My compression driver has a clogged bug screen

[robertbartsch]

I sent this driver out (Altec 802) to a professional for a new diaphragm and a magnetic recharge...

When it returned, I noticed that the fine mesh screen is partially blocked with some corrosion. ..this corrosion is about the size of the top of a Q-Tip...

What should I do?

I may be able to cut the screen out with a long Exacto knife but it may require taking the diaphragm off first... As I recall, these drivers have installment pins to align the diaphragm... ..the screen on these drivers is at the back of the throat NOT at the front like modern JBL drivers...

I'm planning on using the driver on the back of a 511 Altec cast horn and it will be installed OUTSIDE a cabinet in my garage where some bugs may get access...

[robertbartsch]

A different compression driver returned from the same professional re-builder has a missing bug screen... ...since this one will be installed in a cabinet with a cloth cover, so I am somewhat less concerned about future damage from possible nesting bugs in my garage.

Is this just sloppy work?

I have used this professional who is located in Oklahoma many times over the years without issue.

[Earl K]

You've stated that you sent your drivers in for new diaphragms & a recharge of the magnets, right ?

So why would you expect a full rebuild ?

I think that you bought a pair of beaters ( in rough shape ) //> sent them into GPA for new diaphragms & recharging //> the drivers came back as you described, and only now do you give your beaters a critical look over ( & sadly discover the existing bug-screen issue ) .

Under circumstances like these, why would anybody want to fan the flames of moral outrage on your behalf?

:)

[Earl K]

Do the following at your own risk!

With the diaphragm removed ( if mine ) I would use an automotive "Rust Converter" product whose active ingredients are mainly ( Tannic Acid &/or Phosphoric Acid ).

Dabbed onto the metal ( say with Q-Tips ) the solution converts iron oxide to tannic oxide ( which is very black & very powdery when the conversion process is fully finished ). Study CHELATION (https://en.wikipedia.org/wiki/Chelation) to get a backgrounding on the process involved.
- It takes a bit of time to work since the solutions are not particularly acidic ( ie; skin burns take quite a while to form ) ;0) .

The powdery residue can be removed with a vacuum ( hence one of the safety requirements of first removing the fragile diaphragm from the driver.

A couple of applications may be necessary ( dependent on rust depth ).
- Clean with alcohol after treatment ( not water ).

Here's what I use on rust ( created by a local Cdn company, it works quite well );


http://www.rustcheck.com/wp-content/uploads/2016/04/Rust-Converter-Bottle.jpg Rust Converter MSDS pdf (http://www.rustcheck.com/download/rust-check-rust-converter-11005-236ml_eng/)

One must carefully study the MSDS sheets of a product to get the true ( current ) chemical content ( since there are many so-called rust converters in the market-place ).



:)

NOTE : these formulations are under constant review ( since the companies are harassed by federal governments to be more "green" ), so one needs to be vigilante about all claims of "new & improved" .

This is a good quick read (https://www.ncptt.nps.gov/blog/comparative-study-of-commercially-available-rust-converters/) of setting up a comparative study for various rust converter products.
Here are the results of the study in pdf form (https://www.ncptt.nps.gov/wp-content/uploads/metal-paper-88.pdf)
Based on the results, I would like to try Rustoleums Rust-Reformer (https://www.walmart.com/ip/Rust-Oleum-Rust-Reformer-8-oz/16652306) liquid product ( which I have yet to find in Canada ).

IMPORTANT NOTE: The aerosol variants for any of the previously mentioned products are not the same simply because they share the same registered trade name ( it's a "Consumer Protection LoopHole" that corporations get to drive their semi's straight through ).
- All the aerosols ( that I've studied the MSDS sheets for ) drastically differ in chemical composition, when compared to the liquid version .
https://www.rustoleum.com/~/media/DigitalEncyclopedia/Product/RustoleumUSA/CBG/auto/paint-chemicals/rust-reformer/AU_RustReformer_8oz_L.ashx

[audiomagnate]

You've stated that you sent your drivers in for new diaphragms & a recharge of the magnets, right ?

So why would you expect a full rebuild ?

I think that you bought a pair of beaters ( in rough shape ) //> sent them into GPA for new diaphragms & recharging //> the drivers came back as you described, and only now do you give your beaters a critical look over ( & sadly discover the existing bug-screen issue ) .

Under circumstances like these, why would anybody want to fan the flames of moral outrage on your behalf?

:)

On the other hand, assuming one has to disassemble them to charge the magnets, why not take a few seconds to clean the screens?

[robertbartsch]

I paid for a rebuild.

Before I paid for the rebuild service, the rebuilt drivers were sent in error by the vendor to a home residence that I owned but sold +5 years ago even though my correct address, phone number, e-mail were printed on each driver. These were not "beater" drivers and I have owned them since 1975. Apparently, the vendor removed the screen from one driver but left the clogged bug screen in the other driver.

I'm not real happy that I spent several hours tracking down the new home owner to request that they return the 24 pound package to me.

Anyway, I'm not planning to use this vendor again.

[robertbartsch]

...thanks for the rust remover advice Earl!