Topics

Type 502 scope : missing air filter, what gives ?!


Vincent Trouilliez
 

Hi Group,

This is a highly technical question, PhD only please ! LOL

Here goes : I just bought meself a little type 502 classic Tek, love it.

However it came with no air filter, somehow. The square frame to hold it, is there, screwed, but nothing in it, somehow ! However it does have a coarse grill... which presumably doesn't filter anything, but at least keeps one from stuffing his fingers in there and getting them sliced by the fan blades... better than nothing.

At first I thought well, I just got unlucky, I will just have to come up with a way to make a replacement filter, and that's it.

However... I then looked at pics online, of a dozen other 502/502A scopes, including TekWiki, and go figure : NONE of them had the air filter, all had this grill instead.

Now there is a pattern, this can't be just bad luck ! Especially since every time I see any non-502 classic scope for sale, the air filter is never missing.

So.... what's the story behind it? What the hell is going on with the air filter on the 502 ?!? .... the manual does say to regularly clean the air filter, so presumably they were shipped with one from the factory... how comes they now have all been replaced with this grill instead ?!


It does intrigue me ! ^^


Anyone ? :-)


Vincent Trouilliez


Bruce Lane
 

Many early air filters were made from a type of plastic foam which
degraded and decomposed over time, essentially turning into (very messy)
powder. The 502 is most certainly from that era.

The good news: Replacement material is easily obtainable. Check in the
plumbing/heating section of your preferred hardware or home improvement
store for open-cell filter foam (most often used in air conditioners).
It's cheap, and can be easily cut and shaped to the required dimensions.

Keep the peace(es).

On 12-Nov-18 10:37, Vincent Trouilliez wrote:

Hi Group,

This is a highly technical question, PhD only please ! LOL

Here goes : I just bought meself a little type 502 classic Tek, love it.

However it came with no air filter, somehow. The square frame to hold it, is there, screwed, but nothing in it, somehow ! However it does have a coarse grill... which presumably doesn't filter anything, but at least keeps one from stuffing his fingers in there and getting them sliced by the fan blades... better than nothing.
<snippage>


--
---
Bruce Lane, ARS KC7GR
http://www.bluefeathertech.com
kyrrin (at) bluefeathertech dot com
"Quando Omni Flunkus Moritati" (Red Green)


ROLYNN PRECHTL K7DFW
 

Many early air filters were made from a type of plastic foam which
degraded and decomposed over time, essentially turning into (very messy)
powder. The 502 is most certainly from that era.


==========================================================================

Right idea but the wrong era for the 502. The foam filters came along after the 500 series.

The filters used in this series were a square aluminum frame with multiple layers of expanded aluminum mesh inside. The filter action was achieved by spraying a special filter coating on the mesh which caught the bad things. These filters could be washed with soap and water when the filter was removed for service.

The spray (to me) was similar to Pam Spray used for cooking, at least that is what I use instead of special over-priced sprays.

Rolynn
Tek Bvtn and Sunset 1966-1971


YudaMan3 <jamesvyu@...>
 

something like this should work just fine: https://ebay.to/2OGk9bB


Vincent Trouilliez
 

Thanks for the replies everyone, that was quick ! :-)

Glad to see it's easy to find replacement foam, will go shopping then !

According to TekWiki, the 502 was introduced in 1958.

The 317 appeared the following year, 1959... I have 4 of these scopes, all have the metallic wool filter...
... so I guess then that 1958 was the last year that Tektronix fitted these perishable foam filters...


Vincent Trouilliez


John Griessen
 

On 11/12/18 12:37 PM, Vincent Trouilliez wrote:
Hi Group,
This is a highly technical question, PhD only please ! LOL
Here goes : I just bought meself a little type 502 classic Tek, love it.
However it came with no air filter, somehow.
Bonjour Vince,

I have some extras from R7603 that are stainless screen with foam in between.
Maybe I can get it flat enough to post untracked to you as a letter...

Another source for the expanded aluminum mentioned is vent hoods over kitchen stoves.
It's used as a smoke and grease filter that is washable. That might look original.


