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Re: Troubleshooting a 8591e with opt 130

 

Yves,?
?
I had a look at measuring the gain control lines to A12. I saw the control is coming from U107 and U111 on the analog interface and running over the mainboard to A12. It would be best to measure the control lines on A12 to include potential issues with the connectors and motherboard. Without any expander cards I figured it would be dificult to reach the U9 and U10 on the control board. How did you manage to measure those? I might be able to attach logic clips to the IC pins and place the board back in the cage.?
?
I tried to fill the table for as far as I could. To begin with my 8591E doesn't seem to have a 5MHz RBW.?
I wasn't sure what you meant with the db-REF-20dBm column, nor with the -2.5446 300kHz/-20.00dBm.
?
?
In the 30Hz RBW the Aux video was fluctuating quite a bit.?
Next, since correct off didn't change the level, I did a factory default cal. With that it's hard to have the frequency centered, so I did a freq cal only.
?
?
The limited gain resolution of the TinySA used to measure the AuxIF is causing some more fluctuation in the Delta, this can probably be disregarded. I noticed that for your analyzer the delta remains equal. For my analyzer there is a 2dB difference.?
Apart from that the Aux Video voltage seems close to that of your analyzer for the same Mkr levels.?

?
Marco
?
?
?
?
Help with 2.4mm connector gaging

 

I need help determining what is the problem with my 2.4mm female connector gage.
?
I have both male and female, the male works correctly, but the female gage cannot be zeroed properly.
?
Is there anyone with a properly working gage that would be willing to test mu gage to determine if the gage or the master is at fault - I'd pay shipping both ways if you are willing to help.
?
Symptome are as follows:
1) Gage seems to properly measure a number of 2.4mm connectors - I can attach the connector and center the gage at "zero"
2) when using the master, the gage goes off scale to the + (right) side of the scale and cannot be brought back to zero
3) I do not see any obvious problems with the master (damage, dirt, etc.)
?
Results seem to suggest problem is with the master, but I'm at a bit of a loss to understand exactly how it could be that far off.? Is the mastr adjustable in some way??
?
Anyway if someone with properly operating 2.4mm gages would be willing to do a comparison test with my gage, I'd really appreciate it.
?
Cheers!
?
Bruce
Re: VNA Resonance Methodology

 

Jinxie,
Assuming perfect L and C in your parallel resonant circuit in series with 50 ohms:
At high frequencies, it should look like 50 ohms (center of chart), since the C is a low impedance to ground.
At low frequencies it should look like 50 ohms, since the L is a low impedance to ground.
At the resonant frequency it should look like an open (right side of chart), due to the L and C admittances cancelling.
Above resonance it should look like a varying capacitor in series with 50 ohms.? (Trace follows along the 50 ohm circle of the Smith chart)
Below resonance it should look like a varying inductor in series with 50 ohms. ?(Trace follows along the 50 ohm circle of the Smith chart)
Is that more or less what you see?
--John Gord
?
On Sun, Nov 24, 2024 at 11:51 AM, Jinxie wrote:

Sorry - got that wrong! It should be in the center across the entire sweep except for a narrow range around resonance where the trace should move to the far right of the Chart. Correct?
Re: Troubleshooting a 8591e with opt 130

 

¿ªÔÆÌåÓý

Marco,

?

The gain and attenuator control lines are A1, A2, A3, A4 and A5 for the attenuators in the A12 module.

G1, G1 and G3 in the A12 module for the gains, and G4, G5 and G6 in the A14 LOG amplifier.

?

Between CORR ON and OFF, in my case, there is a 6 dB difference, and it is in A12 that there was the change for 6dB.

?

If the REF Level changes, then the attenuators and gains will vary in A12. For A14, nothing changes.

?

The behavior of your 8591E is very strange.

If the A12 module had only a 1dB attenuator enabled in CORR mode, then in CORR=OFF mode, there would be only a 1dB difference.

But this would mean that the level arriving at A12 would be low normally, but you have -5dBm, you should have a 10dB attenuator enabled, and this does not seem to be the case.

And in no corr mode, the noise increased by 10dB...weird.

?

?

Yves
Re: VNA Resonance Methodology

 

Sorry - got that wrong! It should be in the center across the entire sweep except for a narrow range around resonance where the trace should move to the far right of the Chart. Correct?
Re: Fan replacement in general Which type(s) to choose?

