Repairing 7000-series plug-in sockets: Difference between revisions

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A common problem with 7000-series scopes is the socket in the mainframe that accepts the
[[File:Extender_3.jpg|thumb|250px|right|Defective connector in a [[067-0589-00]] extender - connector covers are removed, one contact finger is bent (click to enlarge)]]
plug-in. The fingers of the connector are springy metal. The fingers are supported by a flat piece
A common problem with 7000-series scopes, especially the early models, are the '''sockets in the mainframe that accept the plug-ins'''.  
of plastic on either side of connector. This piece of plastic tends to crack, which causes the connector
fingers to be unsupported, which causes bad electrical connection with the plug-in, which typically
results in erratic failures that sometimes come and go when the plug-in is pushed or pulled slightly.


The fingers of the connector are springy metal. The fingers are supported by a flat piece of plastic on either side of connector.
This piece of plastic tends to become brittle and crack, causing loss of pressure on the connector fingers and resulting in bad electrical connections.
The symptoms are erratic failures that sometimes come and go when the plug-in is pushed or pulled slightly.
Occasionally, individual contact fingers can be damaged as well.
Repair strategies include adding mechanical support to the covers, or transplanting modern connectors.
==Adding mechanical support==
Andreas Schubert describes his experience with a [[7504]] that had this problem:
Andreas Schubert describes his experience with a [[7504]] that had this problem:


<blockquote>
<blockquote>
Bought the nice 7504 Ebay 112036180730 recently, which after some cleaning was  
Bought the nice 7504 Ebay 112036180730 recently, which after some cleaning was  
nearly as new from its cosmetic appearance, but as many of these had the connector  
nearly as new from its cosmetic appearance but, as with many of these, it had the connector  
problem. This made the operation on all plugin places useless with random uncorrelated  
problem. This made the operation on all plug-in places useless with random uncorrelated  
faults.  
faults.  


Had a close inspection, because I wanted to give this to a friend. The contacts itself  
Had a close inspection, because I wanted to give this to a friend. The contacts itself  
are not the problem, but the deterioration of the plastic covers on the sides of these  
are not the problem, but the deterioration of the plastic covers on the sides of these  
connectors. If they loose their strength, the contact pressure is gone. In order to apply  
connectors. If they lose their strength, the contact pressure is gone. In order to apply  
the procedure below, the plastic covers must still be there and not broken . Sorry for  
the procedure below, the plastic covers must still be in place and not broken. Sorry for  
bad pictures, I was in a hurry.  
bad pictures, I was in a hurry.  
</blockquote>
 
<blockquote>
On this 7504 model and surely on (most or all) other 7000 series main connector boards  
On this 7505 model and surely on (most or all) other 7000 series main connector boards  
you see small additional piggyback circuit boards. I found the distance of these to the  
you see small additional piggyback circuit boards. I found the distance of these to the  
connectors to be fairly constant about 5 mm.
connectors to be fairly constant about 5 mm.
</blockquote>
 
<blockquote>
I had boards of what we call Pertinax, synthetic resin paper (FR-2), of 5 mm strength.
I had boards of what we call Pertinax, synthetic resin paper, of 5 mm strength, the width  
The width of the boards was 75 mm and it may not be much more - if you cut it, it must be shorter  
of the boards was 75 mm and it may not be much more - if you cut it, it must be shorter  
than the connector itself, have a look at the other side at the plug-in itself.  
than the connector itself, have a look at the other side. I had to cut eight pieces of 23 mm.  
I had to cut eight pieces of 23 mm.  
</blockquote>
 
<blockquote>
For the raw material see picture 0 below. It surely is possible to use a different nonconductive stiff material instead.  
For the raw material see picture Tekfix0. It surely is possible to use a different non conductive
 
stiff material instead.  
</blockquote>
<blockquote>
Six bits fit quite nicely in the six gaps between piggy back boards and connectors of a  
Six bits fit quite nicely in the six gaps between piggy back boards and connectors of a  
four-plugin unit. On one place the distance was only 4 mm, but the piece was easy to  
four-plugin unit. On one place the distance was only 4 mm, but the piece was easy to  
file down. At some points additional rasping is necessary due to wires or components,  
file down. At some points additional rasping is necessary due to wires or components,  
but most of the gaps are clear of these. the Pertinax is easily treated.  
but most of the gaps are clear of these. The Pertinax is easily treated.  
</blockquote>
 
