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restoring 475a/dm44
Hi all -
I just bought a used 475a/dm44. While the scope seems to works fine, in general, what kind of problems should I expect to see or check? Dried up electrolytics? Thanks. Larry Lewis (Tektronix TM500 group 1976-78) -- _______________________________________________ Sign-up for your own FREE Personalized E-mail at Mail.com 1 cent a minute calls anywhere in the U.S.! |
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Re: On screen display and other CRT items....
Craig Sawyers
I'm coming in late, so pardon if I'm respondingI think you're thinking of the 575, David. I have one just behind me as I type. They do Tunnel Diodes too (with care), and mine will in due course do tubes as well (via an add-on box fed from the 175 connector on the back and the tranny sockets on the front). The only limitation for tubes is the 200V maximum collector (anode) sweep. Those lucky ones who have an option (I think 21?) have a 400V sweep, and that would clearly be even more useful. Craig |
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Warning - Military Manuals
jcastanton
Recently CD collections of military test equipment manuals have
become available. With excitement I bought a collection of "31 Tektronix Manuals". To my disappointment the "manuals" were in fact simple notes; some just parts lists, others simplified calibrations instructions. There are no schematics or service information. Beware. On the question of life of TV and monitor tubes I seem to recollect that life was extended by limiting brightness. Monitor quality certainly makes a difference, we have 15 year old IBM monitors that cost around $3,000 when new but still work perfectly yet only expect modern PC monitors to function for a couple of years before they fail and are discarded as beyond economical repair. |
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Re: On screen display and other CRT items....
From: donlcramer@... [mailto:donlcramer@...]I'm coming in late, so pardon if I'm responding to a non-issue. Someone doesn't recognize the 571. That was Tek's first transistor curve tracer. Looks similar to its predecessor the 570 tube curve tracer. I used one in school, great instrument but superseded by the 576 (smaller, looks more 7000-ish, claims to do FETs as well as bipolars*) and I don't know what-all since then. * You can sort of do FETs on the 571 too, but it won't tell you how. Regards, Dave Wise |
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HP counter - off topic
Craig Sawyers
Hi List
I *know* this is a Tek list - so this is off topic. However, I was so pleased to have sorted out a problem on my HP 5328A timer I just had to crow a little. Ever since I got it, some of the funtions didn't work well (like time interval and ratio). However, when frequency and period measurement died too it was clearly time to do something about it. Now this counter cost me ???22 (around $30) on eBay, so it owed me nothing - but I'm a determined cuss and rarely admit defeat. Followed around 3 days of diagnostics - derailed by errors in the manual (the military version). Eventually it turned out to be a chip on the Function Selector card - labelled Time Base Multiplexer. Now this was a 7454, now obsolete. So having dug out the chip, isolated the output pin and confirmed that it was indeed *that* chip (and not the one it was driving holding its output low) I was then confronted with what to do. Now the chip is a bunch of ANDs and a NOR that does /(AB + CD + EF + GH). So it would have been possible to replace it with a 7400 and a 4-input NOR - except that there is no 4-input NOR in fast TTL, just in slow CMOS (and this chip has to handle a PLL synthesised 100MHz clock). So I transformed the logic funtion to /(AB)./(CD)./(EF)./GH and used a 74F00 (quad 2-input NAND) and 74ALS21 (dual 4-input AND), strung together in place of the original 7454. Works an absolute treat! Cheers Craig |
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Re: Updated WEB
JOSE V. GAVILA (EB5AGV/EC5AAU)
Hi John and all the List,
Impressive collection! I had no idea you had so much stuff. :)Shhhhhhh.... my wife could hear you ;-)! ... What's theIs is a 7D20. Sorry for the poor picture; I took it without flash and, well, it is not one of the best. But I wanted to put the page on the WEB, as it was about a year (!) since last update. BTW, I have doubled the number of items in that year... this is getting dangerous :-)! Thanks to everybody who visited my Test Equipment page. I will let you know when I put there my restoration stories; as usual, I will put pictures before and after work, along explanation of repair and detailed pictures of damaged / faulty zone. Best regards, JOSE ---------------------------------------------------------------------- 73 EB5AGV / EC5AAU - JOSE V. GAVILA La Canyada - Valencia (SPAIN) EB5AGV Vintage Radio Site: European Boatanchors List: |
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Re: Updated WEB
There's a grain of truth in that. I find my wife now reads the TekScopes
emails I receive. She "called me" on my previous comment on her opinion of my Heathkit TV! I suspect I will meet all of you soon enough. We'll all be in a mandated meeting, saying things like "Hi. My name is Don and I am a test equipment junkie". And it will be said that admitting the problem is half the battle. But somehow it seems it is still not a problem for me----which may be a symptom in itself! In a message dated 1/23/02 10:45:53 PM Pacific Standard Time, eb5agv@... writes: Impressive collection! I had no idea you had so much stuff. :)Shhhhhhh.... my wife could hear you ;-)! |
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Re: Updated WEB
Don Black
Hello Jose,
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You have a marvelous collection, including superb test gear and its so well presented on your site too. Just think that any lab. in the world would have killed for such equipment a few decades ago and now it's within reach of us all. I'm looking forward to reading about your restoration work, can you please post a note here when it's an your site so we can all have a look at it. Thanks for sharing it with us. Cheers, Don Black. "JOSE V. GAVILA (EB5AGV/EC5AAU)" wrote: Hello! |
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Re: Who's up to some remote troubleshooting?
