|
Hello all,
?
This is my first post since I joined the list. I have two 8591E Spectrum Analysers, one of which has a completely dead power supply. The other was working, until I powered it up a few weeks ago, when it gave the ADC-2V error. Once again it has a PSU fault, this time the -15V had failed. Investigation revealed a short circuit to GND on the -15V Output from the PSU.
I took the unit apart and traced backwards. I? soon found that C263, a 22uF Tantalum was to blame.
?
Unfortunately this didn't fix the problem fully, there is still only -0.6 V on the output. Like many others I failed in finding much information about the circuits, so needed to investigate further.
?
I don't have an isolation transformer, so I can't safely work on the unit live so I decided to trace the circuits to understand how the supply works. I have completed the first pass trace of all three boards and understand enough now to know that the fault is either in the -15V output regulator, or the reference passed to it from the control board. Once I have completed the circuit trace I should be able to power up the boards independently to test the circuits.
?
I have checked the Output Regulator board and created an electronic schematic and component layout which are attached to this post. I am going to do the same with the other two boards.
?
Hopefully this will help get some of these PSUs repaired, as they seem to be the weakest part of an otherwise generally reliable design.
?
Chris
?
|
Not owning one of these instruments will not stop me from saying thank you in the name of the community. It certainly requires dedication and effort to make such a documentation and the fact you did it is much appreciated. It might help people with other instruments too as I'm sure similarities will be found in some.
?
When a SMPS breaks down it is often a reaction in series and several components fail.
As C263 was short it pulled a lot of current. Therefor anything in the path of that current might have failed. Typically this would be Q263 or the shunt R264, and less likely L251. Depending on the failure mode of Q263 the zener VR261 and Q262 would have failed too. Is the -18V UR still present?
?
I've had a power supply failing on another HP Japan designed device due to a hidden thermal fuse. That fuse was glued underneath a ceramic power resistor. I knew it was there because someone told me about it but it was not visible because some other components where obfuscating the view. It was only by flipping the board that I found 2 additional soldered leads under the power resistor.
?
A decent pair of gloves cannot replace the isolation transformer but it certainly helps taking the risk (and the fear) away. Careful not to connect a scope without differential probe or similar technique.
?
Curious of reading the next update
?
|
I'd like to echo the thank you, your generosity in sharing is much appreciated.
?
I've copied those into my test equipment files.
?
Dave
|
Many thanks from me, too!
Just weeks ago I had the same problem with a shorted tantalum on the -15V bus on my 8593E.
Luckily, my switching power supply did not get damaged.
Nevertheless, I'm eager to see how the switcher is designed, just in case...
?
Tom
|
On Sun, Jan 19, 2025 at 02:04 AM, SwAkE wrote:
I've had a power supply failing on another HP Japan designed device due to a hidden thermal fuse. That fuse was glued underneath a ceramic power resistor.
Reminds me of the dead 5 V, 200 A, computer power supply I once bought at a swap meet. I was pretty sure I could fix it and use it for something else. I even got the PS maker to send me a schematic for a similar product of theirs. That schematic showed a thermal fuse that I could not find.
?
Eventually, I realized the thermal fuse was threaded thru the hollow core of a Brown Devil power resistor. Pretty clever, but impossible to notice when scanning for possible victims.
?
That was the only problem with that PS, but I never found a another use for it, and it got left behind when I retired. Sadly, I think someone just tossed it.
?
--
Jim Adney
Madison, WI USA
|
Hi Chris
First there has already been a great deal of work carried out on the repair of HP8591 power supplies, try Google.
Second there are more than one versions of the power supply in use, possibly as many as six versions if you look at the service manual.
I need the power supply model to help you, for instance 5062-8229. HP also mixed and matched a number of different individual boards in these supplies, for instance the one I have has boards 08594-60025, 08594-60026 and 08594-60024 in it, but it looks like yours maybe different as you list 08594-20035 as the LV output board whereas in mine it is 08594-60025.
The secret with this series of power supplies is that the board interconnection pins always have the same function irrespective of the board type number.
I must warn you that the ONLY instrument that you can possibly use to fault find them is a hand held battery powered DMM as what you might think of as the supply common is actually about 160VDC above true ground.
Let me know just what your supply part number is and the part numbers of the boards so that I can help you.
