Tektronix 2247a 100mhz scope not working right on times/div - Page 1
Forum section: electronics / testgear

author: powerstroke7.3
author_rank: Contributor
timestamp: September 01, 2022, 07:41:14 am
content: I believe that I got this scope this way I had 3 different scopes at 1 point in time and I can't remember which ones were what but I got rid of the other 2 and kept this one and I guess this was the broken 1It only works in certain positions on The Times per division knobhttps://youtu.be/rmCz7nXiKzw

author: wn1fju
author_rank: Frequent Contributor
timestamp: September 01, 2022, 12:10:21 pm
content: If it were a slightly older Tek scope, the sweep times were controlled by a mechanical cam switch which closed little leaf springs on the board. Those were notorious for getting dirty and a gentle cleaning would usually fix all problems. Once in a while, the timing capacitors and/or resistors would go bad, but I've only seen that a couple of times.But, alas, your scope is all digitally controlled. Download the operation manual and the service manual (w140.com) and read through them carefully. You might want to try a few things, such as:1) restore to factory default2) attempt a calibration (probably will fail)3) run the diagnostic programThere are two sweep generators in the scope, A and B. You also might want to try the B sweep and see if that is working. That might give you a clue as to whether the digital control data (common to both A and B) is making it through correctly, or if it is just a problem with the A sweep generation.In any event, the service manual provides some information on how to diagnose/repair sweep problems. Good luck.

author: powerstroke7.3
author_rank: Contributor
timestamp: September 01, 2022, 07:55:31 pm
content: Quote from: wn1fju on September 01, 2022, 12:10:21 pmyeah i have the service manual. I swear these era of scopes are more complicated than newer ones

author: tautech
author_rank: Super Contributor
timestamp: September 01, 2022, 08:08:08 pm
content: Quote from: powerstroke7.3 on September 01, 2022, 07:55:31 pmGranted, 100 milli Hertz scopes are certainly a rarity.

author: powerstroke7.3
author_rank: Contributor
timestamp: September 02, 2022, 06:47:14 am
content: Quote from: tautech on September 01, 2022, 08:08:08 pmall i see for sale are similar ones or even older 3 digit model #s

author: tggzzz
author_rank: Super Contributor
timestamp: September 02, 2022, 07:45:42 am
content: Quote from: powerstroke7.3 on September 02, 2022, 06:47:14 amNo, you see 100 mega Hertz (MHz) scopes for sale. In a similar vein, synthesised oscillators often have specs like 50MHz range with 100mHz resolution.BTW, please don't make the mistake of measuring time in units of conductance, i.e. Siemens (S) vs seconds (s).But back to your point. I'm not familiar with the 22xx scopes, you'll need to RTFM. However, the 24xx scopes have a cal out signal where the frequency changes with the timebase so there are 5(?) cycles visible on the display. Nobody thinks that misfeature was a good idea.

author: adam4521
author_rank: Regular Contributor
timestamp: September 02, 2022, 06:56:21 pm
content: This is what the user interface boards look like, spares from my similar, but less featured, 2245A. On the left, the rotary encoders, buttons and a constellation of status LEDs. In the plastic you can see the holes where the extra buttons of the 2247A would go. On the right, the potentiometers, which poke through the other board. Both are connected via ribbons to the ‘digital’ main board, that in turn controls the ‘analog’ board.To the OP, I could send it to you if you need to salvage a rotary encoder. But it doesn’t sound yet like that is necessarily the root cause. I wonder if this board can be tested in isolation?

author: powerstroke7.3
author_rank: Contributor
timestamp: September 03, 2022, 06:20:13 pm
content: Quote from: tggzzz on September 02, 2022, 07:45:42 amyou went right over my head there. I'm just a dumb ham operator with a extra license. Seriously though I don't understand a bit of what you said. I'm not very advanced at all with any this.

author: powerstroke7.3
author_rank: Contributor
timestamp: September 03, 2022, 06:25:35 pm
content: I've had mine apart a few times but not that far. Mine could stand to be recapped I'm sure and the fan is very noisy. I really dont know how to fix it, but it sure would be nice to have it working correctly. I prefer this to these new dso cheap scopes like this handbrake dso2c10 I'm using because it's all I have to work with.

