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SD-24 guts...

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John Larkin...

Posted: Sat Oct 31, 2009 12:52 pm

Guest

On Sat, 31 Oct 2009 08:53:33 -0700 (PDT), arlo <arlo613 at (no spam) gmail.com>
wrote:

[quote]On Oct 30, 7:26 pm, John Larkin
jjlar... at (no spam) highNOTlandTHIStechnologyPART.com> wrote:
On Fri, 30 Oct 2009 16:04:23 -0700, Joerg <inva... at (no spam) invalid.invalid
wrote:

John Larkin wrote:
We were fixing a broken Tek SD-24 20 GHz TDR/sampling head and took a
bunch of pix. Here's one:

ftp://jjlarkin.lmi.net/SD24_8.JPG

Oh man, that doesn't look like it's going to be fun. I hope you've got
at least a schematic and a wire bonder. But in the Bay Area it should be
possible to find a shop that can do the bonding if needed.

We're just replacing dead eeproms. I wouldn't dream of touching the
wire-bonded stuff. Tek never revealed schematics on the 11801-series
scopes anyhow.

I wonder if, with today's materials, it would be possible to achieve
similar performance with regular SMT parts on a material such as Rogers.

I met Agoston Agoston at a trade show once. He designed most of this
stuff. He has his own little company now, and did a 20 GHz sampler
with surface-mount parts on FR4. Check out his Tek patents. AA had a
deal with Tek that they wouldn't sue him if he didn't go past 20. He
was also involved in the PSPL shock-line 100 GHz super-sampler
project, which may or might not still be a real product.

There's a paper on this page about the 100G thing:

http://www.picosecond.com/product/category.asp?pd_id=17#

I got a half-bridge sampler to work nicely at 7 GHz without a huge
effort.

ftp://jjlarkin.lmi.net/Sampler1.JPG

I'd think that 20 GHz on FR4 should be reasonable with available
surface-mount parts. Aeroflex just announced some 0.08 pF packaged
schottkies.

I just got an SD-30 (50 GHz) sampling head for $1500. There's tons of
cheap Tek gear on the market now.

John

I suspect that sampling phase detector (SPD) modules might provide the
easiest
way to roll your own sampling head beyond about 5GHz. These modules
include an
SRD coupled by small caps to a series pair of Schottky diodes, and
seem to be
stocked by some distributors. The integration of SRD, caps, and
Schottkys
ought to avoid the killer parasitic inductances of common surface
mount
packages without resorting to beam leads or wire bonding.

I don't know if the unspecified(?) series caps in e.g. the Skyworks
SPD
would give an ideal sampling pulse shape for sampling oscilloscope
work.
Another interesting question is whether the SRD in a second SPD (these
are,
after all, fast SRD's stocked by some distributors) could be
pressed into service in a pulse generator usable for TDR.

James
[/quote]
I've looked at the sampling phase detectors, but I suspect they
wouldn't make good oscilloscope-type samplers. Really tiny
surface-mount parts, 0402 and SC79 type stuff, can go pretty fast
these days.

There are some CML gates and comparators that would make nice TDR step
generators, in the 15-40 ps risetime range.

One thing you can do nowadays is build a sampler or TDR that has yukky
step response - ringing, overshoot, whatever - and run it through an
equilization algorithm to make it beautiful. That's a lot easier than
spending man-years tweaking all the uglies out. Deriving the FIR
equalizer is an interesting problem. This is "the deconvolution
problem" a member of the class of "ill-posed problems."

http://en.wikipedia.org/wiki/Well-posed_problem

http://en.wikipedia.org/wiki/Inverse_problem

http://www.math.uu.se/~kiselman/illposed2003.html

Fun to play with.

John

Joerg...

Posted: Sat Oct 31, 2009 1:51 pm

Guest

John Larkin wrote:
[quote]On Fri, 30 Oct 2009 16:04:23 -0700, Joerg <invalid at (no spam) invalid.invalid
wrote:

John Larkin wrote:
We were fixing a broken Tek SD-24 20 GHz TDR/sampling head and took a
bunch of pix. Here's one:

ftp://jjlarkin.lmi.net/SD24_8.JPG

Oh man, that doesn't look like it's going to be fun. I hope you've got
at least a schematic and a wire bonder. But in the Bay Area it should be
possible to find a shop that can do the bonding if needed.

We're just replacing dead eeproms. I wouldn't dream of touching the
wire-bonded stuff. Tek never revealed schematics on the 11801-series
scopes anyhow.

I wonder if, with today's materials, it would be possible to achieve
similar performance with regular SMT parts on a material such as Rogers.