<blockquote>
These make a good pressure to the long sides of the connectors and are adjusted nicely  
These make a good pressure to the long sides of the connectors and are adjusted nicely  
perpendicular if inserted in the gaps and pushed completely down to the main board.
perpendicular if inserted in the gaps and pushed completely down to the main board.
</blockquote>
 
<blockquote>
On the outside, the two remaining pieces must be fixed to the connector side in a different  
On the outside, the two remaining pieces must be fixed to the connector side in a different  
way. I used two metal bars for this and carefully made screw holes to the edges of the  
way. I used two metal bars for this and carefully made screw holes to the edges of the  
connectors. See picture Tekfix1 with plugin , here you can see also why the strips may not  
connectors. See picture 1 with plug-in; here you can see also why the strips may not  
have the same length as the connector.  
have the same length as the connector.  
</blockquote>
 
<blockquote>
It was useful to take the main board off the instrument to perform this work, but I did not  
It was useful to take the main board off the instrument to perform this work., but i did not  
remove the fixed wiring. It took few hours to do this, but was worth the effort. The plug-ins
remove the fixed wiring. It took few hours to do this, but was worth the effort. The plugins
have a tight fit now and the scope is working perfectly well.
have a tight fit now and the scope is working perfectly well.
</blockquote>
</blockquote>


<gallery>
<gallery>
As 7k conn fix 0.jpg
As 7k conn fix 0.jpg|0
As 7k conn fix 1.jpg
As 7k conn fix 1.jpg|1
As 7k conn fix 2.jpg
As 7k conn fix 2.jpg|2
As 7k conn fix 3.jpg
As 7k conn fix 3.jpg|3
As 7k conn fix 4.jpg
As 7k conn fix 4.jpg|4
As 7k conn fix 5.jpg
As 7k conn fix 5.jpg|5
</gallery>
 
==Replacing the connectors with modern equivalents==
 
While the original connectors are custom parts and no direct modern replacement is known to be available,
it is possible to remove the old connector and replace it with a standard 76-pin, 0.1" pitch card-edge connector.
 
(NB: This procedure has not yet been tested with 79xx high-speed instruments, and will quite likely cause unacceptable reflections in a [[7104]], which uses special controlled-impedance sockets.)
 
To extract the old connector, remove the thin plastic side covers, then de-solder the contact fingers individually.  Pliers, a vacuum soldering gun, and applying extra flux are recommended.
 
<gallery>
7503_backplane_r1.jpg                    | [[7503]] backplane shown with one connector replaced, one removed, one original
7503_backplane_r2.jpg                    | Four-layer backplane PCB detail
</gallery>
</gallery>
The old connector can be cut apart to insert a modern card-edge connector between the side standoffs.  The new connector may need to be lightly sanded down at the ends to fit precisely.
Leave a shoulder that can take the pressure of the plug-in being inserted.
Ensure the bottom of the modern connector's card slot is at the correct distance to the old connector's top plane - in other words, don't mount the new connector flush with the old connector's top, or the plug-in will likely not insert all the way.  In the example shown, the new connector needed to be recessed by about 2.5 mm.
<gallery>
7K Backplane connector without covers.jpg | Original connector without side covers
7K Backplane connector replacement 1.jpg  | Core of original connector cut apart, shown with modern connector to be fitted
7K Backplane connector replacement 2.jpg  | Left connector replaced, middle connector mounted but not yet soldered
7K Backplane connector replacement 3.jpg  | Detail of new connector epoxied into supports cut off the old connector body
7K Backplane connector replacement 4.jpg  | Mounting detail
7K Backplane connector replacement 5.jpg  | Mounting detail
7K Backplane connector replacement 6.jpg  | Mounting detail
</gallery>
It might be possible to use a connector with wrap pins if available, however, bending and inserting the pins could be a challenge.
The example shows a connector with solder lugs (Mouser 587-345-076-500-201), extended with short wires.  This will fit easily but takes quite some time to make the 76 connections.
<gallery>
7K Backplane connector replacement 7.jpg | Detail of new connector soldered
7K Backplane connector replacement 8.jpg | Detail of new connector mated with a [[7A17]] plug-in
</gallery>
This example shows a [[067-0589-00|067-0589-00 rigid extender]] where a modern connector with through-hole pins bent to contact the PCB has been used to replace the broken original.
<gallery>
Extender_3.jpg | Defective original connector − one contact finger bent, side covers removed
Tek 067-0589-00 connector replacement 1.jpg | Broken connector replaced with modern alternative
Tek 067-0589-00 connector replacement 2.jpg | Broken connector replaced with modern alternative
Tek 067-0589-00 connector replacement 3.jpg | Modern replacement
</gallery>
[[Category:Repair issues]]
[[Category:Electromechanical components]]

Latest revision as of 05:41, 4 December 2021

Defective connector in a 067-0589-00 extender - connector covers are removed, one contact finger is bent (click to enlarge)

A common problem with 7000-series scopes, especially the early models, are the sockets in the mainframe that accept the plug-ins.

