I have an HP3400A that will not get past the first cal adjustment in the
manual.
I have done troubleshooting and looks like the LDRs are at the end of life.
The spec of greater than 10kΩ measurement is 9kΩ on one set and 2.1kΩ on
the other.
 There are a couple of SS modifications to replace the neon bulb/LDR
circuit.
They were on the old HP Yahoo group but got lost in the IO groups
transition.
One used a DG503 the other an H11F1.

Does anyone have a copy of the modification?

                         Thanks, Mikek

On 2022/09/26 4:40 a.m., amdx wrote:
> I have an HP3400A that will not get past the first cal adjustment in the
> manual.
> I have done troubleshooting and looks like the LDRs are at the end of life.
> The spec of greater than 10kΩ measurement is 9kΩ on one set and 2.1kΩ on
> the other.
>  There are a couple of SS modifications to replace the neon bulb/LDR
> circuit.
> They were on the old HP Yahoo group but got lost in the IO groups
> transition.
> One used a DG503 the other an H11F1.
>
> Does anyone have a copy of the modification?
>
>                          Thanks, Mikek
>
>
Hi Mikek,
Have you tried to see if that old Yahoo group was archived on
archive.org's Wayback machine? Someone may have set it up there.
I find that site a very useful resource for finding lost web info...
John :-#)#
--
(Please post followups or tech inquiries to the USENET newsgroup)
John's Jukes Ltd.
MOVED to #7 - 3979 Marine Way, Burnaby, BC, Canada V5J 5E3
(604)872-5757 (Pinballs, Jukes, Video Games)
www.flippers.com
"Old pinballers never die, they just flip out."

On 9/26/2022 7:17 AM, John Robertson wrote:
> On 2022/09/26 4:40 a.m., amdx wrote:
>> I have an HP3400A that will not get past the first cal adjustment in
>> the manual.
>> I have done troubleshooting and looks like the LDRs are at the end of
>> life.
>> The spec of greater than 10kΩ measurement is 9kΩ on one set and 2.1kΩ
>> on the other.
>>   There are a couple of SS modifications to replace the neon bulb/LDR
>> circuit.
>> They were on the old HP Yahoo group but got lost in the IO groups
>> transition.
>> One used a DG503 the other an H11F1.
>>
>> Does anyone have a copy of the modification?
>>
>>                           Thanks, Mikek
>>
>>
>
> Hi Mikek,
>
> Have you tried to see if that old Yahoo group was archived on
> archive.org's Wayback machine? Someone may have set it up there.
>
> I find that site a very useful resource for finding lost web info...
>
> John :-#)#
I have not tried, and not sure what I'd search to find it. But, enough
data was lost that
many people on the HP IO Group would already have looked to add things
back into the files section.
                                       Mikek

 PS. we lost the The Radioboard with it's years of info, when the new
administrator got Covid and
had major health problems, and didn't renew the webpage, it all disappeared.

On 2022/09/26 6:01 a.m., amdx wrote:
> On 9/26/2022 7:17 AM, John Robertson wrote:
>> On 2022/09/26 4:40 a.m., amdx wrote:
>>> I have an HP3400A that will not get past the first cal adjustment in
>>> the manual.
>>> I have done troubleshooting and looks like the LDRs are at the end of
>>> life.
>>> The spec of greater than 10kΩ measurement is 9kΩ on one set and 2.1kΩ
>>> on the other.
>>>   There are a couple of SS modifications to replace the neon bulb/LDR
>>> circuit.
>>> They were on the old HP Yahoo group but got lost in the IO groups
>>> transition.
>>> One used a DG503 the other an H11F1.
>>>
>>> Does anyone have a copy of the modification?
>>>
>>>                           Thanks, Mikek
>>>
>>>
>>
>> Hi Mikek,
>>
>> Have you tried to see if that old Yahoo group was archived on
>> archive.org's Wayback machine? Someone may have set it up there.
>>
>> I find that site a very useful resource for finding lost web info...
>>
>> John :-#)#
> I have not tried, and not sure what I'd search to find it. But, enough
> data was lost that
> many people on the HP IO Group would already have looked to add things
> back into the files section.
>                                        Mikek
>
>  PS. we lost the The Radioboard with it's years of info, when the new
> administrator got Covid and
> had major health problems, and didn't renew the webpage, it all
> disappeared.
Try this - if you have the URL that you used to use to go to the web
site forum then simply paste it here:
https://web.archive.org/
Give it a try, you have nothing to lose! Archive.org is a great
resource, I recommend folks rummage around it...
John :-#)#
--
(Please post followups or tech inquiries to the USENET newsgroup)
John's Jukes Ltd.
MOVED to #7 - 3979 Marine Way, Burnaby, BC, Canada V5J 5E3
(604)872-5757 (Pinballs, Jukes, Video Games)
www.flippers.com
"Old pinballers never die, they just flip out."

