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Re: I'm old 70+, the 70K system is old; good or bad omen?

 

It may prove more useful to use dissipation factor rather than ESR even though both are a measure of the same thing. Since DF is a ratio of reactance to resistance it varies with frequency and may be more indicative of capacitor quality than plain ESR.
?? There is a good, short article on DF at:
<>

On 11/24/2021 3:05 PM, Gene Silvernail wrote:
Church Roger that,

The thing that helped me down the wrong path is the hybrid package. Electrically? it's radial, mechanical is axial...something new for me.

After extracting my head I re-ran cap and ESR readings.? Capacitance is within range when run at 1khz and drops off at 10 and 100 khz. ESR is around around 1 ohm at 1 khz where it goes over range on 10 and 100 khz, meaning way high for ESR numbers.? Today, SMPS's run much faster extending in MHz. So lower Z and R Caps were needed...so how good of a? ESR number is needed at 40 kHz?...So...

All readings would be good if operating below 1kHz, which they aren't. They don't even make 10kHz so...

Conclusionis they're shot and will replace...


Has anyone ever measured 10 or 100 kHz ESR on any of originals that were still working,

Thanks all the your help

Gene/K7QHO

Sent from my T-Mobile 5G Device
Get Outlook for Android <>
-----------------------------------------------------------------
*From:* [email protected] <[email protected]> on behalf of Dave McGuire <mcguire@...>
*Sent:* Wednesday, November 24, 2021 6:57:38 AM
*To:* [email protected] <[email protected]>
*Subject:* Re: [HP-Agilent-Keysight-equipment] I'm old 70+, the 70K system is old; good or bad omen?
On 11/24/21 7:38 AM, Chuck Harris wrote:
Depending on the manufacturer, the lead arrangement had another
more practical purpose, it made capacitor orientation irrelevant.

The outer leads were welded to the aluminum can, and were by
convention the negative leads.? The inner lead was positive.

It is virtually always the case with radial leaded aluminum
electrolytic capacitors that the outer most lead(s) will be the
negative lead, and the most central lead(s) the positive.

There were some tantalum caps in a similar package that were all
doubles, as I recall.
?? I forgot to mention this.? The capacitors in question here look like
typical cylindrical Al electrolytics, but they have a third lead coming
out from the *top* of the Al can.? See the datasheet for the
Vishay/Sprague 672D series.

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

--
Dave McGuire, AK4HZ
New Kensington, PA





--
Richard Knoppow
dickburk@...
WB6KBL
Re: 70900A Artek CLIP Manual

 
Edited

¿ªÔÆÌåÓý

Bladen I gotta know...where did it live?

Sent from my T-Mobile 5G Device
Get

From: [email protected] <[email protected]> on behalf of Paul Bicknell <admin@...>
Sent: Wednesday, November 24, 2021 11:10:08 AM
To: [email protected] <[email protected]>
Subject: Re: [HP-Agilent-Keysight-equipment] 70900A Artek CLIP Manual
?

Hi all

?

Just a bit of information the list below is not the complete list of the CLIP drawings for the 70900A as it comes in 2 large folders volumes 2 & 3 this is the same arrangement for the 70900B basically a lot of paper work

The complete list can be found in the 70900A service manual Volume 1 on page XVI in the Files on the groups IO HP 70000

Please note? there is a duplication of Part numbers? 70900-60003 is the part number for the power supply Schematic / circuit diagram? the same number is on the power supply component location Drawing

?

I do not have the Artek clip for the 70900A as it was not available when I started and I was fortunate to find an original set of drawings

But I do have the 70900B Artek Clip and that has the power supply Schematic / circuit diagram and the power supply component location Drawing

?

Suggest you give Dave at Artek a call / Email and he will sort it out for you

?

So I hope this helps Regards Paul

?

?

From: [email protected] [mailto:[email protected]] On Behalf Of Gene Silvernail
Sent: 24 November 2021 03:52
To: [email protected]
Subject: [HP-Agilent-Keysight-equipment] 70900A Artek CLIP Manual

?

Working on the PS board of the 70900A and bought the CLIP from Artek. Beautifully clear images, excellent for what's there. Unfortunately, the one thing I really needed it for isn't, that being the PS board. Anyone have any idea where that would that be found? Any help is greatly appreciated.

