Agilent/HP 54845A

[smgvbest]

I am expecting a HP 54845A off eBay tomorrow and will start checking it out soon after I receive it.
In the mean time I did some searching for information and firmware for the scope and found many of the old links in the firmware ugrade guide where broken.  I've done some searching and found them all at the following URL
ftp://ftp.keysight.com/pub/callpub3/ddt/scope/548xx/

If nothing else this has the 4.50 firmware and other files for the scope that others may find handy.

I'll post more when I can, here's the ebay add photo for it

[xrunner]

Very nice catch, I'd sure like to see follow up pics of your checkout. 

[Jwalling]

Nice find. The voice control software is there as well. I've always wanted to try that...

[smgvbest]

I'll get more pics  soon as I can.
I did receive it today and some of you may have seen it on ebay listed as having a network password that could not be removed.   short thing,  it is now removed.   So first off in anyone runs into that issue this is what I did to remove it.   

most of what you see via google talks about getting a command prompt and deleting the *.PWL files.   those files are for local login accounts not network login accounts,   you have to get into the control panel and disable it

so  first create a win98 boot disc,  mine unit has a 1.25" floppy not the LS120 drive so I downloaded bootdisk from keysight.  the only links do not work but I found them on the keysight sight

you'll want this file
ftp://ftp.keysight.com/pub/callpub3/ddt/scope/548xx/Upg_Rec/bootdisk/CD_boot.zip
unzip it and copy to your floppy and boot the scope
once at a dos prompt go to the C: drive and edit the msdos.ini file and enable the bootmenu=1  currently it is bootmenu=0  you can also change the time the menu stays on screen,  I changed mine to 30s via bootwait=30  (doing from memory so may not be the correct one there but should get you there.

once done remove the floppy and reboot
when the menu comes up, select safe mode
go into the control panel and remove all the accounts you dont' want and create one for yourself
also go into the network setup and disable network login

once done, exit and reboot
you'll get a logon screen enter the ID and password you set up
it will setup the new user and eventually you'll have a scope screen

I'll see if I can do a better guided description of that soon

i do see some problems with the FISO?? test for Ch1,  Ch2-4 test ok.
i think this is the one where cleaning the hybrid has helped so I will try that.   I'll try to get some pics of it also

[Tony_G]

I picked up one of those from a DoD auction. Did a few videos on it here:





I ended up using a parallel CD ROM drive that I got on EBay for $20 (including original packaging)

Great scope. If you're going to recovery it then start with the 3.5 (I think) Recovery image, do the 4.3 Upgrade so you get the Web Control and then move to 4.5.

TonyG

[smgvbest]

Hi Tony,

Yep,  I've watched both your videos and Shahriar's on the scope.   thank you both for posting.
I have found it is at 4.5 already so no need to upgrade it unless I can't recover the admin password.

I just spent time more or less optimizing it.   removing old files left behind (mostly screen captures) but I can not remove norton antivirus from it so far.  it wants the network admin password which I've yet to recover.

[Tony_G]

Glad you found them useful.

Just as an FYI on this - HP released the 4.5 update as a partial (I'm guessing people complained about there being a web server on the scope) - If the previous owner went straight to 4.5 from 3.5/3.72 then you won't have that functionality.

Now is it worth it? Well I don't really think so because it requires that you run Java on your machine and that is a steaming pile of security issues wrapped up in a release number.

Good luck with the scope - Look forward to hearing how it turns out.

TonyG

[Samogon]

I picked up one of those from a DoD auction. Did a few videos on it here:

Hi,
I have same calibration problem with channel vertical calibration, and i swapped hybrids.
But it did not go away. So i assume it is in attenuator. I has been driven away with other projects. So your thread resurrected my intent to repair it.

Thanks

[Tony_G]

It sounds like you have the same issue I did - The 54845A fails calibration on channels 1 & 3 (or 2 & 4) and the troubleshooting guide says to swap the hybrids - I tried that and it didn't work but cleaning the contacts did.

Hopefully that helps.

TonyG

[smgvbest]

I just swapped the CH1 & 3 hybrids as well as cleaned them all and same results.