G6HIG Dover UK
On Sunday 19 January 2025 at 09:11:57 GMT, Dave G8KHU via groups.io <david.fielding.uk@...> wrote:
I'd like to echo the thank you, your generosity in sharing is much appreciated. ? I've copied those into my test equipment files. ? Dave
|
Hi George, Points Noted! I was aware that the common rail floats on designs like this. I am trying to avoid doing any live testing, so far I have only powered it up as an assembled unit. I also have a cheap internal battery powered scope that I could use, as long as I set it up with the power off, I wouldn't want to handle it while floating at 160V
My main motivation for tracing the circuits is for my own use, but it should be of use to some people out there. I have searched on Google and found a fair bit of information, but I like to have schematics if possible. As I said I have two of these, they have consecutive serial numbers and the same power supplies, both of which need repair. The markings on the units and components suggest manufacture in late 1995 and supply in early 1996.
PSU A8 5062-8229 Switching Regulator PCB 08594-60034 Control Board????????????????? 08594-60026 Output Regulator???????????? 08594-20035
I'll make sure I include these identities on the documents I generate.
Regards,
Chris G4MWQ
Hi Chris
First there has already been a great deal of work carried out on the repair of HP8591 power supplies, try Google.
Second there are more than one versions of the power supply in use, possibly as many as six versions if you look at the service manual.
I need the power supply model to help you, for instance 5062-8229. HP also mixed and matched a number of different individual boards in these supplies, for instance the one I have has boards 08594-60025, 08594-60026 and 08594-60024 in it, but it looks like yours maybe different as you list 08594-20035 as the LV output board whereas in mine it is 08594-60025.
The secret with this series of power supplies is that the board interconnection pins always have the same function irrespective of the board type number.
I must warn you that the ONLY instrument that you can possibly use to fault find them is a hand held battery powered DMM as what you might think of as the supply common is actually about 160VDC above true ground.
Let me know just what your supply part number is and the part numbers of the boards so that I can help you.
G6HIG Dover UK
On Sunday 19 January 2025 at 09:11:57 GMT, Dave G8KHU via <= [email protected]> wrote:
I'd like to echo the thank you, your generosity in sharing is much appreciated. ? I've copied those into my test equipment files. ? Dave
|
Hi Chris
I fully understand your motivation plus I am very pleased that you are taking the time and trouble to reverse engineer the schematics. Please do not be offended if I say things that you are well aware off, but I have to keep in mind that other individuals, both now and in the future may well be reading this conversation and may not be aware of some of the potential pit falls and dangers. I do have a bench that is setup with a low leakage isolation transformer, however I now hardly ever use it as I can fix virtually all SMPSU’s with not more than a battery DMM, I find that the older I get the more I do with just a simple DMM
In concept as far as the high and low voltage PCB’s are concerned a very useful amount of information can be garnered from the HP schematic for the 08563-60064 supply which is readily available on the internet. The real problem comes with the 08594-60026 control board which HP have never released the schematics for, some years ago I did a partial hand drawn schematic for this board which I have since lost. However I do remember it well enough to repair these boards.
Apart from the inevitable capacitor failures on the output regulator boards I have found that the two most likely failures are of the +15V supply for the control board and the failure of CR306 on the control board.
The control board +15V supply is generated on the switching regulator PCB by a resistive dropper from the high voltage storage capacitors feeding a 14.7 or 15V Zener diode. This Zener, which is VR110 on my 08594-60024 board, goes short circuit with the result that there is no +15V supply to the control board.
If the +15v supply to the control board is present and the power supply still will not turn on I have found on multiple occasions that CR306 on the control board has gone defective (Leakey). It is an SMD device marked AO which translates to an SOT Schottky diode, Agilent type HSMS-2800. The only fix is to replace it.
I hope that this helps.
If all else fails I look forward to seeing your reverse engineered schematics as no doubt will others. It would be nice to learn the serial numbers of your two units which may indicate where they were made and when. I don’t know if you are aware of this but the first five characters of an HP serial number gives the approximate date of manufacture and where manufactured (at least the country).
