Author Topic: HP 1742a 100 Mhz help  (Read 5351 times)

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Offline mrbreeze01

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HP 1742a 100 Mhz help
« on: January 03, 2015, 05:44:48 pm »
 :-//Hello fellow EEV's,  Looking at a nicely priced HP 1742a, and need your comments, opinions, reveiws etc. :scared:
 

Offline tggzzz

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Re: HP 1742a 100 Mhz help
« Reply #1 on: January 03, 2015, 06:02:20 pm »
I have an HP1740A. Very nice machine with no surprises, similar to a Tek 465.

Mine was functional, but I had to repair a PCB track inside (!) the timebase range control rotary switch, replace an electrolytic, and make a label for the timebase range since that was becoming imperfectly visible.

There are other threads on this forum about these machines, which are worth reading.
There are lies, damned lies, statistics - and ADC/DAC specs.
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Offline mrbreeze01

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Re: HP 1742a 100 Mhz help
« Reply #2 on: January 03, 2015, 07:06:37 pm »
After I posted I read newbies and posting, so do feel stupid.  But did read the others and appreciate your reply.
Those issues seemed trivial with yours,great job!!!
 

Offline tautech

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Re: HP 1742a 100 Mhz help
« Reply #3 on: January 03, 2015, 07:28:47 pm »
Like many old CRO's they suffer from a few ailments.
Mainly to do with HV and CRT plate output stages.
I had a 1740a with both these problems as well as a sweep issue.
When right they have a nice crisp trace.

I have another 1740 tucked away for repair at some stage.
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Offline helius

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Re: HP 1742a 100 Mhz help
« Reply #4 on: January 03, 2015, 08:22:54 pm »
One unusual feature of these scopes that not everyone will be aware of is their graticule illumination. It comes from an electron flood gun inside the CRT, so there are no light bulbs to replace.
 

Offline oldway

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Re: HP 1742a 100 Mhz help
« Reply #5 on: January 03, 2015, 08:26:11 pm »
Beautiful analog oscilloscope, with HP quality.
Its only major flaw is its bulk.
It takes a lot of place on the bench.
I have a 1740A (100Mhz) and a 1725A (275Mhz) and I am very satisfied with them.
 

Offline MarkPalmer

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Re: HP 1742a 100 Mhz help
« Reply #6 on: January 04, 2015, 07:30:06 pm »
If the price is nice and it will do what you desire, go for it.  The 1742A is one of the last of the 1700 series, and they are an excellent analog scope.  They offer a few advantages over the Tek 465 for a 100 MHz analog scope- no fan, no difficult to replace incandescent bulbs, much sharper CRT traces, a 50 ohm input selector, and much easier access for repairs if needed.  The 1740A model put HP on par technology wise with Tektronix oscilloscopes in the mid 1970’s and HP eventually surpassed Tek in scope sales.  The 1741A is an excellent analog storage scope from the series too. 

-Mark-
 

Offline GreyWoolfe

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Re: HP 1742a 100 Mhz help
« Reply #7 on: January 04, 2015, 08:49:45 pm »
Price ranges on eBay are interesting.  Working scopes are being offered at around $1000 USD but when looking at sold prices, only 1 was listed and sold for under $60.  Hope the price is right, looks like a nice scope to have.
"Heaven has been described as the place that once you get there all the dogs you ever loved run up to greet you."
 

Offline JuiceKing

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Re: HP 1742a 100 Mhz help
« Reply #8 on: January 04, 2015, 10:13:41 pm »
The feet on the back of those scopes are fragile, and are often missing or break in transit if the scope is shipped standing up with inadequate packing material underneath. Not a big deal unless you like to keep the scope on the floor, tucked under the bench, to save space. You can find replacements on eBay with a bit of patience.
 

Offline tautech

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Re: HP 1742a 100 Mhz help
« Reply #9 on: January 05, 2015, 03:40:39 am »
The feet on the back of those scopes are fragile, and are often missing or break in transit if the scope is shipped standing up with inadequate packing material underneath. Not a big deal unless you like to keep the scope on the floor, tucked under the bench, to save space. You can find replacements on eBay with a bit of patience.
They are more fragile as they age, some even very brittle.
I've spun them up on a lathe from round nylon stock and counter-bored the mounting screw.
Not as pretty as the originals, but works well.
They are necessary to protect the CRT cover plate and the rear BNC's, when one stands it on end or carts it around as a portable unit.
Who'd want to these days as they are weighty units.
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Offline TerraHertz

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Re: HP 1742a 100 Mhz help
« Reply #10 on: January 05, 2015, 10:53:54 am »
I'm using a HP 1743A on my 'random stuff' bench, and it's a nice scope overall. Mine has accumulated enough faults that it's due for some repairs:
  - Scale illumination stopped working recently. The very even electron flood lighting is nice when it's working.
  - The digital 'time interval' measurement system died a couple of months ago. But I rarely used it anyway.
  - There's some slow intermittent variation of the vertical offset, both channels. THIS I need to fix!
  - Channel B 50 ohm termination is open circuit. I expect this is a pretty common fault, due to people forgetting the termination was on, and blowing it up. (It wasn't me!)

My biggest complaint about these HP 174x scopes is that the front panel lettering and dial numbers are small and low-contrast, and unless the room lighting is bright and omni-directional, I can't read them without having a desk lamp (or torch!) directed at the scope face. The buttons tend to shadow their own labels.

Of course like all HP and tech equipment of that era, the biggest plus is the availability of service manuals complete with schematics, theory of operation, cal procedures, etc. Both original paper and pdf.

Collecting old scopes, logic analyzers, and unfinished projects. http://everist.org
 

Offline tggzzz

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Re: HP 1742a 100 Mhz help
« Reply #11 on: January 05, 2015, 12:30:29 pm »
My biggest complaint about these HP 174x scopes is that the front panel lettering and dial numbers are small and low-contrast, and unless the room lighting is bright and omni-directional, I can't read them without having a desk lamp (or torch!) directed at the scope face. The buttons tend to shadow their own labels.

My timebase markings were sufficiently poor contrast and/or erased that I created another on paper, and inserted it under the transparent housing. Now there's no need for a torch.

If you want it, I could let you have my drawing.
There are lies, damned lies, statistics - and ADC/DAC specs.
Glider pilot's aphorism: "there is no substitute for span". Retort: "There is a substitute: skill+imagination. But you can buy span".
Having fun doing more, with less
 

Offline techie1234

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Re: HP 1742a 100 Mhz help
« Reply #12 on: February 16, 2020, 10:37:03 pm »
I'm using a HP 1743A on my 'random stuff' bench, and it's a nice scope overall. Mine has accumulated enough faults that it's due for some repairs:
  - Scale illumination stopped working recently. The very even electron flood lighting is nice when it's working.
I too had my 1743A's scale illumination go intermittent and then stop completely. After a bit of tracing, it came down to a cold solder joint on the P3 interconnect of the LVPS. The soldering on the entire P3 connector was pretty crusty - which seems to be a thing in these, as on my other 1743A it is also not a great soldering job.929718-0
 
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