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Re: Will this capacitor fail?
George and DW
Definitely a 170uF Cap. I would check the ESR on that old cap very carefully, if it checks "good" for capacity, ESR and ripple, leave it alone. I just finished with a 577 and the filter caps all checked good for ESR and Ripple current. In my experience, the 577 was much more plagued with bad tantalum caps. I found 7 bad ones on mine, which completely disabled the thing. Just my opinion and experience, of course. Best of luck in your project. -- Michael Lynch Dardanelle, AR |
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Re: 2235A Vertical Trace Issue
Chuck Harris
Think of a CRT's electron gun as being like a machine gun. Just like
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a machine gun fires bullets at a fixed continuous rate, so does an electron gun with electrons. Let's imagine our electron gun fires off electrons at 10 electrons per second. If you sweep our electron gun across the width of the screen in 10 seconds, there will be about 100 electrons striking the screen, evenly spaced along a line. Similarly, the same thing will happen if the electron gun's beam of electrons travels from the top to the bottom of the screen in 10 seconds. Further suppose the beam goes from top to bottom in only 1 second, while it is also traveling from left to right in 10 seconds. Since the trace is only 10 seconds long, it will still contain a total of 100 electrons, but during the time it is traveling from top to bottom, there will only be 1 second's worth of electrons, or about 10 electrons. Suppose still further that the beam travels top to bottom in 1/10th of a second while it is taking 10 seconds to travel from left to right. The total trace will still contain only 100 electrons, but the section that goes from top to bottom will now contain only 1 or maybe 2 electrons! If we keep reducing the time it takes for our beam to go from top to bottom, while it is taking its 10 seconds to travel from left to right, eventually it will traverse from top to bottom of the screen without recording even a single electron striking the screen. The record of our electron beam's travels will look as though the beam instantly traveled from the top to the bottom of the screen. This is exactly what is happening on your scope. The number of electrons the electron gun shoots at the screen is at a rate that is a million times faster, but parts of the trace where the bean travels great distances in very little time will not have as many electrons hitting the screen as will parts where the beam is puttering along slowly... The beam will appear to have no brightness in those sections where it is traveling really fast.. -Chuck Harris Ed Pavlovic wrote: I'm slowly going through my 2235A scope, replacing the Schaffner line filter and the RIFA capacitors on the Pre Regulator board. The RIFA caps were visibly crazed, so I'm glad I'm replacing them before they failed like the ones in an old computer PSU I have. |
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Re: 7B15, 7B10 questions
On Sun, Nov 19, 2017 at 10:12 AM, Dennis Tillman W7PF wrote:
Hi Dennis: We have 2 7104s... and occasionally I see one for sale, and the picture of it usually shows it operating with the amber "limited viewing time" indicator illuminated. I'd only pay the prices most are asking for a 7104, if I thought I could get a good spare MCP CRT, with some good life left in it. A cheap 7104 might be worth it, just for the parts though. I take it by your post... that even though the janitor tripped over a 7104 in the hallway, outside the research lab, and is now selling it... the CRT should be good, even though it may have operated in "limited viewing time" mode frequently? Best regards and wishes. Roy |
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Re: Will this capacitor fail?
You should be fine. 20% above 200 volts would be 240 volts. BTW, the schematic shows the value C744 as 170 micro farad.
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George KD6NEW On Aug 20, 2019, at 9:16 PM, DW <wilson2115@...> wrote: |
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Re: Need Help Troubleshooting Tektronix PS280
daven9ooq
I would stick with what you have, maybe it's time to do a little service on it, sometimes you need a dual supply or even 3voltages it's rare though.
I should have done more resurch on this before I bought it. But it's the same? era as my TM500 equipment so it should fit right in.?Around 1981.Many thanks !Daven9ooq |
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Re: Thoughts on TDS744A
The condensers you mention were a worldwide scourge. Many millions of them were made when an angry employee stole the electrolyte formula from one company and took it to another. The problem was the formula was not complete. In many cases the electrolyte gasses off slowly and escapes without leaving a residue, but the condenser has no capacitance. Having restored many items using these bad condensers, I strongly recommend that you mark the locations, value, and polarity of all the condensers, remove them all, and then gently scrub the board with hot soapy water. Rinse it thouroughly and dry it in flowing warm air before soldering the new condensers on.