All the best
G6HIG Dover UK
On Monday 20 January 2025 at 14:00:03 GMT, Chris Weir via groups.io <chris.a.weir@...> wrote:
Hi George, Points Noted! I was aware that the common rail floats on designs like this. I am trying to avoid doing any live testing, so far I have only powered it up as an assembled unit. I also have a cheap internal battery powered scope that I could use, as long as I set it up with the power off, I wouldn't want to handle it while floating at 160V
My main motivation for tracing the circuits is for my own use, but it should be of use to some people out there. I have searched on Google and found a fair bit of information, but I like to have schematics if possible. As I said I have two of these, they have consecutive serial numbers and the same power supplies, both of which need repair. The markings on the units and components suggest manufacture in late 1995 and supply in early 1996.
PSU A8 5062-8229 Switching Regulator PCB 08594-60034 Control Board????????????????? 08594-60026 Output Regulator???????????? 08594-20035
I'll make sure I include these identities on the documents I generate.
Regards,
Chris G4MWQ
Hi Chris
First there has already been a great deal of work carried out on the repair of HP8591 power supplies, try Google.
Second there are more than one versions of the power supply in use, possibly as many as six versions if you look at the service manual.
I need the power supply model to help you, for instance 5062-8229. HP also mixed and matched a number of different individual boards in these supplies, for instance the one I have has boards 08594-60025, 08594-60026 and 08594-60024 in it, but it looks like yours maybe different as you list 08594-20035 as the LV output board whereas in mine it is 08594-60025.
The secret with this series of power supplies is that the board interconnection pins always have the same function irrespective of the board type number.
I must warn you that the ONLY instrument that you can possibly use to fault find them is a hand held battery powered DMM as what you might think of as the supply common is actually about 160VDC above true ground.
Let me know just what your supply part number is and the part numbers of the boards so that I can help you.
G6HIG Dover UK
On Sunday 19 January 2025 at 09:11:57 GMT, Dave G8KHU via <= [email protected]> wrote:
I'd like to echo the thank you, your generosity in sharing is much appreciated. ? I've copied those into my test equipment files. ? Dave
|
Just a bit of information, HP part designations follow this rule: 08594-20035 would be a blank/unpopulated board, the populated 08594-20035 board would be 08594-60035. A refurbished (not new) 08594-60035 board would be 08594-69035 or -66035, at a lower price than a new/unused 08594-60035 board.
Don Bitters
|
Hello Chris I have some working power supplies if you need assistance
They are from Hp 8594E models If they Fit your need
best regards Peter
Hello all,
?
This is my first post since I joined the list. I have two 8591E Spectrum Analysers, one of which has a completely dead power supply. The other was working, until I powered it up a few weeks ago, when it gave the ADC-2V error. Once again it has a PSU fault,
this time the -15V had failed. Investigation revealed a short circuit to GND on the -15V Output from the PSU.
I took the unit apart and traced backwards. I? soon found that C263, a 22uF Tantalum was to blame.
?
Unfortunately this didn't fix the problem fully, there is still only -0.6 V on the output. Like many others I failed in finding much information about the circuits, so needed to investigate further.
?
I don't have an isolation transformer, so I can't safely work on the unit live so I decided to trace the circuits to understand how the supply works. I have completed the first pass trace of all three boards and understand enough now to know that the fault
is either in the -15V output regulator, or the reference passed to it from the control board. Once I have completed the circuit trace I should be able to power up the boards independently to test the circuits.
?
I have checked the Output Regulator board and created an electronic schematic and component layout which are attached to this post. I am going to do the same with the other two boards.
?
Hopefully this will help get some of these PSUs repaired, as they seem to be the weakest part of an otherwise generally reliable design.
?
Chris
?
|
No offence taken George, I fully appreciate the legacy nature of these boards and information posted. Thanks for your hints. I have done a complete trace of all three boards, I am currently "translating" and checking my hand drawn rats nest diagrams to post in a legible useable form. I am currently working on the main Switching Regulator. It takes time, as I am having to create quite a few symbols as I go, as well as understanding what is going on.
A big part of my motivation is understanding exactly how these work. I never worked on SMPS so my knowledge is limited.
In this first unit, the supply to the control board must be working, as it is only the -15V that is down. The other supply is completely dead, so I will look at those first when I get to it.
I'll post the serial number prefix later, I knew it indicated production modification state, but not where it was made.
Chris G4MWQ
Hello Chris I have some working power supplies if you need assistance
They are from Hp 8594E models If they Fit your need
best regards Peter
Hello all,
?
This is my first post since I joined the list. I have two 8591E Spectrum Analysers, one of which has a completely dead power supply. The other was working, until I powered it up a few weeks ago, when it gave the ADC-2V error. Once again it has a PSU fault,
this time the -15V had failed. Investigation revealed a short circuit to GND on the -15V Output from the PSU.
