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Repairing 7000-series plug-in sockets: Difference between revisions
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Repairing 7000-series plug-in sockets (view source)
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A common problem with 7000-series scopes are the sockets in the mainframe that accept 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-ins | 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: | 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, | 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 | 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 | 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 | 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. | ||
On this 7504 model and surely on (most or all) other 7000 series main connector boards | |||
On this | |||
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. | ||
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 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 at the plug-in itself. I had to | I had to cut eight pieces of 23 mm. | ||
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. | |||
For the raw material see picture 0 below. It surely is possible to use a different | |||
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. | ||
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. | ||
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 1 with plug-in; 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. | ||
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 plug-ins | ||
| Line 65: | Line 62: | ||
As 7k conn fix 5.jpg|5 | As 7k conn fix 5.jpg|5 | ||
</gallery> | </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> | |||
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]] | |||