Topics

Air filters for big 500 series scopes


Grayson Evans
 

I am trying to figure out an air filter for my two 547's and a 556. I found an air conditioner filter that is close in size, but when I used it, I got too little air flow and the 547 overheated. Probably need to find some material that can be cut to size.
Any ideas?
Thanks! Grayson


Stefan Lindberg
 

What about filters that go with vacuum cleaners? They can be asily cut in size and should go well into the tight space and be easy to breath through

Br
Stefan

________________________________
From: TekScopes@groups.io <TekScopes@groups.io> on behalf of Grayson Evans <wa4gvm@...>
Sent: Monday, October 12, 2020 5:59 PM
To: TekScopes@groups.io <TekScopes@groups.io>
Subject: [TekScopes] Air filters for big 500 series scopes

I am trying to figure out an air filter for my two 547's and a 556. I found an air conditioner filter that is close in size, but when I used it, I got too little air flow and the 547 overheated. Probably need to find some material that can be cut to size.
Any ideas?
Thanks! Grayson


snapdiode
 

I use a 3M Filtrete furnace filter cut to size.

https://www.filtrete.ca/3M/en_CA/filtrete-ca/


John Williams
 

Good morning. I gave up long ago worrying about these air filters. I suspect that they were considerable overkill given the clean working conditions the scopes face today. Plus the much shorter working hours. Most of mine really don’t even get turned on. I have used cot down furnace filters but the fibreglass makes me itch. So many of my scopes don’t have a filter, and they haven’t complained. But I can remember how dusty and dirty many locations were back in the day. Cheers. John.


greenboxmaven
 

I asked the same question months ago. The filter must be very free flowing for the high volume low pressure blower to move enough air through. The original aluminum mesh filter meets this requirement. The material is open enough that you can sort of see through it, and is often used in kitchen exhaust hoods and fans, appliance parts stores should have it. For best results, it needs to be coated with the proper treatment to attract and catch dust. The good thing is it can be cleaned and re-used as long as it is not damaged. I don't think the original filter was ever intended to catch anywhere near as much dirt as modern ones do, but modern high efficiency filters have a lot more air resistance and the blower can't pull enough air through it..

Bruce Gentry, KA2IVY

On 10/12/20 11:59 AM, Grayson Evans wrote:
I am trying to figure out an air filter for my two 547's and a 556. I found an air conditioner filter that is close in size, but when I used it, I got too little air flow and the 547 overheated. Probably need to find some material that can be cut to size.
Any ideas?
Thanks! Grayson





Chuck Harris
 

The aluminum filter material is still available, and as I
recall, the manufacturer that made it way back when is still
in business.

You should be able to buy the exact size with a little searching.
You will have to drill a couple of holes to handle the mounting
screws.

As to the coating, PAM, or other spray cooking oils is so
close to the same that I think it is the same.

-Chuck Harris

greenboxmaven via groups.io wrote:

I asked the same question months ago. The filter must be very free flowing for the
high volume low pressure blower to move enough air through. The original aluminum
mesh filter meets this requirement. The material is open enough that you can sort of
see through it, and is often used in kitchen exhaust hoods and fans, appliance parts
stores should have it.  For best results, it needs to be coated with the proper
treatment to attract and catch dust. The good thing is it can be cleaned and re-used
as long as it is not damaged. I don't think the original filter was ever intended to
catch anywhere near as much dirt as modern ones do, but modern high efficiency
filters have a lot more air resistance and the blower can't pull enough air through it..

     Bruce Gentry, KA2IVY


stevenhorii
 

An easy to use and cut filter material is open cell foam. It is sold as
filter material and is usually about 1/4-inch thick. It is also easily
washable and inexpensive. The material is not designed to be a HEPA filter,
but it will certainly keep down the dust inside the scope. This material is
popular as a coarse (initial) filter for Shop Vac vacuums and by itself in
kitchen range hoods. I have used it on smaller electronics that have a
filter holder over the fan. For use in the larger Tek scopes like a 547,
you will need a piece of backing material like coarse metal screening or
the filter may get sucked into the fan.

Steve H.