I took the unit apart and traced backwards. I? soon found that C263, a 22uF Tantalum was to blame.
?
Unfortunately this didn't fix the problem fully, there is still only -0.6 V on the output. Like many others I failed in finding much information about the circuits, so needed to investigate further.
?
I don't have an isolation transformer, so I can't safely work on the unit live so I decided to trace the circuits to understand how the supply works. I have completed the first pass trace of all three boards and understand enough now to know that the fault
is either in the -15V output regulator, or the reference passed to it from the control board. Once I have completed the circuit trace I should be able to power up the boards independently to test the circuits.
?
I have checked the Output Regulator board and created an electronic schematic and component layout which are attached to this post. I am going to do the same with the other two boards.
?
Hopefully this will help get some of these PSUs repaired, as they seem to be the weakest part of an otherwise generally reliable design.
?
Chris
?
|
The Serial number prefix of my 8591E? analysers is 3547U.
No offence taken George, I fully appreciate the legacy nature of these boards and information posted. Thanks for your hints. I have done a complete trace of all three boards, I am currently "translating" and checking my hand drawn rats nest diagrams to post in a legible useable form. I am currently working on the main Switching Regulator. It takes time, as I am having to create quite a few symbols as I go, as well as understanding what is going on.
A big part of my motivation is understanding exactly how these work. I never worked on SMPS so my knowledge is limited.
In this first unit, the supply to the control board must be working, as it is only the -15V that is down. The other supply is completely dead, so I will look at those first when I get to it.
I'll post the serial number prefix later, I knew it indicated production modification state, but not where it was made.
Chris G4MWQ
Hello Chris I have some working power supplies if you need assistance
They are from Hp 8594E models If they Fit your need
best regards Peter
Hello all,
?
This is my first post since I joined the list. I have two 8591E Spectrum Analysers, one of which has a completely dead power supply. The other was working, until I powered it up a few weeks ago, when it gave the ADC-2V error. Once again it has a PSU fault,
this time the -15V had failed. Investigation revealed a short circuit to GND on the -15V Output from the PSU.
I took the unit apart and traced backwards. I? soon found that C263, a 22uF Tantalum was to blame.
?
Unfortunately this didn't fix the problem fully, there is still only -0.6 V on the output. Like many others I failed in finding much information about the circuits, so needed to investigate further.
?
I don't have an isolation transformer, so I can't safely work on the unit live so I decided to trace the circuits to understand how the supply works. I have completed the first pass trace of all three boards and understand enough now to know that the fault
is either in the -15V output regulator, or the reference passed to it from the control board. Once I have completed the circuit trace I should be able to power up the boards independently to test the circuits.
?
I have checked the Output Regulator board and created an electronic schematic and component layout which are attached to this post. I am going to do the same with the other two boards.
?
Hopefully this will help get some of these PSUs repaired, as they seem to be the weakest part of an otherwise generally reliable design.
?
Chris
?
|
Chris -? Based on my understanding of HP serial numbers, your instrument was made in the US (the 'U'), and its engineering revision is from the 47th week of 1995 (first two digits added to 1960 give year of revision; second pair are week of the year). ?The actual instrument may have been made years later, but it would be no older than late 1995. -Pat
?
> ------ Original Message ------
> From: chris.a.weir@...
> To: [email protected]
> Sent: Tuesday, January 21st 2025, 01:44 PM
> Subject: Re: [HP-Agilent-Keysight-equipment] HP859x Power Supply Schematics
? The Serial number prefix of my 8591E? analysers is 3547U.
?
No offence taken George, I fully appreciate the legacy nature of these boards and information posted. Thanks for your hints. I have done a complete trace of all three boards, I am currently "translating" and checking my hand drawn rats nest diagrams to post in a legible useable form. I am currently working on the main Switching Regulator. It takes time, as I am having to create quite a few symbols as I go, as well as understanding what is going on.?
A big part of my motivation is understanding exactly how these work. I never worked on SMPS so my knowledge is limited.
In this first unit, the supply to the control board must be working, as it is only the -15V that is down. The other supply is completely dead, so I will look at those first when I get to it.?
I'll post the serial number prefix later, I knew it indicated production modification state, but not where it was made. Chris G4MWQ
?
