The 3456a is probably the best deal you can find. I haven't ever had a
problem with mine and it's 6.5 digits. It's not really hard to find
them under $100 in working condition (I paid $75 for mine and have seen
references for as low as $20). The only complaint is it does take up a
little space.

As for serial data, here's a thread on eevblog about building a
serial adapter:


Not the world's smarted gpib adapter, but trivial to implement and it
gives you the serial data through a USB connection. A proper gpib
connector will cost you more than the processor, but the picture in the
post shows a cringe worthy budget approach.

Calibration of any 6.5 digit meter on a hobbiest budget is a challenge,
but if you have access to a recently calibrated 6.5 digit or better
meter you can at least compare it and get an idea of how close it is.

This is starting to get into volt-nuttery and I'll leave calibration
advice to those who know more than me. Suffice it to say I have an
ongoing project restoring a Keithley 2001 7.5 digit meter to tell me if
my other meters are close to spec (note this one cost me $500 for a
broken, maybe repairable example, jury's still out on that).


Paul

On Thu, Apr 09, 2020 at 05:28:53PM +0000, Daniel Koller via groups.io wrote:

Hi All,
? I am wondering what sort of DVM the collective wisdom here might
suggest for precision work.
? I am working on a project for work that involves designing a
precision voltage controlled current source.? But due to the
current pandemic, I am working from home and assembling and testing
stuff in my own well equipped basement shop.? ?The current source
is more or less a design out of Horowitz and Hill's "The Art of
Electronics".? ?I am working to keep the full scale and linearity
of this current source to within 0.1% or better.? ?
? My current best DVM is a Keithley model 173 DMM "4 and 1/2"
digit, 4-wire meter (the leading digit reads to 3).? It's accurate
to ~0.009%+1 digit over 24 hours on the V scales and ~0.035%+1
digit on the Ohms scales.? ?I think it's good enough for what I
need, but it has a few limitations, and I am wondering if it is not
time to upgrade to a real bench instrument.
? ?First of all, my DVM probably hasn't been calibrated in
decades.? ?How do I know it's correct without some externally
calibrated transfer standard?? ?It *may* be a possibility for me to
use a meter at work (sent regularly to calibration services) and
calibrate a portable voltage reference and bring it home.? ?But I
don't have a resistance standard.? ?
? The other problem is that even with 4 wires on the lowest Ohms
setting, I don't have enough resolution to measure a 0.100 Ohm
sense resistor to within 1%.? ?
? ?So, I think I could use a better meter.? ?The HP34401A DVM seems
like a nice meter to have.? It's even used as a circuit design
example in H&H's text.? But they seem to go for several hundreds of
$$ on e-bay.? ?Remember, this is coming out of my hobby budget.
? So, I looked at the? HP3455A / 3456A on e-bay.? These seem to be
significantly cheaper, and I love vintage instruments.? BUT, do I want to take up a new project?? How reliable are these old beasts??
Are they easy to repair and calibrate?? ?What tends to go wrong
with them?
? ?Even though it's more expensive, one major strong point of the
HP34401A is in addition to GPIB, it's got a SERIAL interface on the
back!? That is a whole different ballgame in terms of interfacing to a PC or laptop (and a whole lot easier for me, for sure).? But I
do think I want to have a meter I can use, rather than one I will
have to repair.? ?
? Are there any other models I am missing?? ?Are there any that
come standard with an RS232 interface?? Please let me know and
thank you in advance for your suggestions.
? Dan

??





!DSPAM:5e8f5b63144252295612346!

--
Paul Amaranth, GCIH | Manchester MI, USA
Aurora Group of Michigan, LLC | Security, Systems & Software
paul@... | Unix & Windows

