More Info on Bird Slugs

After my information on the Bird slugs had been on my web pages for some months I received several comments from others who were also interested in doing some surgery on their slugs. In particular I received a very interesting note from Ralf - LA5QEA who took my information and went several steps beyond, providing much more information for we who are "slug surgeons." The following information was taken from his notes to me:

Hi!  I have with great interest read your description on how to open Bird
slugs.  I have always believed that the nylon cup in the front of the slug
was pressed inside the metal button or something like that.  It never came
to my mind that there was a screw behind the front plate or aluminum disk.
However, when I tried to remove the disk according to your method I got
problems, it seems to be a lot of work and it left marks around the edge
of the disk, so I wondered if there could be another method.  I therefore
tried to submerse the widest part of the slug [upside down] into a glass with about 5 mm
of heptanes. (Heptanes = cleaning gasoline)

I used an empty jam glass with a screw cover that prevents the fluid from
evaporating.  After two days I opened the glass and removed the slug from
the liquid.  The disk dropped out of the slug just by touching the edge
with a needle and leaving no marks at all.  The tiny marks you may see on
attached picture are all from my earlier attempt to remove the disk
(before I got the idea to dissolve the glue with heptanes).

          It seems like nothing else inside or outside the slug has been harmed (due to the)            48 hours in heptanes and heptanes vapor.

If all the Bird slugs are glued with the same kind of glue, this method
could be used as an alternative.  But I have only tried to do this on one
single slug, and can therefore not guarantee that this method can be
repeated on every single Bird slug in the world.

If you like you are welcome to add this in any way you like to your description on how to open Bird slugs.....   You may perhaps include a note telling people that heptanes is a highly flammable mixture, and that heptanes vapor mixed with air is explosive if ignited, in the case that someone doesn't know that.

Ralf provided some excellent pictures which add to our "slug surgeon's" collection of knowledge. It should be noted that, although a slug does not have a large quantity of parts, it is still a precision device and its accuracy depends on how and where each piece is located within the body.  Doing surgery on a Bird slug is NOT a job for a beginner or anyone who has not spent many hours working on electronic devices.

NOTE:  Click on any of the pictures for a larger version

The first picture here shows the slug prior to its "operation."  Ralf assures us that he was not running enough power to nearly pin the needle when using this slug in its repaired condition.
The second picture shows the slug once he has used the heptanes. to dissolve the glue  holding the label disc onto the slug body

Looking down on the slug after removing the disc, this view shows the screw which must be removed to separate the larger grooved piece from the body of the slug.


The next picture shows this removal where you can gain access to the inside where the slug components are located.
The final picture shows some of the internal pieces coming up through the machined part of the slug body.

At this point, and assuming the "slug surgeon" has the high level of understanding of electronic and mechanical pieces, what you see inside the slug should be fairly obvious.  A diode, a coil or some manner of a pickup, and a resistor.   There may also be feed-thru capacitors.

Several things are yet to be identified in the Bird slug.  Generally, when a slug is opened there is a resistor and it is often burned completely open or burned so badly that the colors cannot be identified.  Perhaps as more people don the surgeon's smock and open up their slugs, then we can get a better idea about the typical values of the resistors.  Also, the same can be said for the diodes used.  Values are yet to be identified but Ralf and I agree that a good place to start is to use a germanium diode.

One additional thing had to do with heptanes. This was something new to me so I searched the Internet for more information. I found several pieces of highly technical data on heptanes. as well as information on a rock band who shared that name. I asked Ralf for some better information on heptanes. and he provided the following:

Heptanes is just a sort of highly refined gasoline ("bensin" in
Norwegian), but unlike car fuel the smell does not stick to your skin
after it has evaporated like car gasoline normally does. In Norway it is
sold at pharmacies and used to remove glue from adhesive bandage, (from
skin) and fatty stains from textiles etc.

Someone else wrote to say this is probably what we call "benzene" in the USA

If users of our information here discover additional valuable information which could help others, I would appreciate an email to share your discoveries and I will update these pages with that info.  Thanks Ralf


I've received a couple of additional comments from readers of these pages.  I'm not a chemist but these comments refer to the chemistry of some of the materials mentioned above.  John didn't mind me sharing this information with you:


Thanks for your web pages,   (and friends), they are quite helpful

There is some question as to what the solvent Ralf recommended is. I just opened up a Bird slug by soaking it in kerosene overnight, and that worked quite reasonably.

I really doubt that benzene is the solvent in question. For one thing, it's really an extremely toxic chemical, and not one to be used lightly if you can avoid it. Secondly, I'm not at all a chemist, but benzene has 6 carbon atoms, and a heptane should have 7.

I don't want to suggest that kerosene is the safest solvent, or the best one to use, but I do think it is likely to be substantially safer than benzene, and worry a bit at your recommending benzene..."

"....... feel free to mention that I suggested kerosene works fine, and that I think it is safer than benzene."



Another reader named Jack offered this additional information:

"Reading your site I note the word "benzene" which is a quite toxic aromatic hydrocarbon and is much different from hexane. While both have six carbon atoms in their structures, hexane like ethane, propane, butane, pentane, hexane, heptane etc etc are all aliphatic hydrocarbons and are not deemed to be toxic. I recall that in Germany Benzine refers to the aliphatics and Benzol refers to the english named aromatic, benzene!

The site is great. 

Thanks Jack"

David, another reader, sent the following information:

In the US, heptane is available as "undu" brand label remover, or as Bestine brand rubber cement thinner. The Bestine version is much cheaper, and comes in different size cans.  You can find it in art supply stores such as Aaron Brothers.  It makes a great label and glue remover.  You can use it to remove one paper label stuck on top of another label, without damaging either one.

Thanks David                                                                                                                                                                 (Sept. 25, 2007)

This note was received from Nanko - PA0V:

I found alternative way to remove the label disc by blowing it off with presurized air. Remove the teflon cap , and connect a rubber hose to the body with hose clamps.  Now apply few bar pressure and the disc will come loose with a "pop"    Maybe this trick is good enough to add to your Bird slug chapter

It sure is.   Thanks Nanko                                                                                                                                             (Oct. 06, 20070


I appreciate any additional information which will help others working on their Bird slugs.  -- Jim - K5LAD

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