big help!
JRH
themadhippy:
--- Quote ---so I'm guessing they're all in parallel?
--- End quote ---
no,this is the most common arrangement
Tony_G:
As Themadhippy said, these aren't in parallel, R9 is being used as a pull-up resistor so I wouldn't expect that it would have a problem dragging your rail low.
If you think it might be then remove R9 and see if the rail stays at 5V and that you get +5V to R9 (Pin 1 I would assume but you should confirm on the schematic) - If it does then you more than likely have a problem with one of the ICs that are using R9 as a pull-up.
If that all works (in that removing R9 gives a good rail) then you might want to try using a 3.3K resistor to just provide +5V to each pull-up location (e.g. R9 pin 1 to R9 pin X one at a time) and see if you can identify which IC is dragging it down.
All of this assumes that removing R9 enables the rail to stay at +5V if it doesn't then the problem is somewhere else.
Sorry, I can't be more specific.
TonyG
jrharley:
Thanks guys, much appreciated! I'm afraid I'm obnoxiously long on enthusiasm, but woefully short on knowledge, so this is a big help.
Thanks for the diagram themadhippy, that makes sense now. Now I see why they didn't feel like it was necessary to show the package all in one spot on the schematic, among other things.
tonyG, Bodger Alert - I didn't know that there even was such a thing as a "pull-up resistor". Now that I've looked up the concept, I've got a better idea. Thanks for advancing my understanding!
I think at this juncture, I'm inclined to follow your instinct about R9. If it's unlikely that a fault in the unit will cause the fault I'm chasing, then I think I'll put it on the to do list, but keep moving. After all, a digitally naïve, analog assault on this beast, is all I've really got. :-\ But I really like your suggestion on how to test R9 and the chips associated with it, I almost want to do it, just to do it. R9 wouldn't be hard to pull. But "eyes on the prize" right? I'll do some more probing tonight.
Always appreciate the feedback folks,
JRH
Tony_G:
I think that your process of getting the power rails right is the correct first approach to the unit - I'd keep trying to find out why the +5V rail drops to 1.8 (I think you said that) when connected.
Once the rails are right then you can be more "creative" in trying to find the fault.
TonyG
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