Date   

Re: Tek Knob Project - scan and make

Vince Vielhaber
 

I have and do it quite often, just not with rtv or acrylic. I use actual
silicon mold material and plastic resin, all made for making plastic
parts. I don't know if the SC-504 uses the same tiny focus knob as the
SC-503 does, but one of the things on my todo list is to make a new knob
to replace the missing one on my 503. The scope has two identical knobs,
so the one that remains can be my model. Then just take the new knob, put
it on the lathe and drill the center hole. Color matching is the main
problem, tiny set screw for that thing is another.

Vince.



On 12/20/2017 8:53 AM, Chuck Harris wrote:
The knobs are plastic primarily for cost of manufacture.
<snip>

Hello--
Has anyone explored using RTV silicone rubber to form a mold of an
existing
knob, followed by using the mold to cast a replacement knob using
acrylic resin (or another compound)?

73--

Brad  AA1IP






Re: Back from vacation

Chuck Harris
 

A digital curve tracer is simply a digitally controlled
couple of power supplies, and a digitally read voltmeter,
and a program to do the reading and controlling.

Apply current to the base, current to the collector, ground
the emitter, and measure the voltages everywhere... wash rinse
repeat.

I made my first curve tracer using two adjustable bench power
supplies, two resistors, one for the collector load, one for
the base, and an X-Y chart recorder.

I set the base supply's voltage, dropped the pen, adjusted
the collector supply through its range, and let the recorder
draw whatever I was measuring... Vce, Ic, whatever. Lifted
the pen, reset the collector supply to zero, set a new base
supply voltage...

It is adding the human usable displays that added most of the
complexity to the 57X curve tracers.

-Chuck Harris

Dennis Tillman W7PF wrote:

Hi Tam.
How do you convert an analog curve tracer to digital???
Wouldn't it be easier to start from scratch and build a digital curve tracer rather than try to modify an existing analog curve tracer.
They do exist and they have lots of capabilities you can't get in a Tek analog curve tracer. BUT...
As far as I know none of them has the capability to test devices at the same voltage, current, and overall power levels of the Tek curve tracers. At the opposite end of the spectrum I believe the Tek curve tracers are far more sensitive at micro- and nano-amp currents. Versatility would be another consideration where Tek would probably excel over a digital curve tracer.

A few advantages to a digital curve tracer would be network interconnectivity, GPIB programmability, hard copy output, the ability to save and recall results to/from a file, automatic calculation of all parameters, scale factor readout,

I think the big problem you face is how much this is going to cost to build. It is comparatively simple to capture a trace on a scope because there is a one to one mapping of vertical amplitude values to horizontal time values. In the case of XY displays it is essentially the same - a one to one mapping of vertical amplitude values to horizontal amplitude values. But a curve tracer displays parametric values. For every horizontal amplitude value there can be anywhere from one to a hundred vertical amplitude values on a Tek curve tracer depending on how many vertical base steps you use So you have a one to many mapping. That gets very complicated to try and capture which you would have to do if you were modifying an existing Tek curve tracer. But if you design from scratch it gets easier to capture any number of vertical values since you control each base step and horizontal voltage increment.

Good luck with your project.

Dennis

-----Original Message-----
From: TekScopes@groups.io [mailto:TekScopes@groups.io] On Behalf Of Tam Hanna
Sent: Tuesday, December 19, 2017 8:30 PM
To: TekScopes@groups.io
Subject: Re: [TekScopes] Back from vacation

Dennis,
that paper is insane! Wow.

Given that I just resumed - albeit at a very slow pace, it's Christmas and the terrible stress some people make about it is extremely bad for my health - work on my digital upgrade for the Danaher 57x series; please allow me to ask if there is any software feature I could implement to simplify tube testing!

