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Re: 5xx 'Scopes
On Wed, Aug 14, 2019 at 01:24 PM,
I once asked Deane Kidd, when I was in his lab, which he recommended, 576 orDennis, Is there as specific reason that the 577 is the preferred instrument? I have both working instruments and am looking to sell one of the two. I do not know enough about either to say which is better. Looking for some sage advice. Thanks -- Michael Lynch Dardanelle, AR |
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Re: 2445A Sweep and Other Questions
I fixed the one I purchased from eBay with the help from goys here! I'm
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sure you can fix it! Now, I'm not an expert, but in my case it was -after many days and emails and searches on the web....- easy fix (if you can call it that). If I can help with something specific I'll help. My problem was - see my youtube here: Gooood luck! Tony On Wed, Aug 14, 2019 at 4:51 PM Paul Gallimore <paulmk22@...> wrote:
Hi, |
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Round pin connector on minigrabbers
What is the round pin connector on minigrabbers such as 020-0720-00, or, really, on the connecting leads such as 012-0747-00? Can I get that today in bulk?
(Most minigrabbers use the usual 0.64 mm square post we know from wire-wrapping or as ¡°dupont¡± connectors on Chinese equipment. The above ones are round and a bit finer, though.) Gr¨¹?e, Carsten |
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Re: 547 Fan lubrication
Thanks to everyone who responded to my question, it has turned into quite a large and interesting discussion!
I have had the bearings soaking in a naphtha type solvent for the last couple of days and will let them dry out later today. Successive solvent changes now look pretty clear. The rotor shaft journals look fine. The oilite bearings are located in diecast end bells with some sort of fabric around them to retain the lubricant. I'm reluctant to disassemble them further or remove the bearing shells from their housings for fear of damaging them. I've decided to use Mobil-1 oil but not to bake the whole end bell assembly because of lack of facilities and the potential effect on the absorbent fabric. I'll just dribble the oil into the holes in the bearing housings and run the motor for while to let it warm up and soak through. Maybe a blast with the hot air gun will help. The rotor was located axially with a mixture of nylon and fibre washers together with wavy spring washers that look like phosphor bronze. Some of these are quite worn. In his book Stan Griffiths mentions that Tek used to supply replacement teflon washers but I'm sure they would not be available now. However I have found a source of teflon washers of the right size intended for the radio controlled model industry and they should arrive next week. In the meantime the scope is sleeping on its side on my workbench and I'm taking the opportunity to clean the filter and a few more areas. Incidentally the stator of the motor has a date stamp of January 16, 1964. Electronically the scope works perfectly and is a pleasure to use. It's only needed minor maintenance in the 15 years or so since I paid $100 for it. Not bad for a 55 year old classic! Morris |
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Re: Is an early 7A26 a keeper?
Hi Ron and John,
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I was not aware that the signal from both channels were the same up to U1350. That means the attenuator has nothing to do with the gain being off. In that case then the 7A26 is acting like a "difference" amplifier as you said. I prefer to distinguish that configuration (CH1 - CH2) from a "differential" amplifier which is a more complex and flexible design concept. Many people assume they can create a differential amplifier by inverting one channel and adding it to the other channel. What they are really doing is creating a "difference" amplifier. For those who did not understand the difference I wanted to point out the limitations of this technique, to explain what precautions users would need to take, and to caution them not to make assumptions about how well this works. To get reasonable results it helps to understand the limitations of the circuit designs of Tek instruments. For instance, it is important to keep both the Ch1, Ch2, and difference waveforms on the screen at all times is because once a signal goes off screen the recovery time of each channel's amplifier, and the IC summing the two signals, goes way up. Factors like these are a balancing act for circuit design engineers. There is nothing wrong with the choices Tek made. Other companies will make different choices that may give them an advantage in different circumstances. Once you own a true differential amplifier, and a set of differential probes, you will come appreciate what they are capable of. The 7A22 and the 7A13 are the Differential Amplifiers for the 7K series. Each is unique in its own right. The 7A22 is an extremely sensitive low (~1MHz) bandwidth amplifier with the ability to set its LF and HF roll off frequencies. The 7A13 is a 110MHz differential amplifier with precise offset voltage capability. Dennis Tillman W7PF -----Original Message-----
