Keyboard Shortcuts
ctrl + shift + ? :
Show all keyboard shortcuts
ctrl + g :
Navigate to a group
ctrl + shift + f :
Find
ctrl + / :
Quick actions
esc to dismiss
Likes
- TekScopes
- Messages
Search
|
Re: Encouraging beginners: What are we accomplishing?
Chuck Harris
Hi John,
toggle quoted message
Show quoted text
I have to set the record straight. Dennis did not jump on me for describing a way of using an oscilloscope to measure ESR. Quite the opposite, he even tried to help with my poorly received ascii art attempt at displaying a schematic... Curses foiled by groups.io's website's mandatory proportional type font, and their overzealous period police! If anything, I jumped on Dennis, as I think we should be able to discuss such things on this group without fear of reprisal. But perhaps not to the exclusion of talking about scopes. And, it is way off to spend time plotting how we can get some cantankerous old fool that designed his own ESR meter to let us copy his design and sell it among ourselves... Dennis and I are good friends. There really was no jumping going on here... -Chuck Harris John Crighton wrote: Hello Roy, |
|
Re: Encouraging beginners: What are we accomplishing?
Does anyone have any idea, statistically, of how many scopes die from
toggle quoted message
Show quoted text
beginners trying to repair them verses those that die to tube harvesters or relatives who have no interest in "Bob's" old scopes who send them to the recycler? On Wed, May 27, 2020 at 8:42 AM LarryS <vision1@...> wrote:
In answer to your question, ANY time you bring in fresh blood, it's better |
|
Re: Encouraging beginners: What are we accomplishing?
Chuck Harris
Hi Roy,
toggle quoted message
Show quoted text
I guess the first thing is that tektronix made these scopes to be reparable by their customers. That is why they made available such detailed manuals for their scopes. I am pretty sure they figured that if the customer was not up to the challenge, the high price of replacing the scope if they failed, would discourage unqualified repairs. And, for those who would not be discouraged, they had a school for turning unqualified repairmen into repairmen. A major point that everyone should realize is these scopes are scrap in as far as the commercial market goes. That is why they are in the hands of novice owners. If the novice owner botches the repair, it just moves a little closer to the scrap bin. Every major collector's field has this debate at some point. I have heard the museum guys argue the point successfully in front of legislatures that metal detectorists should be jailed for disturbing as yet unknown archeological digs with their explorations. I have heard warbird enthusiasts demand that warbird owners should be jailed for flying (and occasionally crashing) the airplanes they saved from oblivion, and own. I have heard coin collectors cry when some amateur polishes some marginally significant coin, ruining its value... And, I have heard a very, very, few guys like you worry about the damage a novice may do to a scope that you don't even want... I guess we have reached the big time! As for paying $100 for a repair... I repair scopes cheaply, and even I won't work on a 475 for that little. -Chuck Harris Roy Thistle wrote: Hi all TekScopers: |
|
Re: Encouraging beginners: What are we accomplishing?
LarryS
In answer to your question, ANY time you bring in fresh blood, it's better for everyone. Every time. No exceptions. A rising tide floats all boats.
