Re: Tek 2753P Manuals
george edmonds
I have repaired many thousands of SMPSU.s, using a variac is not necessary, but, an in series incandescent light bulb is absolutely vital if you wish to avoid a total self destruction at times. It is easier to be safe than sorry.
73 George G6HIG


Re: Deane Kidd and the Metric System
EricJ
That makes more sense. For myself, I can convert back and forth pretty easily most of the time in my head already after 20+ years of doing it daily. It's pretty easy for me to think in both measurement systems these days.
toggle quoted messageShow quoted text
Eric Sent from my Samsung Galaxy S8.
 Original message From: "Fabio Trevisan fabio.tr3visan@... [TekScopes]" <TekScopes@...> Date: 12/15/17 8:39 AM (GMT06:00) To: TekScopes@... Subject: Re: [TekScopes] Deane Kidd and the Metric System
Guys, I think what Ian Newman meant is that you can easily do that conversion by heart, without resorting to a calculator or a piece of paper to make the full division or multiplication operation. It's a nobrainer to repeatedly double the quotient and the divisor until the divisor reaches 256, and just take note of what the quotient became to get the result directly in 10ths of mm. With an error of just 0.78%! I think it goes particularly intuitive to the ones of us who dealt more with binary logic who can tell by heart most of the smaller powers of 2 and the relation between all of them. Rgrds from Brazil, Fabio 20171215 11:28 GMT02:00 Eric J wyzkydd2358@... [TekScopes] < TekScopes@...>: Same. I was a machinist, toolmaker and welder for 20 years until I injured my back. We always used 25.4 for conversion from inch to metric and vice versa, it is correct and gives the exact conversion. Eric Sent from my Samsung Galaxy S8.  Original message From: "Barry n4buq@... [TekScopes]" <TekScopes@...> Date: 12/14/17 7:48 PM (GMT06:00) To: TekScopes@... Subject: Re: [TekScopes] Deane Kidd and the Metric System I worked in a metric shop for 10 years. I pretty much always used 25.4 as the conversion factor. 0.03937 is a rounded recriprocal of 25.4 which is technically the correct conversion factor between inches and millimeters (and easier for me to remember). Thanks, Barry  N4BUQ  Original Message  From: "Tom Jobe tomjobe@... [TekScopes]" < TekScopes@...> To: TekScopes@... Sent: Thursday, December 14, 2017 6:36:53 PM Subject: Re: [TekScopes] Deane Kidd and the Metric System That is a very neat trick... but consider this simple plan: For the fractional part of the dimension, divide the bottom number into the top number to get its decimal equivalent. Example (7/16" = 7 divided by 16 gives you 0.4375 inches) If there are whole inches involved in the measurement then it becomes 1.4375, 2.4375 etc. Divide the decimal inch number by .03937 and you have your millimeter equivalent. Example ( our 7/16" is 0.4375 decimal inches, we divide it by .03937 and we have our answer of 11.11125 mm. Memorizing the number .03937 solves the whole problem going either way, to or from inches and millimeters. Let's have an example of going from millimeters to inches: If you multiply 100mm by .03937 you will get it's equivalent in inches, 100 x .03937 = 3.937 inches. The number .03937 is simply how many inches are in one millimeter. This .03937 method was the common way that millimeters and inches were dealt with in shops I worked at in the US. tom jobe...


Re: Deane Kidd and the Metric System
Fabio Trevisan
Guys,
I think what Ian Newman meant is that you can easily do that conversion by heart, without resorting to a calculator or a piece of paper to make the full division or multiplication operation. It's a nobrainer to repeatedly double the quotient and the divisor until the divisor reaches 256, and just take note of what the quotient became to get the result directly in 10ths of mm. With an error of just 0.78%! I think it goes particularly intuitive to the ones of us who dealt more with binary logic who can tell by heart most of the smaller powers of 2 and the relation between all of them. Rgrds from Brazil, Fabio 20171215 11:28 GMT02:00 Eric J wyzkydd2358@... [TekScopes] < TekScopes@...>:
[Nontext portions of this message have been removed]


