Topics

DSA 602 acting up (power supply?)


 

Hi Tom,

I'll take care of that! The earths rotation mustn't be too much disturbed either...

:-)
Martin

On 16. Jul 2020, at 02:00, Tom Norman <jtnorman@...> wrote:

Hi Martin-

...

Don't forget to move something of equal weight down when you bring the DSA up from the basement....preserve that building center of mass you were talking about in another post! A refrigerator might be about right.

Tom


greenboxmaven
 

Currency made from rag paper is very good for burnishing contacts so long as it is clean to begin with. It is abrasive enough to remove dirt and many oxides without harming the gold plating on high quality edge connectors. The paper can be sprayed with contact cleaner before use if the dirt is really heavy. The cause of poor connections is very often dust and airborne particles that have landed at the juncture of the flat surface and the spring connectors and been drawn in between the contacing surfaces and pulverized by vibration and temperature cycles. The paste formed levers the contact surfaces apart, and may burn into a residue if the voltage is sufficient. Often, simply pulling a board out and re-inserting it a few times will restore operation, but it is still important to clean the dirt deposits off. For the female part of the connector, find a piece of cardboard of appropriate thickness and fold the edge of the currency over it. I have had excellent results with these techniques for many years.

Bruce Gentry, KA2IVY

On 7/15/20 8:21 PM, stevenhorii wrote:
Years ago I had a service guy for our ultrasound machines show me a trick.
This was for cleaning contact fingers on printed circuit card edge
connectors (not on anything like delicate switch contacts). He would use a
dollar or other currency he had in his wallet and would pinch it around the
edge connector fingers and rub it back and forth a few times. Seemed to
work. Paper is fairly abrasive so it makes sense. Has anyone heard of this?
I have used the idea and never had a problem with rubbing off the plating.
I would not do this on the contacts in those Tek switches.

On Wed, Jul 15, 2020, 19:55 David C. Partridge <
@perdrix> wrote:

AFAIK the white one is the soft one Don't even think of using the hard
ones
on gold pads.

-----Original Message-----
From: TekScopes@groups.io [mailto:TekScopes@groups.io] On Behalf Of Martin
Sent: 15 July 2020 21:31
To: TekScopes@groups.io
Subject: Re: [TekScopes] DSA 602 acting up (power supply?)

Hi Tom,

thanks for the answer and all the details. Right now I have a big repair
job
to finish, an HP8645A with multiple faults. But I'm confident to finish in
a
week or so.

I guess I will recognize the "Hypcon", must be something special. What is
this "white Stadler-Mars eraser"? Is this the one with fiberglass, or the
usual rubber?

Summer holidays are approaching... I must motivate my boys to carry the
other DSA from the basement up in the lab, so I can take care of both of
them. Theres a firmware topic to be clarified, too....

cheers
Martin









stevenhorii
 

Years ago I had a service guy for our ultrasound machines show me a trick.
This was for cleaning contact fingers on printed circuit card edge
connectors (not on anything like delicate switch contacts). He would use a
dollar or other currency he had in his wallet and would pinch it around the
edge connector fingers and rub it back and forth a few times. Seemed to
work. Paper is fairly abrasive so it makes sense. Has anyone heard of this?
I have used the idea and never had a problem with rubbing off the plating.
I would not do this on the contacts in those Tek switches.

On Wed, Jul 15, 2020, 19:55 David C. Partridge <
@perdrix> wrote:

AFAIK the white one is the soft one Don't even think of using the hard
ones
on gold pads.

-----Original Message-----
From: TekScopes@groups.io [mailto:TekScopes@groups.io] On Behalf Of Martin
Sent: 15 July 2020 21:31
To: TekScopes@groups.io
Subject: Re: [TekScopes] DSA 602 acting up (power supply?)

Hi Tom,

thanks for the answer and all the details. Right now I have a big repair
job
to finish, an HP8645A with multiple faults. But I'm confident to finish in
a
week or so.

I guess I will recognize the "Hypcon", must be something special. What is
this "white Stadler-Mars eraser"? Is this the one with fiberglass, or the
usual rubber?

Summer holidays are approaching... I must motivate my boys to carry the
other DSA from the basement up in the lab, so I can take care of both of
them. Theres a firmware topic to be clarified, too....

cheers
Martin









Tom Norman
 

Hi Martin-

The Hypcon connector was invented by Tek, to serve as a means of connecting hybrids to the surrounding circuit board, presumably to minimize connection related impedance matching issues. The M377 chip rests in a square cutout in the circuit board, backed by a heat sink, with the Hypcon connector "on top". The eraser I used is soft white rubber. I don't think there is any fiberglass in it. There are some good illustrations of the connector in the extended service manual for the 11A34 on Kurt's Tekwiki site. That is where I found a copy of the 11301 extended service manual as well.

Don't forget to move something of equal weight down when you bring the DSA up from the basement....preserve that building center of mass you were talking about in another post! A refrigerator might be about right.