toggle quoted message
Show quoted text
Right now, Harley Davidson is facing 'massive restructuring'. Why? Their rider base is literally dying off. I'm involved in several other hobbies and pursuits where young blood is not entering. They are dying. And with it comes a similar intellectual cannibalism. As any discipline dies, like analog scopes, the entry price will be lower and lower. Soon, for rummage sale prices, the once-crown-jewel pieces become affordable. In 1983, how many 60s fastback Mustangs were parked behind gas station garages (remember those?) and could be had for a couple hundred? Many were chopped and otherwise brutalized in ways I can't describe. But such is the price. Today, they're worth more than most people's financials. There were many thousands of units produced of scopes and cars and organs and everything else. Some will live nice lives and some will die horrible deaths and grownups understand this. I've been the careless kid and the fastidious curator, but at both extremes I remembered the Prime Directive: this thing is MINE, not yours. If you're worried about it, you can buy it from me and store it away. If not, tough. If we want a growing following, then we have to let the newbs make their mistakes and learn as we did - yes, even on top tier equipment. If it grows enough, someday my old junk might be worth as much as I think it is now. If not, someone will speak poorly of me as they shovel it all out into a dumpster after my demise. Besides, if it tracks like everything else, one day some others will join your song and these units will skyrocket - at least temporarily. I own a Hammond console. In 1988, it was dumpster fodder. By 2010, it was $10K. Today, it's maybe $4k. These things have a cycle and scopes are certainly no exception. Anyway, help every newb you can. If they want to try their hand, the answer is NEVER "let someone else do it". They're gonna do it wrong. Just as wrong as you and I used to do stuff. The sooner they learn to do it right, the sooner everything gets better. L. -----Original Message-----
From: [email protected] [mailto:[email protected]] On Behalf Of Roy Thistle Sent: Tuesday, May 26, 2020 10:52 PM To: [email protected] Subject: [TekScopes] Encouraging beginners: What are we accomplishing? Hi all TekScopers: Reading through a long thread, recently posted, caused me to wonder.. just what are TekScopers accomplishing with threads like this... and why are we encouraging someone who is "... new to electronics..." to dig into a 475?... one of the most complex, and compact, analog instruments ever designed. I suppose.. in consideration... Michael discouraged the use of a Mr. Carlson super Weller-kluge special, on the 475's pcb(s)... but, ya know... somewhere the thread... the 475 owner hints he paid 20.00 for 475?, and he's also got a nonworking? PM3218 too. So why didn't someone just recommend/... right off the bat... to take the 475 to someone who knows what they are doing... drop another 100.00 on it... and then he'd have one of the best scopes ever made. Or alternatively... and better... just start in on the PM3218...itself a very fine instrument, with a double insulated power supply... and way overkill, for a beginner. Look, I'm not unsympathetic... it's just that...too often.. after parting with some scarce cash... or finding some Tek picked apart in a basement somewhere, where its been languishing for a generation...I've witnessed the havoc wreaked by someone trying to "fix" them. If you want to call me a dumb ass... for thinking this way... well fine... just PM me to do it. I can't promise I'll reply to that... but, I'll read your message. Best regards and wishes. Roy |
|
Re: 475 questions
I have some things to add given that I was in a similar position recently but with a 485.
toggle quoted message
Show quoted text
Go glacerly slow. There are some parts in these wonderful instruments that you will not be able to replace if they get zapped. And you can zap things with static / probing Spend LOTS of time with the schematic especially in the theory of operation section. Tek wrote some of the best technical manuals out there Practice your soldering skill NOT on the 475 get a few soldering projects and build them up soldering is 30% knowledge and 70% feel / Art you just have to do it.. A Lot DO NOT use a cheap iron. Minimum recommendation here is a Hakko 888D or equivalent from a different vender. The last thing you want to do is over heat a trace and de-laminate it from the board. Due to poor temperature regulation or long dwell time. It took me 8 months to fully restore my first 485, but mine was hacked up pretty good by the previous owner. Lots of pots were replaced with fixed resisters. If you going to Calibrate/align the scope you will need to know some high voltage probing -4000 Vdc will blow your meter input with out the proper tools. Proceed with caution and ask a million questions. It is better to ask then to lose a hybrid that you cant replace. Good luck I look forward to hearing about your success Eric On 5/27/2020 4:14 AM, David C. Partridge wrote:
I found that by searching "neon bulb oscilloscope", I found this:I don't believe so. IIRC the neons in the 475 are in the EHT supply circuit and are effectively over-voltage spark gaps. |
|
Re: Encouraging beginners: What are we accomplishing?
