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8596E Spectrum Analyzer Fault

 

Hi guys,
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In the course of investigating some IFTs today, I fired up my 8596E, which started-up normally and displayed the usual min thru ~12Ghz spectrum. However, when I tried to enter the frequency range I wanted to study, it froze up and just would not respond. I was able to enter the start frequency okay, but the very second I entered the stop one, it just locked-up and became super-sluggish and unresponsive to any further input. At the instant, I got a "FREQ UNCAL" message appear on the screen. A *possible* clue is the 'OVEN' message takes a lot longer to go away than it has previously when it was all working fine. However, even when fully warmed up, I am still experiencing the thing freezing-up as described above.
Any ideas what the fault might be?
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Cheers,
Jinxie
 

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First guesses a power supply out of spec or noisy or a stuck key.?

Peter

On Feb 19, 2025, at 10:12?AM, Jinxie via groups.io <paul666@...> wrote:

?
Hi guys,
?
In the course of investigating some IFTs today, I fired up my 8596E, which started-up normally and displayed the usual min thru ~12Ghz spectrum. However, when I tried to enter the frequency range I wanted to study, it froze up and just would not respond. I was able to enter the start frequency okay, but the very second I entered the stop one, it just locked-up and became super-sluggish and unresponsive to any further input. At the instant, I got a "FREQ UNCAL" message appear on the screen. A *possible* clue is the 'OVEN' message takes a lot longer to go away than it has previously when it was all working fine. However, even when fully warmed up, I am still experiencing the thing freezing-up as described above.
Any ideas what the fault might be?
?
Cheers,
Jinxie
 

You might be on to something there! I have noticed that some of the keypad's keys require quite a lot of pressure to actuate; as if they're dirty I suppose. Could that also make them sticky in the sense you mean?

 

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Yes, it can. ?I’ve had several similar type HP front panels do that. Disassembly, lots of q-tips with IPA cleaning panel holes and keys then putting everything back together solves it, if that’s the problem. ?No real cost except an hour of your time.?

Peter

On Feb 19, 2025, at 2:45?PM, Jinxie via groups.io <paul666@...> wrote:

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You might be on to something there! I have noticed that some of the keypad's keys require quite a lot of pressure to actuate; as if they're dirty I suppose. Could that also make them sticky in the sense you mean?

 

Many thanks for that suggestion, Peter; much appreciated. Clearly those keys are in need of cleaning in any event, so that needs doing anyway. It'd be a real bonus if it clears the issue as well!
Cheers,
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J.
 

This doesn't sound like a dirty keyboard issue to me. ?Before digging into the keyboard for cleaning, I would get it in this state and then unplug the keyboard to see if the issue continues.
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I think the processor has gotten swamped dealing with something unexpected. ?Maybe it's busy responding to a peripheral issuing high speed erroneous interrupts, or stuck in a high-priority loop waiting for a response from a peripheral.
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Missed interrupts because the processor is busy with higher priority tasks would explain why the oven is taking longer than usual. ?There's no sensor checking the oven temperature; it's just a timer and that's likely interrupt driven.
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The keyboard appears to be polled (and not interrupt driven) which is why I think it's not a primary suspect.? I definitely agree the power supply is the first thing to check.
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-mark
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On Wed, Feb 19, 2025 at 01:11 PM, Jinxie wrote:

Hi guys,
?
In the course of investigating some IFTs today, I fired up my 8596E, which started-up normally and displayed the usual min thru ~12Ghz spectrum. However, when I tried to enter the frequency range I wanted to study, it froze up and just would not respond. I was able to enter the start frequency okay, but the very second I entered the stop one, it just locked-up and became super-sluggish and unresponsive to any further input. At the instant, I got a "FREQ UNCAL" message appear on the screen. A *possible* clue is the 'OVEN' message takes a lot longer to go away than it has previously when it was all working fine. However, even when fully warmed up, I am still experiencing the thing freezing-up as described above.
Any ideas what the fault might be?
?
Cheers,
Jinxie
 

Thank you, Mark. I would have thought if it was the power supply then the issue would arise spontaneously at any time and not just precisely when I try to enter a frequency limit. But I may be wrong. For sure the keys are very dirty judging by the amount of pressure required to get them to actuate, so I shall clean them first in any event, since they certainly need it. I'll follow up with the other tests once that's out of the way and if the problem persists.
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J.
 

Okay, well, I've been able to bring on the fault condition by simply rotating the datum dial whilst in the 'stop frequency' mode, so dirty keys are now looking increasingly unlikely (though they will require attention).
Since the consensus (such as it is!) is to investigate the PSU, I'll do that next. I'll scope the power rails of the individual low voltage supplies out of the main PSU and check their voltage levels are within spec. That should trap 99% of PSU problems. I'll also check the ESRs of the larger electrolytics and any suspicious bulges whilst I'm at it. Anything else I should look at?
 

Response to commands is usually postponed until the end of the current sweep. If the synth is having trouble locking, or the sweep is slow due to narrowband, or perhaps crossing band edges, command response will be affected. Try adjusting start / stop / span to see if there is a particular range that is slowing things down. And set autocouple to all...
 

Not sure about 'autocouple' but the actual range seems to be irrelevant. I've tried several. It's the instant the 'stop' frequency is entered that brings on the fault, whether that be by keypad or datum knob.
 

Instead of START / STOP, try entering as CENTER and SPAN. ?Just to see if it freezes when it has enough info to start a sweep, or if it is related specifically to the sweep defined by entering the STOP frequency.
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Does it sweep when first powered on, or after preset..?
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Trying to get at whether this is a problem with the sweep synthesis set up, or something related to keypress handling...

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