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Card Edge Connectors on a 7704

 

I just received a 7704 and several of the card edge connectors on the main interface board have their left and right (or A and B?) covers falling off. They are not completely disintegrated yet, though it looks like a previous owner tried to glue them back together, with limited success.

Other than the deteriorating covers on the card edge connectors the scope appears to be working. I can get readout on the two bays whose connectors are intact, though I have not managed to get stable traces, and the CRT seems bright and crisp. Some of the controls are stiff or frozen, but the scope is also quite dirty so some stiff controls are to be expected.

The contacts on the card edge connectors look like they are still in good condition, but I am wary of trying to insert any plug-ins for fear of damaging the contacts. The housings for the contacts do not appear to have been damaged or to have disintegrated yet, so I am wondering what my options are.

Do I absolutely need to have covers in place? Will I damage the connectors if I try to insert a plug-in with the plastic covers missing?

I know that replacing the connectors is a big job, but I happen to have a parts scope that I may be able to harvest connectors from. Is this reasonably doable?

Has anyone tried to 3D print the cover plates?

¡ª Jeff Dutky
 

Jeff the 1970s..1980s plastics loose plasticisers and become brittle and crumble, PCB edgemand Tektronix "harmonica" inline PCB cables.

3D printer do not give an accurate reproduction at such fine r¨¦solution and the 3D mat¨¦riel is poor characteristics.

The original PCB card edges connectors can still be found with persistent search.

We performed such a replacement of PCB edges connection on a 1973 Eventide Instant Flanger studio sound we designed....PCB edge connectors has outgassed!

Bon courage

Jon
 

All you probably need is replacements for the plastic bits that clip onto the sides of the sockets. Without those the contacts won't make contact - at least not consistently.

AFAIK they are only obtainable from another 7000 series mainframe (unless someone has made replacements using 3-D printing - which I suspect may not be possible). Be warned those plastic bits need to be fitted the right way round.

D.

-----Original Message-----
From: [email protected] <[email protected]> On Behalf Of Jeff Dutky
Sent: 01 April 2022 09:05
To: [email protected]
Subject: [TekScopes] Card Edge Connectors on a 7704

I just received a 7704 and several of the card edge connectors on the main interface board have their left and right (or A and B?) covers falling off. They are not completely disintegrated yet, though it looks like a previous owner tried to glue them back together, with limited success.

Other than the deteriorating covers on the card edge connectors the scope appears to be working. I can get readout on the two bays whose connectors are intact, though I have not managed to get stable traces, and the CRT seems bright and crisp. Some of the controls are stiff or frozen, but the scope is also quite dirty so some stiff controls are to be expected.

The contacts on the card edge connectors look like they are still in good condition, but I am wary of trying to insert any plug-ins for fear of damaging the contacts. The housings for the contacts do not appear to have been damaged or to have disintegrated yet, so I am wondering what my options are.

Do I absolutely need to have covers in place? Will I damage the connectors if I try to insert a plug-in with the plastic covers missing?

I know that replacing the connectors is a big job, but I happen to have a parts scope that I may be able to harvest connectors from. Is this reasonably doable?

Has anyone tried to 3D print the cover plates?

¡ª Jeff Dutky
 

David,

that is EXACTLY what I need, and it may explain why one of the remaining slots (B HORIZ) is not working properly: it looks like the lower half of the A cover plate is loose, which is causing me to be unable to get a sweep.

That's actually good news. I have all the original (deteriorated) cover plates, and I have at least one parts scope that might be able to donate cover plates, so this is likely to be a fixable scope.

-- Jeff Dutky
 

Jeff,

You probably already know this but a word of caution. The fingers in that connector are very easily bent. The mid-board trace for one of the fingers in the left vertical slot in my 7704A would not make reliable connection. That trace ran to a via which would not make connection. I tried resoldering it a couple of times and it was simply not going to work as it should and I ended up making small jumper that wrapped around the base of that finger. I was surprised at how fragile that finger-stock is.

