Seeking advice on a precision DVM
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
??
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Greetings all, I need to make some room in my lab again (happens too often) , so I have the following equipment for sale:
- HP 8566B Spectrum Analyzer with interface cables - $500
- HP 8902A Measuring Receiver, 11722A probe - $1200
- Opt 030 - High Selectivity
- Opt 033 - 20.0 / 25.0 KHz Filter
- Opt 037 - Carrier Noise Filter
- Opt 003 - Rear connections for the int/ext LO
Both of these instruments are in working and excellent condition. I do not want to ship these beasts, so please be prepared to pick these up locally in Houston. In order to clear space, I will also donate some pieces of test gear to anyone who purchases one of the above instruments locally. I also have the following refurbished instruments
- HP 3325B / 001 / 002 $350 + shipping - $300
- HP 5335A Counter / 010 / 020 / 030 /040 + shipping - $250
I am willing to ship these two units to the lower 48 states. Please inquiry at my email address: joecline5747@..., not to the group, please. Thanks and regards, Joe, KN5U
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Craigslist HP 8566B Indianapolis
Not mine, but I thought someone might be interested
Wally KC9INK
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Re: Anyone out there fix a partially working 334A I need desperately to get it up and running!
I have both of those models as well that I purchased very inexpensively at an estate sale a few years ago and this conversation has prompted me to drag those out and see the operational status of both.
My 334A seems to work well enough (although the balance controls need some TLC as they've gone "scratchy"); however, I did check the PS rails and both were extremely close to +/- 25VDC. The AUTOMATIC function doesn't appear to work correctly. If I switch to AUTOMATIC, the meter starts to drift off of "balanced" so something may be wrong there. I haven't checked too much else on it.
My 652A's EXPAND function does not work and I intend to investigate that soon. The A3 board is certainly in a convenient place to check that so maybe I can get that functional without too much trouble.
Thanks,
Barry - N4BUQ
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----- Original Message ----- 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!
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Re: 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!
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Re: HP54603B Software Gremlins
Hi Andreas,
There is two different Non-volatile/zero-power ram chips in the module. Both have their own internal backup battery. So the battery in one of them is probably bad.
I would replace both, as the other one probably don't have much time left.
From the manual: Saving Traces Hint
"For traces 1 to 3, the trace is saved in the non-compressed state. For traces
greater than 3, the trace is saved in 64 Kbytes of nonvolatile trace memory with
data compression. After a compressed trace is saved, the available area (in
percent) is displayed."
In my 54657A, there is one Dallas DS1244Y-120 (32kbytes) and a ST M48Z128Y-120PM1 (128kbytes). see picture.
So I would guess that its the ST part in yours that the battery is bad.
BR, Askild
Hi Matthew,
the self test menue has an explicit function that tests RAM and it runs thru without error messages.
The problems seem to occur in the nonvolatile memory of the HP54657A module. The clobbered screen display vaguely shows the original image tilted to one side. It looks more like a classical programmer's bug (wrong increments of an adress pointer while copying data).
Regards????????????? Andreas
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Re: HP54603B Software Gremlins
Hi Matthew,
the self test menue has an explicit function that tests RAM and it runs thru without error messages.
The problems seem to occur in the nonvolatile memory of the HP54657A module. The clobbered screen display vaguely shows the original image tilted to one side. It looks more like a classical programmer's bug (wrong increments of an adress pointer while copying data).
Regards????????????? Andreas
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Re: Hints on removing burned tantalum residue
Dave,
This looks way better, and might now work, but if it was mine I would clean on it some more.
Looking at your hi res photo, there is still some crud around the anode of CR8, around the pin 1 and pin 16 end of U3, as well as what appears to still be? crud hiding under both U2 and U3.? As I mentioned before, I would also consider the pots suspect, particularly after immersion cleaning.? The symptoms of incomplete cleaning usually manifest themselves as instability, particularly at elevated temperature and / or humidity.
As I also mentioned, this type of failure is common on IFR units of this vintage - the record here currently stands at 5 caps that were shorted simultaneously in an old FM/AM 1000S that had not been turned on in over 10 years.
Again, good luck with this repair - Kurt
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Re: Hints on removing burned tantalum residue
Hi Kurt, Thanks for great suggestions. ? I tried the following on the board and am ready to replace capacitor and start testing.? 1) Isopropyl Alcohol and Q tip. Mixed results.? 2) Xylene (goof off) is really good at getting grunge off caps near the epicentre.? 3) Ultrasonic cleaner with soapy water solution. Then?flushed with?clean water. This seems to do a nice job Attached is a picture. Much better than before. Baked the unit for a couple of hours at 40C to dry.? Will let stand for at least a day.?
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
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Re: Optiion upgrade HP 8753C/B (CRT Focus)
I've seen reports of bad trimpots on the XY board causing display issues on the 8753A/B.?