ROLYNN PRECHTL K7DFW
 

According to TekWiki, the 502 was introduced in 1958.

The 317 appeared the following year, 1959... I have 4 of these scopes, all have the metallic wool filter...
... so I guess then that 1958 was the last year that Tektronix fitted these perishable foam filters...

=========================================================================================



The metal filters were used well into the mid 1970's on all large frame 500 series scopes.....think 545B.

The best of my knowledge on this is that all the 500 series used the large metal filters.

Foam filters (small) didn't come into play until the 400 series in the mid 1960's.....think 453.

When in doubt check the Mechanical Section of the manual for a description and part number of the filter.

Rolynn


 

Use of "Scotch Brite" cleaning pads for replacement filters is described
at http://www.w140.com/tekwiki/wiki/Dust_filter

Mike Dinolfo

On 11/12/18 2:58 PM, John Griessen wrote:
On 11/12/18 12:37 PM, Vincent Trouilliez wrote:
Hi Group,

This is a highly technical question, PhD only please !  LOL

Here goes : I just bought meself a little type 502 classic Tek, love it.

However it came with no air filter, somehow.
Bonjour Vince,

I have some extras from R7603 that are stainless screen with foam in
between.
Maybe I can get it flat enough to post untracked to you as a letter...

Another source for the expanded aluminum mentioned is vent hoods over
kitchen stoves.
It's used as a smoke and grease filter that is washable.  That might
look original.



Jack
 

Hi in my view and experience, keep away from foam, Wool will have been 'seriously' cleaned of lanolin and very worthy. It may be possible to make your own from a good vehicle (e.g.
SAAB/ALFA) A/C or even air-filter....but ...back in the '50's and 60's some chaps used flyscreen wire as air filters and discovered they are high impedance to air flow. Your Tektronix
filter will be made to an air-flow 'metering' and particle size exclusion to suit the job and fan longevity.
Regards
Jack


Leon Robinson
 

When using Foam filters in the 500 Series put some hardware cloth or
Metal mesh between the foam and the fan to keep the foam from being
eaten by the fan.Some on the outside will help keep the foam in place.
 
Leon Robinson    K5JLR

Political Correctness is a Political Disease.

From: Bruce Lane <kyrrin@bluefeathertech.com>
To: TekScopes@groups.io
Sent: Monday, November 12, 2018 12:42 PM
Subject: Re: [TekScopes] Type 502 scope : missing air filter, what gives ?!

    Many early air filters were made from a type of plastic foam which
degraded and decomposed over time, essentially turning into (very messy)
powder. The 502 is most certainly from that era.

    The good news: Replacement material is easily obtainable. Check in the
plumbing/heating section of your preferred hardware or home improvement
store for open-cell filter foam (most often used in air conditioners).
It's cheap, and can be easily cut and shaped to the required dimensions.

    Keep the peace(es).

On 12-Nov-18 10:37, Vincent Trouilliez wrote:

Hi Group,

This is a highly technical question, PhD only please !  LOL

Here goes : I just bought meself a little type 502 classic Tek, love it.

However it came with no air filter, somehow. The square frame to hold it, is there, screwed, but nothing in it, somehow ! However it does have a coarse grill... which presumably doesn't filter anything, but at least keeps one from stuffing his fingers in there and getting them sliced by the fan blades... better than nothing.
    <snippage>


--
---
Bruce Lane, ARS KC7GR
http://www.bluefeathertech.com
kyrrin (at) bluefeathertech dot com
"Quando Omni Flunkus Moritati" (Red Green)


Harvey White
 

On Mon, 12 Nov 2018 10:37:11 -0800, you wrote:

Hi Group,

This is a highly technical question, PhD only please ! LOL
As I remember, the filters on the old tube scopes (this qualifies)
were a metal sponge type, a very coarse grill. Cleaning instructions
were to wash it down with hot water (I think) and spray it with a
filter coat which attracts/holds the dirt.

Harvey



Here goes : I just bought meself a little type 502 classic Tek, love it.

