71B Stuck CMT Modules

[Dave Frederickson]

I've noticed that the CMT RAM and EPROM modules for the 71B are difficult to insert and extract compared to the HP modules. I've compared the dimensions between modules and the IDS with no significant differences and checked PCB insertion/removal forces. I can't figure out what the problem is, or more precisely, what I can do to fix it.

Any ideas?

Dave

[rprosperi]

(02-03-2018 09:46 PM)Dave Frederickson Wrote:  I've noticed that the CMT RAM and EPROM modules for the 71B are difficult to insert and extract compared to the HP modules. I've compared the dimensions between modules and the IDS with no significant differences and checked PCB insertion/removal forces. I can't figure out what the problem is, or more precisely, what I can do to fix it.

Any ideas?

Dave

I've noticed the exact same thing, thought it was just the luck of the draw with my samples; I'm glad it's not just me, if you know what I mean...

I typically turn the 71B upside-down and use a hardwood stick with angled tip to 'grab' the lip to pull the module out. No chance with just fingers, and any metal tool will damage the plastic handle (as prior owners have proven).

I've thought about either soap or some dry silicon lubricant on the sides; this will no doubt help a little, but I'm not sure of the long-term effects of having such material on the port walls, so I've held off.

[Dave Frederickson]

With the aid of an empty 71 case I determined that the problem is with the module housing and not the connector. Closer examination of the case and IDS show that the module slot in the case is narrower at the bottom and back of the slot. With the aid of a file I've made some improvement.

Until I get this all figured out I also have a non-maring tool for removing the modules.

Dave

[rprosperi]

(02-03-2018 11:41 PM)Dave Frederickson Wrote:  With the aid of an empty 71 case I determined that the problem is with the module housing and not the connector. Closer examination of the case and IDS show that the module slot in the case is narrower at the bottom and back of the slot. With the aid of a file I've made some improvement.

Did you capture where to mod in any pics?

Are you filing the inside walls of the 71b case (slots), or the module case?

I honestly hate the thought of filing either one ...

[Raymond Del Tondo]

(02-03-2018 09:46 PM)Dave Frederickson Wrote:  I've noticed that the CMT RAM and EPROM modules for the 71B are difficult to insert and extract compared to the HP modules. I've compared the dimensions between modules and the IDS with no significant differences and checked PCB insertion/removal forces. I can't figure out what the problem is, or more precisely, what I can do to fix it.

Actually the CMT module cases are slightly larger than the HP ones. It may just be some micrometers, but it's sufficient to make the slot somewhat too narrow.
The increased friction can be noticed before the module has contact to the PCB.

However even some HP-IL modules sit very tight in the slot. I have seen various HP-71 units where the previous owner tried to remove the HP-IL module without success. Can easily be seen when there are scratches or case deformations in the area where one puts his thumb to remove the module.

One possible solution is to use a plastic stick from the other side, and push the module out. This also works for some of the front slots with CMT modules;-)

[Didier Lachieze]

(02-04-2018 10:22 AM)Raymond Del Tondo Wrote:  However even some HP-IL modules sit very tight in the slot. I have seen various HP-71 units where the previous owner tried to remove the HP-IL module without success. Can easily be seen when there are scratches or case deformations in the area where one puts his thumb to remove the module.

I have a 71b with an HP-IL module that seems stuck inside. I've not been able to remove it by applying a reasonable amount of force. Fortunately there is no scratches nor case deformation due to this, but I was wondering if the previous owner used some glue to keep the HP-IL module in its slot. Glad to know it's not a problem with my unit.

[Dave Frederickson]

(02-04-2018 10:48 AM)Didier Lachieze Wrote:  I have a 71b with an HP-IL module that seems stuck inside. I've not been able to remove it by applying a reasonable amount of force. Fortunately there is no scratches nor case deformation due to this, but I was wondering if the previous owner used some glue to keep the HP-IL module in its slot. Glad to know it's not a problem with my unit.

(02-04-2018 10:22 AM)Raymond Del Tondo Wrote:  One possible solution is to use a plastic stick from the other side, and push the module out. This also works for some of the front slots with CMT modules;-)

This is by far the best method for removing a stuck module, but it only works for the IL module and ports 1 and 2.