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Bruce Gentry, KA2IVY On 8/21/19 5:22 AM, Jay Walling via Groups.Io wrote:
Hi Siggi, |
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Re: 2235A Vertical Trace Issue
The dim traces on the vertical part of a square wave is normal.
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This is due to the speed which they are "drawn" on the CRT face. The faster the rise time of the trace, the dimmer the trace will be. The faster the trace speed, the dimmer the trace. It is like painting with a spray can. If you hold the nozzle down and paint a horizontal line then quickly paint a vertical line, the vertical line will have less paint on it per unit of length than the horizontal line. Glenn On 8/21/2019 1:43 AM, Ed Pavlovic wrote:
I'm slowly going through my 2235A scope, replacing the Schaffner line filter and the RIFA capacitors on the Pre Regulator board. The RIFA caps were visibly crazed, so I'm glad I'm replacing them before they failed like the ones in an old computer PSU I have. --
----------------------------------------------------------------------- Glenn Little ARRL Technical Specialist QCWA LM 28417 Amateur Callsign: WB4UIV wb4uiv@... AMSAT LM 2178 QTH: Goose Creek, SC USA (EM92xx) USSVI LM NRA LM SBE ARRL TAPR "It is not the class of license that the Amateur holds but the class of the Amateur that holds the license" |
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Re: General Radio 874 Connector, inner conductor "bendies"
The General Radio part of the IEC site has many old GR catalogs. They will help identify the connectors used and those available as parts. GR used a couple of variations of binding posts, mostly combined with banana plugs or jacks. I have not checked but think the 274 type dual banana plugs and jacks had the same spacing for decades making them compatible. On many GR instruments with 874 connectors there is a combination binding post mounted under the coaxial connector. These are ground connections but a 274 dual banana plug with fit between the center part of the 874 and the binding post. This is sometimes handy where one is dealing with audio or low frequency RF although it does not have the effective shielding of the 874 connector.
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GR made adapters going to nearly anything from the 874 and both GR and others, like Pomona, made adapters of all sorts for the 274. On 8/20/2019 11:16 PM, Roy Thistle wrote:
On Sat, Aug 17, 2019 at 08:56 AM, Dale H. Cook wrote:I found a 1001A that I though had a BNC output connector; but, it was an 874 to BNC adapter, inserted into the front panel 874. --
Richard Knoppow dickburk@... WB6KBL |
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Re: 7000 series carrying handles - how strong are they?
On Sun, Aug 18, 2019 at 05:54 PM, evan foss wrote:
I've carried the 500s and 7000s, for long distances occasionally 1Km plus, and frequently carried them a couple of hundred meters.. and lots of times carried them 10 to 20 meters, from lab to lab, through the halls... or across the lab. (I know... there is a new invention called wheels; but, the scope carts are always jammed up with junk!) The only times a metal strap broke... and that was before I lifted the scope... the steel strap broke (just by pulling on it)... it was very obviously rotted and rusted through, . A couple of times, on the 500s, I braided a rope (1.5 mm rope/string) handle on, just so I could carry it... when I thought the rusty steel handle present might suddenly fail, under inconvenient circumstances. That said... the steel strap is only as "strong", as the fittings it engages, and the bolts (screws really) that hold the whole assembly to the body of the scope. Checking those are sound, and will continue to be sound, seems prudent. I get the willies too, wondering whether the handle is going to break, on these heavy scopes... but under the weight and strain, I quickly start to trust the steel, and I worry more about banging the front panel into something, and bending those little knobs! I have a 1200 series Tek logic analyzer, that has a bail type handle... but it has one corner of the bottom compressed, upwards... like it was dropped, straight down, from letting go of the handle... and then the thing landing on just one corner... so how does that happen?... the handle is fine. Roy |
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Re: 7000 series carrying handles - how strong are they?
