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Re: A homemade diode power sensor for HP meters

Lothar baier
 

开云体育

You can get the connectors from binder which is preferred if you are in Europe ( RS Components , buerklin, farnell )? or you can buy them from amphenol !

A few words of wisdom though based on experience :

First of use connectors that are gold plated if you use other plating options you can end up with issues at low power levels ( noise ? thermal voltages ???? ) the second thing is that you have to follow the original stackup of the cable , the agilent cable uses 12 wires but 2 wires are shielded separately and you have to keep it that way to avoid problems !

Back when I build up cables what I did is to order a 100ft 11730 cable from agilent which cost me about $1200 , I cut the cable in 3ft sections ordered C091 Amphenol connectors and then used them to build the cables !

?

https://www.mouser.com/datasheet/2/18/C09131C0122002-1285663.pdf

?

?

From: HP-Agilent-Keysight-equipment@groups.io <HP-Agilent-Keysight-equipment@groups.io> On Behalf Of Paul Bicknell via groups.io
Sent: Thursday, May 19, 2022 3:10 PM
To: HP-Agilent-Keysight-equipment@groups.io
Subject: Re: [HP-Agilent-Keysight-equipment] A homemade diode power sensor for HP meters

?

The connecters are available, Binder make 3 types and they did cost ?10 , ? 13 ?and ?16? each

?

Regarding Diode sensors do not forget the 430 meter was made for Diode sensors? also I believe the early 431 A had a switch position for Diode

?

Personally looking for a modern meter ( not expensive ) for wave guide diode detectors but calibrated in dB

Paul

?

From: HP-Agilent-Keysight-equipment@groups.io [mailto:HP-Agilent-Keysight-equipment@groups.io] On Behalf Of Alexandre Souza
Sent: 19 May 2022 20:49
To: HP-Agilent-Keysight-equipment@groups.io
Subject: Re: [HP-Agilent-Keysight-equipment] A homemade diode power sensor for HP meters

?

Talking about power sensor, I got lucky enough to get a (working) 436b and a WORKING \o/ sensor. But unfortunately, got it without the cable. Is there a cheaper source for the cable than ebay?

?

73 de PU2SEX Alexandre

?

---8<---Corte aqui---8<---

---8<---Corte aqui---8<---

?

?

Em qui., 19 de mai. de 2022 às 13:41, visitslovenija <musto102@...> escreveu:

An interesting and long running thread.

Like many, I have a bit of a soft spot for the old HP435 meters and would like to have one working on the bench.

Since broken detectors do show up now and again at a decent price, has anyone successfully reworked one with busted thermocouples and modified for a diode front end? I know it’s small and very fiddly, but is that not easier than trying to build one from scratch?


Re: A homemade diode power sensor for HP meters

Lothar baier
 

The 8484A used a single diode and had no temperature compensation , I think that HP tried to minimize the impact of temperature variations by using a heavier all metal case .... the 8481D uses a thermistor

-----Original Message-----
From: HP-Agilent-Keysight-equipment@groups.io <HP-Agilent-Keysight-equipment@groups.io> On Behalf Of Paul Bicknell via groups.io
Sent: Thursday, May 19, 2022 4:22 PM
To: HP-Agilent-Keysight-equipment@groups.io
Subject: Re: [HP-Agilent-Keysight-equipment] A homemade diode power sensor for HP meters

OK Dave

Re the 8484 I actually have 2 of the black 2 grey and one D version a lot better than my original 430 power meter and Sensor with an N connecter on it So just a thought how dues the 8484A do its temperature compensation as I do not think I have ever looked at the CCT diagram for the 8484 A

Paul

-----Original Message-----
From: HP-Agilent-Keysight-equipment@groups.io [mailto:HP-Agilent-Keysight-equipment@groups.io] On Behalf Of Lothar baier
Sent: 19 May 2022 22:08
To: HP-Agilent-Keysight-equipment@groups.io
Subject: Re: [HP-Agilent-Keysight-equipment] A homemade diode power sensor for HP meters

The 8484A was the first diode sensor that HP produced , it was a horrible piece of equipment prone to drift especially if you got one with the black case .
Eventually HP redesigned the sensor to solve the issues and the new sensor was the 8481D
On May 19, 2022, at 15:37, Paul Bicknell via groups.io <admin@...> wrote:

