SABA: Test Socket Break-Out Box.

 

Test Socket Break-Out Box.

 

For proper alignment for SABA automatics, the following instrument is a useful aid.

 

Raise you hand if you have poked paper clips into the 7 pin miniature “Test socket” (test points X, Y & Z on a Grundig, Emud, Saba , etc., chassis.  Then have the wires fall out in the middle of an alignment?  Or tried to use Alligator Clip leads under side of the chassis and created a spectacular flash/bang?

 

I have (hand raised).  Last week I was working on a Saba Freiburg Vollautomatic 14 with all seven test points assigned on the socket.  After some frustration I took a break and made a “break out box”.

 

 

 

If you would like to build one,  read on.  This is how I put a Test Socket break out box together in a couple of hours.

 

Locate some parts including:

• One donor 7 pin miniature tube (every one should have a few bad tubes they have been holding on to for too long).
• OATAY Plumber’s epoxy (or equivalent). It has a great insulating resistance. And it is inexpensive.
• Seven wires of equal length of about 18 inches.  Use good insulation. You may choose to use this break out box on a live tube socket.  I used Teflon insulated wire good to about 600 vdc.
• A small project box about 4 x 2 x 1 inch.
• Grommet to protect the wires at the entrance to the project box.
• Seven binding posts.
• Tape or heat-shrink tubing to bundle the seven wires.
• Label supplies

 

Take the bad 7 pin miniature glass vacuum tube (Valves to some of you).  Then I clipped of the evacuation tip to let the vacuum out (atmosphere in).  Next put a stiff fiber cutting wheel on the Dremel motor tool. 

 

With gloved hands and safety goggles I slowly cut the base off of the tube.  The tube elements slipped out with the base.  Now I am sure there is a more elegant way of cutting the glass base of a Valve.  So please go ahead and use your favorite method.  The sharp base edge is little concern since it will be filled with OATAY plumbers epoxy later.

 

Snip off all the tube elements leaving as much lead wire as possible.  Then use fine sand paper, emery cloth, your wife’s nail file, etc, to shine up the remaining lead wires (that are attached to the tube (valve) pins.  You may also shine up the tube pins at this time if you desire.

 

Measure out seven 18 inch wires, strip about ¼ inch insulation on each end.  Tin the ends with solder.  I also have separate rosin at the ready.

 

Apply rosin past the tube base lead wires.  And tin the lead wires.

 

Solder one wire per tube base lead.  Be quick!  The thermal shock may crack the glass.  Using rosin past helps reduce the time you have your soldering gun/iron on the tube base.

 

Mix up some plumber’s epoxy and push it into the center of the tube base and around the outside of the wires.  Cover the sharp glass edge of the tube base.  Also insure the tube base lead wires (that you soldered the wires to) do not short/touch together.

 

Once the epoxy is hard, slip three 1” sections of heat shrink over the 7 wire bundle.  You will shrink these later.

 

Prepare you project box.  Lay out how you will arrange your binding posts.  I left room for labels, and a possible tube socket for Hot break-out testing of tubes (specifications creep).

 

Drill and install the binding posts and the 7 wire access hole.  Install the protective wire grommet.  Insert the wire bundle into the box.

 

Start at pin one on the tube base.  Solder that to the first binding post.  I suggest using a black or green for this circuit.  Y or Pin 1 is chassis ground.  Continue soldering wires 2 through 7 verifying each wire’s continuity. 

 

Use a tie wrap as a strain relief on the wire bundle, inside or the project box.

 

Check the continuity again.  If good make up a neat label for the chassis test points X Y and Z.  The pictured unit has additional letters that match the Saba Freiburg Vollautomatic 14 test socket.  I also added numbering for additional functionality. 

 

I have been using this break out box all week.  It saves me lots of time setting up for the different alignment procedures.  It also provides solid reliable connections that are visually identifiable.

 

Voltage P-Y is the "Control Transformer V" FM detector voltage.

 

 

X-Y is the FM audio detector voltage test points.

 

 

 

The three colored "Y" wire in the middle is the two 200K ohm resistors needed to develop the detector balanced "0" current.

 

The only change I would make is putting the black (or green) binding post on point Y.  Y is the chassis ground. 

 

I find this break out box to be quite handy and a great time saver.  I hope it is as convienient for you as it is me. 

 

Good luck and have fun!

 

Paul

 

 

EE:
Dec 5 2010: Titel with SABA and the blue sentence added.

 

 

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Hi Paul,

if I have seen right, you killed a tube to get a socket for your adapter.
Here you can get such plugs for socket adapters or making measuring probes.
I also made adapters for measuring the tube pins in FM Tuners, just 2 inch long 1:1
adapter with blank wires that one can touch the tube pins with an probe from outside the tuner.

address of source
( they also have an english page )

Best Regards

Georg

 

To thank the Author because you find the post helpful or well done.

Georg,

Thanks for the link.  I just spent about an hour looking and dreaming about purchases of German transformers, tubes and the CRT clock. 

I failed to locate the 7 and 9 pin plugs that mate with the tube sockets. I would prefer not to cut glass.  As you mentioned a tube socket test adaptor is a good candidate for extending the test socket.

By the way - I cut a bad tube that I had laying around.  I think we all have a few questionable or bad tubes on our repair bench.  Especially available are the old NTSC US TV tubes.

Paul.

 

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