Hello Chris I have some working power supplies if you need assistance They are from Hp 8594E models If they Fit your need best regards Peter ?
Hello all, ? This is my first post since I joined the list. I have two 8591E Spectrum Analysers, one of which has a completely dead power supply. The other was working, until I powered it up a few weeks ago, when it gave the ADC-2V error. Once again it has a PSU fault, this time the -15V had failed. Investigation revealed a short circuit to GND on the -15V Output from the PSU. I took the unit apart and traced backwards. I? soon found that C263, a 22uF Tantalum was to blame. ? Unfortunately this didn't fix the problem fully, there is still only -0.6 V on the output. Like many others I failed in finding much information about the circuits, so needed to investigate further. ? I don't have an isolation transformer, so I can't safely work on the unit live so I decided to trace the circuits to understand how the supply works. I have completed the first pass trace of all three boards and understand enough now to know that the fault is either in the -15V output regulator, or the reference passed to it from the control board. Once I have completed the circuit trace I should be able to power up the boards independently to test the circuits. ? I have checked the Output Regulator board and created an electronic schematic and component layout which are attached to this post. I am going to do the same with the other two boards. ? Hopefully this will help get some of these PSUs repaired, as they seem to be the weakest part of an otherwise generally reliable design. ? Chris ?
? ?
|
Hi
NO NO NO The U indicates that it was made in the UK, actually in Scotland. In my experience this was possibly the lowest quality facility that HP had.
G6HIG Dover UK On Tuesday 21 January 2025 at 19:23:18 GMT, Cubdriver via groups.io <pbmanning@...> wrote:
Chris -? Based on my understanding of HP serial numbers, your instrument was made in the US (the 'U'), and its engineering revision is from the 47th week of 1995 (first two digits added to 1960 give year of revision; second pair are week of the year). ?The actual instrument may have been made years later, but it would be no older than late 1995. -Pat
?
> ------ Original Message ------
> From: chris.a.weir@...
> To: [email protected]
> Sent: Tuesday, January 21st 2025, 01:44 PM
> Subject: Re: [HP-Agilent-Keysight-equipment] HP859x Power Supply Schematics
? The Serial number prefix of my 8591E? analysers is 3547U.
?
No offence taken George, I fully appreciate the legacy nature of these boards and information posted. Thanks for your hints. I have done a complete trace of all three boards, I am currently "translating" and checking my hand drawn rats nest diagrams to post in a legible useable form. I am currently working on the main Switching Regulator. It takes time, as I am having to create quite a few symbols as I go, as well as understanding what is going on.?
A big part of my motivation is understanding exactly how these work. I never worked on SMPS so my knowledge is limited.
In this first unit, the supply to the control board must be working, as it is only the -15V that is down. The other supply is completely dead, so I will look at those first when I get to it.?
I'll post the serial number prefix later, I knew it indicated production modification state, but not where it was made. Chris G4MWQ
?
Hello Chris I have some working power supplies if you need assistance They are from Hp 8594E models If they Fit your need best regards Peter ?
Hello all, ? This is my first post since I joined the list. I have two 8591E Spectrum Analysers, one of which has a completely dead power supply. The other was working, until I powered it up a few weeks ago, when it gave the ADC-2V error. Once again it has a PSU fault, this time the -15V had failed. Investigation revealed a short circuit to GND on the -15V Output from the PSU. I took the unit apart and traced backwards. I? soon found that C263, a 22uF Tantalum was to blame. ? Unfortunately this didn't fix the problem fully, there is still only -0.6 V on the output. Like many others I failed in finding much information about the circuits, so needed to investigate further. ? I don't have an isolation transformer, so I can't safely work on the unit live so I decided to trace the circuits to understand how the supply works. I have completed the first pass trace of all three boards and understand enough now to know that the fault is either in the -15V output regulator, or the reference passed to it from the control board. Once I have completed the circuit trace I should be able to power up the boards independently to test the circuits. ? I have checked the Output Regulator board and created an electronic schematic and component layout which are attached to this post. I am going to do the same with the other two boards. ? Hopefully this will help get some of these PSUs repaired, as they seem to be the weakest part of an otherwise generally reliable design. ? Chris ?
? ?
|
Hi Chris
I have already indicated where your instrument was made. As to the manufacturing date, HP used a batch manufactured process and the date indicated is the date that the revision was approved for manufacture so it is a good indication of the actual manufacturing year, but not always on low volume products.