Tam
---
With best regards
Tam HANNA (emailing on a BlackBerry PRIV)

Enjoy electronics? Join 6500 other followers by visiting the Crazy Electronics Lab at https://www.instagram.com/tam.hanna/





Re: Tek Knob Project - scan and make

Brad Thompson <brad.thompson@...>
 

On 12/20/2017 8:53 AM, Chuck Harris wrote:
The knobs are plastic primarily for cost of manufacture.
<snip>

Hello--
Has anyone explored using RTV silicone rubber to form a mold of an existing
knob, followed by using the mold to cast a replacement knob using
acrylic resin (or another compound)?

73--

Brad  AA1IP


Re: Tek Knob Project - scan and make

Chuck Harris
 

The knobs are plastic primarily for cost of manufacture.

The plastic defines the color, through-and-through, and
makes the knob feel neutral in temperature... the aluminum
hub provides the strength. Injection molding of knobs is
a mature, automated, process by which they could crank
out knobs by the millions without any operator intervention.

I had a friend that bought one such machine from a bankruptcy
auction, and he just had to fire it up. He filled the hopper
with some miscellaneous plastic pellets that came with the
machine, installed the mold, and filled the other hopper with
aluminum hubs, and set it going. Within an hour his hoppers
were empty, and he had more of these weird colored knobs than
he could ever sell.

However, aluminum, milled, or molded, and then painted
would be an acceptable solution. Its problems of conductivity
are shared with the plastic in that the setscrew, and the
underskirt, provide a pathway for electricity to the
operator. The ridges on the knob are high pressure points
where the paint will wear away eventually.

The conductivity isn't really a problem, as you are supposed
to be a "trained operator", and know that the scope must
be grounded.

Machining the knobs is simple, but highly repetitive. The
dies used in the injection molding process were machined,
and polished.

-Chuck Harris

nojunkmail@cd-envisions.com wrote:

I second the 10x for sharing!

Is there any reason some of these knobs could not be machined out of aluminum (or other material); other than non-originality?

Would aluminum pose any ESD or shock hazards? I see some knobs are made out of aluminum (completely). Why some, why some not?

Some, seem like pretty simple machining to me. Of course it's easier said than done (I am a novice still).

Cheers!

-Dano


Re: Repairing a 466 oscilloscope

Nikolay Belikov
 

Hello Velik,

The motor itself is Siemens 1AD3001-0A, Tek part No 147-0035-00, and the assembly with the board and motor is 670-2245-00. I cannot find a manual for 463, so I cannot confirm that they are the same, but if you have one, you could compare the part numbers.

I live in Russia, so I'm not sure how much it would be to ship internationally, if you will ever be willing to do so. Anyway, thanks a lot!


Re: 7904A readout bounce

NigelP
 

OK, I think this is now the final input from my side on this topic!

I studied the schematic and noted something that I thought odd in comparison to the test schedule F5. I can see that the pot R130 is said to adjust the 1MHz jitter with 1uS/Div. Now, without a detailed analysis it seems to me that R130 is adjusting a "DC" or LF component since it does not have the capacitor associated with all the other compensation pots (except for C200 connected around the op-amp). All other adjustment pots are associated with a capacitor value which tracks the rep-rate value you are trying to compensate (higher value for lower frequency and vice versa). Admittedly all pots do have some level of DC adjustment but R130 circuitry seems to be a bit more DC-aggressive (maybe just my weird way of thinking about things :().

Now when I first tried this F5 procedure, noting that 1MHz did not need any adjustment (there was no jitter) I didn't bother to even try adjusting it, and just concentrated on R132 & R131 which is targeted at 10Hz which is typically where all the problem exhibits itself.

I decided to try out my theory that R130 ought really to be responsible for DC/LF jitter/bouncing correction; and indeed it does! I was able to tune out the 10/100Hz bounce far better than with the supposed correct pots R132/131 :). Re-evaluating the 1MHz rep rate results showed no loss of readout jitter compensation, and indeed I did not even bother to check the C200 adjustment. So simply speaking, first adjust R130 at 10Hz and then follow the procedure as defined in Table5-5.