On Mon, 26 Sep 2022 06:40:26 -0500, amdx <amdx@knology.net> wrote:

>I have an HP3400A that will not get past the first cal adjustment in the
>manual.
>I have done troubleshooting and looks like the LDRs are at the end of life.
>The spec of greater than 10k? measurement is 9k? on one set and 2.1k? on
>the other.
>  There are a couple of SS modifications to replace the neon bulb/LDR
>circuit.
>They were on the old HP Yahoo group but got lost in the IO groups
>transition.
>One used a DG503 the other an H11F1.
>
>Does anyone have a copy of the modification?
>
>                          Thanks, Mikek
>

Just don't use the CdS cells. They are too slow.

I think the old ones degraded from moisture intrusion or something.

On 9/26/2022 11:48 AM, John Larkin wrote:
> On Mon, 26 Sep 2022 06:40:26 -0500, amdx <amdx@knology.net> wrote:
>
>> I have an HP3400A that will not get past the first cal adjustment in the
>> manual.
>> I have done troubleshooting and looks like the LDRs are at the end of life.
>> The spec of greater than 10k? measurement is 9k? on one set and 2.1k? on
>> the other.
>>  There are a couple of SS modifications to replace the neon bulb/LDR
>> circuit.
>> They were on the old HP Yahoo group but got lost in the IO groups
>> transition.
>> One used a DG503 the other an H11F1.
>>
>> Does anyone have a copy of the modification?
>>
>>                          Thanks, Mikek
>>
> Just don't use the CdS cells. They are too slow.
>
> I think the old ones degraded from moisture intrusion or something.
>
They weren't to slow to make this instrument work.

A question, it has been said, the H11F1 has less charge injection than
the DG403,
what is that and what symptom would it cause in a chopper?

I wish the H1F1 came in a quad!

I found this interesting Jim Williams built a whole HP3400 on a pcb 3.5"
by 2.25"
with modern (1995) ICs. The article is near the end of the pdf.
(He used the now unavailable LT1088,thermal RMS-DC converter )
> https://www.analog.com/media/en/technical-documentation/application-notes/an61fa.pdf

                          Mikek

On Monday, September 26, 2022 at 7:40:37 AM UTC-4, amdx wrote:
> I have an HP3400A that will not get past the first cal adjustment in the
> manual.
> I have done troubleshooting and looks like the LDRs are at the end of life.
> The spec of greater than 10kΩ measurement is 9kΩ on one set and 2.1kΩ on
> the other.
> There are a couple of SS modifications to replace the neon bulb/LDR
> circuit.
> They were on the old HP Yahoo group but got lost in the IO groups
> transition.
> One used a DG503 the other an H11F1.
>
> Does anyone have a copy of the modification?
>
> Thanks, Mikek

There's a reason no one builds junk like that anymore...