The fingers of the connector are springy metal. The fingers are supported by a flat piece of plastic on either side of connector. This piece of plastic tends to become brittle and crack, causing loss of pressure on the connector fingers and resulting in bad electrical connections. The symptoms are erratic failures that sometimes come and go when the plug-in is pushed or pulled slightly.

Occasionally, individual contact fingers can be damaged as well.

Repair strategies include adding mechanical support to the covers, or transplanting modern connectors.

Adding mechanical support

Andreas Schubert describes his experience with a 7504 that had this problem:

Bought the nice 7504 Ebay 112036180730 recently, which after some cleaning was nearly as new from its cosmetic appearance but, as with many of these, it had the connector problem. This made the operation on all plug-in places useless with random uncorrelated faults.

Had a close inspection, because I wanted to give this to a friend. The contacts itself are not the problem, but the deterioration of the plastic covers on the sides of these connectors. If they lose their strength, the contact pressure is gone. In order to apply the procedure below, the plastic covers must still be in place and not broken. Sorry for bad pictures, I was in a hurry.

On this 7504 model and surely on (most or all) other 7000 series main connector boards you see small additional piggyback circuit boards. I found the distance of these to the connectors to be fairly constant about 5 mm.

I had boards of what we call Pertinax, synthetic resin paper (FR-2), of 5 mm strength. The width of the boards was 75 mm and it may not be much more - if you cut it, it must be shorter than the connector itself, have a look at the other side at the plug-in itself. I had to cut eight pieces of 23 mm.

For the raw material see picture 0 below. It surely is possible to use a different nonconductive stiff material instead.

Six bits fit quite nicely in the six gaps between piggy back boards and connectors of a four-plugin unit. On one place the distance was only 4 mm, but the piece was easy to file down. At some points additional rasping is necessary due to wires or components, but most of the gaps are clear of these. The Pertinax is easily treated.

These make a good pressure to the long sides of the connectors and are adjusted nicely perpendicular if inserted in the gaps and pushed completely down to the main board.

On the outside, the two remaining pieces must be fixed to the connector side in a different way. I used two metal bars for this and carefully made screw holes to the edges of the connectors. See picture 1 with plug-in; here you can see also why the strips may not have the same length as the connector.

It was useful to take the main board off the instrument to perform this work, but I did not remove the fixed wiring. It took few hours to do this, but was worth the effort. The plug-ins have a tight fit now and the scope is working perfectly well.

Replacing the connectors with modern equivalents

While the original connectors are custom parts and no direct modern replacement is known to be available, it is possible to remove the old connector and replace it with a standard 76-pin, 0.1" pitch card-edge connector.

(NB: This procedure has not yet been tested with 79xx high-speed instruments, and will quite likely cause unacceptable reflections in a 7104, which uses special controlled-impedance sockets.)

To extract the old connector, remove the thin plastic side covers, then de-solder the contact fingers individually. Pliers, a vacuum soldering gun, and applying extra flux are recommended.

The old connector can be cut apart to insert a modern card-edge connector between the side standoffs. The new connector may need to be lightly sanded down at the ends to fit precisely.

Leave a shoulder that can take the pressure of the plug-in being inserted.

Ensure the bottom of the modern connector's card slot is at the correct distance to the old connector's top plane - in other words, don't mount the new connector flush with the old connector's top, or the plug-in will likely not insert all the way. In the example shown, the new connector needed to be recessed by about 2.5 mm.

It might be possible to use a connector with wrap pins if available, however, bending and inserting the pins could be a challenge.

The example shows a connector with solder lugs (Mouser 587-345-076-500-201), extended with short wires. This will fit easily but takes quite some time to make the 76 connections.

This example shows a 067-0589-00 rigid extender where a modern connector with through-hole pins bent to contact the PCB has been used to replace the broken original.