So I now have a quite satisfactorily compensated readout across the full range of test offered by the 067-0587-01 and 067-0587-10 Signal Standardisers. I also found that using the Gain setting on the Standardiser (a full screen height staircase waveform) rather than the Step Response setting gave a far more aggressive signal for the compensation to be adjusted against; it was more visible and in effect the rep rate of the test signal is then one-eighth of the Step test. I can just observe a marginal vertical movement but nothing that is going to bother me.

I did also notice that adjusting R130 against 10/100Hz did actually vary the overall top-to-bottom magnitude of the readout display versus the Y-channel waveform; perhaps to be expected?

So reviewing the F5 test schedule and Table 5-5, firstly (in my manual at least) there appears to be a typo error...... step-5 indicates a rep rate of 100KHz (which is actually step-2) and should read 100Hz. Also in my personal experience the first step should be to adjust R130 at 10Hz and then check at 1MHz (perhaps adjusting only C200 where necessary) before moving on to the other steps in the table.

Comments on the above discoveries from those more knowledgeable/experienced are surely welcomed :).

Nigel


Re: 7904A readout bounce

cmjones01
 

On Tue, Dec 19, 2017 at 5:19 PM, NigelP <nigel-pritchard@outlook.com> wrote:
So, further investigation demonstrates more of what I've already noted. Scenario: 7904A
loaded with 2x 7A26, 7B92A, 7D15 and ALT set on both vertical PIs and mainframe set to
ALT...... if I overlay all four traces on top of each other there is NO bouncing of the readout .
As you increment any trace position towards top/bottom of the screen the bounce gets
increasingly larger reaching around 0.1 major division (therefore readout bounce magnitude
is a direct function of trace vertical position). Sweep speed in the region of 50mS/Div +/-
some shows up nicely, but any variation of sweep speed simply varies the level of visual
annoyance. Any combination of ALT setting produces the same result.
I've just tried this on my 7904A and I also get some readout bounce,
but very little. If I position two traces in ALT mode, one at the top
and one at the bottom of the screen, so they're only just not visible,
the readout bounces a very tiny amount (timebase at 10ms/div), much
less than 0.05 divisions. You really have to look carefully to see it.
If I crank the Y position knobs to their maximum possible extents, I
can get the bounce up to about 0.1 divisions, but that's the extreme.

This 7904A hasn't been refurbished other than a slight tweak to the Y
gain and to one of the thermal compensation adjustments. I use it in
my work almost every day and the readings it gives appear to be
accurate when compared with other instruments I use. It doesn't have
traceable calibration but I'd say it was within spec.

Chris


Re: Tek Knob Project - scan and make

Richard R. Pope
 

Stephan,
I appreciate the suggestion. Yes, they are quite small. So, does anyone out there have one of these very small knobs for the SC-504 that they would be willing to depart with?
Merry Christmas and Thanks,
rich!

On 12/20/2017 2:00 AM, stefan_trethan wrote:
These are just stock knobs from RS components.
I don't think it would be a particularly good way to fix the SC504,
since it has the very small focus knob, and many of the same style on
the front panel.

Perhaps someone else will have one that he can send you?

ST

On Wed, Dec 20, 2017 at 8:55 AM, Richard R. Pope <mechanic_2@charter.net> wrote:
Stephen,
I want to tell you that I'm glad that you posted the links to your
pictures. I accidentally broke the Focus knob on my SC-504 Scope. Are you
able to make another one and how much to do so?
Merry Christmas and Thanks,
rich!

On 12/20/2017 1:48 AM, stefan_trethan wrote:
Here you go Phil:

https://photos.app.goo.gl/R64amqABAORlL9es2
<https://photos.app.goo.gl/R64amqABAORlL9es2>;

ST

On Wed, Dec 20, 2017 at 5:08 AM, Phillip Potter <p.potter@sbcglobal.net>
wrote:
Hi Stefan,

I would be interested in your pictures, but... maybe we should take this
off-list, so as not to offend; LOL! I would like to see how you did it,
but
I have my doubts about my skills with reworking, since I do not have a
drill
press, or a vice. I tend to be a purist but not a prude, and not easily
offended.

