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Re: HP3456A GPIB problem
Thanks for the help sorting out the address information and the HP document. I am driving the GPIB with an NI USB dongle. I have tried it directly connected to the meter and with a cable. Both configurations behave the same, so I believe that the connection is good. Also, the good meter works fine with the cable.
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The bus driver chips and the bus controller chip are out of production, so swapping them is going to be problematic. Swapping the board from the good meter to the bad one would at least narrow the problem down. I REALLY don't want to wind up with 2 non-functional meters though...
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Per Ozan's comment, the REN signal has not changed state in any of the traces I have observed on either the good or the bad meter. it is sitting at 0V. I looked at the bus side and the logic side of the driver and the two are consistent.
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Thanks again everybody!
BobH |
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Re: HP3456A GPIB problem
On Tue, Apr 15, 2025 at 05:22 PM, BobH wrote:
Working on writing a communications library to control my HP3456A DMMs. One of the meters that I have responds to instructions to read and write just fine. The other meter will read the correct value from the meter and responds to serial polls correctly, but will not accept commands like setting the mode or range. Looking at the GPIB bus with a logic analyzer, it accepts the address with sane looking handshaking, but the first byte of the command string never gets an NDAC response. The transaction then times out. The meter does not hang after this or stop updating the display and reading the keypad. The meters both pass the self test. I looked through the service manual and did not see any reference to the self test doing a checksum on the EPROMs. I am using the same code to talk to both meters. Initially, I was expecting a dead bus transceiver chip, but all of the handshaking signals operate correctly in other parts of the transactions. Now, I am thinking that it is either the GPIB controller chip (MC68488) or possibly an EPROM problem. Has anybody run into this or have any thoughts on this? Thanks, BobH===== Hi Bob,
If I understand it correctly faulty device returns values but does not allow you to program ranges etc, so its GPIB/HPIB is not completely dead. I see that you already tried the "talk only" DIP switch but perhaps it is dirty and not registering properly. If you measure with a DVM, does the DIP switch contact go high/low with switch position?
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Other interesting line is the REN line (remote enable). I don't know if it would cause the issue you are seeing but tracing its connectivity would eliminate one possibility.
Ozan
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Re: HP3456A GPIB problem
Ignore previous - No attachment - sorry User Interface to HPIB, so we had to do it all at "Level 1". This was a good learning?experience. To answer one of your questions "What are the first three bytes" these will be the address info with ATN set (Command Mode). The first two characters are "Unlisten" and? "Untalk" other wise?shown as "?U". The third byte will be the device being addressed (Listen or Talk address). If there are more than one Listeners then there would be more than 3 bytes in the Command Mode. After the end of the Command mode sequence, ATN would go false and Bus would be in "Data" mode. I have attached a Document "A Tutorial description of HPIB" which, I believe, describes the Operation?of the Bus very well, including timing. I hope you will find this useful.. I am not privy to earlier Emails in this chain, so I don't know your configuration. However, simplistically, the problem is with one of the following elements: 1 HPIB Controller, including?programming '2 Bad HPIB Cabling 3 The HP3456A Multimeter. While writing this I have just observed in other Email that you have a? "Working" meter.. That kinda takes us to end of story . You got a Bad HP 3456A. since it controls NDAC. I was going to suggest changing your HPIB Cable. There are lots of flaky HPIB Cables out there including ones with Crosstalk problems. I don't know the exact card config for a HP3456A' buf if that is what you got working. then I would want?to swap the HPIB Card from good one in to bad one and see if problem solved.. You can, of course, troublesohoot?at?component Level with which I cannot be of much help. Hope this is helpful Good Luck Bill Lauchlan On Wed, Apr 16, 2025 at 8:33?PM BobH via <wanderingmetalhead=[email protected]> wrote:
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Re: HP3456A GPIB problem