I've had the plasticizer failure in one or more of the comb connectors in my 7000 series plugins. On of them disintegrated completely when disconnected/reconnected and is currently just the bare pins. I really need to look at repairing that one.

Good luck with the repair.

Thanks,
Barry - N4BUQ

----- Original Message -----
From: "Jeff Dutky" <jeff.dutky@...>
To: "tekscopes" <[email protected]>
Sent: Friday, April 1, 2022 8:52:09 AM
Subject: Re: [TekScopes] Card Edge Connectors on a 7704
David,

that is EXACTLY what I need, and it may explain why one of the remaining slots
(B HORIZ) is not working properly: it looks like the lower half of the A cover
plate is loose, which is causing me to be unable to get a sweep.

That's actually good news. I have all the original (deteriorated) cover plates,
and I have at least one parts scope that might be able to donate cover plates,
so this is likely to be a fixable scope.

-- Jeff Dutky
 

Jeff try Walter at Sph¨¨re Research in Canada, he may have the connectors or a spare 7xxx backplane

Jon
 

On Fri, Apr 1, 2022 at 04:12 PM, n4buq wrote:


You probably already know this but a word of caution. The fingers in that
connector are very easily bent. The mid-board trace for one of the fingers in
the left vertical slot in my 7704A would not make reliable connection. That
trace ran to a via which would not make connection. I tried resoldering it a
couple of times and it was simply not going to work as it should and I ended
up making small jumper that wrapped around the base of that finger. I was
surprised at how fragile that finger-stock is.
You have to realize that virtually all contact pressure in those connectors comes from the plastic covers; unsolder the connector, remove the cover and all contacts will land on the floor...

Raymond
 

On Fri, Apr 1, 2022 at 10:35 AM, Raymond Domp Frank wrote:


You have to realize that virtually all contact pressure in those connectors
comes from the plastic covers; unsolder the connector, remove the cover and
all contacts will land on the floor...
Yes. I thought I remembered reading a post from Dennis talking about this but I was not able craft a search to find the thread. I'm a little worried that the main body of the connector, the comb structure that holds the fingers in position, is also on the verge of crumbling, but I'm not about to accelerate the process by poking at it unnecessarily.

Would it be possible to replace these connectors with something more durable or at least less rare? There are EDAC connectors (my notes say part #345-076-520-201 or 345-076-500-201) that fit the card edge fingers, and can be ordered from Digi-Key (not sure how long fulfillment will take). I know that there are other mating structures on the 7k sockets, but I thought that some of them were purely vestigial (the three coax positions at the top, for example).

-- Jeff Dutky
John Griessen
 

On 4/1/22 09:25, Jeff Dutky wrote:
Would it be possible to replace these connectors with something more durable or at least less rare? There are EDAC connectors (my notes say part #345-076-520-201 or 345-076-500-201) that fit the card edge fingers, and can be ordered from Digi-Key (not sure how long fulfillment will take). I know that there are other mating structures on the 7k sockets, but I thought that some of them were purely vestigial (the three coax positions at the top, for example).
When I put together a kit of parts to make 7k flex extenders, I measured 40 plugins and got an idea of the tolerances and had some made by a requested mod to a Taiwanese connector. A standard connector won't have the right number of pins or the end float tolerance needed. The parts ran out a few months ago and no one has asked much about another run, so I guess the world demand has been satisifed with ~250 kits since 2012.

Replacing/repairing the tek ones as-is is very labor intensive...
--
John
 

John,

the EDAC parts I mentioned certainly have the right number of contacts (38 positions, 76 contacts), but I understand that the end play may be wrong. The rigid extender that I bought on eBay, which uses one of the EDAC parts does seem to work, at least with the handful of plug-ins I've tried.

It's a shame that Tek didn't use a key slot in the 7k interface, as that would have made proper mating a bit easier.

I'd be interested in one of your flexible extenders. How many orders would you need to do another run, and what would it cost?

-- Jeff Dutky

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