Re: Anyone willing to make 3D printing of multiplier boxes
I have designed and printed several for the 465-475 etc. I also have printed a stand alone box for 455/475M as well. I can supply an STL for either one.
--
Michael Lynch
Dardanelle, AR
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Re: Anyone willing to make 3D printing of multiplier boxes
encapsulating the HV multipliers is easily done using a "Potting Shell".
they are available cheaply off-the-shelf from many vendors, here's two examples:
a thin-shelled 3D printed box would be pretty fragile, I think.
all the best,
walter
--
Walter Shawlee 2
Sphere Research Corp. 3394 Sunnyside Rd.
West Kelowna, BC, V1Z 2V4 CANADA
Phone: +1 (250-769-1834 -:-
+We're all in one boat, no matter how it looks to you. (WS2)
+All you need is love. (John Lennon)
+But, that doesn't mean other things don't come in handy. (WS2)
+Nature is trying very hard to make us succeed, but nature does not depend on us.
We are not the only experiment. (R. Buckminster Fuller)
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Re: Anyone willing to make 3D printing of multiplier boxes
Hello,
how big are they.
Tam
--
With best regards
Tam HANNA
Enjoy electronics? Join 15k7 other followers by visiting the Crazy Electronics Lab at
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Re: Delay Time Position Vernier
Colin Herbert wrote:
Your other problem is setting the Vernier where it is supposed to sit when you put it all
together again! They don't all sit at 0.00, There is data about where they are supposed
to read when the pot is at the extreme anticlockwise. If you have problems, just make
them known here and you should get the right advice. Don't just adjust it to 0.00 - it is
likely to be wrong.
Is this covered in the service manual? I would be interested in knowing how this needs to be set, as I am planning to move the guts of one 475 into the frame of another, and that would obviously involve disassembling and reassembling the delay vernier. -- Jeff Dutky
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Re: Fix or Part Out a Tek 475A
David Collier wrote:
Yes the trigger slope shafts were bent as well! Now straightened.
How did you straighten the shafts? I mean, other than bending them, did you do anything special? I've got two parts scopes that I'd like to make into one working scope and one parts scope, where the main damage is to the knobs and shafts on the front panels of both scopes (and, like yours, the scopes themselves seem to be in almost perfect working order but for the front panel damage), and I would appreciate any pointers you might have in how to repair the trigger slope switch shafts (I may just have to accept broken knobs, since I haven't found any good source for the trigger level knob, which is what appears to be the common victim of this mistreatment). The 475 seems to be a remarkably durable instrument, even in the face of obvious physical and electrical abuse. I had thought that it was amazing that my father's scope was in such good working order, but it had been treated with kid gloves and stored in a dehumidified basement for most of its life. One of my parts scopes is clogged with black, sooty dust and covered in something like grey paint, but seems to be in even better working order than my father's scope. And the 475A that I'm currently working on clearly had something happen in the HV section, but the rest of the scope appears to be in very good shape (meaning that other functions seem to be working even though the beam intensity amplifier is busted). I was expecting all kinds of things to be damaged: blown diodes, transistors, and ICs, dried out and shorted caps, resistors that had drifted out of spec, dim or busted CRTs, etc., but, aside from the 475A (which is certainly delivering on some of those expectations) things have been quite functional, and I deliberately bought the cheapest, most likely to be busted scopes I could find on eBay! It's a testament to the engineering prowess of the folks who designed and built these machines. -- Jeff Dutky
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Anyone willing to make 3D printing of multiplier boxes
I was wondering if anyone was willing to make the boxes for the multipliers
so ones that go bad can be made. The box would need the holes for the wires
and mounting threads as original. The old epoxy will break down like the
transformers do. Anyone willing to rewind/build replacement transformers
would be welcome. Buying new diodes, condensers, etc. to put in the box
then use silicon sealant will give enough insulation. I know the sealant
works on 21kV. I had to put some on the PDA where the white was no longer
sealing. The clear type I used stopped the arcing and the scope works fine.
The diodes that can be used are 2CL2FM. They are 20kV and heavier capacity
than originals. I know the diode and condenser from ground to the current
limiter/sensing is low voltage. The diode should be very fast with low
reverse current at 600-1000V, e.g. 1N4937, and the condenser is ,01mfd. I
see comments about multipliers going bad. This would be a good way to get
the scope back working.
Mark
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OS-34/URM-32 and OS-4B/AP schematics wanted
I am looking for the schematics of the two military scopes. I prefer paper
or print-out. Thanks.
