Author Topic: HP 54502A - nearly vintage digitizing scope  (Read 6502 times)

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Offline MetraCollector

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HP 54502A - nearly vintage digitizing scope
« on: August 06, 2012, 10:53:08 PM »
Greetings gentlemen !

I would like to introduce you this Hewlett Packard 54502A digitizing oscilloscope in this short teardown.
I bought it for very reasonable price, because seller told me that it show some errors and I hoped it can be repaired.
So let's have a look.

Device after turning on and ran self test:


My friend told me this is very bad. I agree with him :(


This machine was a virgin  ;D because of his sticker "warranty void if removed", so I was likely the first one who opened it after it's last calibration in January 1998 (cal sticker with date).
Dirty and nasty, the same smell when you open an old TV, black dust on HV accessories.




Lot of dust:






Power supply. This looks primitive for me compared to evilness of the mainboard. ;D


I cleaned HV supplies:


Everything clean now. Very easy assembling and dissasembling. However I recommend to seal all screws and write on it where they belong to :)


These orange Nippons are perfect, they always hold their capacity, ESR and tgD even in rough conditions.


I noticed that Packards alway use golden plating on their keyboard accessories :)


Computer. M68000. Where can I get this in gold ceramic ?


Should I replace this Dallas IC ?


Preamps and attenuators


A/D hybrids


More hybrids and ... mmm, thermal oscillator :)


I was talking about evilness of the mainboard. Do you agree with me ? I can count 8 layers in close up of the laminate.
Anyway, it is beautiful, I like these clear laminate that I can read traces in inner layers :)


More hybrids:


I didn't take a photo, but this was very dirty, balls of dust:





I hope you like it, feel free to ask and require more photos.
Now I am going to check power supplies and find out what's wrong with this machine.
Do you have any experience with this HP digiscopes series ?

All of photos here:
https://picasaweb.google.com/100683312221737332313/HP54502A

Regards, Ondrej
« Last Edit: August 06, 2012, 10:58:18 PM by MetraCollector »

Offline firewalker

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Re: HP 54502A - nearly vintage digitizing scope
« Reply #1 on: August 06, 2012, 11:10:25 PM »
Clean everything (contacts etc), reassemble it and test it again. Some times taking apart something will do the trick!  :) :) :)

Nice piece of equipment btw!

Alexander.
Become a realist, stay a dreamer.


Offline Rerouter

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Re: HP 54502A - nearly vintage digitizing scope
« Reply #2 on: August 06, 2012, 11:15:56 PM »
lovely bit of gear, i actually have one of a very similar vintage using a 68000K aswell,
i must say i am annoyed to discover those HV wires unclip, i almost trashed my ones HV supply desoldering its HV transformer,

Online anotherlin

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Re: HP 54502A - nearly vintage digitizing scope
« Reply #3 on: August 07, 2012, 12:15:33 AM »
Any idea of the date of introduction of this beauty ?
"Lots of people have made $100K or more mistakes and didn't get the boot. It's called training, why fire them after such an expensive lesson?" -- EEVblog Electronics Community Forum

Offline tom66

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Re: HP 54502A - nearly vintage digitizing scope
« Reply #4 on: August 07, 2012, 12:28:29 AM »
Had a HP 54501A, made in 1993.

Introduced 1991.

Fault is with the DALLAS IC holding the calibration factors. It must be replaced and a re-cal should be done, though it may be okay without a cal (just not super accurate.)

Offline free_electron

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Re: HP 54502A - nearly vintage digitizing scope
« Reply #5 on: August 07, 2012, 01:51:01 AM »
Change the dallas chip and do a self cal. Most likely the machine will work again.
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Offline aghp

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Re: HP 54502A - nearly vintage digitizing scope
« Reply #6 on: August 07, 2012, 02:13:24 AM »
"Now I am going to check power supplies and find out what's wrong with this machine."

As can see in self test there stay NVRAM FAIL.

Just change it or modify with new compatible NVRAM. (exactly same you can not find maybe)
Or modify it using Gold contact socket + NVRAM socket + low standby current CMOS Ram. (this whole sandwitch is still just enough low that it can go inside through bakcside hole so these can assemble all ready outside. (if need many times take main board out then no need take NVRAM/CMOS out from socket. Advantage in modification is that you can then measure lithium voltage.

I have done it for several HP5450x oscilloscopes (years ago as these was popular here on second hand markets).

Also restored these input attenuators in some cases.

Also  common problem is sometimes power supply. But typically only after extremely long power up hours.
EU: Owon oscilloscopes and in Finland also  some Siglent selected equipments. All with our  lab deep Q.C. in Finland.  Surplus test equipments. Repair service. 40 year experience about electric and electronic repair, service and design. Local Owon SDS-Series  repair service for our customers.

Offline SeanB

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Re: HP 54502A - nearly vintage digitizing scope
« Reply #7 on: August 07, 2012, 03:53:28 AM »
Those can be "modified" to place a new battery on top. There is a thread on that somewhere in the forum.

Offline MetraCollector

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Re: HP 54502A - nearly vintage digitizing scope
« Reply #8 on: August 07, 2012, 06:36:53 AM »
Hello gentlemen again.

I am very pleased to seeing your responses, thank you :)

I read the service manual and ran self-test again to look what's wrong and I was a little bit confused about it, because I tried to load default factory calibration, and it gives me this errors:





This is the error that indicates corrupted Dallas IC you are talking about ?
I am confused because I just thought that this IC can operate without backup battery, that it just loss it's data after power off.
For example, my M1T380 can be calibrated without backup battery, but it loss it's calibration after it is powered off.