On Mon, 26 Sep 2022 12:08:51 -0500, amdx <amdx@knology.net> wrote:

>On 9/26/2022 11:48 AM, John Larkin wrote:
>> On Mon, 26 Sep 2022 06:40:26 -0500, amdx <amdx@knology.net> wrote:
>>
>>> I have an HP3400A that will not get past the first cal adjustment in the
>>> manual.
>>> I have done troubleshooting and looks like the LDRs are at the end of life.
>>> The spec of greater than 10k? measurement is 9k? on one set and 2.1k? on
>>> the other.
>>>  There are a couple of SS modifications to replace the neon bulb/LDR
>>> circuit.
>>> They were on the old HP Yahoo group but got lost in the IO groups
>>> transition.
>>> One used a DG503 the other an H11F1.
>>>
>>> Does anyone have a copy of the modification?
>>>
>>>                          Thanks, Mikek
>>>
>> Just don't use the CdS cells. They are too slow.
>>
>> I think the old ones degraded from moisture intrusion or something.
>>
>They weren't to slow to make this instrument work.

The fast ones are cadmium selenide.

>
>A question, it has been said, the H11F1 has less charge injection than
>the DG403,
>what is that and what symptom would it cause in a chopper?
>
>I wish the H1F1 came in a quad!
>
>I found this interesting Jim Williams built a whole HP3400 on a pcb 3.5"
>by 2.25"
>with modern (1995) ICs. The article is near the end of the pdf.
>(He used the now unavailable LT1088,thermal RMS-DC converter )
>> https://www.analog.com/media/en/technical-documentation/application-notes/an61fa.pdf
>
>                           Mikek
>
>

Nowadays you can use a zero-drift chopper opamp or diffamp, and
compute RMS.

A decent DVM is as good at that old HP meter. Better.

On Mon, 26 Sep 2022 10:40:15 -0700 (PDT), Fred Bloggs
<bloggs.fredbloggs.fred@gmail.com> wrote:

>On Monday, September 26, 2022 at 7:40:37 AM UTC-4, amdx wrote:
>> I have an HP3400A that will not get past the first cal adjustment in the
>> manual.
>> I have done troubleshooting and looks like the LDRs are at the end of life.
>> The spec of greater than 10k? measurement is 9k? on one set and 2.1k? on
>> the other.
>> There are a couple of SS modifications to replace the neon bulb/LDR
>> circuit.
>> They were on the old HP Yahoo group but got lost in the IO groups
>> transition.
>> One used a DG503 the other an H11F1.
>>
>> Does anyone have a copy of the modification?
>>
>> Thanks, Mikek
>
>There's a reason no one builds junk like that anymore...

Choppers, mechanical and photo, were once the only way to make stable
millivolt and microvolt benchtop meters. They were a great step up
from Wheatstone bridges and galvos.

Differential voltmeters were cool. Also chopper based.

On Monday, September 26, 2022 at 1:54:54 PM UTC-4, John Larkin wrote:
> On Mon, 26 Sep 2022 10:40:15 -0700 (PDT), Fred Bloggs
> <bloggs.fred...@gmail.com> wrote:
>
> >On Monday, September 26, 2022 at 7:40:37 AM UTC-4, amdx wrote:
> >> I have an HP3400A that will not get past the first cal adjustment in the
> >> manual.
> >> I have done troubleshooting and looks like the LDRs are at the end of life.
> >> The spec of greater than 10k? measurement is 9k? on one set and 2.1k? on
> >> the other.
> >> There are a couple of SS modifications to replace the neon bulb/LDR
> >> circuit.
> >> They were on the old HP Yahoo group but got lost in the IO groups
> >> transition.
> >> One used a DG503 the other an H11F1.
> >>
> >> Does anyone have a copy of the modification?
> >>
> >> Thanks, Mikek
> >
> >There's a reason no one builds junk like that anymore...
> Choppers, mechanical and photo, were once the only way to make stable
> millivolt and microvolt benchtop meters. They were a great step up
> from Wheatstone bridges and galvos.
>
> Differential voltmeters were cool. Also chopper based.

