HP 54201A Digitizing scope worth buying?

[kaptain_zero]

There's one of these on the the local Kijiji board. Asking price is $100. I wasn't really looking for a scope right now, but at that price, perhaps I should be picking it up?!?!  I had planned on getting a Rigol or some such down the road, more just to have one, rather than having an urgent need for one.... I'm a hack...... I blunder through things most times, I have some rusty electronics knowledge from reading up for my Advanced Ham Radio test.... I can muddle my way through simple schematics, I've build my own automated satellite tracking system that would track low earth orbit satellites with directional antennas, control the communications transceiver and communications software on a PC, but I've never used a scope..... Until recently, I thought they operated with black magic...... now I know they're nothing more than a sophisticated volt meter...... but I'm still not sure I'll know what to do with it!  

A quicky search seems to indicate such a beast might be worth $100 or maybe more..... And having the thing in my "shack" might just push me over the self education edge and force me to learn about it's use.....

Should I get it.... or not?!?!

Regards

Christian aka

Kaptain "Clueless as always" Zero

[rf-loop]

Simply, there are some limits becouse old technology... wfm refres rate slow, capture memory deoth judst as screen...
Slow to handle becouse you really need do all settings with cursor keys/meny/keyboard and there are lot of settings.

But they have been high class professional tools.

They are much better than many peoples think. (with its nature limits as memory and sampling speed)

Just same as many peoples buy digital camera only looking how many megapixels.

Bad thing is that before use it people need go to HP5420x university.

Rigol and Hantek etc... manufacturer have think many things allready...

Here you do all setups... including that you configure what it do and what not as you push "autosetup".

UI is complex... but once you know it as you own pockets -- it is really tool, not toy for nice looking color pictures. Tool for analyze signals. (noiseless, separate ADC's, real trigger (not as Rigol/Hantek toy trigger what is most bad thing in these cheap gigasamplers)

Analog channel quality is extremely good, really professional. Also ADC is good and all channels have own independent ADC..
Capture memory... compare to analog scopes.

It is fun... it also give warning if scope think that aliasing......

Trigger works perfect, timing is extremely high class... BW flatness is extremely good... (it is made for accurate measuremets for over whole BW)  Inputs RF quality is good... but capacitance is still littlebit high.. 14pF

Input MAX is 40V !!

Real time scope... it is max 50MHz and repetitive 300MHz.

This model is developed before next 545xx series "cheap boxes" and lot of before 546xx "plastic box"

Building quality... Rolls-Royce...

With its high limits it is still extremely good scope in some cases.

If I can buy these in good cosmetic and working condition just as USD100 I want buy as many as I can. (if model is D)

But ... this is not easy scope... I can not recommend for first scope.
After 3 days use you still may think scope is broken... but it is not. Using need HP54200 series university first.

But not big money if you want try... if it is OK (all test and self cal routines pass and short meauring test with own eyes...if all pass, you can sell it agen to some enthusiast, maybe if you really can proof it is fully ok you can sell it more. Becouse there is still peoples who know what is difference between Stahlwille and noname wrench tools.

But really, if you are not ready to study how to use it... then do not. In this case it give only frustration and disappoint.
If you need long memory do not buy.
If need pictures to computer, do not buy (yes you can... with real HP-IB)
(with HP IB you can get all capture datapoints... and fully programming... in computer controllden measuring systems this is more nice becouse no need use from front panel complex UI)

[kaptain_zero]

Thanks rf-loop. Very useful information, but alas....... the ad turned out to be a dud. Seller was confused (I'm being polite here) and the scope, as such, does not exist.... at least not for sale. Too bad, it might have been the perfect choice to challenge my brain. I've been on autopilot for waaay too long and need to get back to critical thinking vs just coasting along on previous experience.

Thanks again..... maybe the next one will be for real.

Christian  aka

Kaptain "Drats.... foiled again!" Zero

[grenert]

You could always get an old HP or Tek analog scope.  Cheap, and no "auto" button!  Gotta know what you're doing  
Dave's already taught us what the Holdoff button does...

[Lawsen]

I enjoyed trying the HP-54502A, a 400 MHz, 400 Msamples/s two channels digital oscilloscope.  It is more than enough for audio frequencies found in my seismograph projects.  Here is the problem, a calibrated, clock battery checked and replaced if necessary, and fully restored one costs $395.00 USD from a store in E Bay, Watronics.  Watronics was a former HP oscilloscope engineer (before Agilent) in Loveland, Colorado, U.S.A.  I did not purchase it, because it costs as much as a Rigol.  All HP-5450x oscilloscopes have some phosphour burns.  These are old oscilloscopes from the dot com era.  They are good, but you have to be orientated by someone near by or study the manual yourself in how to use it and its limitations.  It is a very good oscilloscope for its time, when analog dominated the market.  It is a cathode ray tube oscilloscope.  I do not have room in my bedroom for one.  I will pass.  It is a very well made and support available in the U.S.A.  There is a Dallas Time clock battery module in the mother board on the oscilloscope.  Most of them have a exhaused clock battery and needs replacement and calibration.  I wished you luck. 

