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Re: Intermittent REF UNLOCK error message on 8591A Spectrum Analyzer

 

开云体育

Anders,

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So, in green is the active bias stage, R66 serves as the current sense.

In my case, I have 5.186V, which means that the collector current of Q13 is about 9.8mA.

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In blue is the oscillator with CR1 as a varicap for frequency control.

Now, the frequency range of your circuit is too low, I would be tempted to try adjusting with R68, but make a mark on R61 to note the current state of the adjustment, because if it doesn't work, you can reset it to its original position.

Since the frequency is lower than expected, and if R68 doesn't change anything, then the capacitive load is too large, I would suspect the varicap CR1 as the first suspect.

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You can always experiment by disconnecting C81; the frequency should rise higher.

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Yves

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De?: [email protected] <[email protected]> De la part de Anders L??v via groups.io
贰苍惫辞测é?: 4 avril 2025 14:19
??: [email protected]
Objet?: Re: [HP-Agilent-Keysight-equipment] Intermittent REF UNLOCK error message on 8591A Spectrum Analyzer

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Thanky you for the valuable information Yves!


I have now checked a bit further and made sure the VTO_TUNE reached the A9 Third Converter assembly ok.
My VTO_TUNE voltage varies between -0.43 (10 MHz Ref disconnected) to -13.27 Volt (10 MHz Ref connected).

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My 300 MHz VCXO range is 299.872 MHz (10 MHz Ref disconnected) to 299.959 MHz (10 MHz Ref connected) - A total range of 88 kHz which is a bit smaller than yours 111 kHz.

This time I have meassured the frequency at the Cal Out to make the meassurement easier.

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I have desoldered and checked the R68 potentiometer and it was fine.

Do you have any further good ideas?

Best Regards
Anders
Re: 8594E Cal Signal not Found ?

 

Thanks Mark, ya I did all that but did just see this so I will try next.
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Instrument firmware expects the cal output signal to be 300 MHz ± 2 MHz.Sometimestheinstrument default data is not able to tune the cal signal within this range and a “cal signal not found” message may appear on screen. Perform a cal output bypass check by pressing Frequency,-37, Hz, Cal, Cal Freq. This will bypass the cal check and start by calibrating the sweep ramp.
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Andrew
Re: 8594E Cal Signal not Found ?

 

The workaround for the "Cal Signal Not Found" error is covered in the Assembly Level Repair manual.
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If you had to reload all the correction constants, I would start with the "Analyzer Initialization" section in that manual (namely: setting DEFAULT CONFIG) and go from there, if you haven't already done so.
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-mark
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On Fri, Apr 4, 2025 at 02:51 PM, KB2LMN wrote:

After replacing battery I entered the Time Base Correction, Frequency Response Correction & Step Attenuator Corrections.
Now when I go to perform Cal Freq or Cal Amptd I’m getting a Cal Signal Not Found.
I checked the CAL OUT and I’m seeing 300.000824MHz -20dBm on my Spectrum Analyzer.
Input using an HP E4432B Signal Generator set 300MHz -20dBm I’m seeing 300.8MHz at -28dBm.
As I change the Span I get different frequency’s showing?
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Andrew
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8594E Cal Signal not Found ?

 

After replacing battery I entered the Time Base Correction, Frequency Response Correction & Step Attenuator Corrections.
Now when I go to perform Cal Freq or Cal Amptd I’m getting a Cal Signal Not Found.
I checked the CAL OUT and I’m seeing 300.000824MHz -20dBm on my Spectrum Analyzer.
Input using an HP E4432B Signal Generator set 300MHz -20dBm I’m seeing 300.8MHz at -28dBm.
As I change the Span I get different frequency’s showing?
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Andrew
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Re: HP 8594E new issue

 

Great, glad the sync reset worked!
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It makes me wonder, however, if the CRT parameters were corrupt in SRAM, then what else might be corrupt? ?I would take a quick pass through the calibration constants to verify they are still ok. ?And it wouldn't hurt to do a FREQ/AMPLITUDE self-cal when you get a chance.
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Really 6.3V on the battery?? ?It should be around 3.3V for a new battery.
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-mark
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On Fri, Apr 4, 2025 at 01:26 PM, KB2LMN wrote:

Reset worked Config, 6, 6, 3.
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Thank you!!!!
Re: Intermittent REF UNLOCK error message on 8591A Spectrum Analyzer

 

Thanky you for the valuable information Yves!