From: [email protected] [mailto:[email protected]] On Behalf Of John Sent: Wednesday, August 14, 2019 2:25 PM Ron, that is what I figure too. U1350 is the probable culprit as the signals match on channel 1 & 2 up to that point. The readout is OK so it is basically in the gain channel. As I say one day;-)) John Proctor VK2DLP -----Original Message----- From: [email protected] [mailto:[email protected]] On Behalf Of ron roetzer Sent: Wednesday, August 14, 2019 12:20 PM Dennis I should have been more precise, I didn't mean to imply that the 7A26 had differential inputs but that the internal signal path was differential. If you look at the block diagram in section 7 of the manual the signal becomes differential after U1350 (U2350) and continues differentially to the vertical signal output. If either side of the differential pair is not functioning then the output would be 1/2. Ron -----Original Message----- From: [email protected] <[email protected]> On Behalf Of Dennis Tillman W7PF Sent: Wednesday, August 14, 2019 2:43 PM Hi Ron, This is not what is causing the 1/2 gain in one of the two channels but not the other. The 7A26 is not differential. It has two separate input channels. In certain cases the 2nd channel can be inverted and added to the first channel to make a "primitive" difference, but not differential, amplifier. Tek generally makes no claims about the performance of their vertical amplifiers when the signal goes off screen. While the signal is on-screen it is in the linear region of the vertical amplifier and you can expect the bandwidth of the amplifier will meet its stated specs. Provided neither signal by itself goes off screen, and the addition of both signals stays on screen, you will probably remain in the linear region of both channels. If you invert Ch 2 and add both signals together you will get the difference between them provided you use the same probes on each channel and you are careful to calibrate their response as closely as possible. You will also need to calibrate the gain of each channel. Even if you did all this it would be misleading to assume that the on screen result was what a true differential amplifier with matched probes, matched inputs, matched phase response, matched offsets, etc would give you. Dennis Tillman W7PF -----Original Message----- From: [email protected] [mailto:[email protected]] On Behalf Of ron_roetzer@... Sent: Wednesday, August 14, 2019 5:42 AM although I have no specific knowledge of the 7A26, in differential amplifiers if one side is dead then the gain is exactly 1/2 what it should be. -- Dennis Tillman W7PF TekScopes Moderator |
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Re: 2445A Sweep and Other Questions
On Wed, Aug 14, 2019 at 5:51 PM Paul Gallimore <paulmk22@...> wrote:
So, I am trying to assess whether I should sell this on Ebay (UK) as aDefinitely fix'er up, there's nothing like the feeling of restoring a beautiful bit of test gear like this. Gotta be careful though, it's hard to stop once you fixed one :). |
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Re: Need help troubleshootingTektronix PS280 Power supply
Sounds like fun.
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I just bought an Agilent E3630A That does not show any voltage/current on the display. It has not arrived yet, but I¡¯ll be trying to fix it. Good luck, larry On Aug 14, 2019, at 6:22 PM, daven9ooq via Groups.Io <daven9ooq@...> wrote: |
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Re: 2445A Sweep and Other Questions
Hi,
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Fix it and tell us about it. How large is the ripple? Everyone seems to recommend changing the caps in the power supply. You say after warmup, then the problem starts. CAPS?? The manual is online. 2445 and 2465 are very similar. On EEVBlog, another fella is working na 2465. Larry On Aug 14, 2019, at 3:04 PM, Paul Gallimore <paulmk22@...> wrote: |
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Need help troubleshootingTektronix PS280 Power supply
daven9ooq
Hi everyone: This is my first post since the group changed to IO.