ADC test after I swaped CH1&3,  same result

Code: [Select]

**Test Run** : A to D Converter Test  --- 11 MAR 2017 15:42:38
Self Test invoked cal executed.
Error in self test invoked cal - DLL cal.
Error in self test invoked cal - Clk 100Mhz cal.
Error in self test invoked cal - Data Acq cal.
Error in self test invoked cal - Fiso Redundancy cal.
 Test FAILED on channel 1
Fiso's stacked, Hybrid bit is stuck.
000000000000B 000000000000B 000000000000B 000000000000B
000000000000B 000000000000B 000000000000B 000000000000B
Test A to D Converter FAILED.
**Test Run** : A to D Converter Test  --- 11 MAR 2017 15:42:50
Self Test invoked cal executed.
Error in self test invoked cal - DLL cal.
Error in self test invoked cal - Clk 100Mhz cal.
Error in self test invoked cal - Data Acq cal.
Error in self test invoked cal - Fiso Redundancy cal.
Test A to D Converter PASSED.
**Test Run** : A to D Converter Test  --- 11 MAR 2017 15:42:59
Self Test invoked cal executed.
Error in self test invoked cal - DLL cal.
Error in self test invoked cal - Clk 100Mhz cal.
Error in self test invoked cal - Data Acq cal.
Error in self test invoked cal - Fiso Redundancy cal.
Test A to D Converter PASSED.
**Test Run** : A to D Converter Test  --- 11 MAR 2017 15:43:13
Self Test invoked cal executed.
Error in self test invoked cal - DLL cal.
Error in self test invoked cal - Clk 100Mhz cal.
Error in self test invoked cal - Data Acq cal.
Error in self test invoked cal - Fiso Redundancy cal.
Test A to D Converter PASSED.

FISO

Code: [Select]

**Test Run** : FISO Test  --- 11 MAR 2017 15:43:31
Self Test invoked cal executed.
Error in self test invoked cal - DLL cal.
Error in self test invoked cal - Clk 100Mhz cal.
Error in self test invoked cal - Data Acq cal.
Error in self test invoked cal - Fiso Redundancy cal.
FISO test failed on channel 2
FISO data bit error not correctable.
Test FISO FAILED.
So basically  CH1 ADC Fail and CH2 FISO fail I get in the self test.
swapping CH1&3 did not effect the ADC Failure. 
swapping CH2&4 did not effect the FISO Failure

tried to attach some photo's but they are too big,  will uploaded to my server and link to them instead

[Tony_G]

Just for clarity, you swapped the a\d hybrids but the errors stayed on the same channel?

TonyG

[smgvbest]

That is correct
I have also checked the power supply voltages and all are in spec
I did also have it run a CAL and had the following
CH   Vertical   Trigger
1      FAIL        PASS
2      FAIL        FAIL
3      PASS      PASS
4      PASS      PASS
the Common and Ext Trigger also pass

more pics

[Samogon]

Looks like my case. I bet it is attenuator.
I dis test with good known signal and one channel, which is failing calibration showed 5% Vpp less then others. So i was hoping to buy this module off ebay, but people want more than i paid for whole unit.
So i am going to open it and debug it.

[smgvbest]

Looks like my case. I bet it is attenuator.
I dis test with good known signal and one channel, which is failing calibration showed 5% Vpp less then others. So i was hoping to buy this module off ebay, but people want more than i paid for whole unit.
So i am going to open it and debug it.

I was wondering if it might be related to the attenuator.  I am thinking about swaping the attenuators to see what happens.
on the other side though the FISO message is about a stuck bit and I wouldn't think that would be attenuator related though I could be wrong

few MB pics





and Selftest

[Samogon]

Yes it may not be the case
Here is guy nicely described his successful fix.
http://www.dasarodesigns.com/projects/fixing-an-hp-agilent-54845a-infinium-oscilloscope/

[Samogon]

Here is quote from his site

Photo of the acquisition system components. Note that each attenuator / preamp assembly handles two of the four channels. This is so that two of the ADCs can be interleaved to achieve the highest 8Gs/s sampling rate.

Understanding this, it was pretty obvious what the next test should be: to see if the problem was due to the attenuator / preamp assemblies or the acquisition hybrids, I disconnected the semi-rigied coax connecting them and injected a small signal directly into each of the acquisition hybrids. Under this condition, I got a nice clean trace on each channel, proving that the acquisition hybrids are still good. Furthermore, when I re-ran the self-test with the attenuator assembles disconnected, the A to D converter and FISO tests passed! Measuring the voltage on the output from the attenuator / preamp assembles, I see about 1.7V DC, which is consistent with the symptoms. With some more careful examination I was able to identify the trigger signal out pin on the attenuator module and when I injected into this, the trace could be triggered!