Mark
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Re: Delay Time Position Vernier
Ah, thank you Colin. I was wondering about that. My working scope isn't at 0.0, and this one wasn't either. And I have no recollection of what the Army scopes were set to. I can get close 'cuz I do remember that it was very close to 0 and like 1/4 turn ccw on the fine knob.
Long way to go before I'm back to setting this!
Dave
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On Wednesday, November 25, 2020, 03:17:39 PM PST, Colin Herbert via groups.io <colingherbert@...> wrote: Your other problem is setting the Vernier where it is supposed to sit when you put it all together again! They don't all sit at 0.00, There is data about where they are supposed to read when the pot is at the extreme anticlockwise. If you have problems, just make them known here and you should get the right advice. Don't just adjust it to 0.00 - it is likely to be wrong. Colin. -----Original Message----- From: [email protected] [mailto: [email protected]] On Behalf Of Dave Peterson via groups.io Sent: 25 November 2020 21:13 To: [email protected]Subject: [TekScopes] Delay Time Position Vernier Anyone know the trick to removing the Delay Time Position Vernier pot? I have the fine adjustment knob off. Now what!? Befuddled.
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Chuck Harris wrote:
So, I would guess that a smaller resistor was specified when the
board was designed, and it was found to get too hot
but this resistor pair is present in the schematics, not just for the 475A, but also in the early 475 service manual schematics. I know that's not really a refutation of your point, but it sure looks like they meant to do this from really early on. The on-end resistors are clearly visible in the PCB images. I haven't opened up my oldest 475 to check the physical board, but I was planning to do that, and will report back what I find. Also, I know that schematics do not necessarily precede the physical objects they represent, so they may not accurately reflect original intent. I once worked at an engineering company where, as we were packing a large machine to be shipped to the client the lead engineer was taking each part and comparing it to the existing drawings, in order to find parts that had been modified (or completely fabricated) during testing and development. When he would find a part that didn't have a drawing he would quickly gin one up in AutoCAD before the part was packed and shipped. My impression, at the time, was that this was part of our contractual obligations to the client, but it occurs to me now that it may have been entirely internal; so that our people would be able to correctly reassemble the machine at the client site based on the engineering drawings.
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In a word, no.
Anything is possible, I suppose, but asking us to believe that Tek's design team carelessly forgot to check power dissipation is a lot to swallow. This wasn't their first rodeo -- they'd already done the 465, 465B (it was pretty much the same team) and the 475. If you look at the 465, there is a similar series combo in the same general part of the blanking circuit. It is obviously done to reduce capacitance. There is a tiny trimmer of about 1pF across the combo, so clearly they were carefully accounting for fractions of a pF.
I'm sticking with parasitic capacitance concerns as the most likely reason for the choice in the 475A.
The team did make some mistakes (in the 465 in particular; they fixed those in the B version), but forgetting to calculate power dissipation here was not one of them.
Cheers,
Tom
Sent from my iThing, so please forgive the terseness and typos.
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On Nov 25, 2020, at 14:54, "Chuck Harris" <cfharris@...> wrote: I've done this for many, many years, and usually my reason is
I cannot fit a higher wattage resistor in the same space as two
smaller resistors sitting upright like this.
So, I would guess that a smaller resistor was specified when the
board was designed, and it was found to get too hot, so two resistors
of the same wattage, in series were fitted... with no changes in
the circuit board.
-Chuck Harris.
Jeff Dutky wrote:
Chuck Harris wrote:
How do you know tektronix did this? Most of the stuff we have hasn't
been at the factory for 20 or 30 years. The main reasons that I think Tek did this are 1) that the two resistors appear in the schematic in the service manual, and 2) the resistors look like matches for resistors found elsewhere on the unit. Also, the method of vertically mounting the resistors and soldering their upward pointing leads together is found elsewhere on the unit, specifically on the vertical preamp board in the 3rd stage amplifier.
-- Jeff Dutky
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Re: Delay Time Position Vernier
Your other problem is setting the Vernier where it is supposed to sit when you put it all together again! They don't all sit at 0.00, There is data about where they are supposed to read when the pot is at the extreme anticlockwise. If you have problems, just make them known here and you should get the right advice. Don't just adjust it to 0.00 - it is likely to be wrong.
Colin.
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-----Original Message----- From: [email protected] [mailto: [email protected]] On Behalf Of Dave Peterson via groups.io Sent: 25 November 2020 21:13 To: [email protected]Subject: [TekScopes] Delay Time Position Vernier Anyone know the trick to removing the Delay Time Position Vernier pot? I have the fine adjustment knob off. Now what!? Befuddled.