On Sun, Aug 18, 2019 at 03:38 PM, Bruce Griffiths wrote:
unless it is cold worked (like stamping it?)... and then it develops a magnetic response. The strength of which [compared to stainless numbers that are magnetic]¡ I guess... depends on the amount of cold working. Roy |
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Re: General Radio 874 Connector, inner conductor "bendies"
On Sat, Aug 17, 2019 at 08:56 AM, Dale H. Cook wrote:
I found a 1001A that I though had a BNC output connector; but, it was an 874 to BNC adapter, inserted into the front panel 874. I have some GR units, mostly older than 1950, mostly audio, 600 ohm stuff, I guess... mostly in wooden cabinets, so old I guess too... like a 546-C, with binding posts. (sometimes seen referred to 546-0, because of the front panel stenciling?). Anyway, even though I have, and have run across GR stuff... my introduction to the 874 was on Tek stuff (like pulse gens, sample heads, and 7000 plugins)¡ which I was not interested in, at the time... so just made a note of that odd looking connector, on the front panel. I guess that was just the peculiarity of my situation... which led me to think it was an old Tek connector, when it was really GR! Best regards and wishes all. Roy |
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2235A Vertical Trace Issue
I'm slowly going through my 2235A scope, replacing the Schaffner line filter and the RIFA capacitors on the Pre Regulator board. The RIFA caps were visibly crazed, so I'm glad I'm replacing them before they failed like the ones in an old computer PSU I have.
Issue I'm having is the vertical traces are very dim compared to horizontal traces. Most noticeable on a square wave, but if you introduce a horizontal element, a sinewave or sawtooth pattern, the trace looks normal. I'm waiting on parts from Mouser to replace the failure prone inlet caps with new ones, so I'm unable to check voltages and ripple at the moment. Is it just an issue with the width of a vertical trace affecting the brightness on the screen, or is there maybe a deeper issue going on here? Thanks Ed Pavlovic KC9MMM |
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Will this capacitor fail?
I have a Tektronix 577 curve tracer and I am recapping the power supply board that is located at the rear of the instrument. I am looking at replacing C744 which is a 250V 1700uF capacitor. I found a 250V 1800uF capacitor but the capacitor installed is a 275V capacitor though the manual states 250V. I am curious how much voltage typically runs across C744 so I don't destroy a capacitor, thanks
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Re: General Radio 874 Connector, inner conductor "bendies"
While it probably isn't "news" IET Labs still sells GR874 connectors along
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with other GR equipment that they still manufacture. On Sat, Aug 17, 2019 at 11:28 AM Roy Morgan <k1lky68@...> wrote:
The GR 1232A Tuned Amplifier and Null Detector has an 874 connector at the |
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Re: 494 and 2756 Spectrum Analyzer questions...
I have no knowledge of the particular component, I use a chemistry hot
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plate that I have roughly calibrated for pre heating, just dandy for certain surface boards where one leg of the component is tied to a big ground plane. 125 - 175 C is the recommendation usually, your mileage and experience may be different..... On Tuesday, August 20, 2019, John Miles <john@...> wrote:
Any suggestions about the best way to open it inI usually use a Dremel tool with a cutting wheel. The filter takes a lot |
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Re: TDS754A
My 754D once had a problem with random reboots. Turned out that a couple of the conductors in the ribbon cables between the boards had burned out. It was fine after replacing the cable, maybe your 754A is constructed the same way.
