Oscilloscope HP 54600A

[mio83]

Hi!

I was patiently waiting to save some money to buy an entry level Rigol or Siglent digital oscilloscope (now have a 20Mhz analogue). But I found a seemingly nice offer for a 100Mhz HP 54600A for about 130euro (price can be lowered a bit, I think).

Do you think it's still good value for the money as of today, 2020?
If not, what price you'd happily pay for it?

Im interested in upgrading my 20Mhz oscilloscope mainly to:

1) have a bit more bandwidth, 100Mhz seems the right limit since to get to 200Mhz or above I'd need to start spending money also on probes...

2) To have "one shot" trigger possibilities,

3) To be able to see the the wave before the trigger point.

4) Having some basic measurments directly available (pk-to-pk, frequency, etc).


In other words, I am not interested in the so-many functionalities offered by modern scopes... I am still learning (amateur, not student) and want a relatively "simple" device I can (fell like I) master. Also, I am NOT interested in decoding digital transmissions. More into RF and Ham radio.

So the HP 54600A might be good instrument for these goals. And the build quality should be good.

What do you think?

Thanks!

[oPossum]

Be aware the one-shot bandwidth is only 2 MHz for a single channel or 1 MHz for two channels. The ADC runs at 20 MS/s so higher frequencies require ETS (equivalent time sampling) and a repetitive signal.

[Wuerstchenhund]

As oPossum says, the 54600A only samples at 20MSa/s (which is sufficient for a bit over 6MHz), which is not enough to cover 100MHz BW in real-time. And because of the low sample rate, your signal will be susceptible to aliasing by frequency components over the Nyquist frequency (10Mhz).

It also has a minuscule amount of sample memory (kpts in real-time, 4k in ETS).

It's OK if you are looking at repetitive signals or for doing some poor man's version of an eye diagram but as a general pupose scope the 54600A is pretty poor.

If you don't want to spend the $350 or so for a new Rigol DS1054z then the HP 54622A/D could be an option if you find one cheap ($150 or so), it has a higher sample rate and more memory (and in case of the "D" it's actually an MOS) and is a decent general purpose scope.

[SilverSolder]

+1 for HP 54622D for amateur use.

It is well made, easy to use, and has "modernish" features like being able to export a captured waveform on disk, which you can then use to drive circuit simulations (in LTSpice for example) on your PC.  The screen has 1000 pixel horizontal resolution which is better than some modern scopes.

[iMo]

I got this scope in my hands yesterday in perfect condition. Spent last night watching the display.. 

Unbelievable what it could do with its 20MS/sec subsampling and its 68000 @8MHz cpu. Tetris is nice to have too 

Btw., is a service manual "with schematics" somewhere available ??
I've found the user manual with service instructions, but none schematics in there, a pity..

Also, is even possible to see say 100mV 50Hz hum superimposed on say 30MHz 1V sine wave with this gadget (like AM modulation)?

[radiohomebrewer2000]

I have a HP 54600B 100 MHz 2-channel digital scope.  I got it in 2022.  It was my first and still only scope I have.  It got me started.   It works ok.  I used it to test a crystal tester which is a Colpitts oscillator.  The scope showed a nice sine wave.  But it was not perfectly a sine wave.  But I was told by others that this is OK.   However, I noticed the measurement was not stable. It changed every couple of seconds. So, not sure what the true voltage or frequency reading was from the scope. The only reason I knew the exact frequency was that I listened on a nearby Shortwave receiver and connected it to a frequency counter.
So, I do wish there was a way to measure a signal that was stable.  Anybody know?

Just search around on the internet for the manual.  You might find it.

There are a lot of YouTube videos - some of them EEVBlog - of people fixing your model or similar HP scope models.

Do be aware, it has a CRT which is high voltage which can kill you.   So, you must be extremely careful if you ever need to take the lid off the scope.

I was willing to do that.  But I was fortunate that the scope I got off ebay worked.  So, I did not need to take the lid off.  However, there was this annoying rack mount on it that made it take up extra space.  And just using your normal screw driver was unable to remove the screws.  I had to find a screwdriver that had bits for different types of screws to unscrew.  TORX and other screw types I have never heard of.  Not sure why HP used such strange screws.  But, I got that rackmount off.  And it saved some space.

[iMo]

I made some tests with mine, feeding it with my 0-80MHz dds sine generator, aprox 1Vpp and 0.2Vpp, 50ohm.
It had no problems to show the waveforms and their pretty stable Vpp/Vrms voltage.
The frequency - that scope is not a counter just a tool. The frequencies jittered, like 50,00MHz +/- 50kHz. I think that is normal with this kind of scope.

Also I compared it with Rigol 1060CA I have here while measuring 10-40mV 0.1-10Hz signals and the results were identical.

The biggest issue of this scope is its Dallas 1220 battery backuped 16kB memory module.
It resides there for 33years already and keeps the calibration and various manufacturing settings, afaik. Needs to be replaced asap, otherwise the scope may die anytime.