 

Hello Ulf.

For the 115V types found in instruments like the 3314A, I'm also using Papst all metal versions with similar pressure and flow performance than the original, just to be on the safe side. I can confirm that these Papst fans have an issue with vibration. But installing them with a vibration dampening, decoupling silicone mask takes away most of the vibrations, making them a viable choice.

Christian


Am 24. November 2024 15:10:01 MEZ schrieb "Ulf Kylenfall via groups.io" <ulf_r_k@...>:

Forum,
?
Part of instrument repair and refurbishing I am most often
faced with having to replace old worn out fans.
?
Recently, repairing an old 8663A Signal generator,
the old fan had to go. Being located next to the VCO's
was perhaps a good idea.
?
I happily ordered a new Papst Ball-bearing fan which unfortunately
was the "mother of all vibrations". This fan was all metal type.
Needless to say it went out right away.
?
So - What types of bearings in general do you recommend?
and also which brands has the best reputation?
?
Ulf
SM6GXV
?
?
VNA Resonance Methodology

 

Greetings, gentlemen,
?
Earlier today I was trying to establish the resonant frequency of a tank circuit I'd put together. A simple enough task, you might think - as indeed it should be! Now since I was using really old-style components: single layer air-core inductor with air-spaced variable cap I was expecting pretty good Q and a marked 'dip' with my GDO.? Fo in this case was intended to be 1.45Mhz. Anyway, I couldn't get a reliable, repeatable dip so thought I'd switch to using a VNA instead. So I put a 50 ohm resistor in series with the tank and hooked it up to the analyzer. Sanity check: the tank is a parallel arrangement so therefore a 'rejector circuit' (high impedance) at resonance. So testing for S11 (reflection) with the Smith Chart display selected, I was expecting to sweep from 1Mhz to 2Mhz and see a dot/short line on the far right of the chart for the vast majority of the sweep, whilst seeing that move to a dot to dead centre at 1.45Mhz. But that's not what I'm seeing. Have I missed something?
?
Cheers,
Jinxie
Re: Troubleshooting a 8591e with opt 130

 

Yves,?
?
Thanks for the elaboration, you clearly know a lot about these machines!
?
The probe I used was an old Agilent N2862A 10M // 15pF probe, so that's rather high capacitance compared to yours, that might cause some additional influence.
?
One thing caught my eye from your post and it's giving me an eerie feeling. My amplitude peaks don't change when I switch Correct on or off.?
See the two plots below, sorry the indicator line is slightly misaligned but left is Correct ON, right is correct OFF. The main difference is in the noise floor.
Somehow the machine doesn't see this as a correction? Perhaps that's also why there is no fault in the selfcal and conf check while being 15dB off.
?
All my previous measurements I just did a full reset to factory default cal because I already noticed that the difference wasn't there with just correction on and off.
Apparently your spectrum analyzer does properly switch correct on and off.?
?
I can do the same measurements this evening, filling that table to see if we get some more clarification.
?
Marco
Re: 6632B supply stuck in PROT mode, unable to reset.

 

On the flowchart in the service manual when PROT lights it should also show OV, OC, RI, or FS. Then follow the troubleshooting chart. This is also a current sink supply, so you should be able to connect a battery without issue. Except backwards I guess.


On Sun, Nov 24, 2024, 4:25 AM Froggie the Gremlin via <jonpaul=[email protected]> wrote:
Hi there;

Bad proactice to connect a battery to a linear PSU without consideration for reverse current and damage. We use series power R and diodes.

I do not have? 6632B but have many similar? HP? .

Most? have? reverse protection doides (series and shunt) on the outputs. Also some have extenal rear panel? overvoltage prot (OVP)? crowbars.

Check the schematic for your model and SN, one or more protection? diodes may be shorted.

Bon chance


Jon





Re: N8973A Firmware Update issue

 

Hello Olaf,
Glad to help, to the best of my knowledge ;-)
Br.
Antoine
Re: Fan replacement in general Which type(s) to choose?

 

I have had excellent results using NOCTUA fans (type NF Premium Quiet Fan). See noctua.at
Can be purchased locally in Scandinavia.

Allan
Re: Troubleshooting a 8591e with opt 130

 

¿ªÔÆÌåÓý

The RF signal goes through the 3 converters and then goes to the A11 filter module, then to A12 Amplitude control, A13 filter.