[smgvbest]

Here is quote from his site

Photo of the acquisition system components. Note that each attenuator / preamp assembly handles two of the four channels. This is so that two of the ADCs can be interleaved to achieve the highest 8Gs/s sampling rate.

Understanding this, it was pretty obvious what the next test should be: to see if the problem was due to the attenuator / preamp assemblies or the acquisition hybrids, I disconnected the semi-rigied coax connecting them and injected a small signal directly into each of the acquisition hybrids. Under this condition, I got a nice clean trace on each channel, proving that the acquisition hybrids are still good. Furthermore, when I re-ran the self-test with the attenuator assembles disconnected, the A to D converter and FISO tests passed! Measuring the voltage on the output from the attenuator / preamp assembles, I see about 1.7V DC, which is consistent with the symptoms. With some more careful examination I was able to identify the trigger signal out pin on the attenuator module and when I injected into this, the trace could be triggered!

yep,  I read that and tried to disconnect my attenuators.  re-ran the self test and had same fail on A/D and FISO
I also should add with the exception of ch 2 (which fails both verticel and trigger cal) all channels seem to work well.  I put a 120Mhz 1vpp signal on each channel and was able to get a stable signal on all but ch2 which is stuck high like in the posting you quoted so that could be that problem.
Ch1 doesn't seem to have any issues in actually displaying a signal yet fails the verticle cal.   I also put in a 1.5Ghz signal from a still under repair fluke 6082 and aside from jitter (expected, problem with the fluke) channels 1,3 & 4 read it fine.

here's CH1&3 showing the 120Mhz 1Vpp signal


and slightly different view showing CH1&4


adding more pics,  from selftest

[Samogon]

Eah it is plausible thought that attenuator/amplifier is bad. Same as mine.

[smgvbest]

Eah it is plausible thought that attenuator/amplifier is bad. Same as mine.

I will definitely swap them and see if the issue moves to channels 2&4

Does anyone have the Service Utility on 3.5" floppy or a file I can download?

[smgvbest]

So I've swapped CH1&3 on the hybrids and Ch2&4 for the hybrids and the issue remained with CH1/CH2
And now I've swapped the attenuators and the problem stayed with the channel,  ie CH1/CH2.  it did not move with the attenuator.
So the issue it CH1/2 (ADC/FISO) and it's not the hybrids or the attenuators.  hummm

I did get more pics of the board under the attenuators and the back side which I will post also.

[Tony_G]

Silly question but did you try cleaning the sockets and making sure that all of the little pogo pins are moving freely?

TonyG

[smgvbest]

Silly question but did you try cleaning the sockets and making sure that all of the little pogo pins are moving freely?

TonyG

Not a silly question but yes I did clean them but I did not check that all the pins moved freely.
worth a try so I'll do that.

[Tony_G]

Good luck - Hope it's just a simple pin issue.

BTW When you say you swapped attenuators/front-ends, did you completely re-cable them so that 1 & 2 fed into A/D Hybrids 3 & 4? or just swap 1 & 2 around?

You might be able to get away with a test using some pig tail leads instead of hard line.

The reason I'm asking is that the problem may still be in the attenuator but just impacting both channels - When the manual said "swap test" what I took that to be (and I could easily be wrong) was to take a known good attenuator/hybrid and swap it into the channel to ensure that you have isolated the issue.

I'm sure you did that and I'm just showing a reading comprehension problem.

TonyG

[james_s]

Wow that's a serious oscillator in that thing. Looks like a very nicely designed machine.

Depending on what version of Windows it runs, there are tools that can reset or recover the password. It's been a while since I've used them but I've gotten into a few old PCs before that I didn't have the password for.

[smgvbest]

Good luck - Hope it's just a simple pin issue.

BTW When you say you swapped attenuators/front-ends, did you completely re-cable them so that 1 & 2 fed into A/D Hybrids 3 & 4? or just swap 1 & 2 around?

You might be able to get away with a test using some pig tail leads instead of hard line.