Tom


 

AFAIK the white one is the soft one Don't even think of using the hard ones
on gold pads.

-----Original Message-----
From: TekScopes@groups.io [mailto:TekScopes@groups.io] On Behalf Of Martin
Sent: 15 July 2020 21:31
To: TekScopes@groups.io
Subject: Re: [TekScopes] DSA 602 acting up (power supply?)

Hi Tom,

thanks for the answer and all the details. Right now I have a big repair job
to finish, an HP8645A with multiple faults. But I'm confident to finish in a
week or so.

I guess I will recognize the "Hypcon", must be something special. What is
this "white Stadler-Mars eraser"? Is this the one with fiberglass, or the
usual rubber?

Summer holidays are approaching... I must motivate my boys to carry the
other DSA from the basement up in the lab, so I can take care of both of
them. Theres a firmware topic to be clarified, too....

cheers
Martin


 

Hi Tom,

thanks for the answer and all the details. Right now I have a big repair job to finish, an HP8645A with multiple faults. But I'm confident to finish in a week or so.

I guess I will recognize the "Hypcon", must be something special. What is this "white Stadler-Mars eraser"? Is this the one with fiberglass, or the usual rubber?

Summer holidays are approaching... I must motivate my boys to carry the other DSA from the basement up in the lab, so I can take care of both of them. Theres a firmware topic to be clarified, too....

cheers
Martin


Tom Norman
 

Hi Martin-

I don't have much to add on your PS wakeup issue, except to echo your thoughts around temperature extremes potentially being problematic. Might be worth doing a close inspection of the joints in the PS control circuitry. There are detailed service manuals available for the 11301/11302 on the TekWiki site that may detail some similarities to the DSA power supply, which may help your efforts. The DSA power supplies do contain the dreaded RIFA caps, and I have one PS that now has low rail voltages as a result of a RIFA failure. You might proactively replace these if you have not already.

On your 11A72 errors, I recently had a spate of calibration errors in my 11A34 amplifiers (gain and step gain typically), that ultimately got corrected by a good cleaning and torquing of the Hypcon connectors that hold the M377 chips in place and provide contact from the ceramic substrate to the etched circuit board. My DSA is not in the best thermal environment, and I suspect that the temperature cycling may have had something to do with the 11A34 problems I had, but I don't have proof.

What I did learn was a casual cleaning of the Hypcon connector simply will not do. My first couple of attempts using IPA and a fine, medium stiffness art brush was ineffective. After several attempts at cleaning this way, I thought surely there couldn't be an issue remaining with the Hypcons, But the problems remained and the symptoms kept pointing to an issue with the M377s. At one point I had concluded that one of the M377 chips must be failed, and received a humorously curt congratulations from John Addis on having the only M377 known to him to have failed! So, not wanting that distinction, as a last resort and as suggested in the manual, I firmly, but carefully, scrubbed the traces on the M377 hybrids, the embedded connector leaves in the Hypcon and the corresponding traces on the ECB with a white Stadler-Mars drafting eraser. Followed by canned air (another topic),brushing with aforementioned brush (no IPA), and close inspection under magnification for any remaining detritus. Problem solved after a couple of passes through EA. Lastly, these connectors have a torque spec. The best I could do with that was to try to evenly torque, by feel, at what I thought was a reasonable torque.

Your 11A72 doesn't have the M377 preamps, but it does make use of Hypcon connectors on the input and output amps if I remember correctly, so if your amplifier errors return, you may want to try a cleaning. Like you, I'd be suspicious the PS and amp errors could be related, especially if the amp error clears with a "good" PS startup. I felt the same way about my multiple 11A34 amp failures, and at first I thought I had a mainframe issue, but in the end it was "random" multiple failure in the plugins.

Good luck, and hope to hear back on the PS wakeup problem. It will be good to have that documented.

Tom


 

Strangeness... on last switch-on the calibration error was gone. The power supply came on normally.

Since its summer time I always suspect ambient temperature as a possible cause, but this day was rather warm...

No one has heard about a fix of the power supply when not going out of standby?
I think having read something about, some years ago, but couldn't find anything.

cheers
Martin


 

Hi all,

after I replaced the NVRAM battery and some 50 hours of usage my DSA 602 starts acting up again.

This time it seems to be the power supply. During the last 10 or so power cycles, when I switch the unit from standby to on it takes a while before it starts. Sometimes i even have to toggle the switch a second time. Looks like a capacitor issue in the standby supply... is this a know fault, and does someone know hot and where to cure it, given there is no service information on the power supply module available.

Also recently, I got a calibration error on one of my plugins (the 11A72 with 2x1GHz, sitting in the middle). 2 or 3 constants are out of range on one channel. I wonder if this is in any way related to the above problem. I tend to not believe in independent random faults occuring the same time...

cheers
Martin