On Mon, Oct 12, 2020 at 11:59 Grayson Evans <wa4gvm@...> wrote:

I am trying to figure out an air filter for my two 547's and a 556. I
found an air conditioner filter that is close in size, but when I used it,
I got too little air flow and the 547 overheated. Probably need to find
some material that can be cut to size.
Any ideas?
Thanks! Grayson






Keith
 

And if you want to use something a little snazzier for coating that air filter than a spray of PAM, may I suggest K&N filter oil? FWIW, K&N filter oil has a special extra-sticky agent in there that aggressively gathers dust, along with other nasty and probably carcinogenic stuff that keeps the gooey stuff gooey longer than PAM. One spray can of K&N costs about twice what a can of PAM costs, but since it is a specialized material you can tax deduct it as a bench supply/consumable item - which you probably can't with PAM.

One can of K&N costs $8.50 at Wally, and will last approximately two and a half lifetimes and you can use it on your lawnmower foam filter too.

Most importantly, PAM is safe and nontoxic. K&N on the other hand is dangerous, explosive when sprayed, possibly mutagenic and generally dangerous for the unskilled to handle. Of course this means it is probably also the very best choice for air filter oil. :-)

Here's the MSDS. http://kandn.com/msds/99-0516.pdf

But PAM will certainly work too. Just my 2C


Cheers,

Keith


Grayson Evans
 

Since I posted, I've done more searching, and yes, there are several companies that sell the aluminum filters, mostly for cooking exhaust fans. I had not thought about coating the filter with anything. I have another 547 with the original filter. It doesn't seem to be coated with anything, but it's very old.
Never considered PAM. I was thinking a light spray of WD40, but probably will try it dry and see how well it works.
Thanks for the tips!


Roy Thistle
 

On Thu, Oct 15, 2020 at 06:43 AM, Grayson Evans wrote:


I had not thought about coating the filter
I've cleaned the oldest dirtiest (I mean dirty!) original (or as they came with) series 500 Al mesh filters.
I never, when I can get them, throw the filters away... I just simply clean them.
I don't coat them with anything (no oil, or wax, or decene homopolymers!). My thinking (if you want to accuse of that)... my thinking is that the coating will migrate into the scope... eventually... helping to preserve the filth that only a circa 1960s vacuum tube device seems to be a magnet for.
For whatever good it does, I run the filters on clean 500s bareback... and simply, keep the scopes in as clean an environment as can be. If need be, I'll vacuum out the dust, or blow it out (where applicable) with clean, dry, oil-free air.
By the way... WD40 will only leave a small amount of a powdery white non-sticky substance that is probably the wax component. That white stuff will probably just migrate into the scope, as it doesn't really stick to the Al.


DaveH52
 

We had an electrostatic air cleaner on our HVAC system that used expanded aluminum filters. Or how about the same type of filter that is used in a range hood?


Roy Thistle
 

On Thu, Oct 15, 2020 at 12:37 PM, DaveH52 wrote:


type of filter that is used in a range hood
Yes... at least here in the colonies...Al range hood filter material is the samesimilar Al material that was used in the 500 filters (I think it has been mentioned earlier... or in another thread.)
Don't know if the range hood filters are coated? But if not, there's an opportunity there to market a reasonably expensive application specific Pam type spray, for them.
Back in the day... were you guys frying bacon in the test lab? Just wondering.


Chuck Harris
 

Of course range filters are coated... coated with
cooking grease.

The entire purpose of the aluminum style range filters
is to capture the grease from cooking, and keep it stuck
to the filter and out of the ducting. It is mostly a
fire prevention effort.

That is a little different from keeping dust out of
an oscilloscope.

-Chuck Harris

Roy Thistle wrote:

On Thu, Oct 15, 2020 at 12:37 PM, DaveH52 wrote:


type of filter that is used in a range hood
Yes... at least here in the colonies...Al range hood filter material is the samesimilar Al material that was used in the 500 filters (I think it has been mentioned earlier... or in another thread.)
Don't know if the range hood filters are coated? But if not, there's an opportunity there to market a reasonably expensive application specific Pam type spray, for them.
Back in the day... were you guys frying bacon in the test lab? Just wondering.