Pre-Thanks

Gene/K7QHO
Re: Need help printing schematic diagrams - large format printer / plotter

 

Sandra -
I'm going to bother you about the SMA induction soldering work.

What type of connector did you use?? Did it have a seperate center conductor pin or did it use the coax center conductor?
If it was the separate center conductor type, how did you manage the correct pin depth.? I'm making some hardline that will attach to? 3.5mm conductor on one end and the pin depth is going to be very important there.? I'd Like any insight you got during your work with the induction heater for SMA connectors.

Cheers!
Bruce
Re: I'm old 70+, the 70K system is old; good or bad omen?

 

¿ªÔÆÌåÓý

Church Roger that,

The thing that helped me down the wrong path is the hybrid package. Electrically? it's radial, mechanical is axial...something new for me.

After extracting my head I re-ran cap and ESR readings.? Capacitance is within range when run at 1khz and drops off at 10 and 100 khz. ESR is around around 1 ohm at 1 khz where it goes over range on 10 and 100 khz, meaning way high for ESR numbers.? Today, SMPS's run much faster extending in MHz. So lower Z and R Caps were needed...so how good of a? ESR number is needed at 40 kHz?...So...

All readings would be good if operating below 1kHz, which they aren't. They don't even make 10kHz so...

Conclusionis they're shot and will replace...


Has anyone ever measured 10 or 100 kHz ESR on any of originals that were still working,

Thanks all the your help

Gene/K7QHO

Sent from my T-Mobile 5G Device
Get

From: [email protected] <[email protected]> on behalf of Dave McGuire <mcguire@...>
Sent: Wednesday, November 24, 2021 6:57:38 AM
To: [email protected] <[email protected]>
Subject: Re: [HP-Agilent-Keysight-equipment] I'm old 70+, the 70K system is old; good or bad omen?
?
On 11/24/21 7:38 AM, Chuck Harris wrote:
> Depending on the manufacturer, the lead arrangement had another
> more practical purpose, it made capacitor orientation irrelevant.
>
> The outer leads were welded to the aluminum can, and were by
> convention the negative leads.? The inner lead was positive.
>
> It is virtually always the case with radial leaded aluminum
> electrolytic capacitors that the outer most lead(s) will be the
> negative lead, and the most central lead(s) the positive.
>
> There were some tantalum caps in a similar package that were all
> doubles, as I recall.

?? I forgot to mention this.? The capacitors in question here look like
typical cylindrical Al electrolytics, but they have a third lead coming
out from the *top* of the Al can.? See the datasheet for the
Vishay/Sprague 672D series.

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

--
Dave McGuire, AK4HZ
New Kensington, PA
Re: HP 8640B - internal counter suddenly got crazy

 

On 11/24/21 4:23 PM, Jerry Meyerhoff, JDM LABS wrote:
HI Dave, Mike and Frank. Another case of FRTM? first read the manual page 22 of 247.? 5 mc
Not sure why I thought it was 10 mc but that was a canned oscillator I had? .. Well that was quick & easy . Thanks a mil' !!!? Appreciate your kind patience ..
Well, the whole world uses 10MHz for everything, so it's a reasonable assumption. However, the 8640 predates that convention, and quite a few things back then used 5MHz.

Glad the group could assist you in getting it straightened out.

-Dave

--
Dave McGuire, AK4HZ
New Kensington, PA
Re: HP 8640B - internal counter suddenly got crazy

 

HI Dave, Mike and Frank. Another case of FRTM? first read the manual?? page 22 of 247.? 5 mc
Not sure why I thought it was 10 mc but that was a canned oscillator I had? .. Well that was quick & easy . Thanks a mil' !!!? Appreciate your kind patience ..
Next I'll have to post a ? on output attenuator missing / intermittant on some level steps along with level meter not reading .Or maybe 1st look in FAQ's .. <wink>

Happy Thanksgiving !?
--
Cheers Jerry? WA9FIY?? 11.24.2021
Re: 70900A Artek CLIP Manual

 
Edited

¿ªÔÆÌåÓý

Hi all

?

Just a bit of information the list below is not the complete list of the CLIP drawings for the 70900A as it comes in 2 large folders volumes 2 & 3 this is the same arrangement for the 70900B basically a lot of paper work

The complete list can be found in the 70900A service manual Volume 1 on page XVI in the Files on the groups IO HP 70000

Please note? there is a duplication of Part numbers? 70900-60003 is the part number for the power supply Schematic / circuit diagram? the same number is on the power supply component location Drawing

?