Thanks for thinking of my amusement, however, that's very kind of you in
this Holiday Season! ;)

Phil


I can provide a photo, for your amusement.

ST



Re: Tek Knob Project - scan and make

stefan_trethan
 

These are just stock knobs from RS components.
I don't think it would be a particularly good way to fix the SC504,
since it has the very small focus knob, and many of the same style on
the front panel.

Perhaps someone else will have one that he can send you?

ST

On Wed, Dec 20, 2017 at 8:55 AM, Richard R. Pope <mechanic_2@charter.net> wrote:
Stephen,
I want to tell you that I'm glad that you posted the links to your
pictures. I accidentally broke the Focus knob on my SC-504 Scope. Are you
able to make another one and how much to do so?
Merry Christmas and Thanks,
rich!

On 12/20/2017 1:48 AM, stefan_trethan wrote:

Here you go Phil:

https://photos.app.goo.gl/R64amqABAORlL9es2
<https://photos.app.goo.gl/R64amqABAORlL9es2>;

ST

On Wed, Dec 20, 2017 at 5:08 AM, Phillip Potter <p.potter@sbcglobal.net>
wrote:

Hi Stefan,

I would be interested in your pictures, but... maybe we should take this
off-list, so as not to offend; LOL! I would like to see how you did it,
but
I have my doubts about my skills with reworking, since I do not have a
drill
press, or a vice. I tend to be a purist but not a prude, and not easily
offended.

Thanks for thinking of my amusement, however, that's very kind of you in
this Holiday Season! ;)

Phil


I can provide a photo, for your amusement.

ST






Re: Tek Knob Project - scan and make

Dano
 

I second the 10x for sharing!

Is there any reason some of these knobs could not be machined out of aluminum (or other material); other than non-originality?

Would aluminum pose any ESD or shock hazards? I see some knobs are made out of aluminum (completely). Why some, why some not?

Some, seem like pretty simple machining to me. Of course it's easier said than done (I am a novice still).

Cheers!

-Dano


Re: Tek Knob Project - scan and make

Richard R. Pope
 

Stephen,
I want to tell you that I'm glad that you posted the links to your pictures. I accidentally broke the Focus knob on my SC-504 Scope. Are you able to make another one and how much to do so?
Merry Christmas and Thanks,
rich!

On 12/20/2017 1:48 AM, stefan_trethan wrote:
Here you go Phil:

https://photos.app.goo.gl/R64amqABAORlL9es2
<https://photos.app.goo.gl/R64amqABAORlL9es2>;

ST

On Wed, Dec 20, 2017 at 5:08 AM, Phillip Potter <p.potter@sbcglobal.net> wrote:
Hi Stefan,

I would be interested in your pictures, but... maybe we should take this
off-list, so as not to offend; LOL! I would like to see how you did it, but
I have my doubts about my skills with reworking, since I do not have a drill
press, or a vice. I tend to be a purist but not a prude, and not easily
offended.

Thanks for thinking of my amusement, however, that's very kind of you in
this Holiday Season! ;)

Phil


I can provide a photo, for your amusement.

ST


Re: Tek Knob Project - scan and make

stefan_trethan
 

On Wed, Dec 20, 2017 at 5:08 AM, Phillip Potter <p.potter@sbcglobal.net> wrote:
Hi Stefan,

I would be interested in your pictures, but... maybe we should take this
off-list, so as not to offend; LOL! I would like to see how you did it, but
I have my doubts about my skills with reworking, since I do not have a drill
press, or a vice. I tend to be a purist but not a prude, and not easily
offended.

Thanks for thinking of my amusement, however, that's very kind of you in
this Holiday Season! ;)

Phil


I can provide a photo, for your amusement.

ST



Re: Back from vacation

 

Hi Tam.
How do you convert an analog curve tracer to digital???
Wouldn't it be easier to start from scratch and build a digital curve tracer rather than try to modify an existing analog curve tracer.
They do exist and they have lots of capabilities you can't get in a Tek analog curve tracer. BUT...
As far as I know none of them has the capability to test devices at the same voltage, current, and overall power levels of the Tek curve tracers. At the opposite end of the spectrum I believe the Tek curve tracers are far more sensitive at micro- and nano-amp currents. Versatility would be another consideration where Tek would probably excel over a digital curve tracer.

