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Expanded Topics Messages
Date
Re: 34401A issue

 

I saw three and ordered two to have a spare.? Since I have three of this meter and now know about how they can fail I can just replace them as needed.

On 3/9/2025 3:39 PM, Razvan Popescu via groups.io wrote:
Hi Peter,

If I am not mistaken there are 2 Omron relays on the board. If one
failed maybe the other one will fail soon so if you make an order and
have the unit open it is better to replace both.

Regards,
Razvan

On 09/03/2025 20:17, Peter Gottlieb via groups.io wrote:
I have tracked this down to K104 and confirmed by bench test the relay
has a bad side and won't make continuity to the DC high range
attenuator.? With the relay removed I can jumper pins 9 to 13 and get a
voltage reading on the higher range which confirms the rest of the meter
works.
This is an Omron G6AK-274P-STLT-US-5VDC which is commonly available.? I
will get one on order from Mouser.
Peter
Re: PARTS IDENTIFICATION

 

Hi Francesco, just in case this information is still useful to you or anyone else...
These assemblies (mixer plus bracket and two resistors) are from a Marconi X17653 Low-Band Receiver unit, part of the Radar Homing and Warning Receiver (RHWR) system in a Panavia Tornado aircraft.? I bought one of these units from Ebay recently and have been investigating it - the mixer bias supplies are +15V and -15V (connected to the resistors, not directly to the terminals on the mixer).? Thank you for the information about their frequency-range, I might do some more experiments with them.
?
Best regards, Mike Haben
Re: 34401A issue

 

Hi Peter,

If I am not mistaken there are 2 Omron relays on the board. If one
failed maybe the other one will fail soon so if you make an order and
have the unit open it is better to replace both.

Regards,
Razvan

On 09/03/2025 20:17, Peter Gottlieb via groups.io wrote:
I have tracked this down to K104 and confirmed by bench test the relay
has a bad side and won't make continuity to the DC high range
attenuator.? With the relay removed I can jumper pins 9 to 13 and get a
voltage reading on the higher range which confirms the rest of the meter
works.
This is an Omron G6AK-274P-STLT-US-5VDC which is commonly available.? I
will get one on order from Mouser.
Peter
Re: 34401A issue

 

I have tracked this down to K104 and confirmed by bench test the relay has a bad side and won't make continuity to the DC high range attenuator.? With the relay removed I can jumper pins 9 to 13 and get a voltage reading on the higher range which confirms the rest of the meter works.
?
This is an Omron G6AK-274P-STLT-US-5VDC which is commonly available.? I will get one on order from Mouser.
?
Peter
Re: HP 5245L counting/gate problems

 

The 5300-series counters also have the advantage of portability if the battery pack “plug-on” is added.?

Jeremy?
N6WFO?



On Sun, Mar 9, 2025 at 7:11?AM Tom Smith via <n5ama=[email protected]> wrote:
Hi David,
Thanks so much for the reply! My “spare” 5245L counter started working so until I get the repair on the current non HP gear fixed so I won’t be tearing into the busted instrument until those repairs are made. I’ve never had the cover off the 5245 so don’t know what it looks like in there.
In the meantime I bought a 5300B on epay for a reasonable amount and it seems to be working. It’s a smaller counter but just as readable. It may be more difficult to repair because of the smaller size, but for the time being works.
?
Tom N5AMA
Re: HP 5245L counting/gate problems

 

Hi David,
Thanks so much for the reply! My “spare” 5245L counter started working so until I get the repair on the current non HP gear fixed so I won’t be tearing into the busted instrument until those repairs are made. I’ve never had the cover off the 5245 so don’t know what it looks like in there.
In the meantime I bought a 5300B on epay for a reasonable amount and it seems to be working. It’s a smaller counter but just as readable. It may be more difficult to repair because of the smaller size, but for the time being works.
?
Tom N5AMA
Re: hp8921a

 

Re: 3457A calibration data dump / restore

 

