Date   
Re: Air filters for 500 series.

Stephen Hanselman
 

They were also sprayed with filter-coat which sucked up dust, for a while

Steve

-----Original Message-----
From: TekScopes@groups.io <TekScopes@groups.io> On Behalf Of John Williams
Sent: Friday, November 15, 2019 12:48 PM
To: TekScopes@groups.io
Subject: Re: [TekScopes] Air filters for 500 series.

The mesh filters were used to eliminate or at least reduce emr emissions from the scope, which could seriously effect lab equipment. They also filtered air to some degree. Later Tektronix switched to foam filters. They then had to put a metal screen over the opening to reduce emr, as well as to prevent the foam from being sucked into the fan. The mesh filters were basically stove fan filters, and various sizes of these are readily available at the Depot of course.

I reason this way: The scopes may have been used in very dusty dirty environments and therefore needed an air filter. However most of us are running them in the house or garage. As the air in those locations is usually fit to breath, I don’t think a filter is necessary, unless the noise or emr is objectionable. I have used portions of furnace filters, but gave it up as too much of a hassle. So I have some scopes with filters, some without. I have not noticed any appreciable difference. However, maybe if I had a cat or dog (lab cat.?) I would find some hair in the scope or my nose.

I guess the scope is not fully restored unless it has the correct filter with Tektronix label on it. But what the hell.

Re: Air filters for 500 series.

John Williams
 

Yes I still use the same oil coating on the k&n filters in my motorcycles and car. Good for motors, not sure if it’s good for lungs.

Re: Tek 576 noise and looping

Brad Thompson
 

peter bunge wrote on 11/15/2019 3:27 PM:

No, I have not been working on the 576 curve tracer for 8 years but i have
been curious about the looping for at least that long.
Thanks for your explanation which I tested by comparing curves with slow
and fast transistors. I had some trouble trying to find a couple with
matching gain but the high freq (900 MHz) transistor performed perfectly
with nice curves at low current. On the other hand the slow transistor had
huge loops. I would like to concentrate on the noise problem next. It mat
be finger trouble.
<good info snipped>

Hello--

This is a long shot, but I wonder whether there's a thermal issue involved? If the
device's die is poorly attached to its header or if there's a poor thermal connection between
internal lead wires and the die attachment(s) that might cause an offset between the
increasing and decreasing base current.

If it's a leakage effect, I'd expect that germanium transistors (remember those<g>)
would show fat loops.

73--

 Brad  AA1IP

Simple (?) question regarding P6139A probe

Myname
 

Dear Experts,

I do really hope that someone of you can help me. The question: How to remove the ring with the ground lead from the probe? Maybe I haven't read carefully enough but I couldn't find anything specific in the manual (http://w140.com/tek_p6139a.pdf). I do not want to use brute force so as not to damage the delicate part. Any helpful hint is highly appreciated!

Best regards

pudu51

Re: Simple (?) question regarding P6139A probe

GerryR
 

If you look on page 7, remove part 3, the retractable hook, and then you have to unscrew part #4 to then slip the ground ring off.
GerryR
KK4GER

----- Original Message -----
From: "Myname" <pudu1@...>
To: <TekScopes@groups.io>
Sent: Friday, November 15, 2019 7:27 PM
Subject: [TekScopes] Simple (?) question regarding P6139A probe


Dear Experts,

I do really hope that someone of you can help me. The question: How to remove the ring with the ground lead from the probe? Maybe I haven't read carefully enough but I couldn't find anything specific in the manual (http://w140.com/tek_p6139a.pdf). I do not want to use brute force so as not to damage the delicate part. Any helpful hint is highly appreciated!

Best regards

pudu51

Re: Items for Sale

 

Hi Roy,
I attached quadzillatech's post, which included a link to the Nuvistors for sale on eBay, at the end of my post.
Dennis Tillman W7PF

-----Original Message-----
From: Roy Thistle
Sent: Thursday, November 14, 2019 11:16 AM
Subject: Re: [TekScopes] Items for Sale

Hi Dennis:
Yes, for sure.
But, what was he posting that was for sale? (I search on "quadzillatech"... and didn't see anything.) Curiosity killed this cat (me) along time ago.
Best regards and wishes.
Roy.