?Thank you Dave for those kind words of love Paul

-----Original Message-----
From: HP-Agilent-Keysight-equipment@groups.io
[mailto:HP-Agilent-Keysight-equipment@groups.io] On Behalf Of Dave
McGuire
Sent: 19 May 2022 21:26
To: HP-Agilent-Keysight-equipment@groups.io
Subject: Re: [HP-Agilent-Keysight-equipment] A homemade diode power
sensor for HP meters

On 5/19/22 16:19, Paul Bicknell wrote:
Do not worry about Typos as I must be the worst speller on this sight
Of that there can be NO doubt. But we all love you anyway. ;)

-Dave

--
Dave McGuire, AK4HZ
New Kensington, PA











Re: A homemade diode power sensor for HP meters

 

Paul
Was in no way trying to solve everyones needs.
It was just a terrible thing to waste the nice analog devices detector and the poor old HP435 on the shelf.?
With the arduino in there I also get a usb 232 output the prints information. That was just because I could. It wasn't expensive but did require soldering various disassembly and such.
Your diode approach sounds like a better answer to get the hp meter closer to teh?original design.
Regards
Paul.


Re: Keysight VNA Cal Kit definitions webpage is missing

 

All -
Did I miss something I'm looking for a copy of the CAL KIT EDITOR - looked at the links that went buy but did not find a copy - does anyone have a copy tot the CAL KIT COEFFICIENTS editor ??

If so, please let me know where.

Cheers!

Bruce

Quoting Jeff Keyzer <jeff@...>:

Caesar,

Thank you so much for making all of this information available for users of the legacy VNAs. I have used your site at various times over the years and it has always been very helpful.
Sorry to hear about the hosting issues. I wish I could have grabbed a copy of everything before it started to disappear, but I'll try to save a copy of what's left before it's gone forever.

Thanks again, your efforts are appreciated.
Jeff



Re: Keysight VNA Cal Kit definitions webpage is missing

 

Caesar,

I grabbed a copy of this the other day, thank you. I was hoping to find copies of the various cal kit definition zip files that were formerly hosted on the site, as I've used these in the past, but I have since learned that I can recreate these using the tools that are available.
I've used the 8753 series intermittently for over twenty years and I am still learning things.

Thanks again,
Jeff


Re: Keysight VNA Cal Kit definitions webpage is missing

 

Caesar,

Thank you so much for making all of this information available for users of the legacy VNAs. I have used your site at various times over the years and it has always been very helpful.
Sorry to hear about the hosting issues. I wish I could have grabbed a copy of everything before it started to disappear, but I'll try to save a copy of what's left before it's gone forever.

Thanks again, your efforts are appreciated.
Jeff


Re: A homemade diode power sensor for HP meters

 

OK Dave

Re the 8484 I actually have 2 of the black 2 grey and one D version a lot better than my original 430 power meter and Sensor with an N connecter on it
So just a thought how dues the 8484A do its temperature compensation as I do not think I have ever looked at the CCT diagram for the 8484 A

Paul

-----Original Message-----
From: HP-Agilent-Keysight-equipment@groups.io [mailto:HP-Agilent-Keysight-equipment@groups.io] On Behalf Of Lothar baier
Sent: 19 May 2022 22:08
To: HP-Agilent-Keysight-equipment@groups.io
Subject: Re: [HP-Agilent-Keysight-equipment] A homemade diode power sensor for HP meters

The 8484A was the first diode sensor that HP produced , it was a horrible piece of equipment prone to drift especially if you got one with the black case .
Eventually HP redesigned the sensor to solve the issues and the new sensor was the 8481D
On May 19, 2022, at 15:37, Paul Bicknell via groups.io <admin@...> wrote:

?Thank you Dave for those kind words of love Paul

-----Original Message-----
From: HP-Agilent-Keysight-equipment@groups.io
[mailto:HP-Agilent-Keysight-equipment@groups.io] On Behalf Of Dave
McGuire
Sent: 19 May 2022 21:26
To: HP-Agilent-Keysight-equipment@groups.io
Subject: Re: [HP-Agilent-Keysight-equipment] A homemade diode power
sensor for HP meters

On 5/19/22 16:19, Paul Bicknell wrote:
Do not worry about Typos as I must be the worst speller on this sight
Of that there can be NO doubt. But we all love you anyway. ;)