Hi BobH, for my sins, I have worked with HPIB since it started circa 1975 when I was based in HP Loveland,Colorado. In those days we did not have the High Level User Interface to HPIB, so we had to do it all at "Level 1". This was a good learning?experience. To answer one of your questions "What are the first three bytes" these will be the address info with ATN set (Command Mode). The first two characters are "Unlisten" and? "Untalk" other wise?shown as "?U". The third byte will be the device being addressed (Listen or Talk address). If there are more than one Listeners then there would be more than 3 bytes in the Command Mode. After the end of the Command mode sequence, ATN would go false and Bus would be in "Data" mode. I have attached a Document "A Tutorial description of HPIB" which, I believe, describes the Operation?of the Bus very well, including timing. I hope you will find this useful.. I am not privy to earlier Emails in this chain, so I don't know your configuration. However, simplistically, the problem is with one of the following elements: 1 HPIB Controller, including?programming '2 Bad HPIB Cabling 3 The HP3456A Multimeter. While writing this I have just observed in other Email that you have a? "Working" meter.. That kinda takes us to end of story . You got a Bad HP 3456A. since it controls NDAC. I was going to suggest changing your HPIB Cable. There are lots of flaky HPIB Cables out there including ones with Crosstalk problems. I don't know the exact card config for a HP3456A' buf if that is what you got working. then I would want?to swap the HPIB Card from good one in to bad one and see if problem solved.. You can, of course, troublesohoot?at?component Level with which I cannot be of much help. Hope this is helpful Good Luck Bill Lauchlan On Wed, Apr 16, 2025 at 4:10?PM Mark Litwack via <mlitwack=[email protected]> wrote:
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Re: HP3456A GPIB problem
On 2025-04-16 1:50 PM, BobH via groups.io wrote:
There are 3 bytes transferred at the beginning of the transaction, with the last of those 3 containing the target address. Do you know what the first 2 bytes are? The IEEE 1978 spec is not the most readable document...As a typical IEEE-488 Controller, my KISS-488 would start with UNL (Unlisten), UNT (Untalk), then a LAG (Listen Address Group, with the listerner's address in the 5 LSBs), and a TAG (Talk Address Group, similarly, with the talker's address in the 5 LSBs). If your instrument is set as a Talker only, it would not acknowledge the Listener address. Steve Hendrix |
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Re: HP3456A GPIB problem
On the failing meter, DAV and NRFD are behaving in a similar manner to the working meter.
ATN is asserted (close to 0V) while those three bytes are transferring. It is de-asserted in the problem area.
The three bytes are 0xBF 0xC0 0xCB? and the gpib address is 20 (base 10).
Data, DAV, and NRFD look about the same as the working meter, but the data is changing with no visible NDAC.
I think I need to speed the sampling up and take another look.
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Thanks,
BobH |
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Re: Rebuilding the OS on an E5071B
¿ªÔÆÌåÓýThanks,I guess first thing then is pulling the drive again and making sure things actually got written to where they should have.?I¡¯ll see if I can make some headway on the weekend:) -Daniel On Apr 16, 2025, at 09:12, Ed Marciniak via groups.io <ed@...> wrote:
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Re: HP42851A EEPROM Read Error
Thanks for your response Roy.
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No, the HP4285A is always responsive.
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Yes.
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The EEPROM failure is in the HP42851A Precision Q Adapter, not the HP4285A Precision LCR Meter.
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I joined this group because a kind soul has uploaded the service manuals for the 42851A here :)
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As best I can tell, the EEPROM chip in use in the 42851A is the NEC D28C64ACZ-20. It is the only non-74LS chip on the board. I assume it contained factory calibration data.? I checked the 5V rail inside the 42851A and it is reading 4.8V.
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It looks like the EEPROM may be available here: https://www.utsource.net/itm/p/1158581.html?srsltid=AfmBOoqZq_Mzo4eOg7K5GqlcazQzkq6wlIruzsF7ukr1EaxzX_icP7NS
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Re: HP853A+8559A spectrum analyzer.
Hey guys,
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I have found the manual for the 853A. The link provided by Frank is good. I got tricked because it's the user and then service manual back to back, I only read the first contents so I thought it was just user.
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I've checked the little board contacts, they were off indeed as it's missing a screw. Putting them in doesn't change anything thought, not sure what they do?
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Working on the 8559 switches and overall cleaning of everything, I tested the power supply rails. Turns out the 158V on the mainframe is actually 200V, and i'm missing the 100V on the plug-in which is 20V, however the manual there's a safety shutdown that limits the 100V to 20V when there's no plug-in but it's in. The LED is not lit up either. I'll check more of the manual tomorrow while at work to see if I can trace some of this.?