Of course, I would follow your advices, here are some information about these Dallas ICs:
http://www.eevblog.com/forum/product-reviews-photos-and-discussion/defective-hp-54504a-nvram-substitute/msg92282/#msg92282
http://www.mcamafia.de/mcapage0/dsrework.htm
http://classic-computers.org.nz/blog/2009-10-10-renovating-a-dallas-battery-chip.htm
http://www.radiocollection.be/uk/HP54503_uk.html

I consider a new DS1230Y on eBay:
http://www.ebay.com/itm/1PCS-DALLAS-DS1230Y-100-DS1230Y100-1230Y100-IC-NEW-/250912608886?pt=LH_DefaultDomain_0&hash=item3a6b8e9276
Weren't these IC's counterfeited by asian copiers or it is OK to buy it even from China ?

Unluckily, my DS1235Y is soldered into the mainboard. I wonder if it is a good idea just drill to the package to disconnect old battery element and solder a new Li-battery and attach it to the package ?
I do not want to destroy the PCB, even I have an access to profesional equipment in my work. (BTW, I work for ON Semiconductor as a student :) )

What do you suggest to me ?
Thank you and regards Ondrej

Offline aghp

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Re: HP 54502A - nearly vintage digitizing scope
« Reply #9 on: August 07, 2012, 09:15:34 AM »
Turn cal protect switch non protect and do default. What reads then.
Then if all read D just do full selfcal.
(but also in your first image, there is test table where reads:
Failed: Protected Non Volatile RAM.

But in your las image there read that *C in every place = Corrupted.
But then top of screen there read that switch is protected. Turn it unprot and then load factory defaults. There need then read D in every place where now is C.
EU: Owon oscilloscopes and in Finland also  some Siglent selected equipments. All with our  lab deep Q.C. in Finland.  Surplus test equipments. Repair service. 40 year experience about electric and electronic repair, service and design. Local Owon SDS-Series  repair service for our customers.

Offline MetraCollector

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Re: HP 54502A - nearly vintage digitizing scope
« Reply #10 on: August 08, 2012, 01:17:55 AM »
Hello

You all were right, I switched calibration to unprotected and then oscilloscope automatically loaded default calibration, as you can see here:


Selftest also passes without any problems, relays click quite loud :)


Are these reports all-right ?
I am confined about drilling holes into Dallas IC to connect new battery and attach it to the package. Can you someone tell where are connections located ? I have some training DS12887 from old motherboard and I found it by drilling, following instructions from the WWW I wrote above. But this DS1235Y has different pinout, I expect different layout.

Anyway, oscillscope seems to work, offsets are little bit off, but I am very pleased to have almost functional HP :)
I tried some simple Wien's oscillator to test it:


Thank you and regards, Ondrej

Offline Wim_L

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Re: HP 54502A - nearly vintage digitizing scope
« Reply #11 on: August 08, 2012, 02:01:41 AM »
Had the same problem with a 54504A:
http://www.eevblog.com/forum/product-reviews-photos-and-discussion/defective-hp-54504a-nvram-substitute/

I tested it, and it would selfcal perfectly if started from a default setup, and everything worked after that. Of course it lost calibration as soon as it was powered down, but it'd work fine as long as you left it running. If those match your symptoms, it definitely is the Dallas chip. You don't need the exact same model, http://www.maxim-ic.com/app-notes/index.mvp/id/202#q13 (and see the previous thread for more discussion).

A note on removing it: the legs of that chip are covered completely by the package, so cutting the chip out and then desoldering pin by pin won't work. I ended up doing it with hot air, but the heating slightly discoloured the board and made a nearby cap drop out of the board too. Not too bad, no serious damage, but if you have access to a good vacuum desoldering tool you can probably do better.

Mine also had a bit of error on the low frequency adjustment. While you're replacing it anyway, grab yourself a copy of the service manual (search for the model number on the Agilent site, they have a scanned PDF version online) and follow the whole procedure for tests and calibration. Some parts are a bit tricky because you'll have to adjust pots under the power supply, some of those cheap plastic adjustment screwdrivers might come in handy (after cutting them in half, if they're the long type).

Offline MetraCollector

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Re: HP 54502A - nearly vintage digitizing scope
« Reply #12 on: August 19, 2012, 07:11:03 AM »
VOILA  :D

Hardly believe I managed to do it with only chinese sucker and pro's kit solder, but it went much more better then expected :)
It went absolutely with no resistance, almost every pin on the first try, pins were free and when sucked the last pin, I only deattached the IC with no force :)



DS1230Y substituent is on it's way :)
Unluckily have ho socket at home right now, but it is a question of one hour to local store :)
« Last Edit: August 19, 2012, 07:12:39 AM by MetraCollector »

Offline ice595

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Re: HP 54502A - nearly vintage digitizing scope
« Reply #13 on: November 19, 2013, 04:08:35 PM »
If I buy a working HP 54502A oscilloscope from ebay that passes all self-tests, should I be worried about the DALLAS IC failing in the next few years?

Offline Rerouter

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Re: HP 54502A - nearly vintage digitizing scope
« Reply #14 on: November 19, 2013, 08:35:48 PM »
yes, as the battery in the chip will be almost 2 decades old and well past its used by date


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