Hi All,
? I am wondering what sort of DVM the collective wisdom here might suggest for precision work.
? I am working on a project for work that involves designing a precision voltage controlled current source.? But due to the current pandemic, I am working from home and assembling and testing stuff in my own well equipped basement shop.? ?The current source is more or less a design out of Horowitz and Hill's "The Art of Electronics".? ?I am working to keep the full scale and linearity of this current source to within 0.1% or better.? ?
? My current best DVM is a Keithley model 173 DMM "4 and 1/2" digit, 4-wire meter (the leading digit reads to 3).? It's accurate to ~0.009%+1 digit over 24 hours on the V scales and ~0.035%+1 digit on the Ohms scales.? ?I think it's good enough for what I need, but it has a few limitations, and I am wondering if it is not time to upgrade to a real bench instrument.
? ?First of all, my DVM probably hasn't been calibrated in decades.? ?How do I know it's correct without some externally calibrated transfer standard?? ?It *may* be a possibility for me to use a meter at work (sent regularly to calibration services) and calibrate a portable voltage reference and bring it home.? ?But I don't have a resistance standard.? ?
? The other problem is that even with 4 wires on the lowest Ohms setting, I don't have enough resolution to measure a 0.100 Ohm sense resistor to within 1%.? ?
? ?So, I think I could use a better meter.? ?The HP34401A DVM seems like a nice meter to have.? It's even used as a circuit design example in H&H's text.? But they seem to go for several hundreds of $$ on e-bay.? ?Remember, this is coming out of my hobby budget.
? So, I looked at the? HP3455A / 3456A on e-bay.? These seem to be significantly cheaper, and I love vintage instruments.? BUT, do I want to take up a new project?? How reliable are these old beasts?? Are they easy to repair and calibrate?? ?What tends to go wrong with them?
? ?Even though it's more expensive, one major strong point of the HP34401A is in addition to GPIB, it's got a SERIAL interface on the back!? That is a whole different ballgame in terms of interfacing to a PC or laptop (and a whole lot easier for me, for sure).? But I do think I want to have a meter I can use, rather than one I will have to repair.? ?
? Are there any other models I am missing?? ?Are there any that come standard with an RS232 interface?? Please let me know and thank you in advance for your suggestions.
? Dan

??





!DSPAM:5e8f5b63144252295612346!

From: "Steve" <roadkill71@...>
To: [email protected]
Sent: Thursday, April 9, 2020 8:34:52 AM
Subject: Re: [HP-Agilent-Keysight-equipment] Anyone out there fix a partially working 334A I need desperately to get
it up and running!

Not that it means anything but I do see a neon glow from the photo cells and
it appears to be glowing bright. It looks as if someone has worked on this
thing at some point because wire positions are written in pencil on the
inside chassis. Also, I'm supposed to have 2 volts on one of the first two
test points but it's not there. I do have an adjustable positive power
supply but the negative is low and will not adjust in either direction. Man,
I'm putting way too many irons in the fire at the moment, I also have an Hp
652A that needs some work. The 652 may be simple in it's engineering and
circuitry but it's baffling the heck out of me. I had to replace 6 of the
3904's in the power supply to get it to work and the expand WAS working now
the expand operation is dead again. I wonder if these two would make either
good door stops or boat anchors? If good door stops that would at least make
for a good conversation piece!

On Apr 8, 2020, at 8:28 AM, Kurt Swanson <kurt2135@...> wrote:

?Dave,

I do quite a bit of work on IFR service monitors, and have seen this problem many times, both with tantalum and aluminum electrolytics.? I use alcohol and toluene as solvents, and find that I usually have to remove and clean under the components in the affected areas - remove the ICs and clean them and the area under them, and unsolder one lead of the axial parts like resistors and lift them up vertically.? I sometimes use Q Tips to clean, but usually use a solder flux brush that has had the bristles cut short to do the scrubbing. Replace any affected pots.? Early IFR boards are usually not silkscreened, so the tinned surface may stay discolored even after cleaning, but that does not seem to be a problem.? Getting all of the goo off of the areas between the traces is important, though.? In my experience, less thorough cleaning will allow leakage current to continue to flow, which may affect performance.? Be careful doing this, particularly with the blue boards used in early IFR products - they are quite fragile.? I use a Hakko vacuum desoldering tool with good results.

Also, any of those little axial inductors that feed the capacitor that failed are highly suspect: the overcurrent that the capacitor failure causes will often result in shorted turns within the inductor.

Lastly, Viavi has pretty much forgotten about anything labelled IFR - I doubt you will get any assistance from them at all.

Good luck with your repair - Kurt

The 334 has an Automatic Nulling (A6 board) circuit which uses lamps and a
single detector. I see no chopper.