Re: 7904A readout bounce
Roger Evans
I have just had a look to see what my 7934 (same Y amplifier and channel switch) does at slow sweep speeds. If I put one of the Y traces near the top of the screen and one at the bottom and set the sweep speed to 100msec/div then I see a small shift of the top and bottom readout positions as the beam alternates between the two traces. The movement is at most 0.05 of a major division, quarter of a minor division When the upper beam is displayed both readouts move slightly downwards, when the lower beam is displayed the readouts move up slightly. If I put the two traces near each other, anywhere on the screen, the readout does not move. At 10msec/div the movement is about the same but more objectionable, at anything faster than 1msec/div the readouts are steady. This seems consistent with thermal effects and David explained it very clearly.
IWhat sweep speeds are you using and how much movement of the readout do you see? Roger


Re: Deane Kidd and the Metric System
EricJ
Same. I was a machinist, toolmaker and welder for 20 years until I injured my back. We always used 25.4 for conversion from inch to metric and vice versa, it is correct and gives the exact conversion.
toggle quoted messageShow quoted text
Eric Sent from my Samsung Galaxy S8.
 Original message From: "Barry n4buq@... [TekScopes]" <TekScopes@...> Date: 12/14/17 7:48 PM (GMT06:00) To: TekScopes@... Subject: Re: [TekScopes] Deane Kidd and the Metric System
I worked in a metric shop for 10 years. I pretty much always used 25.4 as the conversion factor. 0.03937 is a rounded recriprocal of 25.4 which is technically the correct conversion factor between inches and millimeters (and easier for me to remember). Thanks, Barry  N4BUQ  Original Message  From: "Tom Jobe tomjobe@... [TekScopes]" <TekScopes@...> To: TekScopes@... Sent: Thursday, December 14, 2017 6:36:53 PM Subject: Re: [TekScopes] Deane Kidd and the Metric System That is a very neat trick... but consider this simple plan: For the fractional part of the dimension, divide the bottom number into the top number to get its decimal equivalent. Example (7/16" = 7 divided by 16 gives you 0.4375 inches) If there are whole inches involved in the measurement then it becomes 1.4375, 2.4375 etc. Divide the decimal inch number by .03937 and you have your millimeter equivalent. Example ( our 7/16" is 0.4375 decimal inches, we divide it by .03937 and we have our answer of 11.11125 mm. Memorizing the number .03937 solves the whole problem going either way, to or from inches and millimeters. Let's have an example of going from millimeters to inches: If you multiply 100mm by .03937 you will get it's equivalent in inches, 100 x .03937 = 3.937 inches. The number .03937 is simply how many inches are in one millimeter. This .03937 method was the common way that millimeters and inches were dealt with in shops I worked at in the US. tom jobe...


Re: Deane Kidd and the Metric System
Vince Vielhaber
You guys are all doing it the hard way. When I need to do a conversion I
toggle quoted messageShow quoted text
just ask the Google Home I keep in the shop: Hey Google, what's 283.4mm in inches? And she tells me. Vince.
I worked in a metric shop for 10 years. I pretty much always used 25.4 as


Re: Deane Kidd and the Metric System
stefan_trethan
Come on guys, surely it was a joke!
It's like saying to get from feet to inches divide by 0.08333333. ST On Fri, Dec 15, 2017 at 2:48 AM, Barry n4buq@... [TekScopes] <TekScopes@...> wrote: I worked in a metric shop for 10 years. I pretty much always used 25.4 as the conversion factor. 0.03937 is a rounded recriprocal of 25.4 which is technically the correct conversion factor between inches and millimeters (and easier for me to remember).