https://www.eevblog.com/forum/metrology/project-micro-voltmeter-design/

John Larkin wrote:
> On Mon, 26 Sep 2022 12:08:51 -0500, amdx <amdx@knology.net> wrote:
>
>> On 9/26/2022 11:48 AM, John Larkin wrote:
>>> On Mon, 26 Sep 2022 06:40:26 -0500, amdx <amdx@knology.net> wrote:
>>>
>>>> I have an HP3400A that will not get past the first cal adjustment in the
>>>> manual.
>>>> I have done troubleshooting and looks like the LDRs are at the end of life.
>>>> The spec of greater than 10k? measurement is 9k? on one set and 2.1k? on
>>>> the other.
>>>>  There are a couple of SS modifications to replace the neon bulb/LDR
>>>> circuit.
>>>> They were on the old HP Yahoo group but got lost in the IO groups
>>>> transition.
>>>> One used a DG503 the other an H11F1.
>>>>
>>>> Does anyone have a copy of the modification?
>>>>
>>>>                          Thanks, Mikek
>>>>
>>> Just don't use the CdS cells. They are too slow.
>>>
>>> I think the old ones degraded from moisture intrusion or something.
>>>
>> They weren't to slow to make this instrument work.
>
> The fast ones are cadmium selenide.
>
>>
>> A question, it has been said, the H11F1 has less charge injection than
>> the DG403,
>> what is that and what symptom would it cause in a chopper?
>>
>> I wish the H1F1 came in a quad!
>>
>> I found this interesting Jim Williams built a whole HP3400 on a pcb 3.5"
>> by 2.25"
>> with modern (1995) ICs. The article is near the end of the pdf.
>> (He used the now unavailable LT1088,thermal RMS-DC converter )
>>> https://www.analog.com/media/en/technical-documentation/application-notes/an61fa.pdf
>>
>>                           Mikek
>>
>>
>
> Nowadays you can use a zero-drift chopper opamp or diffamp, and
> compute RMS.
>
> A decent DVM is as good at that old HP meter. Better.
>
>
>
Not at 10 MHz, at least not most of them.

Cheers

Phil Hobbs

--
Dr Philip C D Hobbs
Principal Consultant
ElectroOptical Innovations LLC / Hobbs ElectroOptics
Optics, Electro-optics, Photonics, Analog Electronics
Briarcliff Manor NY 10510

http://electrooptical.net
http://hobbs-eo.com

On Mon, 26 Sep 2022 14:49:25 -0400, Phil Hobbs
<pcdhSpamMeSenseless@electrooptical.net> wrote:

>John Larkin wrote:
>> On Mon, 26 Sep 2022 12:08:51 -0500, amdx <amdx@knology.net> wrote:
>>
>>> On 9/26/2022 11:48 AM, John Larkin wrote:
>>>> On Mon, 26 Sep 2022 06:40:26 -0500, amdx <amdx@knology.net> wrote:
>>>>
>>>>> I have an HP3400A that will not get past the first cal adjustment in the
>>>>> manual.
>>>>> I have done troubleshooting and looks like the LDRs are at the end of life.
>>>>> The spec of greater than 10k? measurement is 9k? on one set and 2.1k? on
>>>>> the other.
>>>>>  There are a couple of SS modifications to replace the neon bulb/LDR
>>>>> circuit.
>>>>> They were on the old HP Yahoo group but got lost in the IO groups
>>>>> transition.
>>>>> One used a DG503 the other an H11F1.
>>>>>
>>>>> Does anyone have a copy of the modification?
>>>>>
>>>>>                          Thanks, Mikek
>>>>>
>>>> Just don't use the CdS cells. They are too slow.
>>>>
>>>> I think the old ones degraded from moisture intrusion or something.
>>>>
>>> They weren't to slow to make this instrument work.
>>
>> The fast ones are cadmium selenide.
>>
>>>
>>> A question, it has been said, the H11F1 has less charge injection than
>>> the DG403,
>>> what is that and what symptom would it cause in a chopper?
>>>
>>> I wish the H1F1 came in a quad!
>>>
>>> I found this interesting Jim Williams built a whole HP3400 on a pcb 3.5"
>>> by 2.25"
>>> with modern (1995) ICs. The article is near the end of the pdf.
>>> (He used the now unavailable LT1088,thermal RMS-DC converter )
>>>> https://www.analog.com/media/en/technical-documentation/application-notes/an61fa.pdf
>>>
>>>                           Mikek
>>>
>>>
>>
>> Nowadays you can use a zero-drift chopper opamp or diffamp, and
>> compute RMS.
>>
>> A decent DVM is as good at that old HP meter. Better.
>>
>>
>>
>Not at 10 MHz, at least not most of them.
>
>Cheers
>
>Phil Hobbs