A word of caution. The U2750 might have been blown in such a way to damage
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circuitry in working plug-in. Personally, I would use this test as a last resort, after verifying other things, like pulling out U1750, sending signal through channel B and checking where does it get lost (or finding out that it was U1750 that was at fault for not releasing commong lines). Regards Miroslav Pokorni ----- Original Message -----
From: "Stan or Patricia Griffiths" <w7ni@...> To: <TekScopes@...> Sent: Tuesday, January 22, 2002 9:58 PM Subject: Re: [TekScopes] Who's up to some remote troubleshooting? Hi Lynn,with IC's in it but here is what I would do, if it were mine, and I had the stuff thatyou have. It sure sounds like U2750 to me . . . and to you too, because you havereplaced it twice with no luck. To be certain it is not U2750, I would like to seethe original U2750 removed from the bad 7A26 installed in the working 7A26, and verifythat it works there. I always worry that something might be blowing every U2750that I plug into the bad 7A26. If that were the case, you could indeed change U2750twice and still not get the 7A26 to work properly . . . and you would have 3 badIC's after that. I would want to see those IC's work in a good 7A26. The next thingI would do is check to make sure the power supplies and grounds are getting to U2750.Could be a bad IC socket. Just a couple of ideas . . .it's not the other scopescope and it's not the 7B53A. Ifand follow it right up to U2750. The input pins to U2750 have the square inputI feed the square wave only into channel A, I can see it on both the thoseand output of U1750.) The DC voltages around U2750 are very close to indicated on the schematic and appear to me to be reasonable. I did |
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Re: Updated WEB
John Miles
Impressive collection! I had no idea you had so much stuff. :) What's the
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plugin in your R7603? It looks like a spectrum analyzer of some sort but I don't recognize it. -- jm ----- Original Message -----
From: "JOSE V. GAVILA (EB5AGV/EC5AAU)" <eb5agv@...> To: <TekScopes@...> Sent: Wednesday, January 23, 2002 2:10 PM Subject: [TekScopes] Updated WEB Hello! |
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Re: On screen display and other CRT items....