The reason I'm asking is that the problem may still be in the attenuator but just impacting both channels - When the manual said "swap test" what I took that to be (and I could easily be wrong) was to take a known good attenuator/hybrid and swap it into the channel to ensure that you have isolated the issue.

I'm sure you did that and I'm just showing a reading comprehension problem.

TonyG

I physically swapped the attenuators so the Ch1/2 moved to CH3/4 and visa-vera.   with Channels 3/4 passing all test and calibrating I am taking that as that attenuator is a good unit as are the hybrids.     when I swapped them CH1/2 and CH3/4 again calibrated and passed all tests on CH3/4
CH2 completely fails.  CH1 fails on the vertical only

I don't have enough of the shorter sma cables to do all 4 channels but could maybe do one at at a time

[nidlaX]

I've seen this unit and other similar units on eBay this month. One of them showed a failure to communicate with the acquisition board in addition to the network password error, so my alarm bells were ringing. Hope you sort this one out!

[Tony_G]

I don't have enough of the shorter sma cables to do all 4 channels but could maybe do one at at a time

To me it seems like this is the best way to go - Can you try to isolate the sockets first and then the hard lines to see if one of those might be at fault?

TonyG

[Samogon]

Well you font need patches, your swaping of attenuators showes clearly that issue doesn't move with attenuator.

[smgvbest]

I've seen this unit and other similar units on eBay this month. One of them showed a failure to communicate with the acquisition board in addition to the network password error, so my alarm bells were ringing. Hope you sort this one out!

this one showed the failure and I can reproduce it by booting to DOS then starting windows on the scope.   if it starts normally no error about the acquisition board.   password was easy,  just boot to dos, modify msdos.ini (yes, ini files) and then reboot into safe mode and remove the passwords

I do have 3 working channels on it.  1,3 and 4 work,   2 seems dead,  1 wont' cal but works fine.

[smgvbest]

Well you font need patches, your swaping of attenuators showes clearly that issue doesn't move with attenuator.

that's what I'm thinking but an willing to try other suggestions

[Samogon]

Even in this state it is very very useful device.
And i glad it is can autoset and trigger even without being calibrated.
And i hardly remember when i was using more than two channels at the time.
Especially taking into account price of 1.5GHz probes
But for personal satisfaction fully working unit more pleasant no doubt.

[Tony_G]

There are several things that can be swapped and a couple of things that can't.

Swappable ones are the A/D Hybrids, Attenuators and hard lines. The ones that can't are the Hybrid sockets and, from looking at the manual, the board to board connector under the attenuator. I've never taken mine off so I don't know if that is the case.

You should be able to resolve where it is by swapping all of that around. I'm starting to lean to issues with those connectors.

TonyG

[Jwalling]

Silly question but did you try cleaning the sockets and making sure that all of the little pogo pins are moving freely?

TonyG

+1 on that. I've seen a number of 54835A/45A scopes that had a pin or two that would compress, but not spring back.
If you're not sure, you can move the sockets around as well.
I actually made a jig that would allow me to take apart the socket without the pins spilling all over allowing me to replace the bad ones.

[smgvbest]

I have to admit my eyes since iLasik suck for close up inspection.  I'll reinspect the pins.   since I had the hybrids out again I swapped CH1/2 hybrids this time and again same results.

looking at the diagram the hybrid socket looks like it's a pogo pin socket correct? so it's not soldered to the board but held in place by the top/bottom plates (hence the need for  something to retain the pins) since CH2 is dead at this point I could try on that one and remove the socket.

I guess it could even be possible the pads on the PCB may be in need of cleaning also.

yeh,  I rarely use more the 2 CH's but it really is the point of it.  I want it repaired.


FWIW,  I backed up the original CAL file in C:\scope\cal  and can restore that cal file anytime which I have done.  it restores it to all channel cal'd but CH2 still remains none functional.   CH1 even though it won't cal reads input perfectly fine across all timebases and vertical ranges so even though it fails ADC it is working.

[smgvbest]

Especially taking into account price of 1.5GHz probes
But for personal satisfaction fully working unit more pleasant no doubt.

the 54845A comes with the 1161A probe which are 500Mhz probes giving a system bandwidth of 1.5Ghz and going for an average of 60-70 each on eBay.   i picked up two with a offer of 100 and got them.   I must have felt confident this scope was fixable since I usually don't pick up accessories if i'm not sure something is fixable. 