You say that only the -15V supply is missing, this could well be a fault on the control board as the -15V reference voltage is generated on the control board.
I have attached a HP schematic which as you will see has an almost identical LV section.and HV section
All the best
G6HIG Dover UK
On Tuesday 21 January 2025 at 18:44:46 GMT, Chris Weir via groups.io <chris.a.weir@...> wrote:
The Serial number prefix of my 8591E? analysers is 3547U.
No offence taken George, I fully appreciate the legacy nature of these boards and information posted. Thanks for your hints. I have done a complete trace of all three boards, I am currently "translating" and checking my hand drawn rats nest diagrams to post in a legible useable form. I am currently working on the main Switching Regulator. It takes time, as I am having to create quite a few symbols as I go, as well as understanding what is going on.
A big part of my motivation is understanding exactly how these work. I never worked on SMPS so my knowledge is limited.
In this first unit, the supply to the control board must be working, as it is only the -15V that is down. The other supply is completely dead, so I will look at those first when I get to it.
I'll post the serial number prefix later, I knew it indicated production modification state, but not where it was made. Chris G4MWQ
Hello Chris I have some working power supplies if you need assistance They are from Hp 8594E models If they Fit your need best regards Peter
Hello all, ? This is my first post since I joined the list. I have two 8591E Spectrum Analysers, one of which has a completely dead power supply. The other was working, until I powered it up a few weeks ago, when it gave the ADC-2V error. Once again it has a PSU fault, this time the -15V had failed. Investigation revealed a short circuit to GND on the -15V Output from the PSU. I took the unit apart and traced backwards. I? soon found that C263, a 22uF Tantalum was to blame. ? Unfortunately this didn't fix the problem fully, there is still only -0.6 V on the output. Like many others I failed in finding much information about the circuits, so needed to investigate further. ? I don't have an isolation transformer, so I can't safely work on the unit live so I decided to trace the circuits to understand how the supply works. I have completed the first pass trace of all three boards and understand enough now to know that the fault is either in the -15V output regulator, or the reference passed to it from the control board. Once I have completed the circuit trace I should be able to power up the boards independently to test the circuits. ? I have checked the Output Regulator board and created an electronic schematic and component layout which are attached to this post. I am going to do the same with the other two boards. ? Hopefully this will help get some of these PSUs repaired, as they seem to be the weakest part of an otherwise generally reliable design. ? Chris ?
|
Ugh - Yeah, I'm an idiot! ?D'oh!! ?If it was US it would have been an 'A'. ?I knew that - it was a test - you passed! ? -Pat
?
> ------ Original Message ------
> From: G6HIG@...
> To: [email protected]
> Sent: Tuesday, January 21st 2025, 02:31 PM
> Subject: Re: [HP-Agilent-Keysight-equipment] HP859x Power Supply Schematics
? Hi
NO NO NO The U indicates that it was made in the UK, actually in Scotland. In my experience this was possibly the lowest quality facility that HP had.
G6HIG Dover UK On Tuesday 21 January 2025 at 19:23:18 GMT, Cubdriver via groups.io <pbmanning@...> wrote: ? ? Chris -? Based on my understanding of HP serial numbers, your instrument was made in the US (the 'U'), and its engineering revision is from the 47th week of 1995 (first two digits added to 1960 give year of revision; second pair are week of the year). ?The actual instrument may have been made years later, but it would be no older than late 1995. -Pat
? > ------ Original Message ------
> From: chris.a.weir@...
> To: [email protected]
> Sent: Tuesday, January 21st 2025, 01:44 PM
> Subject: Re: [HP-Agilent-Keysight-equipment] HP859x Power Supply Schematics
? The Serial number prefix of my 8591E? analysers is 3547U.
?
No offence taken George, I fully appreciate the legacy nature of these boards and information posted. Thanks for your hints. I have done a complete trace of all three boards, I am currently "translating" and checking my hand drawn rats nest diagrams to post in a legible useable form. I am currently working on the main Switching Regulator. It takes time, as I am having to create quite a few symbols as I go, as well as understanding what is going on.?
A big part of my motivation is understanding exactly how these work. I never worked on SMPS so my knowledge is limited.
In this first unit, the supply to the control board must be working, as it is only the -15V that is down. The other supply is completely dead, so I will look at those first when I get to it.?
