Topics

Most common capacitor spot failure in 7K scopes?

Ed Breya
 

I've been working on my 7K power supply/mainframe/plug-in tester box, finalizing the various functions. One of the functions is to look for shorted or partially-shorted Ta caps on the low voltage supplies. Partially-shorted ones can be tracked down with DC applied from a modified 7603 linear supply, operating all the mainframe supplies, with the mainframe's internal supply disconnected. For locating shorted or very low resistance caps or similar faults, the plan is to apply 60 Hz AC to the selected supply, from a current source up to about an amp, and clamped to +/- a diode drop. The current can be traced without contact by a magnetic probe, based on a small magnetic tape head, amplified up, and synchronously demodulated with adjustable phase to maximize response to the real part of the fault current (into the shorted part), rather than any capacitive current in the various bypass caps throughout the system.

I can make it to select and drive any of the internal supplies this way, but it may be OK to simplify it and only drive the most suspect/likely ones - the 15 and 5 volt supplies. In my experience, these are the ones most often faulted by Ta caps in the mainframes and plug-ins. The 50 and 130 volt supplies may have problems too, but I don't recall finding this sort of thing in them - they don't use Ta caps (except for some exceptions), and likely don't need this particular test capability.

What do you all think? Has anyone ever found shorts in the +/-50 or +130 supplies? I believe the 15s and 5s are the ones to focus on, but would like to hear about other stuff before committing it in final design.

Ed

garp66
 

I have used the HP 547a Current Tracer probe to find shorted Tantalum capacitors.
It becomes pretty obvious via the intense red LED brightness(~ proportional to the current flow) which cap has failed.

547a manual:
http://kripton2035.free.fr/Resources/HP%20547A%20Current%20Tracer%20Manual.pdf

rick

garp66
 

The HP 547a Current Tracer theory & use was featured in the December 1976 issue of the HP Journal:

a .pdf can be found at:
https://scss.tcd.ie/SCSSTreasuresCatalog/hardware/TCD-SCSS-T.20160121.006/HPJournal-1976-12.pdf

Dave Seiter
 

Thanks for the reminder!  I knew I had the set, but was missing one of the probes; turns out I have the current probe, not the pulser.  Haven't used any of them in years; now I have a reason to play with the current probe.
-Dave

On Thursday, June 20, 2019, 8:09:22 PM PDT, garp66 <@garp66> wrote:

I have used the HP 547a Current Tracer probe to find shorted Tantalum capacitors.
It becomes pretty obvious via the intense red LED brightness(~ proportional to the current flow) which cap has failed.

547a manual:
http://kripton2035.free.fr/Resources/HP%20547A%20Current%20Tracer%20Manual.pdf

rick

Carsten Bormann
 

On Jun 21, 2019, at 05:09, garp66 <@garp66> wrote:

I have used the HP 547a Current Tracer probe to find shorted Tantalum capacitors.
It becomes pretty obvious via the intense red LED brightness(~ proportional to the current flow) which cap has failed.
How do you get the short-risetime pulses that a 547a requires?

BTW, while talking about 547a and friends:
What is the round connector pin system the these use on its power supply side (and the other 54xa on the grounding side)?
Can you get mating hardware today?

Grüße, Carsten

george edmonds
 

Hi Carsten

The original HP547A was designed to use mini grabbers to power it up, the pulser is a 546A and there was also a logic probe in the same familly.

I do have two HP547A's for sale, but, they are not cheap, on the well know auction site they are selling for about £100 each when they come up which is rare. Mine will be cheaper than this.

If you have any interest please contact me off list at G6HIG at Yahoo dot com

George G6HIG

On Friday, June 21, 2019, 11:24:26 AM GMT+1, Carsten Bormann <cabocabo@...> wrote:

On Jun 21, 2019, at 05:09, garp66 <@garp66> wrote:

I have used the HP 547a Current Tracer probe to find shorted Tantalum capacitors.
It becomes pretty obvious via the intense red LED brightness(~ proportional to the current flow) which cap has failed.
How do you get the short-risetime pulses that a 547a requires?

BTW, while talking about 547a and friends:
What is the round connector pin system the these use on its power supply side (and the other 54xa on the grounding side)?
Can you get mating hardware today?