I been in need of a good Dual Voltage variable power supply for my bench, I been looking around on line for awhile when I came across a Tektronix PS 280, up to that point all that I was seeing is cheap Chineese PS , I already own lots of Tek TM 500 equipment , So I thought the Tek PS280 would fit right in. The PS280 is around late 70's early 80's vintage It was advertised as working on ebay, I but I had my duoghts, I felt I could probably fix it , having built many of my own, I looked up the schematic and manual in advance, I found it on W140.com Tekwiki, I found all the semiconductors were still available ,even the Intersil meter chips. For the money , you couldn't even build one for the hundred bucks + shipping! Although it has the Tek name, it doesn't look like a Tek products that I'm used to seeing, Was after Tek sold out you can tell it was built with a budget in mind, but is of fairly good quality, the two varabile supplys are 0-30volts @2amps they can be run independently or in series or parallel, Neither of the variable sides worked properly, there was some low voltage but nowhere near the range it should have and not a smooth adjustment but very choppy. I ordered the electrolytics and replaced all the caps except for the 5 volt supply that was still working havent checked the ripple yet. Since the board was difficult to remove and I'm working one handed due to a stroke also wanted something I could depend on well into the future. After the recap things were a lot better voltage wise but still not working right to my surprise. The boards looked pristine , no one had their fingers in before me I did find a cold solder joint on one of the 470uf electrolytics , the boards were waved soldered. Upon visual inspection nothing else looked bad ,burnt or smelled bad, I have not been able to find any obvious bad components . There has been many revisions and the schematic is somewhat correct on the general circuitry but not the leadgonds for the connectors, there are many interconnects and wire jumpers on the board but the numbers on the connections don't jive, which makes me think I don't have the correct schematic for the revision. Looking at Tek wiki the one that I have looks like the latest version. The serial number is TW 50125 the main board is marked GPC- 848A-1 B The supply looks like it was farmed out and built under many Brands But has a legit looking Tek Serial number tag. This power supply is unusual to me having built many of my own over the years, it is dual tracking and constant voltage and current that uses a bunch of Asian transistor logic and 4 relays, but uses none of the usual regulator designs like LM317 or LM723 but it does have some of the usual regulators but used only for reference, it starts with a 7815 as a reference that goes into LM741 op amps and LM301 then another 741 to a driver transistor then to the usual series pass transistor a 2N3055. Most of the 7800 series regulators and op amps are bulit proof which makes me think the culprit probably has to be a cold solder joint or a bad zener, or transistor. I only had one basic course of electronics in college the rest is self taught. I'm not able to follow a signal through a maze of transistors and op amps, but I know enough to be dangerous! I would really like to gain a better understanding of this power supply And get it working of couse. Many thanks! in advance. Dave N9OOQ |
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2445A Sweep and Other Questions
Hi,
I acquired a 2445A a few years back and never switched it on until now. I am now starting to look at it for the first time and there are a couple of issues, but I have no scope fixing experience. Plus it's been a while since I did any fault finding on anything truly electronic. So, I am trying to assess whether I should sell this on Ebay (UK) as a broken item, or whether I should take a shot at fixing it up. I have powered it up and there are no reported faults, plus the scope traces appear as they should, as well as on screen characters. However, after a warm-up period (5-10 mins) the sweep stops and I am left with just a vertical trace. Using the J119 test points I can see that the supplies all look good with a DVM, but using Pico scope (laptop based scope) I can see some ripple on the supplies. I have yet to determine whether the ripple is in spec. (Though, I know where the info for that is in the manual) Where do you think I should start with this? Should I just do a bulk capacitor swap out an ask questions later, or are there a few particular ones I should go for? I should also say that some of the on-screen characters seem to get corrupted after a while as well. Any opinions on where I should go with this would be appreciated. Thanks Paul |
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Re: non-gumming oil
It really works well in the task removing label glue. Paper labels I just
let it soak into the label, let it sit and pell off the label, remove the glue then your favourite IPA to remove the WD-40. One thing about WD-40 I have not found a material that it "attacks" Ken On Wed, Aug 14, 2019 at 1:36 PM greenboxmaven via Groups.Io <ka2ivy= [email protected]> wrote: I have seen some lively discussions about WD-40 in switches, pots and |
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Re: non-gumming oil
I have seen some lively discussions about WD-40 in switches, pots and bearings. I have never had any problem using it as a PART of the cleaning process. It will often cut loose crud that nothing else will, but must be completely flushed out once it has done it's job or it will soon become a residue far worse than the original.
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Bruce Gentry, KA2IVY On 8/14/19 1:09 PM, Greg Muir via Groups.Io wrote:
WD-40 |
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Re: non-gumming oil
Chuck Harris
Hi Richard,
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I tend to use Oilite as a generic term for sintered bronze. It seems to be a common usage among older mechanics and machinists... Oilite kind of rolls off the tongue better than sintered bronze. I am pretty sure that Oilite didn't invent sintered bronze, but rather were the first to market oil infused sintered bronze, and claim it was a lifetime lubricated bearing... it most certainly isn't... unless you gauge lifetime to be the devices working life. I am certain that you are right, Oilite is a pre-oiled product, and in light duty, slow speed applications it is used that way quite often... A turntable fits that description. However, in higher speed, heavier duty applications it is all but unheard of to use it that way. Things like blowers that need to be quieter than ball bearing will allow, furnace blowers, bathroom ventilation fans, ... Tektronix 500 series scope fans... In these sorts of applications, an oil reservoir is used. It may be only filled by the motor's manufacturer, but it is a reservoir none the less. Turbine oil has a slightly more noble purpose, being intended for pressurized lubrication systems in jet engines... but that is exactly the same sort of bearing as is serviced by automotive motor oil. Turbocharged engines have turbines that spin faster than 100KRPM, and use a synthetic motor oil, such as mobil 1. Turbine oil, and light weight motor oil work equally well for these lowly light duty motors. I have both on my bench, and which I use is more dependent on which container will fit the motor I am oiling. My 5W30 synthetic motor oil has a 16ga blunt needle, and the turbine oil has a 6" long 3/16" wide straw... ...Very scientific!... -Chuck Harris Richard Knoppow wrote: Look at the Oilite web site. They state that the oil is infused via vacuum. This |
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Re: Is an early 7A26 a keeper?