--
Dennis Tillman W7PF
TekScopes Moderator

Re: Tek 576 noise and looping

peter bunge
 

The post by Dennis talking about Miller capacity prompted me to run a test
with slow transistors and RF transistors which showed no looping with a 900
MHz transistor. You won't see loping at higher currents (10 mA) with either.
The base current is constant for each curve. The collector voltage is a
full wave rectified sine wave and rises to a maximum then returns along the
same path to 0 V. The Collector current should shoot up to a set level and
return along the same path but it does not at very low currents. I think
the miller capacity feeds the decreasing voltage as a bucking charge into
the base turning off the transistor and reducing the current creating the
loop. A fast transistor has lower capacity and does not do this. Try it
with two transistors and see.
The curve is collector current in the vertical plotted against collector
voltage on the horizontal. Ideally the line should jump from zero
instantaneously to a current and stay there as a horizontal line as long as
there is any collector voltage. But nothing is ideal.
I don't believe either one of my Curve Tracers has a fault, I just want to
complete the adjustments which are stuck at the noise test.
Peter.

On Fri, Nov 15, 2019 at 4:15 PM Brad Thompson <brad.thompsonaa1ip@...>
wrote:

peter bunge wrote on 11/15/2019 3:27 PM:

No, I have not been working on the 576 curve tracer for 8 years but i
have
been curious about the looping for at least that long.
Thanks for your explanation which I tested by comparing curves with slow
and fast transistors. I had some trouble trying to find a couple with
matching gain but the high freq (900 MHz) transistor performed perfectly
with nice curves at low current. On the other hand the slow transistor
had
huge loops. I would like to concentrate on the noise problem next. It mat
be finger trouble.
<good info snipped>

Hello--

This is a long shot, but I wonder whether there's a thermal issue
involved? If the
device's die is poorly attached to its header or if there's a poor
thermal connection between
internal lead wires and the die attachment(s) that might cause an offset
between the
increasing and decreasing base current.

If it's a leakage effect, I'd expect that germanium transistors
(remember those<g>)
would show fat loops.

73--

Brad AA1IP



Re: DPO7054 question about Edge button

Tam Hanna
 

Hello,

this is good news!


Do you maybe want to share the footprint?


Tam


--
With best regards
Tam HANNA

Enjoy electronics? Join 15k7 other followers by visiting the Crazy Electronics Lab at https://www.instagram.com/tam.hanna/

Re: Simple (?) question regarding P6139A probe

Myname
 

On Fri, Nov 15, 2019 at 05:15 PM, GerryR wrote:

..., and then you
have to unscrew part #4 ...
Hello GerryR

Many thanks for the quick reply :-)! I had tried that before but the "nut" (= part #4) was so tight that at first I did not dare to unscrew her. But now I've been successful.

Best regards

pudu51

Re: Air filters for 500 series.

Robert Simpson
 

Fans in scopes seem to be fairly weak compared to other fans. For example kitchen exhaust fans, house fans etc. Try blowing through a regular house filter and you can see how restrictive they are. One member in an earlier post indicted flow was more important than filtering.
Bob

tpp1000 on 2465b

James Theonas
 

is the tpp1000 probe compatible with the 2465b?
Thanks to everybody!

Re: tpp1000 on 2465b

John Williams
 

It looks like a $1000+ 1ghz probe might be overkill on a 2465b. However I see no reason why it wouldn’t work.

Re: tpp1000 on 2465b

David DiGiacomo
 

On Sat, Nov 16, 2019 at 11:58 AM James Theonas via Groups.Io
<jamestheonas=yahoo.com@groups.io> wrote:

is the tpp1000 probe compatible with the 2465b?
No, there would be no way to adjust the compensation.

(Not that the compensatable scope input capacitance range is specified.)

Re: Air filters for 500 series.

Keith
 

My 5 series Tek appears to use a very typical 45w Howard Industries fan. These are nothing but glorified refrigerator evaporator fans, and equivalent models are still commonly available.

It looks to me like it would be easy to up the motor wattage a notch while staying in the same frame size. One could then pitch the OEM aluminum fan blades a little steeper by hand (not that hard to do - I've done it on other fans) and maybe tighten up the dimension of the fan flange with some plastic trim or something similar. (That's where the efficiency of these fans really suffers, and the tighter the fit, the better the efficiency. Of course, if the bushings get loose, a tight tolerance fan will hit, but hey...that's why you're supposed to replace those bushings when they "become worn" just as it says in the manual. :-)

FWIW, if anyone is experiencing inadequate airflow, IMO it would be pretty easy to gain 15-20% airflow increases while keeping an original look by doing these or similar steps.

Filter oil - yeah, ditto on the K&N oil. Works great as long as it lasts, which is quite a while in reasonably clean environments.