[smgvbest]

ok, I removed the hybrid from CH2 and found some jewelers magnifying glasses to take a closer look.  I'm pretty sure I see several pins that are compressed.   
can those pins be fixed or would they have to be replaced?
anyone know if i have to replace them what I look for or have a spare socket I can buy from you?

[Samogon]

That is promising

[james_s]

I would try gently poking at them and see if they will un-stick. Be very careful not to damage them though, and take the usual precautions against ESD. Taking apart the socket would be a last resort for me, I can visualize something going BOING and tiny pins bouncing all over the room.

[Tony_G]

As James suggested, try poking them with a non-conductive plastic spudger (or something similar) and giving them a good flush with IPA.

I used a Precision Foam Swab (#SWP-25) from Caig Labs (makers of Deoxit). I find the SWP to be great for cleaning pins and surfaces because of the foam tip.

TonyG

[smgvbest]

Here's a small update.
I tried cleaning them again and no change.   i used a non-conductive screwdriver to push on them and not much boing in them.
I re-read the service manual as it does talk about removing them.  i followed it very carefully and it does emphasize if you remove the 2 screws holding it to the board carefully you may not have to remove the acquisition board and I did not need to but did notice one thing.  one of the heat sink screws is stripped so it doesn't snug down one side of the hybrid as tightly as the other.   that might be the missing link here and part of the problem.

anyways, so gave it a try and I am happy to say the pins are held captive in the socket.  you can flip it and they do not come out.   Now, with it off the board i cleaned both the pins (both sides) and the PCB contacts.  there is some improvement in the pins but still not as much boing as others.

now the flip side of this is CH2 is showing signs of life.  it's not triggering but I do now see a signal on it and I can adjust the vertical scale as well as time base which is far better than it was.  it still fails the FISO test but passes all others.   there's signs of life here. 

since I haven't been able to find anyone with spare parts for this scope I am considering a parts unit to help.

[james_s]

That's certainly promising and suggests that there is/was indeed a problem with the contacts. There are a number of ways to repair the stripped hole, but you have to be careful as some of them can make things worse if you screw it up. You may be able to tap the hole for the next size up screw, maybe even use a self tapping screw. Another option is fill in the hole with metal epoxy and then drill and tap it. If there's nothing on the other side, you could drill it through and put a nut on the back. Yet another option is drill it out to press-fit an threaded insert, with a bit of CA or Loctite that can be a very strong repair. Which, if any of these is feasible depends on the tools you have access to and how you are at machining.

[Jwalling]

If you get to the point that you're sure it is a pin problem, and you can't fix it, you can open up the socket and replace the pins that need replacing. I would recommend you make a jig like mine.
Note that my jig states to put the side of the socket facing the chip down (toward the jig) for a very good reason. You'll never get it back together as the pins won't align with the plastic of the socket - I found out the hard way the first time I attempted this! 

I have a bunch of sockets harvested from scrapped 54810A series scopes (the 54542A series also used the same type of socket). If you need one, I could send it to you for the cost of postage. This will give you a source of pins to use in your socket.

[smgvbest]

I did do the same now to CH1 which is reporting the stuck bit on the ADC and in this case there was no change to CH1
I may pull it again and recheck it.   if nothing else the apprehension is gone in removing the socket.

[james_s]

Is this thing known to be a problematic design? I wouldn't have expected so many problems with sockets and connectors. You might try a bit of Deoxit D5 on the pins and pads, that stuff is almost like magic.

I was getting a stuck bit error on my recently acquired TDS784C and it turned out to be bad solder joints on one of the DMUX ASICs. It can be very challenging to track down issues like this, especially intermittent ones because there are *so many* connections between parts and it only takes one of them to throw a wrench in the works.

[smgvbest]

I know of 4 repairs on these
Signal path
Tony_G
dasaro
myslef

each of us has had some issue with the socket but others have solved problems in cleaning them.  mine seems to go further though or I"m not cleaning we'll enough.  I'll try deoxit it also.

[Tony_G]

Add Jay into that as well and it makes 5.

I think the pins are gold plated so it might make sense to use Deoxit Gold rather than the standard one.

In my case though I must have had only minimal issues because I just cleaned with IPA.