On Tue, Apr 7, 2020 at 12:04 PM Jeremy Nichols <jn6wfo@...> wrote:

Purely out of curiosity, what is the purpose of a chopper in a 334
distortion analyzer? HP used choppers in a lot of their DC voltmeters to
convert the DC to AC. They’d run the AC through some amplifiers and then
convert back to DC to run the meter. That took care of the old DC amplifier
drift problems. Since a distortion analyzer is already working with AC, I
would think a chopper wouldn’t be necessary. Obviously there’s something
I’m missing.

Jeremy

--
Jeremy Nichols

Thanks, all! I forgot about the Auto Null function.

On Tue, Apr 7, 2020 at 12:22 PM Tam Hanna <tamhan@...> wrote:

Yes!!! You are a truffle pig!


Tam

With best regards
Tam HANNA

Enjoy electronics? Join 15k7 other followers by visiting the Crazy Electronics Lab at

On 2020. 04. 07. 21:05, Merchison Burke via wrote:
> Is it the video on the HP 419 meter? ""
>
> On 2020-04-07 11:35 a.m., Tam Hanna wrote:
>> Hello,
>>
>> a dude named CarlsonLabs has had a 2h video on replacing these neons.
>> Never sat through it all the way to the fartingsound, don?t have a
>> link handy but wanted to mention it. If there is interest I can go
>> hunt it down.
>>
>>
>> Tam
>>
>> With best regards
>> Tam HANNA
>>
>> Enjoy electronics? Join 15k7 other followers by visiting the Crazy
>> Electronics Lab at
>>
>> On 2020. 04. 07. 16:41, n4buq wrote:
>>> Same problem with neon-choppers as found in the 410C.? HP replaced
>>> that with a fully solid-state board towards the end of production.?
>>> I wonder if something similar could be done for the 334A?
>>>
>>> Thanks,
>>> Barry - N4BUQ
>>>
>>> ----- Original Message -----
>>>> From: "Chuck Harris" <cfharris@...>
>>>> To: [email protected]
>>>> Sent: Tuesday, April 7, 2020 8:52:18 AM
>>>> Subject: Re: [HP-Agilent-Keysight-equipment] Anyone out there fix a
>>>> partially working 334A I need desperately to get
>>>> it up and running!
>>>>
>>>> The killer problem I have found with 334A's, is they have an optically
>>>> driven chopper that relies on NE2 style neon bulbs, and CdS photo
>>>> resistors
>>>> to do the chopping.
>>>>
>>>> The problem is two fold:? First, the neons get smoky inside, and
>>>> don't put
>>>> out enough light to switch the photo resistors, and second, the CdS
>>>> photo
>>>> resistors sometimes fail.
>>>>
>>>> The neons used have a little radioactive material sintered into their
>>>> electrodes,
>>>> to make them dark fire reliably, and modern replacements don't.?
>>>> And, the
>>>> CdS photo resistors were selected and matched for maximum on/off
>>>> resistance
>>>> spread.? CdS photo resistors run afoul of the RoHS regulations
>>>> because of the
>>>> Cadmium, and are very expensive, if you can get them at all. It is
>>>> unlikely
>>>> you can find the super wide spread selected variety that HP used.
>>>>
>>>> All of the other problems I have seen have been simple capacitor
>>>> replacement
>>>> issues.? The 334A is stocked full of TE/30D style electrolytic
>>>> capacitors,
>>>> and
>>>> their rubber seals have pretty much all turned to stone by now.
>>>>
>>>> Replacing the capacitors won't have any real effect on calibration.
>>>>
>>>> -Chuck Harris
>>>>
>>>> Steve wrote:
>>>>> I have an Hp 334A that powers on and appears to function partially
>>>>> but I’m
>>>>> not sure what all could be wrong with it. If anyone fixes these
>>>>> units at a
>>>>> reasonable price I would be interested in having it put back in
>>>>> top notch
>>>>> shape with a good calibration. I restore vintage hifi and I need
>>>>> to get it
>>>>> up and going as quickly as possible.
>>>>>
>>>>
>>>>
>>>>
>>>
>>>
>>
>>
>>
>
>

--

Jeremy Nichols
6.