Re: 7904A readout bounce
NigelP
Seems odd, but let's be quite specific about what I see; the readout jumps up and then down exactly at the start of each alternate sweep; difficult to imagine that this is a thermal problem... it's almost as if a switch is being thrown one way and the other at the start of each sweep (and indeed somewhere in the sweep circuitry that is probably exactly what is happening.... by design)? Also, the effect is quite flipflop, so not increasing with sweep position but actually at the start of each sweep; one might argue that it's coincident with each sweep gate.
What I have not yet checked is whether fully overlaying two or four alternate traces on the screen minimises the effect; in other words whether it is the shift in vertical displacement of the normal two or four scan lines that is attributing to the readout display shift. Anyway the bottom line is that the thermal compensation adjustment process is not actually solving the issue. I can see that if I adjust (eg R131 @ 50mS sweep) to one extreme or the other I can observe readout jitter going in or out but it doesn't seem to minimise the bounce. Nigel


Re: Tek 2753P Manuals
John Miles
There's not much upside in using the old Variac and/or lightbulb trick to
bring up a switching power supply. The switcher won't generally fail in a way that draws excess AC line current. If a secondary rail is shorted, it will simply refuse to start. Meanwhile, the combination of a shorted secondary rail and an unusual highimpedance or lowvoltage AC power connection may not have been wellcharacterized by the original designer. The best strategy is to just plug it in and hit the power switch.  john, KE5FX Author/maintainer of the 49x service document, FWIW :) From: TekScopes@... [mailto:TekScopes@...] Sent: Thursday, December 14, 2017 5:35 PM To: TekScopes@... Subject: [TekScopes] Re: Tek 2753P Manuals So, I found some manuals for a 494AP which is similar to mine. Also found some 494 repair notes which looks to be a good find. Anyway, I finally got around to powering it up with a dim bulb circuit and a 200W bulb. A couple LEDS on the front came on and the scope backlights but that is it. The bulb in the test circuit also lit to about half brightness I would guess, not sure if it's safe to hook up to the variac and get some power board voltages??? Got the case off, very nice and clean inside, good sign. One of the main filter caps has the plastic a little ruffled on top so maybe that got a little hot at some point. Having a little difficulty getting to the power board, not sure if the go by from the 494 is the same so I am kinda hesitant to go any further trying to disassemble it. Hoping it's just a few electrolytics to replace get her up and going. The downside to this unit is that it is a huge beast of a machine. Have no clue where I will set this up if I ever get it going. http://www.antiqueradios.com/forums/download/file.php?id=198994


Re: Deane Kidd and the Metric System
Tom Gardner
On 14/12/17 22:57, Ian Newman ian_new@... [TekScopes] wrote:
How very annoyingly neat and simple. Annoying because I didn't think of it myself. It makes pi*pi == g == 10 look boring. Anyway, thanks; email saved!


Re: My tek 2465 smokes
Tom Gardner
On 15/12/17 06:51, 'hardy hansen' hardyhansen@... [TekScopes] wrote:
A good starting point would be http://www.condoraudio.com/wpcontent/uploads/Projects/Tektronix2465BOscilloscopeRestorationRepair.pdf


Re: Deane Kidd and the Metric System
Craig Sawyers <c.sawyers@...>
Damn. *Were* you pulling our leg Tom? If so you suckered me into getting on my theory high horse!
Craig definitionMemorizing the number .03937 solves the whole problem going eitherThat is a more difficult and much more imprecise number to remember than 25.4. That is by the precise conversion. Whereas 1/25.4 ~ 0.03937 are the first digits of a repeating decimal(since it can be expressed as 10/254, and a fraction of two integers always returns a repeating decimal, as asimple example 1/9 = 0.11111...). It turns out that the repeat length of 1/254 (and hence of


Re: Deane Kidd and the Metric System
Craig Sawyers <c.sawyers@...>
Memorizing the number .03937 solves the whole problem going either way, to or from inches andThat is a more difficult and much more imprecise number to remember than 25.4. That is by definition the precise conversion. Whereas 1/25.4 ~ 0.03937 are the first digits of a repeating decimal (since it can be expressed as 10/254, and a fraction of two integers always returns a repeating decimal, as a simple example 1/9 = 0.11111...). It turns out that the repeat length of 1/254 (and hence of 10/254 = 1/25.4)) is 42 digits long! Craig