I met Agoston Agoston at a trade show once. He designed most of this
stuff. He has his own little company now, and did a 20 GHz sampler
with surface-mount parts on FR4. Check out his Tek patents. AA had a
deal with Tek that they wouldn't sue him if he didn't go past 20. He
was also involved in the PSPL shock-line 100 GHz super-sampler
project, which may or might not still be a real product.

There's a paper on this page about the 100G thing:

http://www.picosecond.com/product/category.asp?pd_id=17#

[/quote]
Requires registration but was painless. Nice paper, wish he had at least
put a photo of the open enclosure in there.

[quote]
I got a half-bridge sampler to work nicely at 7 GHz without a huge
effort.

ftp://jjlarkin.lmi.net/Sampler1.JPG

I'd think that 20 GHz on FR4 should be reasonable with available
surface-mount parts. Aeroflex just announced some 0.08 pF packaged
schottkies.

[/quote]
Highest I've gone on FR-4 was 2.5GHz. Would have done 5GHz as well but
so far no clients needed that. 20GHz is truly brazen but sometimes we
have to be brazen.

[quote]I just got an SD-30 (50 GHz) sampling head for $1500. There's tons of
cheap Tek gear on the market now.

[/quote]
True. It would be nice though if someone offered a budget sampler head
for regular DSO's or maybe even laptops so you can take it on the road.

--
Regards, Joerg

http://www.analogconsultants.com/

"gmail" domain blocked because of excessive spam.
Use another domain or send PM.

George Herold...

Posted: Mon Nov 02, 2009 4:30 am

Guest

On Oct 31, 9:34 am, Gerhard Hoffmann <dk... at (no spam) hoffmann-hochfrequenz.de>
wrote:
[quote]On Fri, 30 Oct 2009 15:12:31 -0700, John Larkin <jjlar... at (no spam) highNOTlandTHIStechnologyPART.com> wrote:
We were fixing a broken Tek SD-24 20 GHz TDR/sampling head and took a
bunch of pix. Here's one:

ftp://jjlarkin.lmi.net/SD24_8.JPG

Hi, John,

I can ping your server, but when I try to get the file,
the connection is reset. (Firefox or Filezilla)
This has happened for weeks.
Does anybody else have this problem?

regards, Gerhard
[/quote]

Gerhard, I can view the pictures from a fast connection here at
work, But when I use dial up from home I can't view them... I assume
the connection times out. Don't know if that is your problem or
not.

George H.

JW...

Posted: Mon Nov 02, 2009 6:32 am

Guest

On Fri, 30 Oct 2009 16:26:43 -0700 John Larkin
<jjlarkin at (no spam) highNOTlandTHIStechnologyPART.com> wrote in Message id:
<8esme5lhfqjpuab990t4foat0jsq9mp4ng at (no spam) 4ax.com>:

[quote]
I just got an SD-30 (50 GHz) sampling head for $1500. There's tons of
cheap Tek gear on the market now.
[/quote]
WHAT! You didn't negotiate, or they wouldn't budge? Wink

YD...

Posted: Mon Nov 02, 2009 6:47 am

Guest

Late at night, by candle light, Gerhard Hoffmann
<dk4xp at (no spam) hoffmann-hochfrequenz.de> penned this immortal opus:

[quote]On Fri, 30 Oct 2009 15:12:31 -0700, John Larkin <jjlarkin at (no spam) highNOTlandTHIStechnologyPART.com> wrote:

We were fixing a broken Tek SD-24 20 GHz TDR/sampling head and took a
bunch of pix. Here's one:

ftp://jjlarkin.lmi.net/SD24_8.JPG

Hi, John,

I can ping your server, but when I try to get the file,
the connection is reset. (Firefox or Filezilla)
This has happened for weeks.
Does anybody else have this problem?

regards, Gerhard

[/quote]
Works fine for me in Firefox.

- YD.
--
Remove HAT if replying by mail.

John Larkin...

Posted: Mon Nov 02, 2009 10:23 am

Guest

On Mon, 02 Nov 2009 06:32:36 -0500, JW <none at (no spam) dev.null> wrote:

[quote]On Fri, 30 Oct 2009 16:26:43 -0700 John Larkin
jjlarkin at (no spam) highNOTlandTHIStechnologyPART.com> wrote in Message id:
8esme5lhfqjpuab990t4foat0jsq9mp4ng at (no spam) 4ax.com>:

I just got an SD-30 (50 GHz) sampling head for $1500. There's tons of
cheap Tek gear on the market now.

WHAT! You didn't negotiate, or they wouldn't budge? Wink

[/quote]
I made them an offer they shouldn't have refused, namely to tell them
how to fix a bunch of their broken sampling gear in exchange for a
decent price break. They didn't go for it.

Fine; that leaves more broken gear on the market that I can buy cheap
and fix.

John

Joel Koltner...