-Dave

--
Dave McGuire, AK4HZ
New Kensington, PA











Re: A homemade diode power sensor for HP meters

Lothar baier
 

The 8484A was the first diode sensor that HP produced , it was a horrible piece of equipment prone to drift especially if you got one with the black case .
Eventually HP redesigned the sensor to solve the issues and the new sensor was the 8481D

On May 19, 2022, at 15:37, Paul Bicknell via groups.io <admin@...> wrote:

?Thank you Dave for those kind words of love
Paul

-----Original Message-----
From: HP-Agilent-Keysight-equipment@groups.io [mailto:HP-Agilent-Keysight-equipment@groups.io] On Behalf Of Dave McGuire
Sent: 19 May 2022 21:26
To: HP-Agilent-Keysight-equipment@groups.io
Subject: Re: [HP-Agilent-Keysight-equipment] A homemade diode power sensor for HP meters

On 5/19/22 16:19, Paul Bicknell wrote:
Do not worry about Typos as I must be the worst speller on this sight
Of that there can be NO doubt. But we all love you anyway. ;)

-Dave

--
Dave McGuire, AK4HZ
New Kensington, PA











Re: A homemade diode power sensor for HP meters

 

Thank you Dave for those kind words of love
Paul

-----Original Message-----
From: HP-Agilent-Keysight-equipment@groups.io [mailto:HP-Agilent-Keysight-equipment@groups.io] On Behalf Of Dave McGuire
Sent: 19 May 2022 21:26
To: HP-Agilent-Keysight-equipment@groups.io
Subject: Re: [HP-Agilent-Keysight-equipment] A homemade diode power sensor for HP meters

On 5/19/22 16:19, Paul Bicknell wrote:
Do not worry about Typos as I must be the worst speller on this sight
Of that there can be NO doubt. But we all love you anyway. ;)

-Dave

--
Dave McGuire, AK4HZ
New Kensington, PA


Re: A homemade diode power sensor for HP meters

 

On 5/19/22 16:19, Paul Bicknell wrote:
Do not worry about Typos as I must be the worst speller on this sight
Of that there can be NO doubt. But we all love you anyway. ;)

-Dave

--
Dave McGuire, AK4HZ
New Kensington, PA


Re: A homemade diode power sensor for HP meters

 

Hi Bruce
Thank you for confirming the 8484A is a Diode front end and On re reading your previews mail again it is as clear as MUD

Do not worry about Typos as I must be the worst speller on this sight
Paul

-----Original Message-----
From: HP-Agilent-Keysight-equipment@groups.io [mailto:HP-Agilent-Keysight-equipment@groups.io] On Behalf Of Bruce
Sent: 19 May 2022 21:12
To: HP-Agilent-Keysight-equipment@groups.io
Subject: Re: [HP-Agilent-Keysight-equipment] A homemade diode power sensor for HP meters

It is a type - I meant Diode

The 8484 is a DIODE sensor - many other HP diode ensors have a D in the model number as explained B4

Cheers!
Beruce

Quoting Paul Bicknell <admin@...>:

OK Bruce please explain !

You say (The 8484 is a dione power sensor. Many other HP diode
sensors end with t "D" instead of an "A" in the model number.)

I do not understand ?? also is dione in the above line a typo

So Is the 8484A power sensor is a diode front end ??
Paul

-----Original Message-----
From: HP-Agilent-Keysight-equipment@groups.io
[mailto:HP-Agilent-Keysight-equipment@groups.io] On Behalf Of Bruce
Sent: 19 May 2022 20:45
To: HP-Agilent-Keysight-equipment@groups.io
Subject: Re: [HP-Agilent-Keysight-equipment] A homemade diode power
sensor for HP meters

The 8484 is a dione power sensor. Many other HP diode sensors end
with t "D" instead of an "A" in the model number.

E.g. 8485D as opposed to 8485A

Cheers!

Bruce

Quoting Paul Bicknell <admin@...
<mailto:admin@...> >:

From memory the 8484 power sensor is a diode front end



But a working 8481 or 8484 go for about ?120 to ?160 in the UK
equivalent to a day’s wages

And it would take best part of a day to modify busted thermocouples
for a diode by the time you did any calibration

Regards Paul



From: HP-Agilent-Keysight-equipment@groups.io
<mailto:HP-Agilent-Keysight-equipment@groups.io>
[mailto:HP-Agilent-Keysight-equipment@groups.io] On Behalf Of
visitslovenija
Sent: 19 May 2022 11:20
To: HP-Agilent-Keysight-equipment@groups.io
<mailto:HP-Agilent-Keysight-equipment@groups.io>
Subject: Re: [HP-Agilent-Keysight-equipment] A homemade diode power
sensor for HP meters



An interesting and long running thread.