I do not have the Artek clip for the 70900A as it was not available when I started and I was fortunate to find an original set of drawings

But I do have the 70900B Artek Clip and that has the power supply Schematic / circuit diagram and the power supply component location Drawing

?

Suggest you give Dave at Artek a call / Email and he will sort it out for you

?

So I hope this helps Regards Paul

?

?

From: [email protected] [mailto:[email protected]] On Behalf Of Gene Silvernail
Sent: 24 November 2021 03:52
To: [email protected]
Subject: [HP-Agilent-Keysight-equipment] 70900A Artek CLIP Manual

?

Working on the PS board of the 70900A and bought the CLIP from Artek. Beautifully clear images, excellent for what's there. Unfortunately, the one thing I really needed it for isn't, that being the PS board. Anyone have any idea where that would that be found? Any help is greatly appreciated.

Pre-Thanks

Gene/K7QHO
Re: 70900A Artek CLIP Manual

 

As Dave said, the mainfarme contains a power supply that converts line to 40 kHz for distribution to the modules. Each 1/8 module was allowed 20W max. The LO was therefore "stuck" with an allocation of 40W. There are several reasons these capacitors fail in the LO module. For one, most MMS systems were sold into military depots. They were left continuously on, and that is one way electrolytic capacitors wear out. Also, as Dave mentioned, the LO module is particularly packed, so pushing cooling air through was not easy. And finally, it's possible that Sprague no longer was at the top of their game.

For anyone on this list, replacing the capacitors with something similar will be more than adequate as the system will not be running on a Navy ship for 20 years continuously. In fact, looking at Gene's pictures in the other thread, I see a label that tells me where that particular system lived its life.

Attached is a typical module supply schematic. It's not out of the LO module, but it shows the basic idea.

Vladan

MMS Module Supply.png

Re: HP 8640B - internal counter suddenly got crazy

 

On Wed, Nov 24, 2021 at 5:50 PM Dave McGuire <mcguire@...> wrote:

On November 24, 2021 11:43:28 AM "Jerry Meyerhoff, JDM LABS" <jerrybikes1@...> wrote:>Following this thread with keen interest.
Perhaps some advice on this problem will be applicable to my problem :
** Counter displays exactly 1/2 the output frequency on all bands **
8640B SN 1638A05395 OPT 003
The Band knob marked "EXTERNAL DOUBLER"
Always using EXTernal 10 MHz timebase as the internal appears
failed, before I got it . Also the 1/2 frequency problem always there .

Smells like could be in the 'Band-switch" logic , without digging through
manual or troubleshooting guides.
I could be wrong, as I don't have a manual in front of me, but I seem to recall that the 8640's external frequency reference input is 5MHz, not 10MHz
it's actually selectable between 5 MHz and 1 MHz via jumpers located
inside the counter assembly.
And no 10 MHz.
Frank IZ8DWF
Re: HP 8640B - internal counter suddenly got crazy

 

Yes, using a 10 MHz reference instead of a required 5 MHz would result in
reading half of the input frequency. 73 - Mike

Mike B. Feher, N4FS
89 Arnold Blvd.
Howell NJ 07731
848-245-9115

-----Original Message-----
From: [email protected]
<[email protected]> On Behalf Of Dave McGuire
Sent: Wednesday, November 24, 2021 11:50 AM
To: [email protected]
Subject: Re: [HP-Agilent-Keysight-equipment] HP 8640B - internal counter
suddenly got crazy

On November 24, 2021 11:43:28 AM "Jerry Meyerhoff, JDM LABS"
<jerrybikes1@...> wrote:>Following this thread with keen interest.
Perhaps some advice on this problem will be applicable to my problem :
** Counter displays exactly 1/2 the output frequency on all bands **
8640B SN 1638A05395 OPT 003 The Band knob marked "EXTERNAL
DOUBLER"
Always using EXTernal 10 MHz timebase as the internal appears failed,
before I got it . Also the 1/2 frequency problem always there .