Roy
toggle quoted message
Show quoted text
I have to add to this one. As 3 years ago I did JUST that. I had a soldering Iron and a power supply on the bench. And started to dive deeper in to electronics. I made the mistake of taking on a 485 after some you tube videos. Now I do not regret the decision one bit. I call it a mistake because my personal goal was to repair and completely calibrate the 485 so I could use it on my bench. So I jumped down the rabbit hole with both feet. What happened I ended up with 2 completely rebuilt 485¡¯s and one parts unit. It seems the 485 I started on was a real mess from the previous ¡°tech¡± that worked on it. But no magic smoke and no popping of anything unobtanium. So I would have to say go for it but go REALLY slow. Eric On 5/27/2020 3:10 AM, Roy Thistle wrote:
On Tue, May 26, 2020 at 10:05 PM, John Crighton wrote:Roy, if you are not enjoying reading about the repair of the 475 scopeHi John: |
|
Re: 576 collector supply issues
Relay located and a mystery found! K323 is connected to an extra socket on the back of the unit, it's a Bulgin 3 pin socket, connected to K323's coil, the wire that was originally connected to K323's coil and to pin 3 of T301 which is earthed. Guessing this was an external interlock added by the original users (TI according to the asset tag).
|
|
Re: Tek 4041 GPIB Controller
Thanks for posting all this valuable information.
For your problems with the LEMO keyboard connector check the signal levels on the data input. The keyboard input uses TTL logic levels but there is a very heavy internal pull-up resistor on the 4041 keyboard serial data input. You will need to sink about 20mA to get an adequate logic low level and, although this was OK when driven with the older bipolar TTL devices, most modern CMOS-based interface chips would struggle to sink this much current. |
|
Re: Encouraging beginners: What are we accomplishing?
On Tue, May 26, 2020 at 08:51 PM, Roy Thistle wrote:
Hi Roy and hello to the rest of the Tek crew. I guess it really depends on a bunch of variables. I myself would buy scopes that were known not to function for the challenge of "fixing" them. And you know what? I fixed a bunch of scopes. Reading they theory of operation over and over looking at schematics for hours on end, posting here and asking stupid questions. If I would have paid someone to repair my 7633 I wouldn't have been able to afford a 7ct1n to use with it. Now I have tunnel diode pulsers, attenuators , normalizers. Am I an electrical engineer now? Not even close. I'm probably one of the least educated persons here but I have my own collection of pretty awesome Tek scopes. There have been some pads slid off, some traces lifted and a few times that I have failed but there is a great feeling when you power on that scope with no trace and it lights up. Brendan |
|
Re: 475 questions
I found that by searching "neon bulb oscilloscope", I found this: So the bulbs are used as an oscillatorI don't believe so. IIRC the neons in the 475 are in the EHT supply circuit and are effectively over-voltage spark gaps. To add to this discussion - replace nothing until you know it is causing a fault especially if you have limited soldering skills. David |
|
Re: 475 questions
There is /g/TekScopes/photos. Is that a good place for me to post?So long as a) you use either a relevant existing folder, or create a folder for you pix with a sensible name b) you post a link to the image(s) of interest here. David -----Original Message----- From: [email protected] [mailto:[email protected]] On Behalf Of ciclista41 via groups.io Sent: 26 May 2020 23:34 To: [email protected] Subject: Re: [TekScopes] 475 questions Hi Graham, It sounds as if your philosophy of whether to keep or replace suspect components matches mine. My understanding of what each component is doing in a particular circuit is very weak, so I'm not sure what a suitable replacement would be if not the identical part, and these boards were manufactured in late 1982, so it's not exactly current technology. That can be a good thing, because it was intended to be maintainable, rather than tossing an entire board or worse, an entire device, when something goes bad. So, as several have suggested, I keep asking questions! I try to do my own research, too, but sometimes the explanations on websites are over my head or don't match my question closely enough. You guys have been much better in that respect! I agree that I shouldn't be trying further diagnosis until my power rails are up and in spec. But when I poke around and see out-of-spec components on a relatively inaccessible board, I'm inclined to replace them if I can figure out what they should be replaced with. I haven't commented on the attachments debate, but I'm with you for allowing them. There is /g/TekScopes/photos. Is that a good place for me to post? Bruce |
|
Re: 475 questions
Sorry, what's "exp" in the second equation?Hi Bruce, Let's not digress too far from your 475 problem! "exp" stands for the standard exponential function, in programming languages, at calculator key labels and so on. More specifics on cap charge/discharge: . As to C1091/1093 in the manual, that's simply a mistake. A few lines down, C1261 is listed correctly and a quick scan of all 290-0523-00 caps reveals that all or nearly all are listed correctly. Might have been mixture with 281-0523-00 which is 350 V (but other capacitance). Albert |
|
Re: Encouraging beginners: What are we accomplishing?
