Hi Ed.

I can see the oscillation at the input with the input coax both
attached and disconnected. It does drop some 3-4dB in amplitude when
the input of the module is disconnected. I have not been able to see
anything on the input when connecting that to the spectrum analyzer.

Touching the case of Q6 increases the amplitude of the oscillation by
some 20dB, the other transistors give no or little change in the
amplitude.
I can't see any other signs of oscillation than the signal near 27MHz,
altough I suppose Q5 or Q6 could oscillate at UHF, and that the
dampening in the output amplifier attenuates it below the spectrum
analyzer noise floor. I did several sweeps to 7GHz, but was not able
to detect any oscillations.

All of the electrolytics used for decoupling are cheap axial
electrolytics. I suppose someone could have changed those out,
although the solder joints looks original, and there is no traces of
flux on the board. The ESR of all the capacitors at 100KHz is within
reasonable limits. Bypassing with 100nF SMD's did nothing to stop the
oscillations, neither did 10nF.

DC bias level makes sense as far as I can see, the base of Q5 is a bit
high, at 21.9V, but without voltages on the schematic, its hard to
determine if this is correct.

My 11729C has a serial no. near 100, suggesting that this is a early
unit. Another peculiar thing is that there is no 640MHz SMA out on the
back, only the 640MHz BNC input.
The low noise amplifier PCB is marked 11729-60009, and as far as I can
determine, the board and schematic in the 2509A manual match.

BR.
Thomas.

Den l?r. 25. aug. 2018 kl. 23:45 skrev Ed Breya via Groups.Io
<edbreya@...>:

Is the preamp circuit really that different between versions? I would think they'd be close either way. Can you see the oscillations on the output, without any other signals applied? If so, try unplugging the input cable at J1, eliminating any input signal and the cable capacitance, and see if it becomes (at least marginally) stable.

I haven't used or seen the insides of my 11729C in years, so don't recall the looks and accessibility of the modules. Can the preamp be opened up and set up for operation while open, and out in the open for access? If so, then you can use the old pencil trick and poke around the hot nodes to find the sensitive spots. 27 MHz seems rather low for one of these stages to oscillate at - you'd expect something at VHF or up. So, it would likely be due to the preamp's LF feedback loop instability, or in the power amp stage that is much slower. Q6 could maybe use a bead on its base too.

Another possibility is that there are actually two VHF oscillations going on, and the 27 MHz is just one of the mixing products that's in-band for the overall amplifier. If you have a spectrum analyzer handy, try looking at the output, but at way higher frequencies and sensitivities. If nothing shows at the output, try looking at the input, where you may have closer access to any VHF stuff going on in the preamp.

Before digging too deep, it would be good to do a quick check through the stages to be sure the DC bias levels make sense.

You are right to question the PS bypassing arrangement, and try adding some HF bypass caps. However, if these electrolytics are tantalum type (most likely), then they should have good performance even at RF, so the need for extra bypassing is greatly reduced. Worth checking though, just in case.

BTW the schematic I'm looking at says it's A6A1 low noise amplifier board assembly (11729-60009).

Good luck.
Ed

--
With Best regards, Thomas S. Knutsen.

Please avoid sending me Word or PowerPoint attachments.

EVERY BLINKING TIME YOU EDIT YOUR POST THE ENTIRE CORPUS OF THOSE
THAT GET THESE POSTS BY EMAIL GETS ANOTHER COPY OF YOUR DAMN PICTURES!

I have Fios, and 25Mbit/second download speed, and your 25 Mbytes of
pictures takes about a minute to download, what with all of the overhead
of the email encoding of your pictures.

So, I have now received your stupid pictures at least 4 times, maybe
6 times.

-Chuck Harris

RFI-EMI-GUY wrote:

Ok, this has to stop.

This group has always been a text only and no attachments group,
and here comes 20+ Mb of pictures that are of no interest to me,
anyway, but have to be downloaded before I can pass by the message
to delete it.

If attachments, and HTML stay selected on this group, I will be
unsubscribing.

-Chuck Harris

RFI-EMI-GUY wrote:

Will be using the KE5fx GPIB Toolkit for 1st attempts with the HP 70K MMS for Phase-Noise Measurements !
? ?Had not noticed that prior ... ?apologies !

? ? Has anyone installed the GPIB Toolkit ?& PN.exe ?on a Linux box ??





" ?The current version of PN supports the following spectrum analyzer models:

• Tektronix 490P/2750P series
• Tektronix 2782/2784
• HP 8566/8567/8568 series (both -A and -B models)
• HP 8560A/8560E/8590-series portables
• HP 70000 series
• HP 3585A/B
• HP 3588A/3589A
• HP 4195A
• HP 4396A/B
• Advantest R3131
• Advantest R3132, R3162, R3172, and R3182
• Advantest R3264, R3267, and R3273
• Advantest R3463, R3465, R3263, and R3272
• Advantest R3261, R3361, R3265, and R3271
• Advantest TR417x series
• Agilent E4400 ESA/PSA series
• Agilent E4406A VSA
• Rohde & Schwarz FSE series, FSIQ, FSP, FSQ, and FSU
• Anritsu MS8604A and MS8608A
• Anritsu MS2650/MS2660 series

PN is able to support the “classic” models like the HP 8566 because it runs on a GPIB-connected host PC ?"

This transistor is in the +248V regulator in my 141T display section. Did not find a cross reference in my data.
Any suggesstions for a suitable replacement?

Thanks Ernst

Hi Peter,

I quickly checked my 3325A, and it also has the brown PCB areas around the diodes CR1-CR4
Might make it difficult to find a good replacement from a parts unit.