Smells like could be in the 'Band-switch" logic , without digging
through manual or troubleshooting guides.
I could be wrong, as I don't have a manual in front of me, but I seem to
recall that the 8640's external frequency reference input is 5MHz, not 10MHz

-Dave

--
Dave McGuire, AK4HZ
New Kensington, PA
Re: HP 8640B - internal counter suddenly got crazy

 

On November 24, 2021 11:43:28 AM "Jerry Meyerhoff, JDM LABS" <jerrybikes1@...> wrote:>Following this thread with keen interest.
Perhaps some advice on this problem will be applicable to my problem :
** Counter displays exactly 1/2 the output frequency on all bands **
8640B SN 1638A05395 OPT 003
The Band knob marked "EXTERNAL DOUBLER"
Always using EXTernal 10 MHz timebase as the internal appears
failed, before I got it . Also the 1/2 frequency problem always there .

Smells like could be in the 'Band-switch" logic , without digging through
manual or troubleshooting guides.
I could be wrong, as I don't have a manual in front of me, but I seem to recall that the 8640's external frequency reference input is 5MHz, not 10MHz

-Dave

--
Dave McGuire, AK4HZ
New Kensington, PA
Re: HP 8640B - internal counter suddenly got crazy

 

¿ªÔÆÌåÓý

Hello Group.
Following this thread with keen interest.
Perhaps some advice on this problem will be applicable to my problem :
** Counter displays exactly 1/2 the output frequency on all bands **
8640B SN? 1638A05395? OPT? 003
The Band knob marked? "EXTERNAL DOUBLER"
Always using EXTernal 10 MHz timebase as the internal appears
failed, before I got it . Also?the 1/2 frequency problem always there?.
?
Smells like could be in the 'Band-switch" logic , without digging through
manual or troubleshooting guides.
?
Thankful for this wonderful & helpful group & prior advice.?
Best Regards,
Jerry Meyerhoff? , WA9FIY
11.24.2021

--
Cheers Jerry
Re: 70900A Artek CLIP Manual

 

On 11/24/21 8:08 AM, Chuck Harris wrote:
The power supply's schematic probably lives in one of many Chinese
power supply manufacturer's archives.
By the time the 70000K series came around, it was common for HP
to buy their power supplies from outside vendors (OEMs). The OEM's
supplies were inexpensive (a relative term), and were considered
to be interchangeable. They were not generally repaired, but rather
swapped out as a unit.
This isn't the case for 70K-series power supplies; they are 100% HP. They are specialized (and odd) designs. The enclosure has a large power supply that converts line voltage to bulk AC power of 20V P-P at 40kHz, which is then bussed to the MMS slots. Each MMS module has a power supply board that ingests this and converts it to whatever voltage(s) are required within the module.

The extremely cramped nature of the innards of MMS modules is another justification for 100% custom designs. These boards are of odd shapes and are (mostly) different from module to module.

There's no cheap Chinese crap in this top-end series. That "cost cancer" had to spread a lot farther within HP to infect their top-end stuff, and that happened after the 70K series.

See the MMS System Specifications document for more information about this interesting power architecture.

-Dave

--
Dave McGuire, AK4HZ
New Kensington, PA
Re: I'm old 70+, the 70K system is old; good or bad omen?

 

On 11/24/21 7:38 AM, Chuck Harris wrote:
Depending on the manufacturer, the lead arrangement had another
more practical purpose, it made capacitor orientation irrelevant.
The outer leads were welded to the aluminum can, and were by
convention the negative leads. The inner lead was positive.
It is virtually always the case with radial leaded aluminum
electrolytic capacitors that the outer most lead(s) will be the
negative lead, and the most central lead(s) the positive.
There were some tantalum caps in a similar package that were all
doubles, as I recall.
I forgot to mention this. The capacitors in question here look like typical cylindrical Al electrolytics, but they have a third lead coming out from the *top* of the Al can. See the datasheet for the Vishay/Sprague 672D series.

-Dave

--
Dave McGuire, AK4HZ
New Kensington, PA
Re: I'm old 70+, the 70K system is old; good or bad omen?

 

On 11/24/21 7:38 AM, Chuck Harris wrote:
Depending on the manufacturer, the lead arrangement had another
more practical purpose, it made capacitor orientation irrelevant.
The outer leads were welded to the aluminum can, and were by
convention the negative leads. The inner lead was positive.
It is virtually always the case with radial leaded aluminum
electrolytic capacitors that the outer most lead(s) will be the
negative lead, and the most central lead(s) the positive.
There were some tantalum caps in a similar package that were all
doubles, as I recall.
Yes there are. IBM used two types on boards from mainframe/midrange systems, three- and four-lead capacitors. They're usually +-+ or +--+, to solve the orientation problem. These boards were typically not hand-assembled, but making their orientation irrelevant allowed them to use loose parts in vibratory hopper feeders on the assembly line, rather than the more expensive and larger tape-and-reel component feeders.