However it came with no air filter, somehow. The square frame to hold it, is there, screwed, but nothing in it, somehow ! However it does have a coarse grill... which presumably doesn't filter anything, but at least keeps one from stuffing his fingers in there and getting them sliced by the fan blades... better than nothing.

At first I thought well, I just got unlucky, I will just have to come up with a way to make a replacement filter, and that's it.

However... I then looked at pics online, of a dozen other 502/502A scopes, including TekWiki, and go figure : NONE of them had the air filter, all had this grill instead.

Now there is a pattern, this can't be just bad luck ! Especially since every time I see any non-502 classic scope for sale, the air filter is never missing.

So.... what's the story behind it? What the hell is going on with the air filter on the 502 ?!? .... the manual does say to regularly clean the air filter, so presumably they were shipped with one from the factory... how comes they now have all been replaced with this grill instead ?!


It does intrigue me ! ^^


Anyone ? :-)


Vincent Trouilliez




tom jobe <tomjobe@...>
 

Another source of nice air filter foam material is from the air filter 'sock' they use on dirt motorcycles. Your local motorcycle dealer should have both aftermarket and OEM filter 'socks' of different types. This motorcycle air filter foam material might be about the right thickness too.
I think the coarse aluminum grill you have in the filter frame was intended to keep the thin foam in place, give the whole filter assembly some integrity, support the foam filter material and keep it all flat.
I'd also think twice about using abrasive pad material like Scotchbrite as an air filter.
tom jobe...

On 11/12/2018 10:42 AM, Bruce Lane wrote:
Many early air filters were made from a type of plastic foam which
degraded and decomposed over time, essentially turning into (very messy)
powder. The 502 is most certainly from that era.

The good news: Replacement material is easily obtainable. Check in the
plumbing/heating section of your preferred hardware or home improvement
store for open-cell filter foam (most often used in air conditioners).
It's cheap, and can be easily cut and shaped to the required dimensions.

Keep the peace(es).

On 12-Nov-18 10:37, Vincent Trouilliez wrote:

Hi Group,

This is a highly technical question, PhD only please ! LOL

Here goes : I just bought meself a little type 502 classic Tek, love it.

However it came with no air filter, somehow. The square frame to hold it, is there, screwed, but nothing in it, somehow ! However it does have a coarse grill... which presumably doesn't filter anything, but at least keeps one from stuffing his fingers in there and getting them sliced by the fan blades... better than nothing.
<snippage>


ROLYNN PRECHTL K7DFW
 

I think the coarse aluminum grill you have in the filter frame was intended to keep the thin foam in place, give the whole filter assembly some integrity, support the foam filter material and keep it all flat.

===============================================================================


Once again, no foam in the 500 series.

For an idea of the proper type filter that was used see...

<https://www.ebay.com/itm/10-x9-1-4-x1-3-4-Aluminum-Mesh-Washable-Air-Filter/153246336827>;

This is not the proper size but is the correct type/style. The interior of this one is in a wave pattern. The original filters had multiple layers of expanded aluminum mesh. The filter was sprayed with a liquid that caught the dust and held it until the filter was washed with soap and water and then resprayed before replacing.

We did not use foam filters in the 500 series that had a fan.

Rolynn
Tek Bvtn and Sunset 1966-1971


John Griessen
 

On 11/12/18 6:34 PM, ROLYNN PRECHTL K7DFW wrote:
Once again, no foam in the 500 series.
OK, and here's a R7603 filter for reference:

https://www.ecosensory.com/tek/7603-filter-1.jpg


k1ggi
 

Checking a couple of big box scopes, they use the 378-011 filter assembly,
thick stack-up of mesh layers as Rolynn describes mounted in their own
frame. You could almost call it a filter cartridge.

How big is your filter housing, the blue frame that's bolted on the back?
l/w/d?

Ed, k1ggi

-----Original Message-----
From: TekScopes@groups.io [mailto:TekScopes@groups.io] On Behalf Of ROLYNN
PRECHTL K7DFW
Sent: Monday, November 12, 2018 7:34 PM
To: TekScopes@groups.io; tom jobe
Subject: Re: [TekScopes] Type 502 scope : missing air filter, what gives ?!