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Re: Fix or Part Out a Tek 475A
Thanks Tom, Raymond & Jeff,
Yes the trigger slope shafts were bent as well! Now straightened. Display is bright, and power supplies are well within spec for residual hum. All electrolytics are original. Fan motor dissected/oiled and now fine: at the back it has a screw (underneath glue) to adjust free play, all behind the PC board which has to be unsoldered first. Over-engineered! Someone had the Y amp board off because the 100MHz/20MHz/trigger view shaft was wrongly adjusted. I notice 2mV presets on it as well as 5mV presets, though there is only 5mV and greater shown on the rotary switches.
This scope appears to be working well in all respects. No sign of shorting tantalum caps. The mains TX has taps for the optional 12V battery circuit, which I might try. This follows restoration of a Fairchild Dumont 765H (very bright and sharp display); Heathkit IO-14 (now with a TEK trigger circuit), and TEK 191 sig.gen.
I still have two TEK 545B's to restore; one obviously with the well-known epoxy potted EHT transformer problem. Along with one early 1A1 and two 1S1 plugins.
The National R1230/FLR wide band receiver awaits future attention to sharpen up its IF response for practical use on short wave.
Regards
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Re: Tektronix 492A input attenuator repair ????
If it does turn out to be a blown attenuator, perhaps the best option is to use an HP attenuator instead (they are much more available). A small bit of logic is needed to remap control signals and space is tight, but it can be done. I've fixed two this way after giving up any hope of fixing the original attenuator. Essentially 100% of 492 attenuators found on eBay are blown (keywords are "untested", "as-is" and "from working unit").
There is an extensive set of instructions online for the mod. I don't have a link handy, but a minute of googling should lead you to it.
Good luck!
Cheers,
Tom
Sent from my iThing, so please forgive the terseness and typos.
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On Nov 25, 2020, at 14:31, "Bob Koller" <fourdesigns@...> wrote: Unfortunately, there are no parts, except from another Tek attenuator. Is it blown, or are the contacts "dirty"? These were often damaged by DC or excessive input power. If it is damaged, you need to check the first mixer for damage as well. You may be able to find a good attenuator on eBay, perhaps elsewhere, but these can be difficult to find in good condition.
It is possible to disassemble these and make one good unit out of two. The thin film resistive elements can also be inspected. Usually the damage is readily apparent under magnification.
It would be possible to fit a different attenuator, with the correct steps, and frequency range, altering the drive signals as required.
Be sure to take anti static precautions around the mixer.
Good Luck,
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I've done this for many, many years, and usually my reason is
I cannot fit a higher wattage resistor in the same space as two
smaller resistors sitting upright like this.
So, I would guess that a smaller resistor was specified when the
board was designed, and it was found to get too hot, so two resistors
of the same wattage, in series were fitted... with no changes in
the circuit board.
-Chuck Harris.
Jeff Dutky wrote:
toggle quoted message
Show quoted text
Chuck Harris wrote:
How do you know tektronix did this? Most of the stuff we have hasn't
been at the factory for 20 or 30 years. The main reasons that I think Tek did this are 1) that the two resistors appear in the schematic in the service manual, and 2) the resistors look like matches for resistors found elsewhere on the unit. Also, the method of vertically mounting the resistors and soldering their upward pointing leads together is found elsewhere on the unit, specifically on the vertical preamp board in the 3rd stage amplifier.
-- Jeff Dutky
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Re: 2710 Spectrum Analyser 'Cannot count VCO, IF' error
Thanks everyone; thankfully mine is a later production version, post B020319, so hopefully not the unrelaible version.
I've checked the 100MHz reference and have healthy outputs on all 3 reference outputs (no tracking generator option installed), roughly -8dBm on J110, -10dBm on J130, and -12dBm on J140 (all approximate as I'm pushing the bandwidth of my cheap scope probe at 100MHz).
One thing I have discovered is that what I thought was an input to the board on J110, the Beat Signal input, was in fact common mode noise from my LED lighting! There appears to be no signal at all coming from the 1st LO buffer, so that's what I'm now looking at.
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Re: Tektronix 492A input attenuator repair ????
Unfortunately, there are no parts, except from another Tek attenuator. Is it blown, or are the contacts "dirty"? These were often damaged by DC or excessive input power. If it is damaged, you need to check the first mixer for damage as well. You may be able to find a good attenuator on eBay, perhaps elsewhere, but these can be difficult to find in good condition.
