Tell me about the hp/agilent 54501 and similar models...

[alank2]

Hi Everyone,

I've got an analog BK2120 and a couple of Rigol scopes so it isn't a need, but I wouldn't mind having a scope from an era in between analog and TFT digital.  Something like the 54501 that is a digitizing scope but still will a monochrome CRT display.  Which ones are good durable models?  Are they easy to repair when they break?  What type of sampling rates do scopes of these years usually have?

[Wuerstchenhund]

Well, the HP 54500A Series was the first scope with HP's single knob design (i.e. one rotary encoder plus a numerical keypad for making all settings), which was loathed by many because it was so different from the standard (analog) scope controls people were used back then (it shined however when using the scope in analytical role, which is what HP really envisaged at the time). The first (54500A) and second (54500B) generations had the single knob UI, however with the third generation (5452xA/C, 5454xA/C) HP went back to a more traditional interface with separate encoders for vertical and horizontal (although the vertical encoder was multiplexed across all channels).

The various models include:

1st generation:
- 54501A: 100MHz 4ch 10MSa/s
- 54502A: 400MHz 2ch 400MSa/s (6bit ADC)
- 54503A: 500MHz 4ch 20MSa/s
- 54504A: 400MHz 2ch 200MSa/s
- 54510A: 250MHz 2ch 1GS/s

2nd generation:
- 54505B: 300MHz 2ch 500MSa/s
- 54506B: 300MHz 4ch 500MSa/s
- 54510B: 300MHz 2ch 1GSa/s
- 54512B: 300MHz 4ch 1GSa/s


3rd generation:
- 54520A/C: 500MHz 2ch 1GS/s (single channel), 500MSa/s (2 channels)
- 54522A/C: 500MHz 2ch 2GS/s (all channels)
- 54540A/C: 500MHz 4ch 2GS/s (single channel), 1GSa/s (2 channels), 500MSa/s (3 or 4 channels)
- 54542A/C: 500MHz 4ch 2GS/s (all channels)

If I remember right the first gen scopes had up to 4kpts memory, the 2nd gen up to 8k, and the 3rd up to 16k 32k.

FFT was an option for some first generation scopes while it was standard for 2nd and 3rd gen variants.

The third generation scopes were also available with a color TFT (5452xC/5454xC) instead of the green CRT in the 'A' models.

The first and second generation 54500 Series scopes are generally very robust. One weak point is the PSU (an industrial PSU from a company that is now owned by Eaton) which if I remember right is also used in some HP Logic Analyzers, however since there's a lot of space inside the scope retrofitting a different PSU is possible (and has been done). Another weak spot is the Dallas clock/nvram chip, however since the scope doesn't have a clock it's easily replaced with some FRAM which doesn't require a battery.

The third generation scopes however aren't similarly reliable. The PSU (a different type than the on the 1st and 2nd gen scopes) is quite complex and somewhat failure-prone. In addition, the ADC hybrids are mounted on a very fragile ceramic carrier, which connects through a frame with spring-loaded contacts to the acquisition board. The carriers tend to crack, and the springs in the frame can break/lose pressure which makes the contacts unreliable or failing. Fixing it can be a PITA.

However, all 54500 Series scope, no matter what generation, as well as many other instruments from various manufacturers, suffer from overaged Schaffner mains filters, which when dried out tend to blow up and spread some nasty gunk across the insides of your scope. The gunk is also pretty corrosive and will cause damage to the PCBs. Therefore, no matter which 54500 scope you buy, *always* replace the Schaffner mains filter with a new one (do *not* but new/old stock, as you'll end up replacing one dried out filter for another one!). They are still made and not overly expensive (and the newer models have been improved since back then so they will last much longer).


Update: corrected sample memory for 3rd gen scopes; added multi-channel sampling rates for 3rd gen scopes

[Jwalling]

3rd generation:
- 54520A/C: 500MHz 2ch 1GS/s
- 54522A/C: 500MHz 2ch 2GS/s
- 54540A/C: 500MHz 4ch 2GS/s (half-channel)
- 54542A/C: 500MHz 4ch 2GS/s (all channels)

If I remember right the first gen scopes had up to 4kpts memory, the 2nd gen up to 8k, and the 3rd up to 16k.

Minor correction. The third generation above was 32K, and the 54540X was 1GS/s I believe. All the above used the same A/D converters which also contained the 32K of ACQ memory, so in theory one could hack the 1GS/s scopes to sample at 2GS/s.

[Wuerstchenhund]

Minor correction. The third generation above was 32K

Yes, you're right.

and the 54540X was 1GS/s I believe.

No, it's actually 2GSa/s:
http://www.keysight.com/main/redirector.jspx?action=ref&nid=536881115.1.00&lc=eng&cc=US&ckey=1000071135%3Aepsg%3Adow&cname=EDITORIAL&ml=eng

All the above used the same A/D converters which also contained the 32K of ACQ memory, so in theory one could hack the 1GS/s scopes to sample at 2GS/s.

The SM says it''s all the same hybrid (1NB7-8353) which is a 2GSa/s ADC, so it seems the 1GSa/s models are artificially limited.

[Jwalling]

Minor correction. The third generation above was 32K

Yes, you're right.

and the 54540X was 1GS/s I believe.

No, it's actually 2GSa/s:
http://www.keysight.com/main/redirector.jspx?action=ref&nid=536881115.1.00&lc=eng&cc=US&ckey=1000071135%3Aepsg%3Adow&cname=EDITORIAL&ml=eng

I stand corrected. That's what I get when going from memory at my age. 

[Wuerstchenhund]

That's what I get when going from memory at my age. 

Same here. Yeah, getting old sux 

[TAMHAN]

About the PSU: it is also used in some logic analyzers, and the 53310A. So if something really goes Puber on you, you can always sacrifice - even though I would not sacrifice a 53310A as it is more "rare" than a 54xxx scope.

Re the PSUs. Recapping them should be done when still alive, it makes it much more easy. I was there recently:

[alank2]

Thanks for the info guys.