Dennis
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I should have been more precise, I didn't mean to imply that the 7A26 had differential inputs but that the internal signal path was differential. If you look at the block diagram in section 7 of the manual the signal becomes differential after U1350 (U2350) and continues differentially to the vertical signal output. If either side of the differential pair is not functioning then the output would be 1/2. Ron -----Original Message-----
From: [email protected] <[email protected]> On Behalf Of Dennis Tillman W7PF Sent: Wednesday, August 14, 2019 2:43 PM To: [email protected] Subject: Re: [TekScopes] Is an early 7A26 a keeper? Hi Ron, This is not what is causing the 1/2 gain in one of the two channels but not the other. The 7A26 is not differential. It has two separate input channels. In certain cases the 2nd channel can be inverted and added to the first channel to make a "primitive" difference, but not differential, amplifier. Tek generally makes no claims about the performance of their vertical amplifiers when the signal goes off screen. While the signal is on-screen it is in the linear region of the vertical amplifier and you can expect the bandwidth of the amplifier will meet its stated specs. Provided neither signal by itself goes off screen, and the addition of both signals stays on screen, you will probably remain in the linear region of both channels. If you invert Ch 2 and add both signals together you will get the difference between them provided you use the same probes on each channel and you are careful to calibrate their response as closely as possible. You will also need to calibrate the gain of each channel. Even if you did all this it would be misleading to assume that the on screen result was what a true differential amplifier with matched probes, matched inputs, matched phase response, matched offsets, etc would give you. Dennis Tillman W7PF -----Original Message----- From: [email protected] [mailto:[email protected]] On Behalf Of ron_roetzer@... Sent: Wednesday, August 14, 2019 5:42 AM To: [email protected] Subject: Re: [TekScopes] Is an early 7A26 a keeper? although I have no specific knowledge of the 7A26, in differential amplifiers if one side is dead then the gain is exactly 1/2 what it should be. -- Dennis Tillman W7PF TekScopes Moderator |
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Re: 2440 deal
Bob Albert
Wow good news!? I hope one of those will end up here.? Keep me informed.
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Bob818 894-2887 On Wednesday, August 14, 2019, 09:29:00 AM PDT, Robert Simpson via Groups.Io <go_boating_fast@...> wrote:
Snagged two, one already gone. Got a reply from seller and my daughter was able to pick up two. I will get to see them next time she comes up (from SF South bay area). Was excess inventory from the seller's company. Bob |
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Re: Is an early 7A26 a keeper?
Hi Ron,
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This is not what is causing the 1/2 gain in one of the two channels but not the other. The 7A26 is not differential. It has two separate input channels. In certain cases the 2nd channel can be inverted and added to the first channel to make a "primitive" difference, but not differential, amplifier. Tek generally makes no claims about the performance of their vertical amplifiers when the signal goes off screen. While the signal is on-screen it is in the linear region of the vertical amplifier and you can expect the bandwidth of the amplifier will meet its stated specs. Provided neither signal by itself goes off screen, and the addition of both signals stays on screen, you will probably remain in the linear region of both channels. If you invert Ch 2 and add both signals together you will get the difference between them provided you use the same probes on each channel and you are careful to calibrate their response as closely as possible. You will also need to calibrate the gain of each channel. Even if you did all this it would be misleading to assume that the on screen result was what a true differential amplifier with matched probes, matched inputs, matched phase response, matched offsets, etc would give you. Dennis Tillman W7PF -----Original Message-----
From: [email protected] [mailto:[email protected]] On Behalf Of ron_roetzer@... Sent: Wednesday, August 14, 2019 5:42 AM To: [email protected] Subject: Re: [TekScopes] Is an early 7A26 a keeper? although I have no specific knowledge of the 7A26, in differential amplifiers if one side is dead then the gain is exactly 1/2 what it should be. -- Dennis Tillman W7PF TekScopes Moderator |
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Re: 5xx 'Scopes
EVERY Tek curve tracer, except for the limited plugin versions (7CT1N and 5CT1N) have two "sockets" to do A/B comparisons. This includes the 570 (vacuum tube curve tracer), 575, 576, 577, and 370. The 576 and the 577 have similar basic capabilities such as their maximum voltage (1,600V at 100mA, and 1,500V at 200mA respectively), but differ significantly in other ways.