Also it looks like the connectors just screw down - You might want to take Jay up on his offer for one or two and see if they make a difference.

TonyG

[Jwalling]

Add Jay into that as well and it makes 5.

I think the pins are gold plated so it might make sense to use Deoxit Gold rather than the standard one.

In my case though I must have had only minimal issues because I just cleaned with IPA.

Also it looks like the connectors just screw down - You might want to take Jay up on his offer for one or two and see if they make a difference.

TonyG

The sockets are different, so the ones I have are only good for harvesting pins. There's a lot more contacts on the 54845A hybrid and the chip is larger as well.

[Tony_G]

My apologies - Didn't get that from your post - Clearly reading comprehension isn't my strong suit...

It might still be worth swapping the connectors on the 54845A if they haven't been categorically identified as the fault (though it sounds like it's pretty much a given now).

TonyG

[smgvbest]

I'm in the mind it's the sockets as well and in an effort to find ways to spend a bonus check I picked up a second 54845A which should be here tomorrow.   I'll have donner parts then to swap.

i suspect the first issue on the second one is power supply related so I'll start from there.   just wish they wouldn't strip the LS-120's out of these things.
it's also a VIN25 with serial in the 3838 range.

I'll probably re-list the one 54845 or part it out after I've checked all the Hybrids and Attenuates and such.  If nothing else if I list the whole thing I'll include what I know to be wrong with it

edit:
I did reclean CH2 socket with and no improvement on CH2.  Still same Fiso error

[Tony_G]

Ok, I can't wait to get the next update...

How'd it go with the donor sockets?

TonyG

[smgvbest]

so, got the donor unit and it has a bad power supply as I expected.  So first checked out its acquisition board and the only channel that passes self test was CH2.  So what I've done and pull the attenuator from the donor first and tried it.   No change on my CH2 also no change to CH1.
the CH3/4 attenuator SMB connector was busted on the donor unit so that attenuator is no good.

I have some things to do today but tonight or tomorrow I'll pull the entire CH2 hybrid and socket off the donor and first try the socket then if needed try the hybrid.

one thing I did notice after using the flir one is it looks like the CH2 DAC is running hotter than the rest but i don't think excessively.  datasheet says -40c to 80c and it's well within that range at ~50c.

after I replace the socket and swap hybrids I may set CH3 and CH2 up with same signal in and settings and compare the DAC pins. 
I'm reaching the point I think there are some other failures on the board hopefully with jelly bean parts

[Samogon]

According to your description, you bought it from express_auctions.
If so, they sell cannibalized units or after failed attempts to repair.

[james_s]

I've noticed they seem to sell basket case equipment with inflated shipping prices, at least 3x what it actually costs to ship. Their auctions pollute my searches with junk, at least the distinctive red backdrop helps me filter them out. Prices would not be too unreasonable for truly untested stuff but most of it looks like junk that has already been stripped of any really good parts.

[smgvbest]

So I don't leave you hanging,  I hurt my back so might be a few days before I get back to working on the scope.

[Tony_G]

Sorry to hear that - Hope you get better soon - I'm sure lugging these scopes around didn't help.

TonyG

[smgvbest]

So I transplaneted the full socket from the working channel 2 on the donor unit to the much better off unit CH2 and got some result   FISO Fail.
so I tried moving the hybrid from the donor over and CH2 got all kinds of errors.  FISO, ADC, GAIN to start.   put the orignal back in a back to only FISO fail.   the donor hybrid in all i got was a flat line.   so no go on that,   but what is it really telling me I wonder?

[Tony_G]

So the donor hybrid passed self test in the donor machine but generated a mass of errors in the primary machine?

[smgvbest]

correct, even verified the waveform i put in to test on the donor was correct 100Mhz @ 1Vpp read as 100.05Mhz @1.027Vpp.

[Tony_G]

Any updates?

[smgvbest]

Been tied up with other things but so far cleaning/replacing sockets hasn't revived CH2.  it did change and instead of being totally unresponsive it's does display something though no signal at all and setting the level on this one channel doesn't work either.

CH1 displays a good signal and seems to respond well but will not calibrate. 

So no now change.
looks like it's down to board level troubleshooting now and without schematics.   wooohoooo

I'll update as I can,

[Samogon]

I have same model and it is in the repair project too, so if you need to compare measurements i would try to help.