Dear Don,
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I assumed that 40 k to 80 k applied to scope CRTs, not raster driven. Somehow, and possibly wrongly, I assume that scope CRT is made more durable than raster one, if for no other reason then for size and price expectations. The scope CRT does have more glass penetration points (a draw back), but glass envelope can be made thicker considering the size of the whole device. I plucked 10 k number from life of 'Long Life Tubes', you know, E800F as opposed to standard EF800, though somewhat longer life would be expected when you shell out few thousand bucks for a tube. It surprised me when Walter said that he found lot of 'gassy' tubes. I always associated that with TV CRTs (I view TV as something at par with PC in cheapness). Walter, was gassing perhaps coming from pin abuse (bent pins close to glass)? The PC monitors should not be brought into this comparison; in olden days they were the cheapest thing that could be found and I do not think that much has changed. To give you an idea about attitudes in PC industry (and some laughs or concerns perhaps), let me digress. Few years ago I went to a seminar on switch mode power supplies, given by Linear Technology. Apparently, switch mode ICs are competitive commodity and Linear Tech is trying to sell theirs as a 'cut above'. Their head application guy, Jim Williams, usually says: 'before we had switch mode ICs we were telling customers not to use switch mode power supplies (SMPS) because of noise and now we say that is the only thing'. During lunch I set at the table with one of SMPS application guys and he was telling about trip to Taiwan. They were at a mother board supplier (name withheld) and Linear Tech guy pointed that with low value inductor (hence cheap) ripple current was killing electrolytics. Taiwanese guy asked 'what is the problem when warranty on product is 30 days'. In contrast to junky PCs, I had a VT220 terminal for 10 years. Intensity was turned up as high as it would go, to be able to read screen in office light. The monitor was opened up ones to increase maximum intensity limit and it still lives; the terminal operated in 24/7 regime. It is true that VT220 shuts down CRT after no key strokes or input data for ??? an hour. But, company also had a half a dozen of monitors hung on test systems, which were getting periodic input from computer at intervals from 15 minutes to couple of hours, so they were driven hard. I do not think that any CRT failed, though there were few failures. I did not let terminals be repaired (I could buy replacement for under $50), but few, that technicians sneaked by, never turned up bad CRT. Funny that you mention high intensity in auto sweep mode. It looks like all test technicians love that; and they are usually young, with good eyes. The furthest that I got with that problem was that technicians would sometime turn down brightness when I walk into test department. At place where I worked, I know that technicians did not understand concept of synchronizing signal and probably upped brightness to be able to see something in trace as it flies by. Their use of scope has always been a mystery to me: how do you know what you are looking at with only one probe and no external trigger? What is 571? I could not find it in Stan's book, neither in 1995 Tucker catalog. Regards Miroslav Pokorni ----- Original Message -----
From: <donlcramer@...> To: <TekScopes@...> Sent: Tuesday, January 22, 2002 11:22 PM Subject: Re: [TekScopes] On screen display and other CRT items.... I was initially surprised by the 40-80Kh number also. The difference Ithink is that in a scope the tube is not driven as often (duty factor) or ashard (especially white background applications) as a CRT is in a raster scanto last a lot longer now than 10-15 years ago. Remember those old 12"series desktop computers)? If we left those greenscreens on 24/7 on our burn-inreplaced, the production operators would turn them down at night before they wenthome, and left them down whenever they did not have to see the display. Inlater years (the systems ran 17 years I'm proud to say), we couldn't even find"screen saver" pictures on them when not in use.through two shifts, 5+ days a week, in auto sweep mode (with the brightness turnedup too high to boot). To the best of my knowledge, we've never pulled a CRTin any of the scopes, and most of those go back more than 10 years (includinga couple Tek 465Bs, Leader 100Mhz dual trace, a couple Tek 2200 series).Any more we would junk them for whatever cause if they failed--I have two Igot that way. One (465B) I restored and the other (TAS465) I haven't found amoons ago) which exhibits the double peaking on the intensity control thatothers have mentioned. The trace is pretty dim when cold, though improves with arunning. Quite frankly, I don't think there is anyone left besides me that can runit anyway so it is in a way "out to pasture". I've wondered if a replacement |
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Updated WEB
JOSE V. GAVILA (EB5AGV/EC5AAU)
Hello!
I have updated my WEB pages to best show my test equipment illness...errr, collection ;-). Look at: Then click on the 'Latest additions' section over the 'Test Equipment Collection'. I plan to add lots more info and pictures, linked from that page. But I needed to start from somewhere, hi! Hope you enjoy it. Regards, JOSE ---------------------------------------------------------------------- 73 EB5AGV / EC5AAU - JOSE V. GAVILA La Canyada - Valencia (SPAIN) EB5AGV Vintage Radio Site: European Boatanchors List: |
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Re: Anybody need these Tek tubes?
Phil (VA3UX)
Hi Walter.
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I could probably use the 5642's and 12AU6's for my pile of 500 series scopes. The 8136's - not sure what they're for but I'll check my manuals to see if they're used in anything I have. Those old 555's and 556's have so damn many tubes in them that I can't remember the tube line-ups anymore. Thanks Phil Turcotte Grimsby, Ontario At 06:12 AM 1/23/2002 +0000, you wrote:
Recent comments about Tek matched tubes reminded me I had some |
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Re: I found a nice 7CT1N :-)!