Re: My tek 2465 smokes
cmjones01
On 15 Dec 2017 7:52 a.m., "'hardy hansen' hardyhansen@...
[TekScopes]" <TekScopes@...> wrote After not having used my tek 2465 for a whilenow it really smokesdo vagely recall it have been seen before?? The smoke is probably from the mains input filter capacitors which, after a few decades, crack and admit moisture, then fail with a cloud of smoke. The proper fix is to replace the capacitors. The fix I use is just to wait for the smoke to stop (it does, eventually) and carry on using the scope. The operation of the instrument is not affected by these capacitors, but there's a chance it won't meet its conducted radio interference spec if they've failed. You are free to decide whether this is something you care about. Chris


Re: My tek 2465 smokes
Ed Breya
You said it smokes, but does it run? Open it up and look for the source. Could be one of the infamous bad Xcaps, or something else burning up and ready to crap out entirely. It's best to look while there's still some smoke left.
Ed


My tek 2465 smokes
hardyhansendk
Hello
After not having used my tek 2465 for a whilenow it really smokesdo vagely recall it have been seen before?? Any advise welcome as i am not in a position right now to dig very deep because of health issues. Thanks Hardy. Fra: TekScopes@... [mailto:TekScopes@...] Sendt: 14. december 2017 17:58 Til: TekScopes@... Emne: Re: [TekScopes] My 2462A died suddenly El 14/12/2017 a las 10:47 a.m., machine guy @Mac [TekScopes] escribió: Hi, I replaced U1062 and U1064 because there were laying around. but I don't have U1066. Now what I can see is that there is 11V on one gate of the Q1060 or Q1070 and on the other there are only 5V. Looks that U1066 is bad? Capacitors are ok. Thank you for responding on your holydays. Joachim <http://www.avg.com/emailsignature?utm_medium=email&utm_source=link&utm_campaign=sigemail&utm_content=emailclient> Virusfri. <http://www.avg.com/emailsignature?utm_medium=email&utm_source=link&utm_campaign=sigemail&utm_content=emailclient> www.avg.com [Nontext portions of this message have been removed]


Re: Deane Kidd and the Metric System
stefan_trethan
Thanks, Ian, for that neat trick with the 256 method. I'll use it for sure.
And thank you Tom, for pulling our leg. ;) ST On Fri, Dec 15, 2017 at 1:36 AM, Tom Jobe tomjobe@... [TekScopes] <TekScopes@...> wrote: That is a very neat trick... but consider this simple plan:


Re: c12 camera
Glydeck
I love this!
Sent from my iPad On Dec 14, 2017, at 8:04 AM, 'Craig Sawyers' c.sawyers@... [TekScopes] <TekScopes@...> wrote: [Nontext portions of this message have been removed]


Replacement caps for 465B
n4buq
Anyone have a good list / supplier for the electrolytic caps in the LVPS of a 465B? I had some of the adapter discs made (the kind that take a snapin cap) so looking for that form factor.
Here's the specs from the manual: C4419 5000uF 25V +100% / 0% C4429 1200uF 100V +75% / 10% C4439 550uF 100V +75% / 10% C4521 5500uF 30V +100% / 10% C4531 5000uF 25V +100% / 10% Was considering the same 6800uF, 35V, 20% cap (Mouser P/N 647LGU1V682MELZ) for C4419, C4521, and C4531. Given they're originally +100% caps, I presume that'd be okay? Anyone have better choices? Thanks, Barry  N4BUQ


Re: Deane Kidd and the Metric System
n4buq
I worked in a metric shop for 10 years. I pretty much always used 25.4 as the conversion factor. 0.03937 is a rounded recriprocal of 25.4 which is technically the correct conversion factor between inches and millimeters (and easier for me to remember).
toggle quoted messageShow quoted text
Thanks, Barry  N4BUQ
 Original Message 
From: "Tom Jobe tomjobe@... [TekScopes]" <TekScopes@...>