Hi Jared,
?
Thanks for your inputs. The 3457A doesn't use an NVRAM chip (as other HP instruments do), it uses a low-power CMOS static RAM with a permanent supply provided by a lithium battery. The problem is that the battery has a finite life, and its replacement is made difficult by the fact that it is soldered to the PCB and doesn't have a socket. After a few decades, the battery must be replaced while maintaining an uninterrupted supply to the SRAM.
?
Of course, performing this replacement without interrupting the SRAM supply is tricky and carries some risk of losing the calibration data in the SRAM. Getting some protection from this risk was the reason behind my question to this group. Apparently, dumping the precious calibration data from the SRAM to a PC file can be done, but I couldn't find any information on how to reload the data from the PC to the 3457's SRAM if the data is lost. I'm sure there must be a way of doing this via the HP-IB, since this is the way HP performed the full calibration in manufacturing. This would be via a set of special HP-IB commands, which are likely to be documented in the calibration software which HP made available at the time the 3457A was manufactured, but which I couldn't find.
?
There could be similar HP-IB commands for other DVMs, for example the 3478A or the 3458A. These commands would enable a successful reload of the calibration data from a PC file to the SRAM.
?
Thanks again,
?
Joel
?
?
Re: hp8921a

 

开云体育

Re:-? ".a error does show"

What is the exact error message?

A photo of the screen would be good.

(Cropped and processed to keep the file size sensible.? Saved in a format everyone can see.? .jpg for example.)

Regards.

Dave 'KBV.
Re: 3457A calibration data dump / restore

 

Apparently there are security countermeasures in place to prevent the cal data being written back in via GPIB (Understandable for this sort of equipment, can't have bad actors poking around ruining critical measurements...), so for now the only way to restore the cal data is to write to the NVRAM chip directly in a chip reader.
?
My skills are very much not in decompiling firmware, so I'm of no help, but if anyone out there were to figure out how to restore the cal data via GPIB, a lot of us would be quite happy...

I wonder if there are some secret commands, or if the replacement of an NVRAM by Keysight is always followed by a full calibration anyway, making the whole thing moot for them?
?
?
Jared
Re: 8656B HPIB connector

 

Hi Peter, thanks for the advice. I have completed the other repairs? and powered the unit up. amazingly frequency and amplitude appear to be pretty much spot on. Not bad for a unit that hadn't been powered on for close to 20 years.
?I have lost all the retaining screws for teh back panel, and assumed they were M3, but that seems a fraction small. Can someone tell me what size and thread they are so I can try and source some. Don't want the back falling off now I have the mains fixed.
?
Also are there any common issues with capacitors etc? Probably worth replacing any that need doing whilst it is partially dismantled
?
Wayne
VK2WDE
Re: hp8921a

 

smps included
12volt rail ?12V 3A 36W
?5 volt rail 5V 6A 30W
43 volt rail 24V 1A 25W???Quantity 2
+ and - 14volt rails 15V 2A 30W???Quantity 2
Re: HP 8643A and Capacitors

 

On March 8, 2025 11:52:56 AM "Roy J. Tellason, Sr. via groups.io" <roy@...> wrote:
On Friday 07 March 2025 04:32:38 pm Dave McGuire via groups.io wrote:
Ugh, the number of times that has happened to me. It's one of the
reasons I left corporate work years ago and vowed never to return. They
take a good design with carefully-chosen components and send it to "cost
engineering"...Reliable gold pins turn into cheap tinned ones causing
overheating connectors, nice low-ESR capacitors get turned into cheap
garbage causing switching regulators to not work, etc...then my design
work gets maligned as a result!

Suits.
I think of that as a swear word...
I typed it as such.

-Dave

--
Dave McGuire, AK4HZ
New Kensington, PA
Re: hp8921a

 

On Sat, Mar 8, 2025 at 06:12 AM, Robert G8RPI wrote:
Have you included the +40V supply in your set-up.
?
Robert.
?
yes all rails are included 43volt +12 and +5 and +14.4 and -14.3.it powers up diags screen all good but i am wondering the batt monitor and because no signal on it the system has turned the macine off .a error does show?
?
Re: HP 8643A and Capacitors

 

Rgr Dave.....funniest was when the purchasing department saved a few pennies on an NPN TO92 transistor when a salesman told them it was the same thing as a 2N3906. Yes, electrically, yes same TO92 package, but it had European a EBC pin arrangement.? They didn't consult Engineering. When a few hundred PCBs came in, with something like 1000 of those transistors............it didn't work.??? DUH.? Rework cost how many dollars???