Lawsen  

[rf-loop]

You could always get an old HP or Tek analog scope.  Cheap, and no "auto" button!  Gotta know what you're doing  
Dave's already taught us what the Holdoff button does...

Even very old HP54200A/D series have "auto" button. But you can also configure it. Example you may want disable time scan, then it search only voltage setting... and lot of more settings.

But, this autosetup is not very fast and it can also make mistake end you see only some randoms... there is specifications data what tell what it do and what it do not, and as HP have done... this info is perfect. (just as HP old calculator manua have one part what explain all small erros in calculations.. how it may cumulate errors ... but if you read manual you know exactly and can also calculate limes for errors!)

[rf-loop]

I enjoyed trying the HP-54502A, a 400 MHz, 400 Msamples/s two channels digital oscilloscope.  It is more than enough for audio frequencies found in my seismograph projects.  Here is the problem, a calibrated, clock battery checked and replaced if necessary, and fully restored one costs $395.00 USD from a store in E Bay, Watronics.  Watronics was a former HP oscilloscope engineer (before Agilent) in Loveland, Colorado, U.S.A.  I did not purchase it, because it costs as much as a Rigol.  All HP-5450x oscilloscopes have some phosphour burns.  These are old oscilloscopes from the dot com era.  They are good, but you have to be orientated by someone near by or study the manual yourself in how to use it and its limitations.  It is a very good oscilloscope for its time, when analog dominated the market.  It is a cathode ray tube oscilloscope.  I do not have room in my bedroom for one.  I will pass.  It is a very well made and support available in the U.S.A.  There is a Dallas Time clock battery module in the mother board on the oscilloscope.  Most of them have a exhaused clock battery and needs replacement and calibration.  I wished you luck. 

Lawsen  

54502 is nice RF scope but one disadvantage... it have 6 bit ADC. But analog channel is good, (just as impotant as lense in camera).

There is NO battery what you can check in NVRAM in HP5450x series. I have many times look this watronics info and maybe it is littlebit "business oriented info"...
Cal factors etc example user settings are in NVRAM what have Lithium cells. This battery voltage is nearly impossible measure. And even if make some trick to measure it voltage... it do not tell much. Becouse this type lithium cell have nearly constant voltage to the final end of live with this kind of load. (bateries are inside Dallas NVRAM chip and it do NOT give Vbatt to any pin out from this IC.
In system test menu there is NVRAM OK. In real it do not tell anything but yes it can tell you what you can see... do you need blinking light in window that now there is sun!
Normally (dependent of storage temp and use) this NVRAM battery can last more than 20 years. (Ihave seen lot of these HP's and also repair them)
There is maybe different HW versions of this scope so my knowledge is only what I have seen.
Most of these scopes have been used in system and they have been powered on long times. Some burn on the monitor do not mean anything. In normal use it do not affect. If it looks bad, put some filter over the screen.

NVRAM is soldered directly to multi layer main board. It is easy to change. And from scratch scope itself can develop all data what is inside this NVRAM, just different what some Tektronix have.
It need only do FULL selfcalibration exactly as service manual tell.
If can not get this original type of NVRAM it can replace with NVRAM socket and compatible low standby current CMOS RAM.

[dimlow]

I recently replaced the NVRAM chip in my 54502A, was easy to do and calibrate. Sourced the NVRAM from Maxim as a sample, cost me nothing to fix. If you can find one of these scopes with NVRAM problems i would not worry about buying it. Even if it only has a 6 bit ADC ( I thought 8 Bit) it still out performs my Rigol for accuracy.

[rf-loop]

I recently replaced the NVRAM chip in my 54502A, was easy to do and calibrate. Sourced the NVRAM from Maxim as a sample, cost me nothing to fix. If you can find one of these scopes with NVRAM problems i would not worry about buying it. Even if it only has a 6 bit ADC ( I thought 8 Bit) it still out performs my Rigol for accuracy.

Yes, Maxim is good source for this.
Many peoples afraid these scopes just becouse they do not know and many peoples do not want tell... becouse...

One other problem is input attenuators. (they are special modules assembled front of main board and only need open screws, You can chance these but... also in many cases they can repair... exept if they have burned with over voltage. many times they have different problem. But special flip-flop relays can service if really know how to do... dust is one problem and sometimes some stupid peoples have use some aerosol "contact aerosols" ... these contact aerosol peoples need isolate to some islands and give only just food.

"Even if it only has a 6 bit ADC ( I thought 8 Bit) it still out performs my Rigol for accuracy."

Yes of course it beat Rigol just as 10-1.
But look price... how many tens of Rigols you can buy... one input attenuator price is more than one new whole rigol 50MHz.

Also it have separate independent ADC's. And they are not analog devices cheaps....

These HP's are designed by real professionals with long and deep experience about professional measurements. Still there are things what can do better. But... difficult in this technology what was 20-25 years ago. Yes there are also better old models. 5450x serie was some kind of economy and middle class.