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.

excuse my mistake,

I have done restoration 427A and 204B side by side on the table.
The 22.5V Battery is correct. Can be swapped by 2 pcs of 9V Blocks lithium for backup light , they deliver 10.2V each.

This problem with the mercury cells was the 204B Oscillator (same case)

Martin


Am 07.04.2020 um 18:51 schrieb Richard Knoppow:

Original battery is 22.5V. They are available but expensive. I made a battery pack using two 8 cell battery holders for AA cells and left one cell out putting a wire in place of the battery. probably using all the cells for 24 volts is OK. The thing will run on 18 volts from two 9 volt batteries in series, easier to do but might not last long. It will run on somewhat less than 15 volts, probably the 13.5V mentioned below is the absolute minimum.
?? The story I heard when at -hp- was that the price was about the cheapest -hp- could build any instrument because of the cost of the standard cabinet frames and the cost of doing business, i.e. all the paper work needed to manufacture and sell anything. For some reason I am fond of this instrument despite better meters being available. I think the first thing is to clean the switches carefully and do a complete calibration. Watch out for corroded PCB connectors, lots of push on ones. Most connector problems can be fixed by just exercising them. Maybe cute is a good description. Anyway, I've always been fond of them.

On 4/7/2020 8:56 AM, Martin M wrote:

hello Dave,

yes, specials:
The Power Line Supply is a Option and not always inside.
427A have a Set of 4 obsolete 6.75V mercury batterys,
if they are tired and there is no PSU, build it self.

The instrument needs ±13,5V.
Another way is to use 2 pcs. of 9V Blocks, it will work with them also.

Martin

Am 07.04.2020 um 06:17 schrieb Dave McGuire:

On 4/7/20 12:14 AM, Paul Bicknell wrote:

Just switched on a 427A volt meter that I rescues a few weeks ago

Just wondering is their any think special about it and is it worth spending
any time on as it reads low

?? I've never put my hands on one, but I checked out the specs a bit.? It
doesn't seem particularly noteworthy in any specific way, but it sure
does look like a nice handy all-around bench meter with a nice big meter
face.

????????????? -Dave

Original battery is 22.5V. They are available but expensive. I made a battery pack using two 8 cell battery holders for AA cells and left one cell out putting a wire in place of the battery. probably using all the cells for 24 volts is OK. The thing will run on 18 volts from two 9 volt batteries in series, easier to do but might not last long. It will run on somewhat less than 15 volts, probably the 13.5V mentioned below is the absolute minimum.
?? The story I heard when at -hp- was that the price was about the cheapest -hp- could build any instrument because of the cost of the standard cabinet frames and the cost of doing business, i.e. all the paper work needed to manufacture and sell anything. For some reason I am fond of this instrument despite better meters being available. I think the first thing is to clean the switches carefully and do a complete calibration. Watch out for corroded PCB connectors, lots of push on ones. Most connector problems can be fixed by just exercising them. Maybe cute is a good description. Anyway, I've always been fond of them.

On 4/7/2020 8:56 AM, Martin M wrote:

hello Dave,

yes, specials:
The Power Line Supply is a Option and not always inside.
427A have a Set of 4 obsolete 6.75V mercury batterys,
if they are tired and there is no PSU, build it self.

The instrument needs ±13,5V.
Another way is to use 2 pcs. of 9V Blocks, it will work with them also.

Martin

Am 07.04.2020 um 06:17 schrieb Dave McGuire:

On 4/7/20 12:14 AM, Paul Bicknell wrote:

Just switched on a 427A volt meter that I rescues a few weeks ago

Just wondering is their any think special about it and is it worth spending
any time on as it reads low

?? I've never put my hands on one, but I checked out the specs a bit.? It
doesn't seem particularly noteworthy in any specific way, but it sure
does look like a nice handy all-around bench meter with a nice big meter
face.

????????????? -Dave

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.

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.

On 4/7/20 12:04 PM, Jeremy Nichols 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.?

Unless my memory is failing, it's not strictly a chopper, but it's
part of the automatic tuning system. The choppers are
digitally-controlled switches, but I believe the LDR-based subsystem in
the 33x distortion analyzers are more "analog" in nature, to follow the
fundamental frequency automatically.

-Dave

Thanks Nigel,
I have found the IFR group. I should have looked first. ?
Thanks
Dave

On Apr 7, 2020, at 2:50 AM, nigel adams via groups.io
<nigel.adams@...> wrote:

? Have you tried the IFR group as well - there are people who have
this stuff and might be able to help.
------------------------------------------------------------------------
*From:* [email protected]
<[email protected]> on behalf of Dave Miller
<ve7hr@...>
*Sent:* 07 April 2020 03:55:29
*To:* [email protected]
<[email protected]>
*Subject:* [HP-Agilent-Keysight-equipment] Hints on removing burned
tantalum residue
?
Not directly HP related but this is where the knowledge is.
I am starting to repair an IFR-1200S that had an incident.
<IMG_0884.jpeg>
<IMG_0886.jpeg>


A 150 uF 15V tantalum went up in smoke.
What is the best solvent to remove the residue on the rest of the PCB.
Isopropyl does not take all of it off? Want to get it all clean before
I replace parts and continue the repair.
Thanks
Dave?