A few advantages to a digital curve tracer would be network interconnectivity, GPIB programmability, hard copy output, the ability to save and recall results to/from a file, automatic calculation of all parameters, scale factor readout,

I think the big problem you face is how much this is going to cost to build. It is comparatively simple to capture a trace on a scope because there is a one to one mapping of vertical amplitude values to horizontal time values. In the case of XY displays it is essentially the same - a one to one mapping of vertical amplitude values to horizontal amplitude values. But a curve tracer displays parametric values. For every horizontal amplitude value there can be anywhere from one to a hundred vertical amplitude values on a Tek curve tracer depending on how many vertical base steps you use So you have a one to many mapping. That gets very complicated to try and capture which you would have to do if you were modifying an existing Tek curve tracer. But if you design from scratch it gets easier to capture any number of vertical values since you control each base step and horizontal voltage increment.

Good luck with your project.

Dennis

-----Original Message-----
From: TekScopes@groups.io [mailto:TekScopes@groups.io] On Behalf Of Tam Hanna
Sent: Tuesday, December 19, 2017 8:30 PM
To: TekScopes@groups.io
Subject: Re: [TekScopes] Back from vacation

Dennis,
that paper is insane! Wow.

Given that I just resumed - albeit at a very slow pace, it's Christmas and the terrible stress some people make about it is extremely bad for my health - work on my digital upgrade for the Danaher 57x series; please allow me to ask if there is any software feature I could implement to simplify tube testing!

Tam
---
With best regards
Tam HANNA (emailing on a BlackBerry PRIV)

Enjoy electronics? Join 6500 other followers by visiting the Crazy Electronics Lab at https://www.instagram.com/tam.hanna/





--
Dennis Tillman W7PF
TekScopes Moderator


Re: Tek Knob Project - scan and make

Velik Kazakov
 

Very interesting - will try this today. Soundс good. 10x for sharing!

Velik Kazakov


Re: Repairing a 466 oscilloscope

Velik Kazakov
 

Hi,
were you from. If you live in Bulgaria, maybe I can help. Have some 463 for spares and think the fans are the same. Just need to check when have a time. BTW looking in to SM to find the 466 motor type, but no success. Do you know the motor part number?

regards,
Velik


Re: Tek Knob Project - scan and make

ROLYNN PRECHTL K7DFW
 

Has anyone tried the UV cure glue that is being advertised? I bought a package of the glue and the UV LED device from Bondic, but I haven't used it yet.
========================================================

When I first heard of the UV cured glue I thought that it would be a good idea. Looking through the internet regarding the process pointed out one very important issue.

The UV cure only works when the glue is on the surface (like a scab according on one person). It won't work in cracks as the UV LED can't access the glue.


Rolynn


Re: Newbie saying "Hello!"

Phillip Potter
 

Hi Dano,

I, too, am a new member, working on my used scope... lots to do.

Anyway, welcome and Merry Christmas and Happy New Year!

Phil


Re: Tek Knob Project - scan and make

Dave Seiter
 

That's a great method for repairing knobs!
-Dave

From: Chuck Harris <cfharris@erols.com>
To: TekScopes@groups.io
Sent: Tuesday, December 19, 2017 8:13 PM
Subject: Re: [TekScopes] Tek Knob Project - scan and make

Fundamentally, the problem is the plastic shrinks over
time, but the aluminum insert doesn't.  When the plastic
has shrunken enough, it cracks.

What to do...

Well, the answer is very simple.  You must make the hole
for the insert a tiny little bit bigger.

Here's how...