At this point we have the AUX IF signal available at the back of the instrument at 21.4MHz.

From this point, the signal can take two different paths: the one from A14 LOG-LIN amplifier/detector for the standard resBW from 5MHz to 1kHz, and finally the second path, option 130 which contains narrowband filters (300Hz,100Hz,30Hz...).

Option 130 has its own LOG-LIN amplifier/detector.

The output of A14 and option 130, is the AUX VIDEO signal available at the back of the instrument.

Depending on the selection of the resBW, a multiplexer will choose one or the other.

?

So, the question arises, since the signal for option 130 follows the same path to the input of A14 (AUX, IF) and option 130 does not have a level problem, then logically the problem would be with A14 LOG amplifier/detector.

This would be true, if no other conditions change from the previous circuits when switching between option 130 and normal mode with A14.

?

I checked all the data we took, and the data at TP5 gave us some similarities and some not.

But our probes did not have the same impact on TP5 (hot spot). I would say that TP5 may not be the best point of comparison.

?

The probe effect:

Your probe

mkr level with probe on tp5 mkr level no probe

Log -14.2 -4.3

Lin -21.6 -20.2

You get 9.9 dB with or without probe for LOG mode, and 1.4 for LIN mode.

?

In my case

mkr level with probe on tp5 mkr level no probe

Log -25.9 -20.0

Lin -23.1 -21.2

I get 5.9dB with or without probe for LOG mode, and 1.9dB for LIN mode.

The probe used TEK P6138 10MOhms 10pF.

?

------------------------------

I studied your comments about the two SELFCAL videos.

On my Spectrum, the video display limiter was enabled, that's why the limiting level is different. But in the following image, I have disabled it.

?

I take the example here of the 1MHz resBW, but the remarks apply to all filters between 5MHz and 1kHz. During the amplitude calibration, the filters are aligned to have the correct filter width.

We see that the signal is limited at the top of the screen, but this is not the real limit, by putting a marker we can find the limiting point. With this configuration for the 1MHz filter, in my case it is -6.57dBm. I used an external signal to find this limitation. When the 1MHz filter is aligned, the measured level is -11.63 dBm, so the filter is aligned 5dB before the compression point. The firmware searches for the peak, then the two points at -3dB. The filter is readjusted in width to have a value within the specifications, then switches to linear mode for the level adjusted to -20dBm.

With your 8591E, the level reaches -4.74dBm, it's high, but it seems that the filter is reaching an alignment.

Starting check 1.06MHz

tests#1 560kHz

tests#1 780kHz

tests#1 880kHz

tests#1 960kHz

tests#1 1.01MHz

goes to LIN mode for the level at -20dBm

So, the level at 21.4MHz would be stronger on your Spectrum, as well as the limiting point since you have -4.74dBm, without knowing where the real limiting level is.

?

So, as you pointed out, is this an imbalance between LIN and LOG MODE. You start from -4.74dBm to -20dBm, or 15.3dB. But on my Spectrum, I go from -11.63 to -20dBm or 8.4dB.

?

But there is no error message, and you are left with an error of 15dB after the SELFCAL, while in my case everything is correct with a level of -20dBm as expected.

?

?

?

?

?

?

Here are the measurements from the input to the AUX IF, and AUX VIDEO signal for all filters passing through A14 or option 130.

I made a gain calculation between AUX IF and the input which is actually -20dBm.

?

With AMP CORR ON, there is 24dB between the display and the measurement at AUX IF, 34dB for option 130.

?

If AMP CORR = OFF, I still have 24 dB, but 28dB for option 130.

?

This would mean that the correction applied is in the A12 stage, before the LOG amp.

Maybe the error comes from there, the correction would not be applied correctly?

Maybe the control signals should be measured on A12.

?

I will check all these controls and see the behavior between CORR ON and OFF

?

Yves
Re: Fan replacement in general Which type(s) to choose?

 

I've replaced a couple of fans in HP equipment, and I personally looked for units that would present a CFM value - meaning to me they have some consideration for the critical part of their performance - and that they're low noise (the reason I would typically replace them). Some fans made these days are barely audible?at full speed.?
Radu.?