Like many, I have a bit of a soft spot for the old HP435 meters and
would like to have one working on the bench.

Since broken detectors do show up now and again at a decent price,
has anyone successfully reworked one with busted thermocouples and
modified for a diode front end? I know it’s small and very fiddly,
but is that not easier than trying to build one from scratch?















Re: A homemade diode power sensor for HP meters

 

It is a type - I meant Diode

The 8484 is a DIODE sensor - many other HP diode ensors have a D in the model number as explained B4

Cheers!
Beruce

Quoting Paul Bicknell <admin@...>:

OK Bruce please explain !

You say (The 8484 is a dione power sensor. Many other HP diode sensors end with t "D" instead of an "A" in the model number.)

I do not understand ?? also is dione in the above line a typo

So Is the 8484A power sensor is a diode front end ??
Paul

-----Original Message-----
From: HP-Agilent-Keysight-equipment@groups.io [mailto:HP-Agilent-Keysight-equipment@groups.io] On Behalf Of Bruce
Sent: 19 May 2022 20:45
To: HP-Agilent-Keysight-equipment@groups.io
Subject: Re: [HP-Agilent-Keysight-equipment] A homemade diode power sensor for HP meters

The 8484 is a dione power sensor. Many other HP diode sensors end with t "D" instead of an "A" in the model number.

E.g. 8485D as opposed to 8485A

Cheers!

Bruce

Quoting Paul Bicknell <admin@... <mailto:admin@...> >:

From memory the 8484 power sensor is a diode front end



But a working 8481 or 8484 go for about ?120 to ?160 in the UK
equivalent to a day’s wages

And it would take best part of a day to modify busted thermocouples
for a diode by the time you did any calibration

Regards Paul



From: HP-Agilent-Keysight-equipment@groups.io <mailto:HP-Agilent-Keysight-equipment@groups.io>
[mailto:HP-Agilent-Keysight-equipment@groups.io] On Behalf Of
visitslovenija
Sent: 19 May 2022 11:20
To: HP-Agilent-Keysight-equipment@groups.io <mailto:HP-Agilent-Keysight-equipment@groups.io>
Subject: Re: [HP-Agilent-Keysight-equipment] A homemade diode power
sensor for HP meters



An interesting and long running thread.

Like many, I have a bit of a soft spot for the old HP435 meters and
would like to have one working on the bench.

Since broken detectors do show up now and again at a decent price, has
anyone successfully reworked one with busted thermocouples and
modified for a diode front end? I know it’s small and very fiddly, but
is that not easier than trying to build one from scratch?















Re: A homemade diode power sensor for HP meters

 

开云体育

The connecters are available, Binder make 3 types and they did cost ?10 , ? 13 ?and ?16? each

?

Regarding Diode sensors do not forget the 430 meter was made for Diode sensors? also I believe the early 431 A had a switch position for Diode

?

Personally looking for a modern meter ( not expensive ) for wave guide diode detectors but calibrated in dB

Paul

?

From: HP-Agilent-Keysight-equipment@groups.io [mailto:HP-Agilent-Keysight-equipment@groups.io] On Behalf Of Alexandre Souza
Sent: 19 May 2022 20:49
To: HP-Agilent-Keysight-equipment@groups.io
Subject: Re: [HP-Agilent-Keysight-equipment] A homemade diode power sensor for HP meters

?

Talking about power sensor, I got lucky enough to get a (working) 436b and a WORKING \o/ sensor. But unfortunately, got it without the cable. Is there a cheaper source for the cable than ebay?

?

73 de PU2SEX Alexandre

?

---8<---Corte aqui---8<---

---8<---Corte aqui---8<---

?

?

Em qui., 19 de mai. de 2022 às 13:41, visitslovenija <musto102@...> escreveu:

An interesting and long running thread.

Like many, I have a bit of a soft spot for the old HP435 meters and would like to have one working on the bench.

Since broken detectors do show up now and again at a decent price, has anyone successfully reworked one with busted thermocouples and modified for a diode front end? I know it’s small and very fiddly, but is that not easier than trying to build one from scratch?


