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Author Topic: Agilent/HP 54845A  (Read 3397 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
(Yes, I am a Woman :p )
 

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 )
 

Offline 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
(Yes, I am a Woman :p )
 

Offline 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?
 

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
(Yes, I am a Woman :p )
 

Offline 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
(Yes, I am a Woman :p )
 


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