[smgvbest]

certainly appreciate the offer and likewise. I can do the same.
been taking a break and working on a R&S SMIQ03 with a 111 ALC error. 

[Tony_G]

Was replying to another 548xx thread and just wondered what happened with the repairs (yours and Samogon's)

TonyG

[Samogon]

Mine is still sitting collecting dust, i am doing so many projects and was carried away. Time is what we miss most.

[smgvbest]

Was replying to another 548xx thread and just wondered what happened with the repairs (yours and Samogon's)

TonyG

Taking a break while I work on a SMIQ06B (almost fixed) and a Standford Research PS350 (fixed)
I do think I have a board level issue here not a attenuator or Hybrid issue.  Mainly due to the fact the issue doesn't move with either and with tongue at right angle, wind blowing just rights.  bird chirping correct song I occasionally get a signal on CH2. it won't lock and is really picky but there is some life there.

would love a schematic for this thing but not holding my breath. 
I'm thinking my next step is to put same signal in on CH1 and Ch2 then start probing the board looking at those signals

[Tony_G]

Sorry to hear that - In the other thread though I did learn something new:

you can launch scope.exe using the service command  " scope.exe /service" that gives extra options in the self test menu where you can set attenuator click and othe roptions

Might be worth giving that a go if you haven't already.

TonyG

[Dexter2]

I also have the 54845A for some years now it works fine but would not pass the Trigger calibration.

I suspect the AUX out section as all chips in this part of the PCB have been replaced before i bought the unit. I would be eternally grateful if somebody could please check the rise time and amplitude of the AUX out signal set to “probe comp” and wired directly to a channel with a short BNC. I have about 560ps rise time and have tried quite some cables as I though my cable hat to much capacitance. There is an old video on YouTube from Roger Stenbock that does a demo of a unit and has 350ps.

It would be much help to me to even know where to start. I can also do some compare measurements if one of you needs some info.

Below an image of my AUX out section with replaced chips i have fited. If some of you has a photo of where the original chips can be seen I would also much appreciate it.

[Tony_G]

If you don't get a response before I get back from vacation then reply here again on the first week of Aug and I'll do that for you.

TonyG

[Dexter2]

Thanks Tony

If you don't get a response before I get back from vacation then reply here again on the first week of Aug and I'll do that for you.

TonyG

[Jwalling]

Below an image of my AUX out section with replaced chips i have fited. If some of you has a photo of where the original chips can be seen I would also much appreciate it.

Would a close-up picture of that area be of any use? That I could do.

[Dexter2]

Below an image of my AUX out section with replaced chips i have fited. If some of you has a photo of where the original chips can be seen I would also much appreciate it.

Would a close-up picture of that area be of any use? That I could do.

Hi,
Yes, a detailed close-up would help. I could then see what the original chips are as mine ware replaced, and I cannot be certain that they are the correct ones (grade etc...). Measuring the AUX out rise time is also quite simple if your scope is working. You just connect AUX out to one channel set to 50ohm via a short BNC and measure the rise time as you would on any signal with build in quick measurement function for Rise-Time.

[Jwalling]

These good enough?

Not a working scope. This is just an ACQ board I bought for $50 or so a few years ago, which was complete with A/D converters and attenuators. I've since been using it as a parts donor. Such a deal!

[Dexter2]

Thanks Jwalling,

I double checked and the HEL58 and HA5002 and also other chips in the MUX section and they are correct ones. They match up with your PCB, HA5002 is even better temperature grade on my board than the original. I hoped that the one that replaced them before me made an error. It seems it will be harder to track down the problem. It will be interesting to see what rise time Tony_G or someone else can measure if its the same ~560ps as with my AUXOUT or ~350ps what would be also more logical test signal for a 1.5Ghz scope.

[Dexter2]

These good enough?

Not a working scope. This is just an ACQ board I bought for $50 or so a few years ago, which was complete with A/D converters and attenuators. I've since been using it as a parts donor. Such a deal!

One question, would you sell the donor PCB what is left of it, if it not defective on its own? Or at least the board without the A/D converters and attenuators? As all my 4 channels behave completely the same, and generally perform ok, next to about 100-200ps trigger delay I’m most certain that my attenuators and A/Ds are OK.