I'll post the serial number prefix later, I knew it indicated production modification state, but not where it was made. Chris G4MWQ
?
Hello Chris I have some working power supplies if you need assistance They are from Hp 8594E models If they Fit your need best regards Peter ?
Hello all, ? This is my first post since I joined the list. I have two 8591E Spectrum Analysers, one of which has a completely dead power supply. The other was working, until I powered it up a few weeks ago, when it gave the ADC-2V error. Once again it has a PSU fault, this time the -15V had failed. Investigation revealed a short circuit to GND on the -15V Output from the PSU. I took the unit apart and traced backwards. I? soon found that C263, a 22uF Tantalum was to blame. ? Unfortunately this didn't fix the problem fully, there is still only -0.6 V on the output. Like many others I failed in finding much information about the circuits, so needed to investigate further. ? I don't have an isolation transformer, so I can't safely work on the unit live so I decided to trace the circuits to understand how the supply works. I have completed the first pass trace of all three boards and understand enough now to know that the fault is either in the -15V output regulator, or the reference passed to it from the control board. Once I have completed the circuit trace I should be able to power up the boards independently to test the circuits. ? I have checked the Output Regulator board and created an electronic schematic and component layout which are attached to this post. I am going to do the same with the other two boards. ? Hopefully this will help get some of these PSUs repaired, as they seem to be the weakest part of an otherwise generally reliable design. ? Chris ?
? ?
|
The Serial Number dating correlates well with the other information. All the component date codes I've seen have been 1995. There is also a label saying battery installed 25/1/96 on the back. (I have changed the battery). I got these analysers from my workplace, the company was reducing in size and both were considered surplus and BER and were scrapped. They both had damaged front end attenuators which I was able to repair- perhaps not to original specification, but they are good enough.
Thanks for the circuit diagram George. While not the exact schematic, many parts of it are identical so it is a great help. It has allowed me to identify some components that were difficult, and helped me understand the functions of some parts of the circuit. I haven't yet tried to further locate the fault, I don't have a permanent bench set up unfortunately due to lack of space. I don't expect it to be too hard to find once I get set up.
Chris G4MWQ
Ugh - Yeah, I'm an idiot!? D'oh!!? If it was US it would have been an 'A'.? I knew that - it was a test - you passed! ? -Pat
? > ------ Original Message ------
> From: G6HIG=[email protected]
> To: [email protected]
> Sent: Tuesday, January 21st 2025, 02:31 PM
> Subject: Re: [HP-Agilent-Keysight-equipment] HP859x Power Supply Schematics
? Hi
NO NO NO The U indicates that it was made in the UK, actually in Scotland. In my experience this was possibly the lowest quality facility that HP had.
G6HIG Dover UK On Tuesday 21 January 2025 at 19:23:18 GMT, Cubdriver via <pbmanning= [email protected]> wrote: ? ? Chris -? Based on my understanding of HP serial numbers, your instrument was made in the US (the 'U'), and its engineering revision is from the 47th week of 1995 (first two digits added to 1960 give year of revision; second pair are week of the year).? The actual instrument may have been made years later, but it would be no older than late 1995. -Pat
? > ------ Original Message ------
> From: chris.a.weir=[email protected]
> To: [email protected]
> Sent: Tuesday, January 21st 2025, 01:44 PM
> Subject: Re: [HP-Agilent-Keysight-equipment] HP859x Power Supply Schematics
? The Serial number prefix of my 8591E? analysers is 3547U.
?
No offence taken George, I fully appreciate the legacy nature of these boards and information posted. Thanks for your hints. I have done a complete trace of all three boards, I am currently "translating" and checking my hand drawn rats nest diagrams to post in a legible useable form. I am currently working on the main Switching Regulator. It takes time, as I am having to create quite a few symbols as I go, as well as understanding what is going on.?
A big part of my motivation is understanding exactly how these work. I never worked on SMPS so my knowledge is limited.
In this first unit, the supply to the control board must be working, as it is only the -15V that is down. The other supply is completely dead, so I will look at those first when I get to it.?
I'll post the serial number prefix later, I knew it indicated production modification state, but not where it was made. Chris G4MWQ
?
Hello Chris I have some working power supplies if you need assistance They are from Hp 8594E models If they Fit your need best regards Peter ?