Grüße, Carsten

Paul Amaranth
 

Prices on those have been going up recently, I think folks are finally figuring
out that it's a fantastic tool.

I have a set and it generally takes longer to get things set up than to find
a shorted part.

Paul

On Fri, Jun 21, 2019 at 04:36:45AM +0000, Dave Seiter wrote:
Thanks for the reminder!  I knew I had the set, but was missing one of the probes; turns out I have the current probe, not the pulser.  Haven't used any of them in years; now I have a reason to play with the current probe.
-Dave
On Thursday, June 20, 2019, 8:09:22 PM PDT, garp66 <@garp66> wrote:

I have used the HP 547a Current Tracer probe to find shorted Tantalum capacitors.
It becomes pretty obvious via the intense red LED brightness(~ proportional to the current flow) which cap has failed.

547a manual:
http://kripton2035.free.fr/Resources/HP%20547A%20Current%20Tracer%20Manual.pdf

rick








!DSPAM:5d0c5ef8203591517594934!
--
Paul Amaranth, GCIH | Manchester MI, USA
Aurora Group of Michigan, LLC | Security, Systems & Software
paul@... | Unix & Windows

Dave Daniel
 

Where does one find a set (545, 546, 547 and accessories)?

DaveD

Sent from a small flat thingy

On Jun 21, 2019, at 08:39, Paul Amaranth <paul@...> wrote:

Prices on those have been going up recently, I think folks are finally figuring
out that it's a fantastic tool.

I have a set and it generally takes longer to get things set up than to find
a shorted part.

Paul

On Fri, Jun 21, 2019 at 04:36:45AM +0000, Dave Seiter wrote:
Thanks for the reminder! I knew I had the set, but was missing one of the probes; turns out I have the current probe, not the pulser. Haven't used any of them in years; now I have a reason to play with the current probe.
-Dave
On Thursday, June 20, 2019, 8:09:22 PM PDT, garp66 <@garp66> wrote:

I have used the HP 547a Current Tracer probe to find shorted Tantalum capacitors.
It becomes pretty obvious via the intense red LED brightness(~ proportional to the current flow) which cap has failed.

547a manual:
http://kripton2035.free.fr/Resources/HP%20547A%20Current%20Tracer%20Manual.pdf

rick








!DSPAM:5d0c5ef8203591517594934!
--
Paul Amaranth, GCIH | Manchester MI, USA
Aurora Group of Michigan, LLC | Security, Systems & Software
paul@... | Unix & Windows


ArtekManuals
 

Ebay and Hamfest Flea Markets
Dave
Nr1DX
manuals@...

On 6/21/2019 8:42 AM, Dave Daniel wrote:
Where does one find a set (545, 546, 547 and accessories)?

DaveD

Sent from a small flat thingy

On Jun 21, 2019, at 08:39, Paul Amaranth <paul@...> wrote:

Prices on those have been going up recently, I think folks are finally figuring
out that it's a fantastic tool.

I have a set and it generally takes longer to get things set up than to find
a shorted part.

Paul

On Fri, Jun 21, 2019 at 04:36:45AM +0000, Dave Seiter wrote:
Thanks for the reminder! I knew I had the set, but was missing one of the probes; turns out I have the current probe, not the pulser. Haven't used any of them in years; now I have a reason to play with the current probe.
-Dave
On Thursday, June 20, 2019, 8:09:22 PM PDT, garp66 <@garp66> wrote:

I have used the HP 547a Current Tracer probe to find shorted Tantalum capacitors.
It becomes pretty obvious via the intense red LED brightness(~ proportional to the current flow) which cap has failed.

547a manual:
http://kripton2035.free.fr/Resources/HP%20547A%20Current%20Tracer%20Manual.pdf

rick








!DSPAM:5d0c5ef8203591517594934!
--
Paul Amaranth, GCIH | Manchester MI, USA
Aurora Group of Michigan, LLC | Security, Systems & Software
paul@... | Unix & Windows


--
Dave
Manuals@...
www.ArtekManuals.com

Carsten Bormann
 

On Jun 21, 2019, at 13:20, george edmonds via Groups.Io <G6HIG=yahoo.com@groups.io> wrote:

The original HP547A was designed to use mini grabbers to power it up, the pulser is a 546A and there was also a logic probe in the same familly.
Yes. I’m trying to put together a more permanent way to supply the probe; it would be great to find the connectors mating to the ones that go into the grabbers now (and that would also allow me to apply a better ground lead to the pulser, which seems to have the same connector).