Finally, similar shredded wheat metal filter material is available from restaurant supply houses. (Grease traps use a similar material) and the C channel that makes up the filter frame is common as well. This, just in case someone wants to fabricate a "near correct" filter for their 5 series. FWIW

Cheers

TEK 494P 1st LO mixer

kmatus4365@...
 

Hi to all members of the group. I'm new here though I have read many post in silence. Today I turn to you b/c I am looking for a 1st LO mixer 119-1017-00 or, alternatively for a 119-1353-00. No way to get one here in Vienna/Austria. Any replies greatly appreciated. Karl

Re: TEK 494P 1st LO mixer

John Williams
 

Hi Karl glad to see you here. I can’t help you,but hopefully someone in the group can. Regards, John

Re: Air filters for 500 series.

Chuck Harris
 

Overheating of the 500 series scopes, including the 555, was not
a problem. Not at all.

Overheating of the lab the scope was in, well that was a different
story.

Why fix it if it isn't broken?

Your mod may increase the airflow, assuming the filter isn't so
restrictive that the fan is working up against a wall, but it
will also increase the noise. Something most people don't need or
want.

You say that the fan is nothing but a glorified refrigerator
evaporator fan, given that tek spec'd these fans in the late 1940's,
and late 1940's refrigerators didn't have evaporator fans, are
you sure that refrigerator evaporator fans aren't really nothing
but glorified oscilloscope fans? ;-)

-Chuck Harris

coolblueglow@... wrote:

My 5 series Tek appears to use a very typical 45w Howard Industries fan. These are nothing but glorified refrigerator evaporator fans, and equivalent models are still commonly available.

It looks to me like it would be easy to up the motor wattage a notch while staying in the same frame size. One could then pitch the OEM aluminum fan blades a little steeper by hand (not that hard to do - I've done it on other fans) and maybe tighten up the dimension of the fan flange with some plastic trim or something similar. (That's where the efficiency of these fans really suffers, and the tighter the fit, the better the efficiency. Of course, if the bushings get loose, a tight tolerance fan will hit, but hey...that's why you're supposed to replace those bushings when they "become worn" just as it says in the manual. :-)

FWIW, if anyone is experiencing inadequate airflow, IMO it would be pretty easy to gain 15-20% airflow increases while keeping an original look by doing these or similar steps.

Filter oil - yeah, ditto on the K&N oil. Works great as long as it lasts, which is quite a while in reasonably clean environments.

Finally, similar shredded wheat metal filter material is available from restaurant supply houses. (Grease traps use a similar material) and the C channel that makes up the filter frame is common as well. This, just in case someone wants to fabricate a "near correct" filter for their 5 series. FWIW

Cheers



475 repair parts

 

All,
I rescued a 475 the other day. I met the guy at a gas station and handed him 20 bux. It in the back of his pickup on top of a load of firewood. Anyway I cleaned it up and have a couple of caps on the way. One of the trigger level/polarity pots didn’t survive the ride. I’m looking for a 311-1192-00 trigger level pot with switch

Thanks
Chris W9RP

Re: Air filters for 500 series.

John Williams
 

Right Chuck I agree. Thee biggest reason for overheating was poor maintenance. The filter was often not cleaned properly, but I think that even a dirty filter would still pass enough air to sufficiently cool the scope. More likely was a poorly maintained fan motor. If the motor was not regularly or properly lubricated, that would lead to it gradually slowing until finally seizing. Then the technician would pour oil into the oil holes on the motor but it would be too late. Oil would run down and coat the rear of the scope, which would eventually become a dirt encrusted mess. The only solution is to remove the fan, disassemble the motor and clean the crap out of the bushings. I have worked on some that even this extreme repair didn’t fix. That’s where a few spares come in handy. I also notice the dirtiest scopes are usually only dirty from the top, underneath they are pretty clean. I don’t know why this is, it’s as though they sat in a basement with the covers off.

7844 power supply

Peter Gottlieb
 

A couple of weeks ago I mentioned a 7844 which instantly blew the line fuse but which had previously worked.

It was suggested I look at the line rectifier and bulk caps.

I finally finished the project on my bench and put the scope there. The problem turned out to be that the two main switching transistors were shorted.  After replacing them all was not well though.  The supply kept trying to come up, making a weak rattling sound.  I could see it was trying.  Then ever once in a while it would come up, fan run, and scope start, but then within a few seconds go back to rattling.  Then in the midst of considering where to look next it just stopped.  Now, nothing.  HV is on the main caps and the neon is rapidly flashing, but nothing else.

These supplies are infamous for being a pain in the neck.  Has anyone seen this and have any hints for what I should look for?

Peter