On Tue, May 26, 2020 at 10:05 PM, John Crighton wrote:
Hi John: Yes!... if you do not like the topic... then don't read it. What then, I ask, is the logical consequence of that claim? And, just for the record... I think all this ESR stuff is 95% foolishness... I don't even have one Topic about ESR meters on TekScopes... if one post even. And, Dennis didn't tell me to do anything about ESR meters. That's something you are making up. About Chuck... I don't know: in my estimation Chuck can look after himself... pretty good really. Yes we can celebrate the marvelous-ness of generosity, that of national solidarity in the time of crisis, and of wonderful serendipity, among other things; but, I broached none of that in my post... none of it. And, a particularly incoherent response, relative to the questions that I did raise, does nothing to address them... nor shows those questions were directed towards anyone in particular, or about anyone in particular. They are not. What I posted was my opinion, based on my experience, and I stand by it. Best regards and wishes. All the best. Roy. |
|
Re: 475 questions
Bruce,
All of those dipped tantalum caps can be suspect, especially when you are experiencing power supply issues. They usually fail shorted, and in spectacular fashion, generally with a cloud of ¡°magic smoke¡± escaping. You cannot assume them to always be bad. I have many of these scopes and have had to replace a few of these type of caps in various scopes and other instruments as well. I just repaired a 7A13 Differential Comparitor which had 5 bad tantalum caps on board. This was, by far, the worst single case of shorted tantalum caps that I have encountered. -- Michael Lynch Dardanelle, AR |
|
Re: 475 questions
Michael,
toggle quoted message
Show quoted text
Ah! Like the incandescent bulb in my over current protection circuit that gave me the confidence to turn the scope on the first time. Similar concept, as the filament in the bulb has very low resistance until it gets hot, then the greatly increased resistance draws current from the device that is drawing too much current and prevents further damage. The neon probably has a more precise turn on voltage than the incandescent bulb, though. Thanks for the correction! Bruce On Tue, May 26, 2020 at 10:28 PM, Mlynch001 wrote:
|
|
Re: 475 questions
Graham,
toggle quoted message
Show quoted text
Well, my scope is peppered with the kind in the photo. Maybe they re-spec'ed the caps later in production, or maybe the US Army bought enough in their contract with Tek that they were able to spec what they wanted. Mine is from November of 1982, if the date code on the AC power cord box inside the case just above the transformer is original. I went ahead and pulled the two tantalums out of the circuit to measure them. I broke a lead off the first one, pulling too hard. Because I only have access from the top of this A7 board unless I remove it, which I don't want to do, my solder sucker wasn't able to slide over the clipped end of the leads, and I had to just use a sharp tip on my iron. Did much better on the second one, which came out easily by that second method. I then used the sucker to remove the remaining solder from the holes in the board for when I replace the broken one. Yes, you were right to question my belief that they were bad. Out of circuit, they both tested well within the green on my ESR tester. So much for being able to reliably test capacitors in circuit with that thing. They weren't even close to being in spec when tested with it in circuit. I was thinking that these dipped tantalums were generally bad in boards this old based on numerous threads in this forum and others saying how often these were bad. Some said they routinely replace them all when they see them in a scope of this era. I have tested dozens on this board and only found about a handful that this tester considered bad. So, considering that these two were among the worst that I tested in circuit, I decided to pull them, as they'd be less easily accessible later when the A8 board is back in place. So this makes me question whether the tantalums in this board are among the infamous ones. I hope not, obviously. Your statement that my photo showed what looked like a very '80's tantalum made me think maybe the infamous ones are some earlier 60's or 70's version. How can I know, other than pulling them all? At this point, I don't see the point of pulling any of them unless they show up as faulty later, when there is a trace on the scope and I can run it through its paces and make sure it's working as it should. Speaking of working as it should, Tektronics calls for several specialized calibration tools in the manual. If the scope is running well, with no serious issues other than calibration, can it be calibrated without resorting to the purchase of such tools? I briefly noted some shops wanting a couple of hundred dollars to calibrate a scope. Definitely don't want to do that! If I thought I had to have someone else calibrate it, I probably wouldn't have taken on the project and just invested in a new digital scope. Bruce On Tue, May 26, 2020 at 09:09 PM, VK1GVC wrote:
|
|
Re: Encouraging beginners: What are we accomplishing?