Put the knob back together and wrap it with a small
rubber band... snug's good, not killer tight... spread
the wraps over the whole knob. Then, using a soldering
iron, apply heat to the shaft hole in the aluminum insert
in short intervals... 1 second heat, 5 seconds watch...
until you see the rubber band start to shrink the knob
back into shape, and then quickly cool the insert with
compressed air.  When it starts, it goes quickly, and if
you let it get too hot, all of the knob's plastic will
melt, and the rubber band will distort the knob.

Now, the cracks will be just hairlines, and can be easily
fixed using a solvent glue, such as methylene chloride.

Don't use crazy glue, duco, silicone seal, epoxy...  You
will just make a mess.

-Chuck Harris (who has done this lots of times)

Phillip Potter wrote:
Hi Anthony,

Yep, that is in evidence! I squeezed them as tightly as I could and applied the
juice, in an attempt to shore them up, but I am not optimistic that they will last
very long. The ones that had been previously re-glued were a mess and I just put the
juice over the top of the former botched job.

Thanks for the reply.

Phil


On 12/19/2017 7:36 PM, Anthony via Groups.Io wrote:
  If you look at intact knobs, they usually have a hairline crack on one side. They
will survive a long time this way as the crack releases stress in the part. But I
suspect the plastic in the knobs has shrunk over time against the aluminum inserts,
causing them to eventually break.


Re: Tek Knob Project - scan and make

Dave Seiter
 

That would be an interesting project.  I have a Type W plugin that has a split white DC balance knob.  IIRC, this is a common problem. I believe there is a similar knob used elsewhere that has the same problem.  They should be simple objects to print, but the set screws are really small and I don't have a hex key that will fit. (It's smaller than .05", which is usually the smallest you see on Tek gear).  I was also wondering if it would be possible to print the 7K series backplane connector covers.
I haven't tried printing with ABS yet, although my printer is capable of it.
-Dave

-------------------2. Homemade 3D prints in ABS can be vapor smoothed and look beautiful with no other manual post-processing of the print. They can also be painted.

Alternatively, various professional printing services can print those knobs nicely from various materials, for a low cost: the knobs have small volume and that’s what mostly affects the price.


7A14 Bad first mixer? SUBJECT SHOULD BE 7L14

 

Hi Dallas,
You mean 7L14,not 7A14. I suggest you change the subject line and resend your email to avoid any confusion. You will also get a greater response to a 7L14 subject since the 7A14 is a very uncommon Current Amplifier plugin.
Dennis Tillman W7PF

-----Original Message-----
Sent: Tuesday, December 19, 2017 3:30 PM
Subject: Re: [TekScopes] 7A14 Bad first mixer?

Hi Dallas,

I actually "won" this item in a previous listing, but the seller's reserve price was not met, so no joy. No second chance offer, the item was just re-listed a day after, what we're looking at right now. I'm actually looking for a 7L5 with no luck for almost a year, I bid on this 7L14 out of despair, kind of.

I would not say the mixer is bad on this one, however the attenuator is not set as the manual/practice recommends. 10dB of attenuation is offset by +10 dB of IF gain, so the display actually makes sense, if I'm not mistaken.
The noise floor may be a bit higher than expected, not really sure, can't see the RBW clearly. However something else worries me, digital storage is off or not working on this one. It is enabled by default on power up, so you'd need to switch it off deliberately, for eBay pics? Digital storage performs averaging that shows the noise floor more clearly, a reason to have it on.

With the current price this one seems a long shot for me, since I'm on the opposite side of the Planet. If you really want/need it, just pass a message and I'll stay clear. Whoever goes for it is going to need luck, my previous bid was ridiculously high for my standard, and still did not crack the reserve price.

Best Regards,
Nenad Filipovic


On Tue, Dec 19, 2017 at 8:30 PM, Dallas Smith <dosmith2@outlook.com> wrote:

Hello, I glad we are now at Groups.io. All my Yahoo accounts have been
terminated.
Found this on Flea Bay: 282771846825
It looks like the first mixer is bad? The -30 dB gain is turned up to
hide it?
What does anyone think?
Still a good buy, can repair the mixer.

Dallas



--
Dennis Tillman W7PF
TekScopes Moderator

33441 - 33460 of 176299