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Re: Testing Scope Probes

 

No I'm not counting the capacitance twice.?

Rp is a measure of parallel resistance not parallel capacitance. At 400-500MHz, the 10073C will load a circuit in a similar way to the loading caused by a perfect 60R resistor in parallel with about a 7pF perfect capacitor. i.e. just as I drew it on the circuit.

Have you ever measured a x10 scope probe using an analyser??
Re: Testing Scope Probes

 

On Thu, Apr 11, 2024 at 02:45 PM, Robert G8RPI wrote:
Crossed with Raymonds reply.
You saved my day...

Raymond
Re: Testing Scope Probes

 

On Thu, Apr 11, 2024 at 02:37 PM, Robert G8RPI wrote:
But you have Rp and 7pF probe capacitance.
That is counting the input capacitance twice.
Hi Robert,
Is that meant as an answer to my question? I'd say (HP spec) Rp = 2.2MOhm, Cp = 12pF, resulting in |Xc| less than 30Ohm @ 500MHz, or no? I'm confused...

Raymond
Re: Testing Scope Probes

 

Crossed with Raymonds reply.
I was assuming the probe input capacitance was 12pF. Seems odd to split the reactive impedance.

Robert.
Re: HP8568B battery replacement

 

On Thu, Apr 11, 2024 at 10:57 AM, Gianni Becattini wrote:
My had both, but I concluded that the big one (HP-67 style) was not used, so I changed only that on board and it works.

Hi Gianni,

I'm one of the many that have admired your beautiful books from the beginning but haven't posted about that.

As regards your above post, I'm not sure what you mean by "both": Two NiCds? BTW, the HP-67 also uses the smaller 3-cell (HP-35 style) battery, the HP-97 (and HP-91) use the bigger, 4-cell type.

Raymond
Re: Testing Scope Probes

 

But you have Rp and 7pF probe capacitance.
That is counting the input capacitance twice.
Re: Testing Scope Probes

 

> By contrast, a 10073C will typically look like about 60R in parallel with about 7pF across 400MHz to 500MHz.
>
Not relevant for the discussion but what's the math behind that? HP 10073C data 2.2MOhm // 12pF.

Raymond
Agilent E4406A Pulling down the power supply not starting

 

I have one E4406A with the same problem. I didn't disassemble it. I saw comments that could be the power source. Do I check the power source directly?
It has the same characteristic sound. And it does the same as the video in these links. Strange that before it was working perfectly.
Re: Fume extractor recommendation

 

¿ªÔÆÌåÓý

It would have been interesting to measure the lead levels in consumer electronics techs 50 years ago (and still today) who lit cigarettes with soldering irons. Adding lead to that menagere of poisons had to have been a death wish. I have seen sheet metal workers and plumbers do it. Cartoons in old QST magazines showed a group of hams building a transmitter and doing it as well.

? Bruce Gentry, KA2IVY






On 4/11/24 0:42, Chuck Harris wrote:

Hi Radu,

You don't say what your scare was, but if your doctor
deduced that the lead levels in your body are high, it
likely didn't come soldering circuit boards.

If you have lead in your blood, look first at hygene.

Lead won't penetrate your skin to any significant degree
from handling it, but it will from eating with unwashed
hands that have been handling lead.

Don't eat, drink, or put anything in your mouth while at
your bench.  Don't rub your eyes!  Always scrub your hands
after leaving your bench.

I have watched a lot of technicians chewing on wire
connectors, and wire insulation and using their mouths as 
a 3rd hand.  Don't!

Lead water pipes, and fresh lead soldered joints in water
pipes are an excellent way of building up the lead in your
body.

Workers that need to watch out for lead fumes typically work
around large circuit board wave soldering machines, or in a
factory making or recycling lead batteries.

Fume hoods used in soldering typically are just to reduce
irritation from flux smoke.

-Chuck Harris


On Wed, 10 Apr 2024 17:30:08 -0700 "Radu Bogdan Dicher"
<vondicher@...> wrote:

Hi all,
I've had a recent scare with potentially evil metals that can
vaporize - you know who you are.... - and absolutely need a good, and
hopefully affordable, solution for my bench soldering needs. And
hopefully, not just something I'll put on there for peace of mind but
have no idea if it really does anything. I really want this to work.

Are there any such things this community can recommend? I don't think
I can go used on this kind of thing, not knowing what Martian "deadly
on sight" materials the thing may have exhausted in its life. Nor I
really feel I can trust the vanilla low balling specimens on AMZ.
Being a health-related thing, I feel it kind of needs a trustworthy
solution, but my budget for this is limited.

Thank you for your input!
Radu.

Re: Testing Scope Probes

 

The R2 value of 60R is the equivalent Rp (parallel resistance) of the 10073C at about 500MHz. If you measured the 10073C with an impedance analyser down at low frequencies (eg in the kHz region) Rp would be about 2.2Meg ohm as you stated.
However, up at RF frequencies this value will fall at a fairly steady rate. A typical x10 probe might see Rp decline by a nominal factor of three every octave for example.

By 500MHz the Rp of the 10073C could easily be about 60 ohms.

The delta at 350MHz is about 1.5dB for the HB simulation. This is still poor enough to spoil the integrity of the Tee method in my opinion.
Re: Testing Scope Probes

 

Hi,
Where is R2 derived from? The 10073C input resistance is 2M2 not 60R. You have included the capacitance so can't be that unless you are double accounting?

What is the delta at 350MHz?

Robert.
Re: Testing Scope Probes

 

Of course, what this means in reality, is that you can expect to achieve slightly confusing results if you used this Tee setup to test the 10073C against a near perfect Zo probe for frequency response up to 500MHz.