[Jwalling]

Hi,

I've no idea of the working status of the board, but I'm not interested in selling it, sorry.

[Tony_G]

I suspect the AUX out section as all chips in this part of the PCB have been replaced before i bought the unit. I would be eternally grateful if somebody could please check the rise time and amplitude of the AUX out signal set to “probe comp” and wired directly to a channel with a short BNC. I have about 560ps rise time and have tried quite some cables as I though my cable hat to much capacitance. There is an old video on YouTube from Roger Stenbock that does a demo of a unit and has 350ps.

It would be much help to me to even know where to start. I can also do some compare measurements if one of you needs some info.

Here is mine:



Based on my experience doing this I suspect that you don't have 50 ohms turned on:



TonyG

[Tony_G]

Not sure what the cross posting/dupe etiquette is but I wanted to make sure you didn't miss the other thread

Just saw this come up on an auction site and thought it might help, if the price is right of course:

http://www.go-dove.com/en/auction/view?id=12334874

No relationship with the site or seller, except that I bought pieces through the auction site before.

Apologies in advance if this isn't allowed.

[Dexter2]

Many thanks Tony_G for all information,

I was to quick and done my first measurement wrong with input set to 1Meg as you mentioned, but also realized my error in the meantime. Setting it to 50ohm I get also a rise time around 300ps and a signal of about 350mVpp what is expected. So, this is good but still my Trigger calibration does not pass  I have tried to do the Trigger system performance tests from the service manual with a signal generator (100,500,1000Mhz) and all pass. So, this is all strange. If have also measured the trigger delay of my scope AUX out set to Trigger out and it measures 25ns, can you maybe check this also?

I even recorded the whole calibration procedure. Put a low load 1.5Ghz active probe to look what goes on during calibration. I was quite surprised that quite some different waveforms come out when the scope performs the calibration. Other scope was set to 500mV/4ms per division, trigger set to -140mV and sensitive to both edges, persistence off. What is maybe strange that to the end of calibration nothing happens it’s all quiet for quite some minutes...

Video of CH2 calibration (CH1 is longer but as both fail i did onlly the video of CH2)
https://drive.google.com/open?id=0B-jLzsxL7QoAanpFQUhrWUV3ZVE

[Tony_G]

Many thanks Tony_G for all information,

No worries - Happy to help out here.

If have also measured the trigger delay of my scope AUX out set to Trigger out and it measures 25ns, can you maybe check this also?

It's early morning for me and I'm still dealing with jet lag so I'm not understanding what you're asking here - Could you expand?

Thanks,

TonyG

[Dexter2]

If have also measured the trigger delay of my scope AUX out set to Trigger out and it measures 25ns, can you maybe check this also?

It's early morning for me and I'm still dealing with jet lag so I'm not understanding what you're asking here - Could you expand?

When you go to Calibration menu you select something like "Trig Out" for the AUX output. The scope will output the same signal as for the "Probe Comp" but will trigger internally not to the actual sampled signal when you go to main screen. AUX out is connected to channel 1 and input is set to 50ohm. With markers, you can measure the delay between the displayed trigger point and when the signal is rising. Mine has a delay of about 25ns. I did not find a specification for this in the service manual, so a comparison value would be helpful.

The linked video is just the recording what comes out of my AUX out during my failed CH2 calibration, so this would also be helpful, but some time is needed to make it and you need an extra scope with a low load active probe not to interfere the procedure.

[Tony_G]

Thanks - Much clearer - Here is what I'm seeing:



You can see that Tmin/Tmax are right around 25ns. Tmin does jump to -25nS occasionally but I don't think that is a material result.

Unfortunately I don't have a high impedance active probe so I can help with the waveforms for config.

TonyG

[Dexter2]

This behavior is also the same as with mine. I thought something can be seen here as I get also a "Trigger delay error" when calibrating. But the it seams the problem is elsewhere.

Maybe you can also do the "AUX out" sniffing with a passive probe during calibration on CH2, and the same setup I tried. The calibration will fail but you don't have to save it... There is to many different waveforms with different timabases to quantify during calibration but maybe it would give me an idea if my scope does not output something it should during the whole procedure... But I understand if you will rather not do it.

This problem is really driving me nuts, if nothing I will probably have to buy another working to fix this, or leave it as is, as during normal operation it works normal. Again Thanks for all Tony_G.