These capacitors come in both the yellow dipped tantalum bead styles, usually no more than 1/2" tall, as well as small black molded rectangular blocks, about 3/8" tall and anywhere from 3/16" to 3/8" wide, and 1/8" thick or less.

-Dave

--
Dave McGuire, AK4HZ
New Kensington, PA
Re: 70900A Artek CLIP Manual

 

The 70900X and 70XXXX power supplies were never bought outside (obvious, the 3 lead capacitors). The A3 power supplply board is on the 70900B CLIP
On Wednesday, November 24, 2021, 02:09:16 PM GMT+1, Chuck Harris <cfharris@...> wrote:


The power supply's schematic probably lives in one of many Chinese
power supply manufacturer's archives.

By the time the 70000K series came around, it was common for HP
to buy their power supplies from outside vendors (OEMs).? The OEM's
supplies were inexpensive (a relative term), and were considered
to be interchangeable.? They were not generally repaired, but rather
swapped out as a unit.

Switching supplies have been refined to a point where the IC's, etc
are arranged so that they can be used on single sided boards.? For
safety, because of the voltages involved, they were laid out in a
straight forward way.? UL requires the line side, and the grounded
side be well marked with zebra lines, and warnings.

There are only two topologies in common use: 1) bootstrapped, and 2)
power factor correcting.

Bootstraped will always have a pair of largish HV electrolytic
capacitors on the AC end of the supply that rectify/double the power
line voltage.? You can count on there being a 120V/240V line selection
switch/strap somewhere.

Power factor correcting will usually have a single large HV
electrolytic capacitor, 900V or so, that can take any line voltage from
90V to 300V, without any user intervention.

Anyway, there are books galore on the two normal topologies, and once
you have determined which you have, it is quite easy to follow the signals
across the circuit board... the board is as good as the schematics the
Chinese made for these supplies.

Those that fix these sorts of boards don't use schematics, but rather
use their senses (eyes, nose...), ESR meters, and knowledge of the parts
that generally fail.

-Chuck Harris


On Tue, 23 Nov 2021 19:52:15 -0800 "Gene Silvernail"
<genesilvernail@...> wrote:
> Working on the PS board of the 70900A and bought the CLIP from Artek.
> Beautifully clear images, excellent for what's there. Unfortunately,
> the one thing I really needed it for isn't, that being the PS board.
> Anyone have any idea where that would that be found? Any help is
> greatly appreciated.
>
> Pre-Thanks
>
> Gene/K7QHO
>
> Attachments:
> dummyfile.0.part:
> /g/HP-Agilent-Keysight-equipment/attachment/120425/0
>
>
>
>
>






Re: 70900A Artek CLIP Manual

 

The power supply's schematic probably lives in one of many Chinese
power supply manufacturer's archives.

By the time the 70000K series came around, it was common for HP
to buy their power supplies from outside vendors (OEMs). The OEM's
supplies were inexpensive (a relative term), and were considered
to be interchangeable. They were not generally repaired, but rather
swapped out as a unit.

Switching supplies have been refined to a point where the IC's, etc
are arranged so that they can be used on single sided boards. For
safety, because of the voltages involved, they were laid out in a
straight forward way. UL requires the line side, and the grounded
side be well marked with zebra lines, and warnings.

There are only two topologies in common use: 1) bootstrapped, and 2)
power factor correcting.

Bootstraped will always have a pair of largish HV electrolytic
capacitors on the AC end of the supply that rectify/double the power
line voltage. You can count on there being a 120V/240V line selection
switch/strap somewhere.

Power factor correcting will usually have a single large HV
electrolytic capacitor, 900V or so, that can take any line voltage from
90V to 300V, without any user intervention.

Anyway, there are books galore on the two normal topologies, and once
you have determined which you have, it is quite easy to follow the signals
across the circuit board... the board is as good as the schematics the
Chinese made for these supplies.

Those that fix these sorts of boards don't use schematics, but rather
use their senses (eyes, nose...), ESR meters, and knowledge of the parts
that generally fail.