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Also the guy who gave it to me found some extra spares switches and boards for it, i'll go pick them up tomorrow.
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Thanks,
Arnaud. |
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Re: HP42851A EEPROM Read Error
On Wed, Apr 16, 2025 at 10:56 AM, <nkirkby@...> wrote:
I've never fixed an EEPROM failure before. Is anyone here familiar with this device's EEPROM contents?Is the instrument frozen after that? Can you get to the 'CATALOG" page?
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The eeprom stores the 'current' instrument setting
you might be able to do that.
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you might be able to use the memory card, if you have it.
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There was a service manual for it; but, I don't have it.
Dp you know... or can you find out... what eeprom that they used?
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sometimes you can substitute them.
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Re: 4342A Q-Meter Lubrication
I had an almost identical experience restoring my 4342A and certainly echo the comments about not using WD-40 for long term lubrication. I used clock oil for mine. The only other comment I have is about the annunciator lights. The little incandescent lamps in my unit were mostly burnt out or had corroded leads that fell off on being touched. While I was in there I replaced them all with warm white LEDs and there was plenty of room to fit the associated resistors.?
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Morris VK3DOC |
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Re: HP Agilent 8753ES VNA repair [Help]
¿ªÔÆÌåÓýHi ? Glad to hear you were able to repair your 8753ES¡Great VNA! ? Yves |
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Re: HP3456A GPIB problem
Besides NDAC, is DAV and NRFD behaving properly?? What is the value of ATN at the time the other two bytes are transferred?? And what are the values of those two bytes?
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If ATN is asserted, the bytes are interface control messages, and you can look up the meaning in the "Remote Message Coding" table.? I don't have a copy of the 1978 spec, but in the 2003 spec it is Table 44.
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Besides the hang, do you see any differences on the bus between the two meters leading up to the hang?
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You might find this document a little more digestible. although you still need the spec for the finer details:
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When debugging weird GPIB issues, it's usually worthwhile to monitor all the bus signals.
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-mark
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On Wed, Apr 16, 2025 at 01:50 PM, BobH wrote:
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Re: Tool to remove "fancy" BNC nut (0590-1251)
On Sun, Apr 13, 2025 at 08:08 AM, Steve Hendrix wrote:
A 14mm or 15mm socket, perhaps? I have also seen 'sockets' that slip over the BNC connector, and have slots that engage the locking posts on the BNC connector. (Those than engage, and hold on the female connector)
You are supposed to apply counter clockwise torque... to rotate the BNC... and not apply the torque to the panel nut (... like you would with a wrench, socket, or nut driver.)
Not so sure about that.
But... I have done it... and it does loosen the nut back enough to allow removing the nut more easily.
I would think... if the nut is really tightly fastened down, the BNC posts would, bend, or tear.
But, it is another way... to perhaps... loosen the nut. |
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Re: 4342A Q-Meter Lubrication
Nice pictures. I have one of these beasts too, so am always interested in info about the guts. Mine all works fine so I never needed to dig in except for pulling the cover to admire the electro-mechanical wonder.
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Before you get in too deep, I'd advise never to use WD-40 as a "permanent" lube in precision mechanisms. It's great for getting things loose and moving again, but it should be washed out afterward and replaced by a light (low viscosity) petroleum-based oil. AFAIK WD-40 uses a vegetable oil base, so it tends to oxidize (and polymerize) over a fairly short time, becoming a thick goo and seizing up what it fixed. It took maybe forty or fifty years for the original lube in the machine to go bad, while the WD-40 might take just a few years. I have proven this to myself a number of times over the years, most recently on some HP8620As where the control knob shafts tend to seize up. WD-40 did its thing just fine, but after two or three years, one of them seized up again, while a couple of others were still OK. The results can vary a lot, depending on the actual conditions of everything, but I'm convinced it will happen inevitably.
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On loose, heavy things from door hinges to tractors, I use it liberally, but I would not trust it for the HP4342A and such. Good luck in getting it all going.
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Ed |
MattSNE
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