Re: A homemade diode power sensor for HP meters

 

开云体育

OK Bruce? please explain !

You say ? (The 8484 is a dione power sensor.? Many other HP diode sensors end with t "D" instead of an "A" in the model number.)

I do not understand ??? also is dione in the above line a typo

So Is the 8484A power sensor is a diode? front end ??

Paul

-----Original Message-----
From: HP-Agilent-Keysight-equipment@groups.io [mailto:HP-Agilent-Keysight-equipment@groups.io] On Behalf Of Bruce
Sent: 19 May 2022 20:45
To: HP-Agilent-Keysight-equipment@groups.io
Subject: Re: [HP-Agilent-Keysight-equipment] A homemade diode power sensor for HP meters

The 8484 is a dione power sensor.? Many other HP diode sensors end with t "D" instead of an "A" in the model number.

E.g. 8485D as opposed to 8485A

Cheers!

Bruce

Quoting Paul Bicknell <admin@...>:

> From memory the 8484 power sensor is a diode? front end

>

>

>

> But a working 8481? or 8484 go for about ?120 to ?160 in the UK

> equivalent to a day’s wages

>

> And it would take best part of a day to modify busted thermocouples

> for a diode by the time you did any calibration

>

> Regards Paul

>

>

>

> From: HP-Agilent-Keysight-equipment@groups.io

> [mailto:HP-Agilent-Keysight-equipment@groups.io] On Behalf Of

> visitslovenija

> Sent: 19 May 2022 11:20

> To: HP-Agilent-Keysight-equipment@groups.io

> Subject: Re: [HP-Agilent-Keysight-equipment] A homemade diode power

> sensor for HP meters

>

>

>

> An interesting and long running thread.

>

> Like many, I have a bit of a soft spot for the old HP435 meters and

> would like to have one working on the bench.

>

> Since broken detectors do show up now and again at a decent price, has

> anyone successfully reworked one with busted thermocouples and

> modified for a diode front end? I know it’s small and very fiddly, but

> is that not easier than trying to build one from scratch?

>

>

>

>

>

>






Re: A homemade diode power sensor for HP meters

 

开云体育

Hi Paul

sounds like you have re engendered the 435? and you say you have achieved a 65 dB dynamic range? that is excellent

and good for most Amateurs to ?6 Ghz ?but a lot want 10 Ghz? ?suggest you write it up for one of the magazines that Pay

just as mater of interest? other than lots of Time ( I assume Weeks ) how much did it cost excluding the donor 435

?

Personally I repair the 432 and 435 meter usually it is the meter face and help UK Amateurs out with parts

Paul

?

From: HP-Agilent-Keysight-equipment@groups.io [mailto:HP-Agilent-Keysight-equipment@groups.io] On Behalf Of paulswed
Sent: 19 May 2022 18:52
To: HP-Agilent-Keysight-equipment@groups.io
Subject: Re: [HP-Agilent-Keysight-equipment] A homemade diode power sensor for HP meters

?

The diode approach would be the way to go. Like many of you I also like the large scale HP power meters. You can pick the bodies up for nothing. Though suddenly there seems to be a magical market for a body without sensors.

An approach I recently took that has worked was to leverage the analog devices power sensors into a 435 body. This approach really couldn't use anything?inside of the 435.

The Analog device sensor in a small box with very flexible?cable goes to an arduino that maps the linear to the log scale of the 435.

Since the sensor works from?+15 to -50db I reused the switch to select new scaling in 10 db steps. Also to create a broad range 0 to -50 db scale.

I like the meter a lot and it now sets on top?the real HP-435.

The real one for very accurate readings to 18 GHz the new one good to 6 GHz. It really works well as I rarely need .25 db accuracy on anything.

The Linear to log was quite a challenge as I learned.

Though the meter is very nice this was a complex project so not sure its useful to many.

If the diode approach can work as Dave says then that would be the best approach with the least building challenge.

If you don't need 18GHz bandwidth maybe you can get away with larger components.

Regards

Paul

WB8TSL


Re: A homemade diode power sensor for HP meters

 

Talking about power sensor, I got lucky enough to get a (working) 436b and a WORKING \o/ sensor. But unfortunately, got it without the cable. Is there a cheaper source for the cable than ebay?