I agree with you, John. At first I was dismayed at Bruce's many posts, but then I thought, hey, I have no experience with the 475 and no interest in one, so I'll just delete the darn posts! Simple as that!
toggle quoted message
Show quoted text
Bruce, knock yourself out! Post as much as you need to to get the information you need to fix your scope. Good luck! Jim Ford ------ Original Message ------
From: "John Crighton" <john.crighton@...> To: [email protected] Sent: 5/26/2020 10:04:29 PM Subject: Re: [TekScopes] Encouraging beginners: What are we accomplishing? Hello Roy, |
|
Re: Encouraging beginners: What are we accomplishing?
Hello Roy,
toggle quoted message
Show quoted text
I am really surprised at you of all people sounding like a wet blanket. The owner of this tekscope group told you in no uncertain terms if you want to talk about ESR Meters to go and form your own group. Which to your credit you did just that. I also did not like the way that the owner of this group, Dennis Tillman, jumped on Mr Chuck Harris for describing how to use an oscilloscope with a function generator to check capacitors for value and ESR. Shutting someone up for describing how to use an oscilloscope on an oscilloscope group is to me just plain crazy. Those are rules that you have to obey, like them or not. Roy, if you are not enjoying reading about the repair of the 475 scope by a beginner then do not read the thread. It is that simple! I think it is marvellous that so many people on this group are willing to help an individul fix his 475 scope. What a great thing to do, while we are in corona virus lock down. My fellow countryman Graham VK1GVC, down in Canberra is doing a great job helping Bruce and so so are all the othere people. The side benefit for me and no doubt others on this group is that Bruce is asking basic questions as a beginner that other people on this group might not dare to ask for fear of looking foolish. Keep asking questions Bruce. I want you to fix this scope. Regards, John Crighton Sydney ----- Original Message -----
From: "Roy Thistle" <roy.thistle@...> To: <[email protected]> Sent: Wednesday, May 27, 2020 1:51 PM Subject: [TekScopes] Encouraging beginners: What are we accomplishing? Hi all TekScopers: Reading through a long thread, recently posted, caused me to wonder.. just what are TekScopers accomplishing with threads like this... and why are we encouraging someone who is "... new to electronics..." to dig into a 475?... one of the most complex, and compact, analog instruments ever designed. I suppose.. in consideration... Michael discouraged the use of a Mr. Carlson super Weller-kluge special, on the 475's pcb(s)... but, ya know... somewhere the thread... the 475 owner hints he paid 20.00 for 475?, and he's also got a nonworking? PM3218 too. So why didn't someone just recommend/... right off the bat... to take the 475 to someone who knows what they are doing... drop another 100.00 on it... and then he'd have one of the best scopes ever made. Or alternatively... and better... just start in on the PM3218...itself a very fine instrument, with a double insulated power supply... and way overkill, for a beginner. Look, I'm not unsympathetic... it's just that...too often.. after parting with some scarce cash... or finding some Tek picked apart in a basement somewhere, where its been languishing for a generation...I've witnessed the havoc wreaked by someone trying to "fix" them. If you want to call me a dumb ass... for thinking this way... well fine... just PM me to do it. I can't promise I'll reply to that... but, I'll read your message. Best regards and wishes. Roy --- This email has been checked for viruses by AVG. |
David C. Partridge
Mlynch001
to navigate to use esc to dismiss