It is possible to disassemble these and make one good unit out of two. The thin film resistive elements can also be inspected. Usually the damage is readily apparent under magnification.
It would be possible to fit a different attenuator, with the correct steps, and frequency range, altering the drive signals as required.
Be sure to take anti static precautions around the mixer.
Good Luck,
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Re: Delay Time Position Vernier
On Wed, Nov 25, 2020 at 03:51 PM, Dave Peterson wrote:
I have a pair of snap-ring pliers that kind of work.
I do not have the factory tool, but I have a set of snap ring pliers that have round tips that work pretty well. I use masking tape over the outside of the vernier ring to prevent inadvertent damage if the pliers slip. -- Michael Lynch Dardanelle, AR
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Re: Why you MUST USE the PayPal "FRIENDS and FAMILY" option for Peter's book
Hi Jeff, I've been with Paypal for over 20 years. They have security measures in place like every other bank. I've never had an issue with paying or receiving money from anyone either. I won't use any other payment option, unless someone wants to send a check or postal money order. I'd like to know what your issues are because I have a LOT of stuff that I'd like to list here for sale and if there is some issues that are making things difficult to pay for things, I'd like to know about it Thanks!!! On 25 Nov 2020 at 8:56, Jeff Dutky wrote: Dennis,
I have finally been allowed to confirm receipt of the book in
PayPal.
While I appreciate the effort you have put into this, the experience
with PayPal has only reinforced my already negative opinion of the
company and service. I understand why you chose to use it, but I
feel as if they have gone out of their way to make things as
difficult and unfriendly as possible. I am sure, however, that the
book will be more than worth the anxiety and frustration.
Thanks again for putting this together.
-- Jeff Dutky
John Goller, K9UWA & Jean Goller, N9PXF Antique Radio Restorations k9uwa@... Visit our Web Site at: 4836 Ranch Road Leo, IN 46765 USA 1-260-637-6426
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Re: Delay Time Position Vernier
Ah! Great!
I have a pair of snap-ring pliers that kind of work. I gave it a bit of a tug, but didn't want to get aggressive with it not knowing that I was yanking on the right part or not.
I have the right idea then. Just needed to know what the right part to yank on was.
Thanks!
Dave
"You don't pay me to kick it. You pay me to know WHERE to kick it". (old repairman's joke).
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To get a high-wattage resistance, there are a couple of options: Get a bigger resistor; or make it out of a series or parallel combination of lower power resistors.
Tek chose a series combination, and chose not to implement that combination in the pcb artwork, but did show it in the schematic as a series combination. To me, that suggests a very deliberate choice not done in haste. The voltages are too low for flashover concerns to have been the reason here. I think that something else besides that or a parts shortage drove the decision.
To first order, the shunt capacitance in pF of a resistor equals the power rating in watts. A 1W resistor, or two half-watt resistors in parallel, has about 1pF in parasitic capacitance. But a series combination creates a 1W resistor with only 0.25pF capacitance. That's a consideration in a high-swing, high slew-rate blanking circuit, where you can easily burn ~10mA driving each pF of parasitic load cap.
To reap the full benefits of the series connection, you would want to float the common point above the pcb, which is exactly what they did.
I regularly use this method in rf circuits. The trade off is an increase in series inductance, but in this circuit, we're looking at 15 kilohms, so parasitic inductance is a non-issue.
-- Cheers,
Tom
Sent from an iThing, so please pardon the typos and brevity
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On Nov 25, 2020, at 1:12 PM, "Terry Gray via groups.io" <tlgray42@...> wrote: In my >60 years experience with this type of equipment I have seen these two series resistors (modification?) in many different situations and I agree with Jeff 100%. He has it right. Terry
On Wednesday, November 25, 2020, 02:44:56 PM CST, Jeff Dutky <jeff.dutky@...> wrote:
Chuck Harris wrote:
How do you know tektronix did this? Most of the stuff we have hasn't
been at the factory for 20 or 30 years. The main reasons that I think Tek did this are 1) that the two resistors appear in the schematic in the service manual, and 2) the resistors look like matches for resistors found elsewhere on the unit. Also, the method of vertically mounting the resistors and soldering their upward pointing leads together is found elsewhere on the unit, specifically on the vertical preamp board in the 3rd stage amplifier.
-- Jeff Dutky
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Mlynch001
Dave Peterson
Michael W. Lynch