JOSE V. GAVILA (EB5AGV/EC5AAU)
Hi Mark,
(I copy this to the List as think somebody else could be interested. Please, correct me if I am wrong!) The 7CT1N connector I was thinking of was a header with the threeWell, I don't want to earn money with this but produce something useful :-). I have access to double sided PCB sheets (copper on both sides), so it could be the basis to produce the PCBs. To support a perpendicular panel, I would use some kind of PCB header, with gripping action. Perhaps you can do a fast draw of your idea; if you want, we can share this at my WEB site and ask for further improvements. What do you think? Certainly CNC is the way to go. Just what I need... more tools :-)Well, I did not buy it for hobby purpose... but having it at my workbench really helps, hi! Regards, JOSE ---------------------------------------------------------------------- 73 EB5AGV / EC5AAU - JOSE V. GAVILA La Canyada - Valencia (SPAIN) EB5AGV Vintage Radio Site: European Boatanchors List: |
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Re: I found a nice 7CT1N :-)!
L. Mark Pilant
Hi Jose.
The 7CT1N connector I was thinking of was a header with the three banana plugs in the back (to plug into the 7CT1N) a flat bottom (perpendicular to the back) a sloping front with room for two sockets and the A/B switch, and a short front. If I was particularly ambitious, I'm make up several of the basic header assemblies and have the sloping panel be removable. I bet there would be a small market for these; but I don't know what the profit margins would be :-) Certainly CHC is the way to go. Just what I need... more tools :-) (I'm a tool addict a well as a test equipment addict :-) :-) 73 - Mark N1VQW |
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Re: I found a nice 7CT1N :-)!
JOSE V. GAVILA (EB5AGV/EC5AAU)
Hi Mark and all the List,
First, thanks a lot for the nice explanation; my unit will come with a photocopy of the user's and service manual. I hope it is of good quality... One of the things on my list of things to do is to build a selectionHere I can sure help :-)!. I own a CNC precission milling machine... One of my very next projects is to build an small PCB with the three banana jacks and a choice of transistor sockets or perhaps a header to connect there an adapter with two sockets and an A/B switch. What do you think?. I am sure we could end with an interesting design! Regards, JOSE ---------------------------------------------------------------------- 73 EB5AGV / EC5AAU - JOSE V. GAVILA La Canyada - Valencia (SPAIN) EB5AGV Vintage Radio Site: European Boatanchors List: |
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Re: I found a nice 7CT1N :-)!
L. Mark Pilant
Jose and Dick, I have a 7CT1N as well as a manual :-) so I may be
able to help. In a nutshell, the 7CT1N may be used in any (vertical or timebase) slot. There is a push button on the front panel which you use to indicate the slot in which it is being used. Since you need an amplifier plugin, using it in one of the timebase slots is the easiest. Then you simply pull the little white/cream colored cable out from the 7CT1n front panel and connect it to the vertical input channel of the plugin. If you use the 7CT1n in a vertical slot, you need to make sure you use a timebase plugin allowing external access to the amplifier section. (Such as the 7B50, 7B52, 7B53, and 7B70 plugins.) That should get all the basic connections done. From there, all the remaining controls should be pretty easy to figure out. BTW, I have mine in a 7704A with two 7A26 vertical plugins, the 7CT1N, and a 7B80 timebase. This allows me to use it as a regular (three channel :-) scope or a curve tracer. Although I don't use it much as a scope since I usually use my 7904. One of the things on my list of things to do is to build a selection of plugin connectors for the 7CT1N to make it a little easier to test devices. I'll also include an A/B switch and two sockets to also make comparisons easy. (I really like this feature on the Tek 575.) That's it for now. 73 - Mark N1VQW |
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Re: Who's up to some remote troubleshooting?
JOSE V. GAVILA (EB5AGV/EC5AAU)
Hi Lynn,
I have a service manual for the 7A26 and could scan any schematics part you need, if that helps. Regards, JOSE ---------------------------------------------------------------------- 73 EB5AGV / EC5AAU - JOSE V. GAVILA La Canyada - Valencia (SPAIN) EB5AGV Vintage Radio Site: European Boatanchors List: |
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