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The 576 has an optional 176 high current "front porch" capable of testing power transistors. The 576 has readouts (not on-screen) which assist casual users in avoiding mistakes when making basic device measurements. The 577 comes in a non-storage (577-D2) and storage 577-(D1) CRT version. It has an optional 176 "front porch" which can test single, dual, or quad OpAmps, SCRs, 3 Terminal Positive and Negative Voltage Regulators. Both the 576 and the 577 were designed to make the majority of semiconductor measurements that any circuit designer would be interested in quantifying. I once asked Deane Kidd, when I was in his lab, which he recommended, 576 or 577. His answer was definitive: the 577 hands down. So that is what I found to replace my 575 10 years ago. I have had both the 577-D2 and 577-D1 over the years since and there is no question that the 577-D1 (storage) version has more capabilities although the storage is tricky to adjust and is sometimes annoying. I am now fortunate to own both a 576 and a 577 and all the optional "front porches" so I can test just about anything. Sean: I believe you are thinking of the low cost adapter board I designed to test vacuum tubes on a Tek semiconductor curve tracer. My adapter is not limited to the 576. It works on ANY Tek curve tracer (575, 576, 577, 7CT1N, and 5CT1N). Contact me OFF-LIST at "dennis at ridesoft dot com" if you would like a copy of the paper I wrote about testing vacuum tubes on Tek curve tracers. Dennis Tillman W7PF -----Original Message-----
From: Chuck Harris Sent: Wednesday, August 14, 2019 5:17 AM I would have to beg to differ, the 577 has the same left/right sockets, left/right lever switch, and as such, comparison capability as the 576. It even uses the same dual transistor plugin adapters. It (with the right option) even has a split screen storage capability. What it doesn't have is any form of on screen readout display of the settings. -Chuck Harris [email protected] wrote: On Tue, Aug 13, 2019 at 07:59 AM, Mlynch001 wrote:One of the best finds of mine was a very nice Type 576 Curve TracerThat's exactly the model I would like to find. The 577 is smaller but lacks the ability to do A-B comparison testing. The 576 can do vacuum tubes too, with the right test fixture if I'm not mistaken. -- Dennis Tillman W7PF TekScopes Moderator |
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Re: non-gumming oil
Look at the Oilite web site. They state that the oil is infused via vacuum. This is what I always understood about how Oilite bearings were made. There are sintered bearings that are meant for an external oil reservoir but the Oilite type is lubricated during manufacture and is not supposed to need any other lubrication although the web site describes the use of a light wax to eliminate break-in.
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In the past I was involved in rebuilding sound recording equipment with Oilite bearings. They were not easily replacable. I used turbine oil of a type recommended by the lab of one of the larger oil companies. He gave us a sample, about a quart, I never used it up. Turbine oil is a very highly refined oil. On 8/14/2019 10:45 AM, Stephen Hanselman wrote:
Sorry Chuck, --
Richard Knoppow dickburk@... WB6KBL |
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Re: non-gumming oil
You're right it was, I saw this on a Science channel show.
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S -----Original Message-----
From: [email protected] <[email protected]> On Behalf Of Jim Ford Sent: Wednesday, August 14, 2019 10:41 AM To: [email protected] Subject: Re: [TekScopes] non-gumming oil The WD stands for Water Displacing, by the way. 40 is presumably because it was the 40th substance the manufacturer tried.Jim FordSent from my Verizon, Samsung Galaxy smartphone -------- Original message --------From: "Greg Muir via Groups.Io" <big_sky_explorer@...> Date: 8/14/19 10:09 AM (GMT-08:00) To: [email protected] Subject: Re: [TekScopes] non-gumming oil WD-40Spent a couple of years working in the tropics with extremely high humidity. I used to protect tools from rusting by wiping them with WD-40 then storing unused tools in plastic bags. What I found after coming back after several months to use them was that the light hydrocarbons used in the product had evaporated leaving behind a petroleum based product with the consistency of something between 90 weight oil and Cosmoline.From this I learned that it is only good for a very few purposes (aside from the original intent of the product for coating the outsides of missiles to prevent corrosion) is to protect items from rust and corrosion (with some subsequent clean-up effort), a penetrent and, on occasion, a gummed label remover. When I hear of someone using it to lubricate potentiometers, switches and such, I wince.A footnote: while at the project it was interesting to find that all of the local outlets sold WD-40 in gallon cans, an indication that I was probably not the only one facing rust and corrosion issues.Greg |
Mlynch001
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