Cheap oscilloscopes do RMS.

It's impressive how expensive electronic instruments used to be. A 30
MHz scope cost more than a Chevrolet.

John Larkin wrote:
> On Mon, 26 Sep 2022 14:49:25 -0400, Phil Hobbs
> <pcdhSpamMeSenseless@electrooptical.net> wrote:
>
>> John Larkin wrote:
>>> On Mon, 26 Sep 2022 12:08:51 -0500, amdx <amdx@knology.net> wrote:
>>>
>>>> On 9/26/2022 11:48 AM, John Larkin wrote:
>>>>> On Mon, 26 Sep 2022 06:40:26 -0500, amdx <amdx@knology.net> wrote:
>>>>>
>>>>>> I have an HP3400A that will not get past the first cal adjustment in the
>>>>>> manual.
>>>>>> I have done troubleshooting and looks like the LDRs are at the end of life.
>>>>>> The spec of greater than 10k? measurement is 9k? on one set and 2.1k? on
>>>>>> the other.
>>>>>>  There are a couple of SS modifications to replace the neon bulb/LDR
>>>>>> circuit.
>>>>>> They were on the old HP Yahoo group but got lost in the IO groups
>>>>>> transition.
>>>>>> One used a DG503 the other an H11F1.
>>>>>>
>>>>>> Does anyone have a copy of the modification?
>>>>>>
>>>>>>                          Thanks, Mikek
>>>>>>
>>>>> Just don't use the CdS cells. They are too slow.
>>>>>
>>>>> I think the old ones degraded from moisture intrusion or something.
>>>>>
>>>> They weren't to slow to make this instrument work.
>>>
>>> The fast ones are cadmium selenide.
>>>
>>>>
>>>> A question, it has been said, the H11F1 has less charge injection than
>>>> the DG403,
>>>> what is that and what symptom would it cause in a chopper?
>>>>
>>>> I wish the H1F1 came in a quad!
>>>>
>>>> I found this interesting Jim Williams built a whole HP3400 on a pcb 3.5"
>>>> by 2.25"
>>>> with modern (1995) ICs. The article is near the end of the pdf.
>>>> (He used the now unavailable LT1088,thermal RMS-DC converter )
>>>>> https://www.analog.com/media/en/technical-documentation/application-notes/an61fa.pdf
>>>>
>>>>                           Mikek
>>>>
>>>>
>>>
>>> Nowadays you can use a zero-drift chopper opamp or diffamp, and
>>> compute RMS.
>>>
>>> A decent DVM is as good at that old HP meter. Better.
>>>
>>>
>>>
>> Not at 10 MHz, at least not most of them.

>
> Cheap oscilloscopes do RMS.

But not well, at a crest factor of 10. I have a couple of 3400As as
well as other meters of that sort. They're super useful for tweaking
stuff, for a start.

>
> It's impressive how expensive electronic instruments used to be. A 30
> MHz scope cost more than a Chevrolet.

Chevrolets are better now too. ;)

Cheers

Phil Hobbs

--
Dr Philip C D Hobbs
Principal Consultant
ElectroOptical Innovations LLC / Hobbs ElectroOptics
Optics, Electro-optics, Photonics, Analog Electronics
Briarcliff Manor NY 10510

http://electrooptical.net
http://hobbs-eo.com