DaveH52
 

Run it through a dishwasher, or soak it in soapy water and scrub it with a soft brush, then let it dry if you're worried about any coating. A brand new one shouldn't be coated with anything that won't wash off. Just don't try one that been used over a stove!


Dave Daniel
 

A good way to clean these is to soak them in a solution of Professional Brewer's Wash.

On 10/17/2020 2:54 AM, DaveH52 wrote:
Run it through a dishwasher, or soak it in soapy water and scrub it with a soft brush, then let it dry if you're worried about any coating. A brand new one shouldn't be coated with anything that won't wash off. Just don't try one that been used over a stove!



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Chuck Harris
 

You might want to be careful with that. The ribbons are
aluminum, and likely to dissolve if they run into anything
that is too caustic.

Professional cleaners often have characteristics that are
dangerous when used outside of their designated task.

Professional brewers tend to use nothing that isn't glass,
stainless steel, or a few kinds of plastic, in contact with
their wort, or finished beer.

-Chuck Harris (one time amateur brewer)

Dave Daniel wrote:

A good way to clean these is to soak them in a solution of Professional Brewer's Wash.


On 10/17/2020 2:54 AM, DaveH52 wrote:
Run it through a dishwasher, or soak it in soapy water and scrub it with a soft
brush, then let it dry if you're worried about any coating. A brand new one
shouldn't be coated with anything that won't wash off. Just don't try one that been
used over a stove!





Roy Thistle
 

On Thu, Oct 15, 2020 at 08:46 PM, Chuck Harris wrote:


Of course range filters are coated... coated with
cooking grease.
Well... I was out here in the colonies... masked and by the local home despot... and I decided to hike over to the kitchen section.
I asked the probrotradesman kitchen guy if those aluminum range filters come coated with cooking grease. He said... not as he knows for... and thinks they aren't sprayed with anything... but, might be a good idea if there was something to spray them with.
Anyway... ya, I think the manufacturers don't coat them.


Roy Thistle
 

On Sat, Oct 17, 2020 at 01:54 AM, Dave Daniel wrote:


soak them in a solution of Professional Brewer's Was
Those tend to be alkaline peroxide based cleaners. (Alkaline peroxides are good at dissolving microbes, and grease; but can/do attack some metals. Sometimes, passivators are used, to help protect the metal.)
I used a trisodium phosphate solution, which is an alkaline phosphate based cleaner. Trisodium phosphate is a very good degreaser; but, it can/will attack some unpassivated metals.
After some time, aluminum forms a very strong, but thin thin layer, of Aluminum oxide, that acts as passivation. On these very old filters (decades old?), the surface of the aluminum is bound to have oxidized.
I've cleaned up aluminum 500 series filters several times using trisodium phosphate. And, very dirty filters cleaned up so as they looked like new. However, milage may vary... and thus, caveat emptor.


Chuck Harris
 

What we have here is a failure to communicate.

After you use your stove to cook a pan full of bacon,
your filter will be coated with cooking grease... specifically,
bacon grease.

Then you make hamburgers, and they will then have a coating
of bacon grease and hamburger grease... Fry some eggs, and
they will have a coating of bacon grease, hamburger grease,
and butter....

New, they are coated with nothing but the mill oil from
when they were machined. After you use them for the first
time, they are coated with cooking grease until you do the
hideous task of cleaning them.

-Chuck Harris

Roy Thistle wrote:

On Thu, Oct 15, 2020 at 08:46 PM, Chuck Harris wrote:


Of course range filters are coated... coated with
cooking grease.
Well... I was out here in the colonies... masked and by the local home despot... and I decided to hike over to the kitchen section.
I asked the probrotradesman kitchen guy if those aluminum range filters come coated with cooking grease. He said... not as he knows for... and thinks they aren't sprayed with anything... but, might be a good idea if there was something to spray them with.
Anyway... ya, I think the manufacturers don't coat them.






snapdiode
 

My range hood has two metal filters that I clean weekly by spraying both sides with Scrubbing Bubbles, I let it soak for five minutes, then rinse off with hot tap water.
I do it in the bathtub where the shower thingy is removable.
This cleans em up real good.