On 3/8/2025 4:55 PM, Roy J. Tellason, Sr. via groups.io wrote:
On Friday 07 March 2025 04:32:38 pm Dave McGuire via groups.io wrote:
?Ugh, the number of times that has happened to me. ?It's one of the
reasons I left corporate work years ago and vowed never to return. ?They
take a good design with carefully-chosen components and send it to "cost
engineering"...Reliable gold pins turn into cheap tinned ones causing
overheating connectors, nice low-ESR capacitors get turned into cheap
garbage causing switching regulators to not work, etc...then my design
work gets maligned as a result!

? ?Suits.
I think of that as a swear word...
Re: HP 8643A and Capacitors

 

On Friday 07 March 2025 04:32:38 pm Dave McGuire via groups.io wrote:
?Ugh, the number of times that has happened to me. ?It's one of the
reasons I left corporate work years ago and vowed never to return. ?They
take a good design with carefully-chosen components and send it to "cost
engineering"...Reliable gold pins turn into cheap tinned ones causing
overheating connectors, nice low-ESR capacitors get turned into cheap
garbage causing switching regulators to not work, etc...then my design
work gets maligned as a result!

? ?Suits.
I think of that as a swear word...

--
Member of the toughest, meanest, deadliest, most unrelenting -- and
ablest -- form of life in this section of space, ?a critter that can
be killed but can't be tamed. ?--Robert A. Heinlein, "The Puppet Masters"
-
Information is more dangerous than cannon to a society ruled by lies. --James
M Dakin
Re: Looking for info on HP 10534C RF mixer component

 

Info on the?10534C can be found in the HPAK Microwave Accessory Catalog.

Don Bitters
Re: hp8921a

 

Have you included the +40V supply in your set-up.
?
Robert.
hp8921a

 

hi guys my hp8921a power? supply has failed and i have installed smps power supplies to power it .these are working ok however i have no reception or spectrum anyalser .the original power supply must put out a signal to the micro that shows it to be working because a error of i think? it was power supply fault which the detection line comes from the secvondary ac before the diode.any assistance would be great.
Re: I need a new/used lab computer

 

开云体育

Hi again.

Viable (PROVEN!) good backups are essential of course.? There are any number of choices how to do that.? Local, or "in the cloud".? Manually started, or done for you in the background.

Heck, encrypted archives in a DropBox folder are easy to do.? (Do NOT rely, on the built in encryption in the popular zip archive tools.? Use Aescrypt to get it done correctly.)?

Just do NOT loose the passwords you use!? There is no way to recover them if you do loose them.

"Locknote" is a good encrypted notepad, that can be used to store other passwords etc.? Windows only, though it runs under WINE if needed.? ? Again, do NOT loose that password!? You can keep it on a USB stick, as it is self contained, no "Install" needed.?? But again, keep a backup somewhere!

It is possible create a similar largely secure (at rest) facility under Linux, using aescrypt and a shell script.? What I've done works well, but it's robustness under attack has not been tested.

And again, do NOT loose the main password!

The important stuff, is what "you" create and need, as well as configuration and driver files etc.? The OS is less of a problem, as you (should) still have the original install media, yes?? (You did create such when you first commissioned the PC, didn't you?? Like it asked you to do.)

Whole disk backup (imaging) is also possible, but not so much as a daily basis, but at least the pain of what you have to reinstall/recreate is minimal, compared to a total loss.? (CloneZilla is good, it's a bootable USB or DVD, and you'll need an external drive to put the image on.)??

Remember too, as talked about before, GRC.com's "Spinrite" software can keep a hard drive (and SSD) happy, and give you warnings of future impending failure.

OK, not "Free", but what price insurance, and your time??

As Ed Breya says, also keep an eye on the main board, and PSU.? They suffer the usual component failures over time, much like other kit.?? But I can attest that replacing power rail decoupling caps on modern main boards is a right pain in the *** to do.? They are not designed at all for any sort of service/repair/rework.?? Of course, you'll do that in an ESD safe way too.

Likewise any critical (to you) unique interface I/O boards.

You do have backups of any needed driver install files, don't you?

Lastly, upgrading to a newer OS.? (Win11 from say Win7.)?? You may find some commercial third party software, will not install on the new OS, NI's GPIB drivers etc is one such.?? The chances are, the actual software to do the job will run, just that the installer baulks at the new OS saying a newer version of the NI software is needed.?? Then, you find that the newer version doesn’t support the GPIB card you have!?? Don't ask how many times I got hit by that in the past workplace.

73.

Dave 'KBV.
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