Products > Test Equipment
HP8595E spectrum Analyzer: readings at -40dB and CAL SIGNAL NOT FOUND
auato:
I still have the HP8595e disassembled on my bench.
The problem seemed to be the third relay (40dB). On some rare occasions it did not release when the instrument was turned on or when the preset button was pressed
But now that I've discovered it furtively, as you can imagine, it's been working perfectly everytime for days. >:D
@rfloop thanks for the detailed image, I am checking again near the red arrows with a microscope. Honestly before reassembling it I was thinking of spraying something like WD40 or isopropyl alcohol under the magnet of the third relay but I recalled the @rfloop's advice leaving them perfectly dry. I'm attaching some images taken by a microscope and as you can see they are not perfecrly clean
I was also thinking about replacing the battery because I've had the instrument for more than 7 years and I also bought it as a second hand tool and I don't know if it's worth doing this operation now. The battery is a Panasonic CR2477 and measures precisely 3.06V
MarkL:
--- Quote from: auato on December 28, 2023, 08:54:43 pm ---...
I was also thinking about replacing the battery because I've had the instrument for more than 7 years and I also bought it as a second hand tool and I don't know if it's worth doing this operation now. The battery is a Panasonic CR2477 and measures precisely 3.06V
--- End quote ---
Whether you decide to replace the battery or not, I would recommend doing the correction constants backup procedure, mentioned previously in this thread. Some of the numbers may change slightly depending the repairs needed for the attenuator, but at least you'll have them in case the battery dies unexpectedly. It's free and takes 10 or 15 minutes.
As far as the bad actuator is concerned, I think it would be worthwhile to compare the driving waveform on the bad actuator against a good actuator when switching in and out. It could still be a mechanical issue, but maybe there's a problem with the driver.
rf-loop:
--- Quote from: auato on December 28, 2023, 08:54:43 pm ---I still have the HP8595e disassembled on my bench.
@rfloop thanks for the detailed image, I am checking again near the red arrows with a microscope. Honestly before reassembling it I was thinking of spraying something like WD40 or isopropyl alcohol under the magnet of the third relay but I recalled the @rfloop's advice leaving them perfectly dry. I'm attaching some images taken by a microscope and as you can see they are not perfecrly clean
--- End quote ---
Yes, do NOT use something like WD40 there. There is danger that it can also go inside attenuator cave through nylon pin actuators holes.
These low pressure contact surfaces there must be absolutely clean and dry from any kind of oil. Oil on contact surfaces may delay or even prevent contact and also contact surfaces "self cleaning" do not anymore work properly (because oily surface collects and keep all possible small dust particles). Also if open attenuator cave these contact surfaces need keep clean and NO OIL.
There is nothing what need oil after attenuator is manufactured! Some wd40 etc can do only bad things or very bad things.
It need also keep in mind that many RF circuits may have some ceramic etc materials what need keep untouched and newer ever use some WD40 or similar things... after they are absorbed to these materials then high-frequency performance values are even permanently destroyed/changed.
In your images it looks like enough clean.
I have some old day measured these nylon needles movement dimensions and how much it tolerate reduced amount of movement in both ends.
It tolerate ~0.1mm ... I know it because in some emergency case I have temporarily used some ~0.1mm too thin O-rings and check that it works well including still enough "marginal" for reliable contacts. But in this case longevity is perhaps highly reduced if attenuator is under heavy use (continuous stepping in a short period of time, such as in some test applications of product lines, etc) (these O-rings and the upper and lower surfaces of the nylon needle also act as dampers where the kinetic energy turns into heat and can at worst fry these rings - you know when you listen to the buzz of the attenuator when it is driven continuously 24/7 at maximum speed (controlled via HP-IB under test automation system)
scopeman:
On the cal constants I made an excel spreadsheet for recording those for my HP8593E and 8593E. I have attached a copy along with one I found years ago Hopefully it will be useful to you.
Sam
scopeman:
Missed the last two.
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