Hello all, ? This is my first post since I joined the list. I have two 8591E Spectrum Analysers, one of which has a completely dead power supply. The other was working, until I powered it up a few weeks ago, when it gave the ADC-2V error. Once again it has a PSU fault, this time the -15V had failed. Investigation revealed a short circuit to GND on the -15V Output from the PSU. I took the unit apart and traced backwards. I? soon found that C263, a 22uF Tantalum was to blame. ? Unfortunately this didn't fix the problem fully, there is still only -0.6 V on the output. Like many others I failed in finding much information about the circuits, so needed to investigate further. ? I don't have an isolation transformer, so I can't safely work on the unit live so I decided to trace the circuits to understand how the supply works. I have completed the first pass trace of all three boards and understand enough now to know that the fault is either in the -15V output regulator, or the reference passed to it from the control board. Once I have completed the circuit trace I should be able to power up the boards independently to test the circuits. ? I have checked the Output Regulator board and created an electronic schematic and component layout which are attached to this post. I am going to do the same with the other two boards. ? Hopefully this will help get some of these PSUs repaired, as they seem to be the weakest part of an otherwise generally reliable design. ? Chris ?
? ?
|
An update on my 8591E PSUs. I had thought I still had a fault after replacing the short circuit capacitor. I tested the Output regulator Board in isolation, and found the +/-15V linear regulators are working correctly. When installe in the analyser the -15V was still at about -0.6V.
I swapped the PSU into my other 8591E, and everything worked, so I seem to have another fault somewhere else, overloading the -15V. I'm putting this asside for the moment and moving on to the second PSU which is also faulty.
Most of the time this PSU is completely dead, and the front panel indicator is off. Twice it has started up and run for maybe a minute, before all the PSU LEDs except -24V go out and then it starts up again, sometimes it stays up for a few seconds, sometimes it shuts down almost immediately. on both occasions, turning off and on led to the completely dead state again.
?
By substituting boards from the working PSU I have isolated the problem to the surface mount control board.
?
In the meantime I have nearly finished the documentation of the schematics of the whole PSU. I have the layouts to do for the Switching Regulator Board (in progress) and the Control Board.
?
One odd thing is that R102 has failed open circuit on both PSUs. One has visible charring.  C105 ?
It appears to be a snubber in series with C105.
I need to order some capacitors to replace the 100nF X2 and 2.2nF Y paper capacitors and also the 215R resistors.
As there are no obvious faults on the Control Board, I need to build a test jig to power up the various sections and hopefully locate the issue.
?
Chris G4MWQ
?
|
Further update. I've diagnosed the fault on the Control Board, Leaky CR206, as suggested by George. I couldn't find my HSMS-2800s, so have fitted a 5082-2800 until I get some. Now need to sort out the bandwidth cal failure.
Chris G4MWQ
An update on my 8591E PSUs. I had thought I still had a fault after replacing the short circuit capacitor. I tested the Output regulator Board in isolation, and found the +/-15V linear regulators are working correctly. When installe in the analyser the -15V was still at about -0.6V.
I swapped the PSU into my other 8591E, and everything worked, so I seem to have another fault somewhere else, overloading the -15V. I'm putting this asside for the moment and moving on to the second PSU which is also faulty.
Most of the time this PSU is completely dead, and the front panel indicator is off. Twice it has started up and run for maybe a minute, before all the PSU LEDs except -24V go out and then it starts up again, sometimes it stays up for a few seconds, sometimes it shuts down almost immediately. on both occasions, turning off and on led to the completely dead state again.
?
By substituting boards from the working PSU I have isolated the problem to the surface mount control board.
?
In the meantime I have nearly finished the documentation of the schematics of the whole PSU. I have the layouts to do for the Switching Regulator Board (in progress) and the Control Board.
?
One odd thing is that R102 has failed open circuit on both PSUs. One has visible charring.  C105 ?
It appears to be a snubber in series with C105.
I need to order some capacitors to replace the 100nF X2 and 2.2nF Y paper capacitors and also the 215R resistors.
As there are no obvious faults on the Control Board, I need to build a test jig to power up the various sections and hopefully locate the issue.
?
Chris G4MWQ
?
|
Anyone who downloaded my schematics of the Output Regulator should update them with those I have just uploaded to the files section, along with the schematics of the other two boards. I found a couple of errors, and I have updated some signal names to better reflect their function.
?
Chris
|
Cubdriver