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Author Topic: Agilent/HP 54845A  (Read 6812 times)

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Offline smgvbest

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Re: Agilent/HP 54845A
« Reply #50 on: March 19, 2017, 03:23:14 AM »
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 :)


Sandra
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Offline Samogon

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Re: Agilent/HP 54845A
« Reply #51 on: March 19, 2017, 04:06:42 AM »
According to your description, you bought it from express_auctions.
If so, they sell cannibalized units or after failed attempts to repair.
 

Offline james_s

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Re: Agilent/HP 54845A
« Reply #52 on: March 19, 2017, 05:19:26 AM »
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.
 
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Offline smgvbest

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Re: Agilent/HP 54845A
« Reply #53 on: March 21, 2017, 09:52:47 AM »
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.
Sandra
(Yes, I am a Woman :p )
 

Online Tony_G

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Re: Agilent/HP 54845A
« Reply #54 on: March 21, 2017, 10:53:06 AM »
Sorry to hear that - Hope you get better soon - I'm sure lugging these scopes around didn't help.

TonyG
 

Offline smgvbest

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Re: Agilent/HP 54845A
« Reply #55 on: March 23, 2017, 10:09:07 AM »
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????

Sandra
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Online Tony_G

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Re: Agilent/HP 54845A
« Reply #56 on: March 23, 2017, 10:15:09 AM »
So the donor hybrid passed self test in the donor machine but generated a mass of errors in the primary machine?
 
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Offline smgvbest

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Re: Agilent/HP 54845A
« Reply #57 on: March 23, 2017, 11:10:33 AM »
correct, even verified the waveform i put in to test on the donor was correct 100Mhz @ 1Vpp read as 100.05Mhz @1.027Vpp.
Sandra
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Online Tony_G

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Re: Agilent/HP 54845A
« Reply #58 on: March 31, 2017, 03:52:28 PM »
Any updates?
 

Offline smgvbest

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Re: Agilent/HP 54845A
« Reply #59 on: April 10, 2017, 12:05:26 PM »
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,
Sandra
(Yes, I am a Woman :p )
 

Offline Samogon

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Re: Agilent/HP 54845A
« Reply #60 on: April 10, 2017, 12:25:54 PM »
I have same model and it is in the repair project too, so if you need to compare measurements i would try to help.
 
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Offline smgvbest

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Re: Agilent/HP 54845A
« Reply #61 on: April 17, 2017, 05:11:08 PM »
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. 
Sandra
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Online Tony_G

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Re: Agilent/HP 54845A
« Reply #62 on: July 09, 2017, 12:55:02 PM »
Was replying to another 548xx thread and just wondered what happened with the repairs (yours and Samogon's)

TonyG
 

Offline Samogon

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Re: Agilent/HP 54845A
« Reply #63 on: July 09, 2017, 02:08:10 PM »
Mine is still sitting collecting dust, i am doing so many projects and was carried away. Time is what we miss most.
 

Offline smgvbest

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06B
« Reply #64 on: July 11, 2017, 01:58:32 AM »
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
Sandra
(Yes, I am a Woman :p )
 

Online Tony_G

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Re: Agilent/HP 54845A
« Reply #65 on: July 11, 2017, 02:07:37 AM »
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

 

Offline Dexter2

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Re: Agilent/HP 54845A
« Reply #66 on: July 14, 2017, 09:13:21 PM »
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.
 

Online Tony_G

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Re: Agilent/HP 54845A
« Reply #67 on: July 15, 2017, 12:56:16 PM »
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
 
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Offline Dexter2

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Re: Agilent/HP 54845A
« Reply #68 on: July 17, 2017, 06:45:02 AM »
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
 

Offline Jwalling

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Re: Agilent/HP 54845A
« Reply #69 on: July 17, 2017, 07:12:58 AM »
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.
Jay

System error. Strike any user to continue.
 

Offline Dexter2

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Re: Agilent/HP 54845A
« Reply #70 on: July 18, 2017, 03:14:10 AM »
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.
 

Offline Jwalling

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Re: Agilent/HP 54845A
« Reply #71 on: July 18, 2017, 03:59:41 AM »
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!
« Last Edit: July 18, 2017, 04:02:10 AM by Jwalling »
Jay

System error. Strike any user to continue.
 
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Offline Dexter2

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Re: Agilent/HP 54845A
« Reply #72 on: July 18, 2017, 05:30:35 AM »
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.
 

Offline Dexter2

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Re: Agilent/HP 54845A
« Reply #73 on: July 18, 2017, 08:06:46 AM »
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.
 

Offline Jwalling

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Re: Agilent/HP 54845A
« Reply #74 on: July 18, 2017, 07:18:19 PM »
Hi,

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

System error. Strike any user to continue.
 


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