On Sun, Nov 24, 2024 at 6:32?AM saipan59 (Pete) via <saipan1959=[email protected]> wrote:
Another thought:
Many "muffin style" fans can be speed-controlled with a PWM signal. So, consider adding a small board with a 555 chip so that you can adjust the speed for optimal airflow with minimum noise and vibration.
?
Pete
?
Re: Fan replacement in general Which type(s) to choose?

 

Another thought:
Many "muffin style" fans can be speed-controlled with a PWM signal. So, consider adding a small board with a 555 chip so that you can adjust the speed for optimal airflow with minimum noise and vibration.
?
Pete
?
Re: Fan replacement in general Which type(s) to choose?

 

Before retiring from HP, choosing a fan type was handled by the Mechanical folks (I wrote firmware to manage fan speeds and cooling).
However, I can say that Nidec was a brand that we used a lot in "enterprise" computer storage equipment.
?
Pete
?
Fan replacement in general Which type(s) to choose?

 

Forum,
?
Part of instrument repair and refurbishing I am most often
faced with having to replace old worn out fans.
?
Recently, repairing an old 8663A Signal generator,
the old fan had to go. Being located next to the VCO's
was perhaps a good idea.
?
I happily ordered a new Papst Ball-bearing fan which unfortunately
was the "mother of all vibrations". This fan was all metal type.
Needless to say it went out right away.
?
So - What types of bearings in general do you recommend?
and also which brands has the best reputation?
?
Ulf
SM6GXV
?
?
Re: Troubleshooting a 8591e with opt 130

 

Yves,
?
In the meantime did some additional checking. I figured the biggest difference seemed to be in the TP1 temperature voltage.
I did a simulation of the circuitry but both our tp1 voltages seem to be reasonable. The main influence on the voltage level is the IVT potentiometer, R88. This one is glued to R33 on my board with some grey gunk. So I can't check if the value is reasonable compared to the pot setting. I didn't see any glue on your board, wondering if that was done in the factory.
Does look somebody has been fiddling with the potmeters in the past:
?
After checking TP5 I figured the next interesting point might be J1 which has the output signal of the log amplifier board
The output ratio seems to be slightly off from TP5, being 17dB.?
?
During these measurements I found something which surprised me. To measure the signal I removed the cable from the Log amp to the Opt 130 and connected the TinySa to J1 of the Log amp, as expected the signal on the 8591E disappeared. When I reduced the RBW to below 1khz, the signal reappeared on the 8591e. Note, the jumper wasn't placed on the LogAmp.?
I was expecting the signal always to come from the logamp to opt130 but on futher check of the schematics it seems the AUX IF is used to feed the signal to the opt130. There is no schematic of the 130 in the CLIP sadly.
?
I also spent some time whipping up a python script together with ChatGPT to render the rs232 HPGL output, getting there, just some issues remaining with the select indicators under the labels in the right side menu. If there is any interest for this script in the group i'll gladly share it
?
Marco
?
Re: 6632B supply stuck in PROT mode, unable to reset.

 

Hi there;

Bad proactice to connect a battery to a linear PSU without consideration for reverse current and damage. We use series power R and diodes.

I do not have 6632B but have many similar HP .

Most have reverse protection doides (series and shunt) on the outputs. Also some have extenal rear panel overvoltage prot (OVP) crowbars.

Check the schematic for your model and SN, one or more protection diodes may be shorted.

Bon chance


Jon
Re: HP 6114A - looking for R8A, 15.82K 0.1% 1ppm resistor

 

OMG! I didn't know they actually had prices on their website!
$16'ish for a 0.5W, or $13'ish for a 0.3W custom resistor, .2ppm, 0.01%?
?
Incredible!??

Dave
Re: HP 6114A - looking for R8A, 15.82K 0.1% 1ppm resistor

 

Thanks everyone, and especially Radu for the info on TCC!? Definitely a resource for me to bookmark.
?
I did substitute the resistor using a 15K and 820 ohm resistor in series from my parts bin, sorting through the population to make up something as close to the original 15.82K as possible, at least at room temp.? The resistors I have on hand are just run of the mill 1/4W 5% carbon film, so really poor tempco.
?
Once installed everything works as expected, other than not being exactly the correct voltage as the substitution wasn't spot on.? Still it proved me to that there's nothing else wrong going on.
?
For now it's buttoned back up while I search out if I can find an exact'ish part at a good price, or decide I can live with a cheaper substitute.?
?
Dave
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