If we assume that the Zo probe is perfectly flat to several GHz and it has an input Z of about 500R at 500MHz then the simulation tells us that there will not be a level playing field when comparing the two probes. The BNC tee will give the 10073C a 2-3dB voltage 'boost' at 500MHz in steady state. It may be the case that the 10073C will appear to match or even outperform the Zo probe at 500MHz in terms of frequency response if you chose this test method. Obviously, this is a false result.
Re: Testing Scope Probes

 

If you aren't happy/familiar with a HB simulation, then see below for a SPICE simulation. The result is the same although the SPICE simulation will show how it settles in steady state. So it may be more intuitive in this respect. Note again that the highest voltage occurs across the low impedance 10073C. This may seem counter-intuitive, but this is how the system will settle in steady state. There will be lots of reflections happening in the system because the 50R BNC Tee is mis-terminated on both of its outputs.
Re: Testing Scope Probes

 

I don't know if this helps, but look at the simulation below. This assumes a dielectric constant of 2 for the BNC Tee and a distance of 46mm between the probes. The simulation is a harmonic balance simulation at 500MHz.
You can see there is about a 2.9dB difference in voltage between the two nodes TP1 and TP2 at 500MHz. The HB simulation assumes steady state has been reached.

It's entirely up to you if you want to declare this difference as 'negligible'. However, I urge you to study it closely. The 10073C has a lower impedance at 500MHz yet it has the higher voltage compared to the higher impedance Zo probe. This happens at equilibrium (steady state) after lots of reflections back and forth. Most people would expect the voltage to be higher at the Zo probe TP2 but it isn't.

You have to analyse how the system achieves steady state in order to understand that there will a 2-3dB difference between TP1 and TP2 at 500MHz.
Re: HP8568B battery replacement

 

My had both, but I concluded that the big one (HP-67 style) was not used, so I changed only that on board and it works.
Re: Testing Scope Probes

 

JMR said:
"If the 3.5GHz 'known good probe' probe is a passive Zo probe, it might look like 500R in parallel with 1pF up at UHF. By contrast, a 10073C will typically look like about 60R in parallel with about 7pF across 400MHz to 500MHz. Quite a difference.
This is going to upset the balance of Robert's BNC Tee based system. There's no way it will have any integrity up at 500MHz if I assume the distance between the probes is going to be about 45mm. This allows for the length of the Tee piece and some additional length for each BNC probe adaptor. This is a significant length at 500MHz. It should be obvious that the voltages arriving at the inputs of the two probes won't be the same at 500MHz, it isn't a valid test method for this reason."

Firstly the measurement is only up to 350MHz but even if we are talking 500MHz the wavelength is 600mm If the T is? 50mm across the differnce between the two loads is 25mm (probably less) so only 15 degrees phase difference.? Noting that we are trying to determine a 3dB bandwidth in a non-phase sensitive level measurement I would consider that the error is insignificant.

?

?
Re: HP8568B battery replacement

 

I'm not absolutely sure of the details, but as I recall, the 8568A (and 8566A) to "B" conversions changed it from an off-board 3-cell NiCd HP35 calculator-style pack, to a single 3V Li-ion cell soldered right on the (new design) processor board. Some of the info may be missing because of all the big changes involved. There were total swap-outs of the brain system, plus a field-installed A-B upgrade offered around the same time.

If you have a "B" of whichever, you should find the backup Li cell on the uP board, in the right-rear board cage compartment of the RF section, viewed from the top, as I recall. Or was it the bottom? The structure is such that the 8566 RF unit is accessed upside down, and I don't recall if the 8568 is the same. I know for sure that whatever the arrangement, the uP board is right next to the GPIB board, so just find that from the outside. It's not obvious from the inside, since there's an Al lid that covers the digital controller boards. Removal of a single screw should release it.

Ed
Re: HP8568B battery replacement

 

Never mind,

Procedure starts on page 1-13 of the Installation & verification Manual - 8568B-IVM.pdf

Regards

Lou
VK3ALB


On Thu, Apr 11, 2024 at 3:53?PM Lou Blasco via <vk3alb=[email protected]> wrote:
Hi,

I have a HP8568B reporting the battery?is low. I have some 8568B manuals from Artek but I can't find anything in them?that looks like battery replacement instructions. I know I have to take a picture or transcribe the calibration measurements before I start.

Can someone guide me to the correct document number please?

FWIW, this is what I have.

9018-05833.pdf
9018-05834.pdf
9018-05860.pdf
9018-05919.pdf
9018-06816.pdf
85662A-TSM.pdf
85670A-85680B-TRM-V1.pdf
85670A-85680B-TRM-V2.pdf
8568B-IVM.pdf
8568B-PTA-2.pdf
8568B-PTA.pdf

Regards

Lou
VK3ALB
HP8568B battery replacement

 

Hi,

I have a HP8568B reporting the battery?is low. I have some 8568B manuals from Artek but I can't find anything in them?that looks like battery replacement instructions. I know I have to take a picture or transcribe the calibration measurements before I start.

Can someone guide me to the correct document number please?

FWIW, this is what I have.

9018-05833.pdf
9018-05834.pdf
9018-05860.pdf
9018-05919.pdf
9018-06816.pdf
85662A-TSM.pdf
85670A-85680B-TRM-V1.pdf
85670A-85680B-TRM-V2.pdf
8568B-IVM.pdf
8568B-PTA-2.pdf
8568B-PTA.pdf

Regards

Lou
VK3ALB
Re: Fume extractor recommendation

 















Greg
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