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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
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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.
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Re: Back from vacation
Chuck Harris
A digital curve tracer is simply a digitally controlled
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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.
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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
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Re: Tek Knob Project - scan and make
Chuck Harris
The knobs are plastic primarily for cost of manufacture.
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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!
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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!
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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
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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: 7904AI'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
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Re: Tek Knob Project - scan and make
Richard R. Pope
Stephan,
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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.
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Re: Tek Knob Project - scan and make
stefan_trethan
These are just stock knobs from RS components.
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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,
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Re: Tek Knob Project - scan and make
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
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Re: Tek Knob Project - scan and make
Richard R. Pope
Stephen,
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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:
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Re: Tek Knob Project - scan and make
stefan_trethan
Here you go Phil:
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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,
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Re: Back from vacation
Hi Tam.
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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
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Re: Tek Knob Project - scan and make
Velik Kazakov
Very interesting - will try this today. Soundс good. 10x for sharing!
Velik Kazakov
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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
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Re: Tek Knob Project - scan and make
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
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Re: Newbie saying "Hello!"
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
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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,
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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.
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7A14 Bad first mixer? SUBJECT SHOULD BE 7L14
Hi Dallas,
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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 -- Dennis Tillman W7PF TekScopes Moderator
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