My unit does not have the oven oscillator, so can't compare.

cheers,

Marc.

Hi,
You cannot write to any Flash card in a HP 892x radio test set. No "ATA" PCMCIA flash cards (inc CF adaptors) can be read by an 892x. Most of those you have should be readable in your 8920B once you have got the files on to them.
Getting the files on to them has a couple of issues:
1/ Some Flash cards need an external 12V supply and most laptops and PCMCIA adaptors don't provide this despite it being part of the specification.
2/ The card format is not DOS / FAT so you need to use specialst software to write to the card. They are sometimes called "linear" cards and act like RAM/ROM rather than a disk
I have sucessfully used Elan PCMCIA adaptors and their Memory Card Explorer software on a PC. Unfortunatly Elan have gone out of business and even before their products were expensive.
An EPROM programmer with a PCMCIA adaptor can also be used.

Robert G8RPI.

I hope this is not inappropriate for the group.


I have a working 16702A in good condition EXCEPT that the built in display does not work, I have used it with an external display for some time. It has no cards. I am located in the Bay Area.

N/

I have some others that I may be willing to sell if there is interest as well 16702A fully working with 1 logic analyzer card, 16500C also in very good condition with 1 logic analyzer card.

On 08/25/2018 06:01 PM, RFI-EMI-GUY wrote:

[Edited Message Follows]
[Reason: added PS]


I have this slew of PCMCIA FLASH memory cards and I need help in
determining which if any will work with my HP8920B. The manuals are not
very descriptive and I don't want to damage anything in trying. I have
some test programs in battery backed SRAM PCMCIA and would like them on
FLASH for long term . Help? Thanks Joe? PS If anything it would be
helpful to know which ones not to bother trying.

Just FYI, every time you "edit your post", the rest of us get another
copy of all of those pictures in our email.

-Dave

--
Dave McGuire, AK4HZ
New Kensington, PA

开云体育

I have a 3325A which recently stopped working.? I've traced the problem to a very high load from one particular PCB and will track down the (most likely) bad tantalum.

However, I noticed that the power supply PCB shows signs of overtemperature around the four large diodes.? The board is quite brown.? Even without the problem PCB connected, those diodes as well as the pass transistors on the heatsink run pretty hot.? It looks like repairs have been made in that area by someone else in the past.? The fan seems to be operating normally.? Has anyone else noticed this?

I'm thinking of finding a replacement power supply PCB or buying a parts unit hoping the power supply is in better shape.? Before I go to ebay, does anyone have a parts unit?

Also, the oven oscillator, while close to proper frequency, is showing quite a lot of short term drift, close to 0.5 PPM over the span of minutes, up and down.? While I don't need super precision usually, this is obviously wrong and should also be replaced.

I have this slew of PCMCIA FLASH memory cards and I need help in determining which if any will work with my HP8920B. The manuals are not very descriptive and I don't want to damage anything in trying. I have some test programs in battery backed SRAM PCMCIA and would like them on FLASH for long term . Help? Thanks Joe? PS If anything it would be helpful to know which ones not to bother trying.

Is the preamp circuit really that different between versions? I would think they'd be close either way. Can you see the oscillations on the output, without any other signals applied? If so, try unplugging the input cable at J1, eliminating any input signal and the cable capacitance, and see if it becomes (at least marginally) stable.

I haven't used or seen the insides of my 11729C in years, so don't recall the looks and accessibility of the modules. Can the preamp be opened up and set up for operation while open, and out in the open for access? If so, then you can use the old pencil trick and poke around the hot nodes to find the sensitive spots. 27 MHz seems rather low for one of these stages to oscillate at - you'd expect something at VHF or up. So, it would likely be due to the preamp's LF feedback loop instability, or in the power amp stage that is much slower. Q6 could maybe use a bead on its base too.

Another possibility is that there are actually two VHF oscillations going on, and the 27 MHz is just one of the mixing products that's in-band for the overall amplifier. If you have a spectrum analyzer handy, try looking at the output, but at way higher frequencies and sensitivities. If nothing shows at the output, try looking at the input, where you may have closer access to any VHF stuff going on in the preamp.

Before digging too deep, it would be good to do a quick check through the stages to be sure the DC bias levels make sense.

You are right to question the PS bypassing arrangement, and try adding some HF bypass caps. However, if these electrolytics are tantalum type (most likely), then they should have good performance even at RF, so the need for extra bypassing is greatly reduced. Worth checking though, just in case.

BTW the schematic I'm looking at says it's A6A1 low noise amplifier board assembly (11729-60009).

Good luck.
Ed

Does anyone have ?*any* ?HP 70K MMS (HP 70000 system ) ?software to deposit into an Open archive ?

? ?Anyone know of any HP 70K MMS era related HP Engineers, Service Techs, or MMS end-users that can be contacted, that might be able to help ?

Please let us know.

thank you !!

hi Chuck,

As a roadmap, how about ?~3 photos ?of the 8656 ?A10 board & C18, with the C18 markings & associated physical space (with a ruler) ?

thank you,
rick

Yes. I (and everyone else here) uses decibels every day, but isn't it
odd that we use 1/10th of a Bel as a "base unit" of sorts? We talk
about 0.1dB or 0.01dB all the time, but why not a centiBel or a milliBel?

The common use of 1/10th probably has its roots in telephony (as the
unit itself does) for some very real-world reason, but it still seems
odd that it took hold.

-Dave

--
Dave McGuire, AK4HZ
New Kensington, PA