Posted: Mon Nov 02, 2009 12:25 pm

Guest

"John Larkin" <jjlarkin at (no spam) highNOTlandTHIStechnologyPART.com> wrote in message
news:v6ute592njq76re6uq3adhvshbpbep1gb6 at (no spam) 4ax.com...
[quote]I made them an offer they shouldn't have refused, namely to tell them
how to fix a bunch of their broken sampling gear in exchange for a
decent price break. They didn't go for it.
[/quote]
Many used test equipment vendors don't have the means or abilities to repair
anything even if they wanted to. I'm frankly surprised just how low-tech a lot
of these operations are; many just know the description of the item and
wouldn't have the foggiest notion as to how to use it.

You're right about equipment being cheap right now... I picked up a Tek 8561E
6GHz spectrum analyzer for a song; down to under 1/10th the original price for
a 10-year-old instrument. :-)

---Joel

Joerg...

Posted: Mon Nov 02, 2009 12:33 pm

Guest

ChrisQ...

Posted: Mon Nov 02, 2009 12:33 pm

Guest

John Larkin wrote:
[quote]On Mon, 02 Nov 2009 06:32:36 -0500, JW <none at (no spam) dev.null> wrote:

On Fri, 30 Oct 2009 16:26:43 -0700 John Larkin
jjlarkin at (no spam) highNOTlandTHIStechnologyPART.com> wrote in Message id:
8esme5lhfqjpuab990t4foat0jsq9mp4ng at (no spam) 4ax.com>:

I just got an SD-30 (50 GHz) sampling head for $1500. There's tons of
cheap Tek gear on the market now.
WHAT! You didn't negotiate, or they wouldn't budge? ;)

I made them an offer they shouldn't have refused, namely to tell them
how to fix a bunch of their broken sampling gear in exchange for a
decent price break. They didn't go for it.

Fine; that leaves more broken gear on the market that I can buy cheap
and fix.

John

[/quote]
One thing that you might find relevant is that faults sometimes just go
away. I bought a 54112 scope on Ebay for 40 ukp last year, which had
memory and module post test failures. The first thing was to remove all
the boards, clean the edge connectors etc and reseat, but the module
post still failed. I left the thing on for a week solid, then repowered
up and while the post test passed, one of the 4 channels was quite
noisy. Left it running for a few more days and the noise went away and
it's been good since. Even ran the calibration procedure fine as well.

Thinking about it, the failure mode seems to be one of damp getting into
the ic packages and causing leakage. A lot of the older test gear may
have been left in unheated stores for many years prior to disposal and a
thorough baking seems to be quite good for them. Have recovered a couple
of other instruments this way as well...

Regards,

Chris

Nico Coesel...

Posted: Mon Nov 02, 2009 1:17 pm

Guest

"Joel Koltner" <zapwireDASHgroups at (no spam) yahoo.com> wrote:

[quote]"John Larkin" <jjlarkin at (no spam) highNOTlandTHIStechnologyPART.com> wrote in message
news:v6ute592njq76re6uq3adhvshbpbep1gb6 at (no spam) 4ax.com...
I made them an offer they shouldn't have refused, namely to tell them
how to fix a bunch of their broken sampling gear in exchange for a
decent price break. They didn't go for it.

Many used test equipment vendors don't have the means or abilities to repair
anything even if they wanted to. I'm frankly surprised just how low-tech a lot
of these operations are; many just know the description of the item and
wouldn't have the foggiest notion as to how to use it.

You're right about equipment being cheap right now... I picked up a Tek 8561E
6GHz spectrum analyzer for a song; down to under 1/10th the original price for
a 10-year-old instrument. Smile

[/quote]
Agreed. I bought a nice TLA704 logic analyser with acq. module and
probes for 300 US$. Thats at least 1/50th of the original price. Maybe
the seller would have knocked off another 100 US$ the next round but I
didn't want to risk that. All it needed to get going was a new hard
drive (=the hard drive from my old laptop). Being able to fix this
sort of stuff really pays off.

It did make me think about the depreciation of measurement equipment.
Its worse than cars!

--
Failure does not prove something is impossible, failure simply
indicates you are not using the right tools...
"If it doesn't fit, use a bigger hammer!"
--------------------------------------------------------------

Michael A. Terrell...

Posted: Mon Nov 02, 2009 2:15 pm

Guest

Joerg wrote:
[quote]
John Larkin wrote:
On Mon, 02 Nov 2009 06:32:36 -0500, JW <none at (no spam) dev.null> wrote:

On Fri, 30 Oct 2009 16:26:43 -0700 John Larkin
jjlarkin at (no spam) highNOTlandTHIStechnologyPART.com> wrote in Message id:
8esme5lhfqjpuab990t4foat0jsq9mp4ng at (no spam) 4ax.com>:

I just got an SD-30 (50 GHz) sampling head for $1500. There's tons of
cheap Tek gear on the market now.
WHAT! You didn't negotiate, or they wouldn't budge? ;)

I made them an offer they shouldn't have refused, namely to tell them
how to fix a bunch of their broken sampling gear in exchange for a
decent price break. They didn't go for it.