I think the coarse aluminum grill you have in the filter frame was
intended to keep the thin foam in place, give the whole filter assembly some
integrity, support the foam filter material and keep it all flat.


============================================================================
===


Once again, no foam in the 500 series.

For an idea of the proper type filter that was used see...

<https://www.ebay.com/itm/10-x9-1-4-x1-3-4-Aluminum-Mesh-Washable-Air-Filter
/153246336827>

This is not the proper size but is the correct type/style. The interior of
this one is in a wave pattern. The original filters had multiple layers of
expanded aluminum mesh. The filter was sprayed with a liquid that caught the
dust and held it until the filter was washed with soap and water and then
resprayed before replacing.

We did not use foam filters in the 500 series that had a fan.

Rolynn
Tek Bvtn and Sunset 1966-1971


ROLYNN PRECHTL K7DFW
 

OK, and here's a R7603 filter for reference:

https://www.ecosensory.com/tek/7603-filter-1.jpg

==========================================================================

Different animal. The 7603 was introduced in the early 1970's.

We're looking at instruments from the 1950's and 1960's.

The 500 series with fans use filters that have an enclosed aluminum frame and are 7/8 inch thick. They are 100% aluminum including the internal filter mesh


Rolynn


Jack
 

Hi John...I mentioned the filter would be designed for rejection of a certain minimum particle size whilst allowing at least a minimum quantity of air to pass. What-ever our suggestions
the design criteria should be and its MTBF should be met as a critical function. Arbitrary choices may not meet that important criteria so Tektronix should be contacted to see if
other filter materials it uses will meet the criteria for the model in question...Would you agree?
My regards
Jack


Frank DuVal
 

Well, just like in cars, there is always someone saying theirs is different.

My 544 I bought about 1980 at a hamfest came with a foam filter that finally fell apart, like foam does.

Maybe Tektronix did not supply it that way, but it is the way I bought it.

Frank DuVal

On 11/12/2018 8:55 PM, ROLYNN PRECHTL K7DFW wrote:

Different animal. The 7603 was introduced in the early 1970's.

We're looking at instruments from the 1950's and 1960's.

The 500 series with fans use filters that have an enclosed aluminum frame and are 7/8 inch thick. They are 100% aluminum including the internal filter mesh


Rolynn


petertech99h
 

Lots of good comments on making replacement filter for scopes!  I've made a few replacements myself, no big deal.

On your vintage scope, check some date codes on parts and see when your scope was actually made!!

Pete

On Monday, November 12, 2018, 10:01:10 PM EST, Frank DuVal via Groups.Io <corvairduval=netscape.net@groups.io> wrote:

Well, just like in cars, there is always someone saying theirs is different.

My 544 I bought about 1980 at a hamfest came with a foam filter that
finally fell apart, like foam does.

Maybe Tektronix did not supply it that way, but it is the way I bought it.

Frank DuVal

On 11/12/2018 8:55 PM, ROLYNN PRECHTL K7DFW wrote:

Different animal. The 7603 was introduced in the early 1970's.

We're looking at instruments from the 1950's and 1960's.

The 500 series with fans use filters that have an enclosed aluminum frame and are 7/8 inch thick. They are 100% aluminum including the internal filter mesh


Rolynn


ROLYNN PRECHTL K7DFW
 

My 544 I bought about 1980 at a hamfest came with a foam filter that finally fell apart, like foam does.
Maybe Tektronix did not supply it that way, but it is the way I bought it.


==============================================================================

The owner(s) of that 544 had 14 years or so to change from the original metal mesh filter. It most certainly wasn't sold with foam.

I speak not as a hobbyist but as a former Staff Engineer for Beaverton Plant 2, Building 39, which produced the 545B, 519, 529, 602, 611 and others. Working there was a pleasure and Tektronix was the best employer of my lifetime.

Rolynn
Tek Employee #72173 1966-1971