(Sorry if this is too off-topic for tekscopes, maybe I should have asked on the HP group.)

Grüße, Carsten

Harvey White
 

On 6/20/2019 11:09 PM, garp66 wrote:
I have used the HP 547a Current Tracer probe to find shorted Tantalum capacitors.
It becomes pretty obvious via the intense red LED brightness(~ proportional to the current flow) which cap has failed.
I hadn't thought of this, which is a nice application.  However, aren't you measuring ripple current to the cap?  I looked to see if the probe measures straight DC, and it appears not.

Harvey



547a manual:
http://kripton2035.free.fr/Resources/HP%20547A%20Current%20Tracer%20Manual.pdf

rick




Paul Amaranth
 

You either use a FG or the current pulser to inject current pulses
on the supply rails, then just follow it around. The probe is
sensitive enough that it will follow traces on the other side
of the board (or inside on multilayer boards).

Pretty slick. I found a shorted tant in a 2432a one time in
about 5 minutes; even led me to the right board.

Paul

On Fri, Jun 21, 2019 at 10:38:40AM -0400, Harvey White wrote:

On 6/20/2019 11:09 PM, garp66 wrote:
I have used the HP 547a Current Tracer probe to find shorted Tantalum capacitors.
It becomes pretty obvious via the intense red LED brightness(~ proportional to the current flow) which cap has failed.
I hadn't thought of this, which is a nice application.  However, aren't you
measuring ripple current to the cap?  I looked to see if the probe measures
straight DC, and it appears not.

Harvey



547a manual:
http://kripton2035.free.fr/Resources/HP%20547A%20Current%20Tracer%20Manual.pdf

rick








!DSPAM:5d0cebfb215029366918516!
--
Paul Amaranth, GCIH | Manchester MI, USA
Aurora Group of Michigan, LLC | Security, Systems & Software
paul@... | Unix & Windows

Brian Symons
 

HP made a fairly rarely seen accessory for the HP 545A, 546A, & 547A probes that converts a BNC connector to the two round power pins for the 54x series probes.
It is just a BNC connector with moulded in sockets for the power connectors to plug into.

The Adaptor, Straight or Coaxial Adaptor, Straight had a part number of 1250-1948 & I have examples with both HP & ITT Pomona & labels.

You may wish to get one of them to use as a basis for your "more permanent way to supply the probe."

Regards,
Brian.

On 21-Jun.-19 23:51, Carsten Bormann wrote:
On Jun 21, 2019, at 13:20, george edmonds via Groups.Io <G6HIG=yahoo.com@groups.io> wrote:
The original HP547A was designed to use mini grabbers to power it up, the pulser is a 546A and there was also a logic probe in the same familly.
Yes. I’m trying to put together a more permanent way to supply the probe; it would be great to find the connectors mating to the ones that go into the grabbers now (and that would also allow me to apply a better ground lead to the pulser, which seems to have the same connector).

(Sorry if this is too off-topic for tekscopes, maybe I should have asked on the HP group.)

Grüße, Carsten

Ed Breya
 

There are many methods and devices available for short-tracing, not just the old HP one. You can also find modern off-shelf ones, or rig up your own simple setups with the right gear and parts. Perhaps a separate thread should be opened for this, which I think is on-topic here since it's a common problem in fixing our scopes and such.

However, my original question was aimed at figuring out if just doing tracing on the + and - 15V, and +5V, are sufficient to cover like 99 percent of the cases, or if there are enough similar situations on the +/-50V and +130V to warrant just doing all of them. The connections, selections, and driving capability will be built into the test box, so it affects the complexity of the signal routing and protection involved.

Ed

garp66
 

Sometimes I use a common 9V battery cell with clip leads to independently power up the HP 547a Current Tracer, independent of the PCB that I am testing, thus isolating the PCB board power(either On or Off). The Logic Pulser HP 546a can also be powered independently with a 9V cell. One can also connect the 9V battery neg. terminal to the PCB-under-test Or not, depending on various test issues, TBD, that one encounters.