However I had a B with CRT issues and didn't find any bad pots. It did respond well to CRT rejuvenation and I also had to clean soot and reseal the HT attachment to the tube to stop it arcing.
I did the CRT rejuvenation very conservatively compared to guides I have read, basically the bare minimum required until it started drawing current. Unfortunately I sold the unit some time ago and I haven't heard of any issues (I promised to take it back if the CRT went bad after the repair)
Cheers, Roger
My 8753A had a CRT with low intensity as well as beeing unfocused.
I have not tried to rejuvinate the CRT, but I took the monitor apart and made a deep
cleaning of the HV circuit board. Vacuuming of the electrostatic dust and then
wiping the board as clean as I could with a dampened cloth.
Also the CRT was taken out and cleaned.
The intensity is still low but the focus could then be adjusted to satisfaction.
I guess that leakage currents caused by the dust and dendrites formed
by pollution and moisture in a 30+ year old instrument can be a problem.
Cheers
Ulf Kylenfall
SM6GXV
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Re: Optiion upgrade HP 8753C/B (CRT Focus)
In the future, clean the boards with 100% alcohol and blow dry with compressed air.
Best to wash off with de-ionized water but the alcohol alone will work.? Do a final rinse with the alcohol after scrubbing the boards with alcohol and tooth brush.
George
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I could help you with that.? Can you tell me the problem?? Is it just the oscillator or the receiver/analyzer or do you not know?
George Hnatiuk
EMAIL:? ghnatiuk@...
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Re: Hints on removing burned tantalum residue
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
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Re: Anyone out there fix a partially working 334A I need desperately to get it up and running!
I'm sorry Michael, I misremembered. Before I looked in the
manual, I remembered lamps, of some sort, and CdS photoresistors,
and it registered as a choppers.
It is actually a Wien Bridge. Three of the four legs are CdS
photoresistors. One lamp feeds two of the photoresistors, and
the other feeds a single photoresistor.
The last time I worked on 334's was about 1984. I am surprised that
I remembered as much as I do.
-Chuck Harris
Michael A. Terrell wrote:
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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
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Re: Anyone out there fix a partially working 334A I need desperately to get it up and running!
Collective wisdom, y'all.
Stay safe...now that Jzonsson de Peffel also got ill, I am
starting to worry a bit. To me, he appeared as the pinnacle of a
healthy happy strong man...
With best regards
Tam HANNA
Enjoy electronics? Join 15k7 other followers by visiting the Crazy Electronics Lab at
On 2020. 04. 07. 22:06, Jeremy Nichols
wrote:
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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.
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Re: Anyone out there fix a partially working 334A I need desperately to get it up and running!
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
6.
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Re: Anyone out there fix a partially working 334A I need desperately to get it up and running!
I haven't used it in a while, I've been using a leader LDM-170 but feel more confident in triusting the 334A. First problem is that you can't "Set" anything unless you have an extremely high voltage signal going in @1VAC then you can fake go through all the steps. second, the auto function works but I'm not sure if it's 100% or not. I'm in Knoxville Tn.
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Re: Hints on removing burned tantalum residue
Guys,
Just in case it helps, the names Marconi Instruments / IFR / Aeroflex / Cobham / Viavi are all
historical parts of the same company from 1998 onwards.
With regards to IFR, this operation was/is still located in Whichita, Kansas, although much of the former operation no longer exists. The only historical records and knowledge will be with the group you found already.
On the Marconi side, mostly UK, there are extensive records as a very good archive of manuals, catalogues, photographs and uFiche were kept.
There are some IFR manuals in the UK archive but not much else.
A lot of those manuals are somewhat specific to aviation/aerospace rather than general purpose test instruments.
Much of what a lot of us seek is knowledge/experience on the products as well as information - whilst there are those of us left who can do so, i¡¯m sure we will gladly help where possible.
Regards
Nigel
Hi Roy,
I have been getting some good information?there.
Dave
On Tue, Apr 7, 2020 at 07:02 AM, Dave Miller wrote:
I have found the IFR group
Hi Dave:
If you could post the links you found, that would be great.
There appears to be many things associated with the names IFR and Aeorflex
Cheers and best wishes.
Roy
--
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Re: Hints on removing burned tantalum residue
Hi Roy,
I have been getting some good information?there. Dave
On Tue, Apr 7, 2020 at 07:02 AM, Dave Miller wrote:
I have found the IFR group
Hi Dave:
If you could post the links you found, that would be great.
There appears to be many things associated with the names IFR and Aeorflex
Cheers and best wishes.
Roy
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Re: Hints on removing burned tantalum residue
On Tue, Apr 7, 2020 at 07:02 AM, Dave Miller wrote:
I have found the IFR group
Hi Dave: If you could post the links you found, that would be great. There appears to be many things associated with the names IFR and Aeorflex Cheers and best wishes. Roy
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Steve
Michael A. Terrell