I have now checked a bit further and made sure the VTO_TUNE reached the A9 Third Converter assembly ok.
My VTO_TUNE voltage varies between -0.43 (10 MHz Ref disconnected) to -13.27 Volt (10 MHz Ref connected).
?
My 300 MHz VCXO range is 299.872 MHz (10 MHz Ref disconnected) to 299.959 MHz (10 MHz Ref connected) - A total range of 88 kHz which is a bit smaller than yours 111 kHz.
This time I have meassured the frequency at the Cal Out to make the meassurement easier.
?
I have desoldered and checked the R68 potentiometer and it was fine.

Do you have any further good ideas?

Best Regards
Anders
Re: Manuals for an HP3456B DMM?

 

I picked up the meters today. They are model 3456A. Both work, but need some cleanup. The power switch on on unit sticks on and the front/rear terminal switch is dirty. A quick checkout shows both reading within a few mV of my 34401A. Now I need to port my GPIB tools to talk to them.
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Re: HP 8594E new issue

 

Reset worked Config, 6, 6, 3.
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Thank you!!!!
Re: HP 8594E new issue

 

6.3Vdc
Re: Intermittent REF UNLOCK error message on 8591A Spectrum Analyzer

 

开云体育

Hi,

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I tested this with my 8591A.

I used an external generator for the 10 MHz reference.

I measured the 300 MHz signal returning to the A15 COUNTER LOCK module.

This way, I tested the path from the 10 MHz IN to A15, and the return from A9 THIRD CONVERTER at 300 MHz.

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I measured the 300 MHz return at the spectrum, but kept the PLL closed loop using a T-connector.

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The maximum range of the VCXO was 299.976-300.087 MHz, or 300 MHz -24/+87 kHz, but this is doubled if you measure the 600 MHz output.

The RF amplitude of this signal was approximately -4.5 dBm upon arrival at the A15 COUNTER LOCK module.

The DC control voltage coming from the A15 COUNTER LOCK module (J4-40) to A9 was -0.253/-13.2 Volts, and -4.645V was the voltage for an accurate input 10 MHz reference.

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For adjustment, you can see from the wiring diagram that R68 presumably allows for range centering.

I haven't checked the manual yet, but I did check this potentiometer, as I've had several issues with defective potentiometers in this Spectrum series.

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Yves

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De?: [email protected] <[email protected]> De la part de Anders L??v via groups.io
贰苍惫辞测é?: 4 avril 2025 02:10
??: [email protected]
Objet?: Re: [HP-Agilent-Keysight-equipment] Intermittent REF UNLOCK error message on 8591A Spectrum Analyzer

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After further digging into my Ref Unlock error message on the HP8591A Spectrum Analyzer I have found the following.

The 600 MHz SAW oscillator on A9 Third Converter assembly seems to oscillate at only 599.744 MHz on its own (without 10 MHz reference connected).

With the 10 MHz reference connected, the frequency only comes up to 599.920 MHz - It does not reach 600 MHz.

The VTO_TUNE signal between the Counterclock assembly and the A9 Third Converter assembly is maxed so it can not tune the 600 MHz SAW oscillator any further.

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Can the 600 MHz SAW oscillator be tweaked in some way or is the next step to replace the A9 Third Converter assembly?
Re: HP 8594E new issue

 

Also, how is the voltage on your new battery?
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-mark
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Re: HP 8594E new issue

 

Odd that D13 would now be off.? We'll assume the 68230 and related circuitry is ok for the moment.
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Along the same lines as what Yves suggested, you could also try resetting the CRT to DEFAULT SYNC.? Flying blind, it would be:
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? CONFIG
? Softkey #6 (MORE)
? Softkey #6 (MORE)
? Softkey #3 (DEFAULT SYNC)
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You could also try setting DEFAULT CONFIG:
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? CONFIG
? Softkey #6 (MORE)
? Softkey #4 (DEFAULT CONFIG)
? Softkey #4 (DEFAULT CONFIG)? (second press needed to confirm)
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Another thought is to try resetting the contents of the SRAM completely by grounding the + side of the supercap through a 10 ohm resistor to ground and hold it there for about 10 seconds (obviously with the power off). ?You'll then have to go through the initialization procedure on page 204. ?I know you were trying to avoid doing that in the first place, but it seems the most likely explanation is that something got corrupted in the SRAM during the battery replacement procedure.
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-mark
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On Fri, Apr 4, 2025 at 10:37 AM, KB2LMN wrote:

Mark I took the boards back out and cleaned all the contacts good and seeded them in and out a few times now the lite D13 is off. I do still have the screen issue shown in the video. I also tried what Yves suggested with no luck.
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Andrew
Re: HP 8594E new issue

 

Mark I took the boards back out and cleaned all the contacts good and seeded them in and out a few times now the lite D13 is off. I do still have the screen issue shown in the video. I also tried what Yves suggested with no luck.
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Andrew
Re: RF Alignment Failure in Agilent CXA signal analyzer N9000A

 

Hi, Hardyhansendk.
Thank you for your response, As you mentioned about W9 cal signals, When I tested there I'm getting 50Mhz with -60dB not -25dB, it would be helpful if you share info regarding that. Once again thank you for your response.
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Regards,
San.
Re: Intermittent REF UNLOCK error message on 8591A Spectrum Analyzer

 

After further digging into my Ref Unlock error message on the HP8591A Spectrum Analyzer I have found the following.
The 600 MHz SAW oscillator on A9 Third Converter assembly seems to oscillate at only 599.744 MHz on its own (without 10 MHz reference connected).
With the 10 MHz reference connected, the frequency only comes up to 599.920 MHz - It does not reach 600 MHz.
The VTO_TUNE signal between the Counterclock assembly and the A9 Third Converter assembly is maxed so it can not tune the 600 MHz SAW oscillator any further.
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Can the 600 MHz SAW oscillator be tweaked in some way or is the next step to replace the A9 Third Converter assembly?
Re: HP 8594E new issue

 

Mark yes the display was normal.
Re: HP 8594E new issue

 

All LEDs should go off once boot is complete and the initial hardware check is finished. ?D13 being left on indicates there is a problem with the 68230 (U57) Parallel Interface/Timer. ?See Table 14-3 in the Assembly Repair manual for LED decoding.
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It doesn't necessarily mean that U57 is bad; it could be something that's being tested that is connected to U57.
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I assume you had a normal display before you replaced the battery? ?Is the SRAM card completely seated?
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-mark
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On Thu, Apr 3, 2025 at 07:58 PM, KB2LMN wrote:

Ok I replaced the battery this am and all went great, yes I did copy the info as the manual states.
my new issue is the display as you will see in this video. I thought maybe I missed a connection when I re-assembled so I took all apart and checked and nothing was disconnected or wrong.
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The Voltages look good according to the Power Supply indicator lights.
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D1 - D16 all lite when powered on and go off with the exception on D13 as I believe this is normal?
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Any suggestions would be appreciated.?
Re: HP 8594E new issue

 

开云体育

Hi,

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I think you may have lost the calibration constants, at least the ones related to the display.

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You'll have to do a blind test.

The soft buttons near the screen, the top one is #1 and the bottom one is #6.

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CAL

MORE (soft button #6)

Soft button #4 for vertical adjustment

Soft button #5 for horizontal adjustment

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Use the knob or the up and down arrows to see if you can synchronize the image.

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Yves
HP 8594E new issue

 

Ok I replaced the battery this am and all went great, yes I did copy the info as the manual states.
my new issue is the display as you will see in this video. I thought maybe I missed a connection when I re-assembled so I took all apart and checked and nothing was disconnected or wrong.
?
?
The Voltages look good according to the Power Supply indicator lights.
?
D1 - D16 all lite when powered on and go off with the exception on D13 as I believe this is normal?
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Any suggestions would be appreciated.?
Re: HP8920B Blowing Fuse

 

Hi Jeff. I feel your pain. And FYI, the power supply is a pain to work on. The PCB is held by a number of plastic stand-off type things that you have to squeeze closed and work the board out. But if you go this route, Q1 is a likely suspect.
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I have attached the schematic of the power supply, at least this is what I have seen in the 8920's I've worked on.
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Good luck!
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Mark
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Artesyn A9 PSU Schematic 710227-001rN.pdf
Artesyn A9 PSU Schematic 710227-001rN.pdf

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