-Chuck Harris

On Tue, 23 Nov 2021 19:52:15 -0800 "Gene Silvernail"
<genesilvernail@...> wrote:
Working on the PS board of the 70900A and bought the CLIP from Artek.
Beautifully clear images, excellent for what's there. Unfortunately,
the one thing I really needed it for isn't, that being the PS board.
Anyone have any idea where that would that be found? Any help is
greatly appreciated.

Pre-Thanks

Gene/K7QHO

Attachments:
dummyfile.0.part:
/g/HP-Agilent-Keysight-equipment/attachment/120425/0
Re: I'm old 70+, the 70K system is old; good or bad omen?

 

Depending on the manufacturer, the lead arrangement had another
more practical purpose, it made capacitor orientation irrelevant.

The outer leads were welded to the aluminum can, and were by
convention the negative leads. The inner lead was positive.

It is virtually always the case with radial leaded aluminum
electrolytic capacitors that the outer most lead(s) will be the
negative lead, and the most central lead(s) the positive.

There were some tantalum caps in a similar package that were all
doubles, as I recall.

-Chuck Harris


On Tue, 23 Nov 2021 20:03:55 -0800 "Gene Silvernail"
<genesilvernail@...> wrote:
Thanks Kuba,



Yeh coming from the era of tubes I had assumed a dual cap¡­so much for
assuming.

Now that¡¯s starting to make sense with the single component
designator, but leaves the question which 2 out of the 3 leads make
up the capacitor and what purpose does the third lead serve. Is it a
non-electrical, mechanical only?

I¡¯m working without a schematic even though I bought the CLIP from
Artek which is minus the PS board.



Pre-Thanks



Gene/K7QHO



From: [email protected]
<[email protected]> On Behalf Of Kuba Ober
Sent: Tuesday, November 23, 2021 7:26 PM To:
[email protected] Subject: Re:
[HP-Agilent-Keysight-equipment] I'm old 70+, the 70K system is old;
good or bad omen?



My assumption would be that the number of legs has not much to do
with anything: it¡¯s a single capacitor each with 3 or 4 legs. Very
common in that era. I¡¯ e got lots of contemporaneous Tektronix
equipment that has the same capacitor styles.



The double and triple electrolytics were a thing in the vacuum tube
era.



Cheers, Kuba





23 nov. 2021 kl. 9:54 em skrev Gene Silvernail
<genesilvernail@... <mailto:genesilvernail@...> >:

?

Thanks Paul,



Just got the component location PDF on the site which provides me the
PS cap numbers; also ordered the 70900A CLIP. However, looking at
them I¡¯m confused further with the 3 leads. Only 1 component number
associated with a dual capacitor¡­huh? Hopefully the schematic will
clarify this.



Regards



Gene



From: [email protected]
<mailto:[email protected]>
<[email protected]
<mailto:[email protected]> > On Behalf Of Paul
Bicknell Sent: Tuesday, November 23, 2021 12:56 PM To:
[email protected]
<mailto:[email protected]> Subject: Re:
[HP-Agilent-Keysight-equipment] I'm old 70+, the 70K system is old;
good or bad omen?



Hi Gene

sorry made a mistake the 3 legged caps are on the Vishay N -cap and
can be found on the hp 70000 groups site. Regards Paul







Re: HP 8640B - internal counter suddenly got crazy

 

On Wed, Nov 24, 2021 at 10:03 AM Emanuele Girlando via groups.io
<emanuele_girlando@...> wrote:

Francesco, we cross posted.

If not EECL, what?
The most intriguing behavior is "External counter input works OK in the 0-10Mhz range, but doubles
the reading in the 10-512Mhz range (BUT not if signal is coming from output REF (rear panel) !!"
aux output you mean? One of the rear there're two output connectors,
one is only for the 5 MHz (or 1 MHz) fixed internal reference.
The counter input works well only between a certain range of input
signal amplitude. The aux output has a fixed amplitude.
So if the counter works fine with the external input at a fixed
amplitude, I'd really check switch contacts first.
Frank
Re: HP 8640B - internal counter suddenly got crazy

 

Francesco, we cross posted.

If not EECL, what?
The most intriguing behavior is "External counter input works OK in the 0-10Mhz range, but doubles
the reading in the 10-512Mhz range (BUT not if signal is coming from output REF (rear panel) !!"

I'll double check the band switch wipers... they seem in place and none found floating inside the instrument..
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