[radiohomebrewer2000]

iMo,
I usually measure Voltage in mVpk-pk and Frequency in MHz using my socpe.  Both give me in the ball park figure because every few seconds the values change.  The wave form is there and is steady.    So, yes, the voltage bounces around within 50kHz.

The VFO is the VFO used in the NorCal 40B CW Transceiver Kit.   You can do a search for it using call sign NM0S. 
https://sites.google.com/nm0s.com/home/norcal-40b

My mVp-p was in the 700s while another ham's was in the 800s and it needed to be as close to 1A as it can get.  But the ham who had the voltage in the 800s knew what he was doing.  I needed to know the frequency in order to know if I needed to add or remove turns for a toroid inductor that I wound.  The manual mentioned 63 turns but other hams recommended 60 or 61 and they were correct.  I simply pushed the turns closer together to bring it down and used the C50 trimmer to bring it down to what I was looking for:  2110 kHz.  Since the local oscillator has a crystal at 4915 kHz and 2110 kHz summed together gives me 7025 kHz for the 40meter ham band.    Since the frequency bounced around (not knowing the proper words to use here), I used my frequency counter to measure the frequency from the VFO and it gave me a stable reading.

Similar thing happened when I built a G3UUR Crystal Tester to find matched crystals for the 4.915 MHz crystals I had, the frequency bounced around.  It did give me a ball park of what the frequency was.  But I had a shortwave receiver (really my HF transceiver) and frequency counter as well to tell me what it was. 

I think you use the word "jittered".  Is that what I should use instead of "bounced around"?

Should I take this conversation to the Ham Radio forum now?

I ask because I would like to know how to make my measurements stable.

Thanks,
Daniel

[Demon Xanth]

We have a 54601A on a test bench here. It works, but I wouldn't go out of my way to buy one.

[iMo]

@Daniel - yep, the design of your VFO - that is a topic for the RF Ham radio section..

[radiohomebrewer2000]

iMo,
I have created a new topic in the appropriate Ham Radio forum about my issue with a stable measurement of voltage and frequency.

https://www.eevblog.com/forum/rf-microwave/how-to-get-a-stable-measure-of-v-and-freq-using-an-oscilloscope-on-a-vfo/

- Daniel

[radiohomebrewer2000]

iMo,
Do you have any suggestions on how to replace this Dallas memory module or where to find them?  Are they expensive?

It gets to a point where a question is asked - is it worth the money and time to do it?

I am thinking about giving this scope to my brother or niece and I do not want the scope to fail on them later.  Then again, they might not want it.  Same can be said about how some people look at the old Heathkit HW-101 transceiver - I could not even give it away to them...  They want the shiny new...   Yet, when someone offered me this same transceiver for free when I because a new ham, I pounced on it at the urging of other hams - take it...  And I am glad I did because I learned things from the old rig you could not learn from the newer rigs.

The biggest issue of this scope is its Dallas 1220 battery backuped 16kB memory module.
It resides there for 33years already and keeps the calibration and various manufacturing settings, afaik. Needs to be replaced asap, otherwise the scope may die anytime.

[iMo]

https://www.tindie.com/products/tebo/dallas-ds1220-replacement-without-battery-2/

[radiohomebrewer2000]

iMo,

Thank you. 

If I get everything, the price is still cheap at US$18.50.  I can solder the header pins myself. 

The hard part is removing it and putting the new part in.  And without getting shocked by the CRT. 

But, how do you transfer the settings from the old part to the new part? 

Is there anything else I need to do?  Does the +5 power needed (I think) come from the scope PCB?  Or is this something else I need to figure out how to power it?  Sorry for all the dumb questions. 

Any links to good tutorials or videos would be good too.

I do see a lot of videos on YouTube on this topic.

Thanks again,
- Daniel

[iMo]

When you read the stuff in my link above - the module has been specifically developed for his 546xx scope replacement(s)..

You have to de-solder the Dallas module from the pcb, read and store the data off the Dallas chip (you would need a programmer for it, there is a YT video on that - do search), then you have to program the data back into the new module, then to solder a DIL socket into the pcb, then put the new module into the socket..

[radiohomebrewer2000]

iMo,
Thank you.  I watched the video.   So, I probably need to get a programmer that can read both the DALLAS and the ROM but also be able to write to the DALLAS replacement.

Interesting how he needed to change the caps because they were leaking even though the scope works. 

I did see a comment on the video that said:
"You do not NEED to save the Dallas chip.  Replace it and power cycle the scope.  Then run it's internal calibration.  Done."

I am not sure how true that is.

[iMo]

I saw an YT video where the guy did the calibration on a 54xxx that way - he simply replaced the Dallas and ran the calibration (you have to connect the rear BNC with a BNC on the front panel during the calibration).
Perhaps it works fine that way - what the service manual says?
PS: The 54600A/B's SM says for the Vertical selfcal you need to connect the rear output to the specific input, for Delay selfcal you have to connect a pulse generator set to 100 kHz and 1 V p-p and with a rise
time less than 5 ns to both channels 1 and 2 (50ohm).