Fine; that leaves more broken gear on the market that I can buy cheap
and fix.

Question: You've mentioned dead EEPROMs a few times here. How do you
determine what data has to go into the new one?

[/quote]

Clone the chip in a working unit.

--
The movie 'Deliverance' isn't a documentary!

Joerg...

Posted: Mon Nov 02, 2009 2:17 pm

Guest

Gerhard Hoffmann wrote:
[quote]On Fri, 30 Oct 2009 15:12:31 -0700, John Larkin <jjlarkin at (no spam) highNOTlandTHIStechnologyPART.com> wrote:

We were fixing a broken Tek SD-24 20 GHz TDR/sampling head and took a
bunch of pix. Here's one:

ftp://jjlarkin.lmi.net/SD24_8.JPG

Hi, John,

I can ping your server, but when I try to get the file,
the connection is reset. (Firefox or Filezilla)
This has happened for weeks.
Does anybody else have this problem?

[/quote]
Works fine here but I am only 100 miles from John so latencies are much
smaller than the usual 200msec between here and Europe.

Check whether your router has a setting called "fragmentation". If
disabled this could cause the problem.

--
Regards, Joerg

http://www.analogconsultants.com/

"gmail" domain blocked because of excessive spam.
Use another domain or send PM.

John Larkin...

Posted: Mon Nov 02, 2009 2:19 pm

Guest

On Mon, 02 Nov 2009 14:15:25 -0500, "Michael A. Terrell"
<mike.terrell at (no spam) earthlink.net> wrote:

[quote]
Joerg wrote:

John Larkin wrote:
On Mon, 02 Nov 2009 06:32:36 -0500, JW <none at (no spam) dev.null> wrote:

On Fri, 30 Oct 2009 16:26:43 -0700 John Larkin
jjlarkin at (no spam) highNOTlandTHIStechnologyPART.com> wrote in Message id:
8esme5lhfqjpuab990t4foat0jsq9mp4ng at (no spam) 4ax.com>:

I just got an SD-30 (50 GHz) sampling head for $1500. There's tons of
cheap Tek gear on the market now.
WHAT! You didn't negotiate, or they wouldn't budge? ;)

I made them an offer they shouldn't have refused, namely to tell them
how to fix a bunch of their broken sampling gear in exchange for a
decent price break. They didn't go for it.

Fine; that leaves more broken gear on the market that I can buy cheap
and fix.

Question: You've mentioned dead EEPROMs a few times here. How do you
determine what data has to go into the new one?

Clone the chip in a working unit.
[/quote]
Yup. Then recalibrate.

John

Michael A. Terrell...

Posted: Mon Nov 02, 2009 2:33 pm

Guest

John Larkin wrote:
[quote]
On Mon, 02 Nov 2009 14:15:25 -0500, "Michael A. Terrell"
mike.terrell at (no spam) earthlink.net> wrote:

Joerg wrote:

John Larkin wrote:
On Mon, 02 Nov 2009 06:32:36 -0500, JW <none at (no spam) dev.null> wrote:

On Fri, 30 Oct 2009 16:26:43 -0700 John Larkin
jjlarkin at (no spam) highNOTlandTHIStechnologyPART.com> wrote in Message id:
8esme5lhfqjpuab990t4foat0jsq9mp4ng at (no spam) 4ax.com>:

I just got an SD-30 (50 GHz) sampling head for $1500. There's tons of
cheap Tek gear on the market now.
WHAT! You didn't negotiate, or they wouldn't budge? ;)

I made them an offer they shouldn't have refused, namely to tell them
how to fix a bunch of their broken sampling gear in exchange for a
decent price break. They didn't go for it.

Fine; that leaves more broken gear on the market that I can buy cheap
and fix.

Question: You've mentioned dead EEPROMs a few times here. How do you
determine what data has to go into the new one?

Clone the chip in a working unit.

Yup. Then recalibrate.

John
[/quote]

It took me a while, but I finally convinced the cal lab at Microdyne
to read and archive every EPROM in everything they serviced, for future
use.

--
The movie 'Deliverance' isn't a documentary!

Herbert Knapp...

Posted: Mon Nov 02, 2009 2:57 pm

Guest

Gerhard Hoffmann wrote:
[quote]Hi, John,

I can ping your server, but when I try to get the file,
the connection is reset. (Firefox or Filezilla)
This has happened for weeks.
Does anybody else have this problem?

regards, Gerhard
[/quote]
Hi,

I had a similar problem. Using a proxy for FTP solved the problem for me.

Best regards,
Herbert

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