73 de PU2SEX Alexandre

---8<---Corte aqui---8<---
---8<---Corte aqui---8<---


Em qui., 19 de mai. de 2022 às 13:41, visitslovenija <musto102@...> escreveu:

An interesting and long running thread.

Like many, I have a bit of a soft spot for the old HP435 meters and would like to have one working on the bench.

Since broken detectors do show up now and again at a decent price, has anyone successfully reworked one with busted thermocouples and modified for a diode front end? I know it’s small and very fiddly, but is that not easier than trying to build one from scratch?


Re: A homemade diode power sensor for HP meters

 

The 8484 is a dione power sensor. Many other HP diode sensors end with t "D" instead of an "A" in the model number.

E.g. 8485D as opposed to 8485A

Cheers!

Bruce

Quoting Paul Bicknell <admin@...>:

From memory the 8484 power sensor is a diode front end



But a working 8481 or 8484 go for about ?120 to ?160 in the UK equivalent to a day’s wages

And it would take best part of a day to modify busted thermocouples for a diode by the time you did any calibration

Regards Paul



From: HP-Agilent-Keysight-equipment@groups.io [mailto:HP-Agilent-Keysight-equipment@groups.io] On Behalf Of visitslovenija
Sent: 19 May 2022 11:20
To: HP-Agilent-Keysight-equipment@groups.io
Subject: Re: [HP-Agilent-Keysight-equipment] A homemade diode power sensor for HP meters



An interesting and long running thread.

Like many, I have a bit of a soft spot for the old HP435 meters and would like to have one working on the bench.

Since broken detectors do show up now and again at a decent price, has anyone successfully reworked one with busted thermocouples and modified for a diode front end? I know it’s small and very fiddly, but is that not easier than trying to build one from scratch?






Re: Converting a 3336A signal gen to 3336C

 

Updates & errors in my previous post :

  1. Display keyboard panel is A5 not A4...
  2. High accuracy attenuator is still there...its center behind the "modify" potentiometer control...whats is removed is the "balanced output module" designated A11 for the 3336A and A10 for the 3336B

To avoid more "hacking" of the 3336A front panel in the conversion to a 3336C, I cut traces to SW37 & its button led and tacked all this on to SW36 pads. 50 & 75 outputs are not "centered" like the 3336C but this way buttons are aligned with corresponding outputs. I left SW38 (now useless) in.

A metal plate was affixed to he back of the front panal to fill the 2 square holes closest to the "modify" pot in front panel...round holes were drilled in that plate and a 50 ohms bnc and a 75 ohms "F" female connector were put there.

Claude



Claude


Re: A homemade diode power sensor for HP meters

 

开云体育

From memory the 8484 power sensor is a diode? front end

?

But a working 8481? or 8484 go for about ?120 to ?160 in the UK equivalent to a day’s wages?

And it would take best part of a day to modify busted thermocouples for a diode by the time you did any calibration

Regards Paul

?

From: HP-Agilent-Keysight-equipment@groups.io [mailto:HP-Agilent-Keysight-equipment@groups.io] On Behalf Of visitslovenija
Sent: 19 May 2022 11:20
To: HP-Agilent-Keysight-equipment@groups.io
Subject: Re: [HP-Agilent-Keysight-equipment] A homemade diode power sensor for HP meters

?

An interesting and long running thread.

Like many, I have a bit of a soft spot for the old HP435 meters and would like to have one working on the bench.

Since broken detectors do show up now and again at a decent price, has anyone successfully reworked one with busted thermocouples and modified for a diode front end? I know it’s small and very fiddly, but is that not easier than trying to build one from scratch?


Re: hp 16702 LA connectivity questio: GPIB, RS-232 > USB, Ethernet

 

On Thu, May 19, 2022 at 11:20 AM Mark Litwack <mlitwack@...> wrote:

I don't see that there was ever a GPIB option for the 167xx series.
There is actually a TI 9914 GPIB controller populated on the
16700-series logic analyzer CPU board, along with a 75ALS160 and
74ALS164, and a 24-pin header populated where a back panel GPIB
connector could have been populated instead. That is because the
16700-series logic analyzer CPU board was originally used for the
E4406A. There are E4406-xxxxx stickers on some of the programmable
components of the 16700 CPU board. In the E4406A application the back
panel GPIB connector is populated on the CPU board.

Maybe there were plans to make use of the GPIB controller in the
16700-series logic analyzer application that never materialized.