Cheers, Neil ________________________________ From: [email protected] <[email protected]> on behalf of Stephen Hanselman via Groups.Io <kc4sw.io@...> Sent: August 20, 2019 8:02 AM To: [email protected] <[email protected]> Subject: Re: [TekScopes] TDS754A I would suggest you open it up remove the proc board and PS cover. Then blow out the dust. We have found any ¡°new¡± unit to our facility was fairly dirty. The split wall between the PS and HVPS is perforated but with small holes which clog easily. Regards, Stephen Hanselman Datagate Systems, LLC 3107 North Deer Run Road #24 Carson City, Nevada, 89701 (775) 882-5117 office (775) 720-6020 mobile s.hanselman@... www.datagatesystems.com<> a Service Disabled, Veteran Owned Small Business DISCLAIMER: This e-mail and any attachments are intended only for use by the addressee(s) named herein and may contain legally privileged and/or proprietary information. If you are not the intended recipient, any dissemination, distribution or copying of this e-mail and any attachments is strictly prohibited. If you have received this e-mail in error, please immediately notify me and permanently delete the original and all copies and printouts of this e-mail and any attachments. On Aug 20, 2019, at 07:37, Siggi <siggi@...> wrote: |
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Re: 494 and 2756 Spectrum Analyzer questions...
Any suggestions about the best way to open it inI usually use a Dremel tool with a cutting wheel. The filter takes a lot of vibration, unfortunately, and a respirator is needed unless you want to breathe a lot of lead particles. But it does get the job done. Some have used propane torches successfully, but transferring just the right amount of heat to melt the solder is harder than it sounds. I've done more than my share of damage with propane torches, operating under the usual rationale ("I know what I'm doing, this'll only take a few seconds.") After some time, the rear end with the integratedheat sink gets to hot toGood question, not that I know of. At least some departments at Tektronix used a straightforward watts-per-cubic-inch metric to determine whether something was going to get too hot. Fans were recommended for instruments consuming more than 50 mW/in^3, and the documentation I've seen (Common Design Parts Catalog volume 2 from 1983) indicates that the surface area of the enclosure is also supposed to be taken into consideration. So the thinking may have been that the large surface area of the 275x rack mount enclosure was enough to avoid the need for additional ventilation or a bigger fan, when in reality the instrument might have ended up hotter than the benchtop version. Much of the box is empty, so they would have needed to consider how the heat was supposed to reach the enclosure boundary in the first place. Perhaps that process needed some more work. Maybe someone on the list remembers more about how these decisions were made back in the day? -- john, KE5FX |
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Re: Need Help Troubleshooting Tektronix PS280
daven9ooq
Sent from Mail for Windows 10
Hi the schematic from the TekWiki shows reference to PS28¡ª512-1 my main board showsGPC-848A-1 B the schematic is component wise fairly accurate but all the jumpers and connections are completely different. Some versions had a separate fuse board my main board consists of the 2 variable supplys with filters bleeders rectifiers and 4relays and fuses. Nothing is blown all traces intact. Voltage readings on the main reference 7815 are pin 1-29.7vdc. 2-14.98vdc 3 40.5 vdc this is weird as pin 2 is supposed to be ground even says so on the schematic, but appears to be output pin 3 should be out , but it works! Slave side is similar like a symmetrical reverse image , and looks to be independent but in fact some adjustments do have a relationship with the other side. The last stage before the series pass transistor is labeled dynamic load control. The first 741 op amp readings are pin 1 .0043vdc, 2-14.98v 3-14.98 4 gnd 5.044 6-5.483v. 7- 29.72v 8.NC That is as far as I got so far. Many thanks Dave |
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Re: Fan direction on TEK485
On Tue, Aug 20, 2019 at 5:54 PM Jokken Feldhaar <jochen_feldhaar@...>
wrote: Hey Jochen,designThe 485 has the wonderful temp controlled Siemens motor and impeller you are absolutely right, I just went to look at my 485. My apologies for the (my) confusion. It does have the Siemens brushless motor though :). I was thinking of the 2465, which has the same motor and an impeller, but the opposite airflow direction. The 2465 most certainly draws air in through the case through strategically placed perforations in the case, which are placed over some of the hybrids, and blows it out the back Both the 485 and the 2465 are as close to silent as makes no difference though, which is a great feature in any scope. Siggi |
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