These two small simple bits of HP test gear have well proven their worth-in-weight for many many years.

An HP AP Note (.pdf) # 163-2, on these probes is available:
http://hpmemoryproject.org/an/pdf/an_163-2.pdf

A HP Bench Brief (.pdf) is also useful:
http://hparchive.com/Bench_Briefs/HP-Bench-Briefs-1977-09-10.pdf

rick

Stephen Hanselman
 

For really difficult shorts we used a 2100A power supply 5VDC, the shorts and bad components became obvious quickly. I know it sounds like a joke, but it was used and works fairly well.

Regards,

Stephen Hanselman
Datagate Systems, LLC

On Jun 21, 2019, at 10:21, garp66 <@garp66> wrote:

Sometimes I use a common 9V battery cell with clip leads to independently power up the HP 547a Current Tracer, independent of the PCB that I am testing, thus isolating the PCB board power(either On or Off). The Logic Pulser HP 546a can also be powered independently with a 9V cell. One can also connect the 9V battery neg. terminal to the PCB-under-test Or not, depending on various test issues, TBD, that one encounters.

These two small simple bits of HP test gear have well proven their worth-in-weight for many many years.

An HP AP Note (.pdf) # 163-2, on these probes is available:
http://hpmemoryproject.org/an/pdf/an_163-2.pdf

A HP Bench Brief (.pdf) is also useful:
http://hparchive.com/Bench_Briefs/HP-Bench-Briefs-1977-09-10.pdf

rick


Dave Daniel
 

I haven't seen any on ebay. I have been looking for one of the kits (5021A, 5022A or 5023A in the 1977 catalog). I haven't been to any hamfests yet since moving - I'll have to correct that. I suppose I can check Astro Too....

DaveD

On 6/21/2019 8:46 AM, ArtekManuals wrote:
Ebay and Hamfest Flea Markets
Dave
Nr1DX
manuals@...

On 6/21/2019 8:42 AM, Dave Daniel wrote:
Where does one find a set (545, 546, 547 and accessories)?

DaveD

Sent from a small flat thingy

On Jun 21, 2019, at 08:39, Paul Amaranth <paul@...> wrote:

Prices on those have been going up recently, I think folks are finally figuring
out that it's a fantastic tool.

I have a set and it generally takes longer to get things set up than to find
a shorted part.

  Paul

On Fri, Jun 21, 2019 at 04:36:45AM +0000, Dave Seiter wrote:
Thanks for the reminder!  I knew I had the set, but was missing one of the probes; turns out I have the current probe, not the pulser.  Haven't used any of them in years; now I have a reason to play with the current probe.
-Dave
    On Thursday, June 20, 2019, 8:09:22 PM PDT, garp66 <@garp66> wrote:

I have used the HP 547a Current Tracer probe to find shorted Tantalum capacitors.
It becomes pretty obvious via the intense red LED brightness(~ proportional to the current flow) which cap has failed.

547a manual:
http://kripton2035.free.fr/Resources/HP%20547A%20Current%20Tracer%20Manual.pdf

rick








!DSPAM:5d0c5ef8203591517594934!
--
Paul Amaranth, GCIH             | Manchester MI, USA
Aurora Group of Michigan, LLC   |   Security, Systems & Software
paul@...              |   Unix & Windows



Dave Seiter
 

If you have a dead logic analyzer probe laying around, the individual probe tips might have the same square ID/OD as the probe power pins.  
-Dave

On Friday, June 21, 2019, 6:51:54 AM PDT, Carsten Bormann <cabocabo@...> wrote:

On Jun 21, 2019, at 13:20, george edmonds via Groups.Io <G6HIG=yahoo.com@groups.io> wrote:

The original HP547A was designed to use mini grabbers to power it up, the pulser is a 546A and there was also a logic probe in the same familly.
Yes.  I’m trying to put together a more permanent way to supply the probe; it would be great to find the connectors mating to the ones that go into the grabbers now (and that would also allow me to apply a better ground lead to the pulser, which seems to have the same connector).

(Sorry if this is too off-topic for tekscopes, maybe I should have asked on the HP group.)

Grüße, Carsten