author: tggzzz
author_rank: Super Contributor
timestamp: September 03, 2022, 07:12:07 pm
content: Quote from: powerstroke7.3 on September 03, 2022, 06:20:13 pmMy first two paragraphs are stuff I learned in school physics lessons, several years before I went to university.https://studyrocket.co.uk/revision/a-level-physics-aqa/measurements-their-errors/use-of-si-units-their-prefixes(S Siemens conductance a.k.a. inverse resistance, mhos is another derived unit, less commonly used than the ones mentioned in that link. A FET's principal parameter is its transconductance gm, in the same way as a BJT's have current gain hfe.The last paragraph is specific to a range of scopes. RTFM for more information. If you don't have the FM, get it athttps://w140.com/tekwiki/wiki/2247

author: powerstroke7.3
author_rank: Contributor
timestamp: September 03, 2022, 10:35:33 pm
content: Quote from: tggzzz on September 03, 2022, 07:12:07 pmyou might as well be talking Greek to me. Thanks though, I think.

author: tautech
author_rank: Super Contributor
timestamp: September 03, 2022, 10:40:51 pm
content: Quote from: powerstroke7.3 on September 03, 2022, 10:35:33 pmVery simply in English as you don't understand Greek......FFS get you multipliers correct as this is an engineering forum.

author: tggzzz
author_rank: Super Contributor
timestamp: September 04, 2022, 12:04:10 am
content: Quote from: powerstroke7.3 on September 03, 2022, 10:35:33 pmI'm beginning to wonder if you see the difference between 0.001 and 1,000,000.I'm beginning to wonder if you can follow a link and understand the schoolchild level stuff it contains. (A-level physics is for 16-18yo kids)I'm beginning to wonder if you have heard of a wonderful new tool at google.com

author: powerstroke7.3
author_rank: Contributor
timestamp: September 04, 2022, 10:46:31 am
content: Quote from: tggzzz on September 04, 2022, 12:04:10 amdont you have someone else to bother? Excuse me for not capitalizing the m in mega Hertz. You knew what I meant. Now move along. Do someone else a favor not me. I don't need your help unless you know something about the scope.

author: tggzzz
author_rank: Super Contributor
timestamp: September 04, 2022, 11:05:08 am
content: Quote from: powerstroke7.3 on September 04, 2022, 10:46:31 amI refer you to someone else's post:https://www.eevblog.com/forum/testgear/tektronix-2247a-100mhz-scope-not-working-right-on-timesdiv/msg4397824/#msg4397824Do you actually want help or to be spoonfed? I refer you to the last paragraph of this post:https://www.eevblog.com/forum/testgear/tektronix-2247a-100mhz-scope-not-working-right-on-timesdiv/msg4397467/#msg4397467

author: wn1fju
author_rank: Frequent Contributor
timestamp: September 04, 2022, 12:00:42 pm
content: Look, the guy typed in "mhz" instead of "MHz." We all get it, we all know what he meant. What exactly is the purpose in berating the poor guy? He has a tough enough problem with the complicated 2247A scope ahead of him.I have fixed several hundred pieces of test equipment over the years. I know how to obtain/read manuals, I know how to search through the forums, I know how to use Google. But every once in a while, I've asked a question on the forum in the (usually slim) chance that someone had experienced the exact same failure and had a simple solution. I don't fault powerstroke7.3 for that.On the eevBlog forums, we should be encouraging people, not discouraging them. Perhaps he would be better served on the Tek forum (https://forum.tek.com/viewforum.php?f=568) or on the Tektronix groups.io forum.

author: tggzzz
author_rank: Super Contributor
timestamp: September 04, 2022, 12:13:37 pm
content: Quote from: wn1fju on September 04, 2022, 12:00:42 pmThat's a fair observation and question.If you look at the initial posts:he made a mistake (as we all do), and was gently correctedseveraltimes. But he refused to listen to the correctionasuggestedcause for his observations was mentionedseveraltimes, along with where to finddefinitiveinformation. He chose not to listen to the suggestion, and not to go and look at the solid informationIt is pleasing to be able to help someone that listens and thinks and follows up suggestions, if you get the implication!

author: wn1fju
author_rank: Frequent Contributor
timestamp: September 04, 2022, 02:21:03 pm
content: I didn't really get the feeling that he ignored the suggestions. It has only been a couple of days and if it were me, I would still be trying to go through the extensive service manual trying to understand the circuitry before diving in. I'm sure he was turned off by some of the posts and again, if it were me, I probably would never look at this particular thread again.Final thought: All my working career, I was impatient, tempestuous, and "took no prisoners." I'm sure I was a joy to work with! But as I get older (I will turn 70 in a few weeks), I am starting to adopt the old adage, "you can catch more flies with honey than with vinegar." Case in point - my neighbor's dogs have tormented me for years with their barking. I have expressed my displeasure to the owner many, many times and have threatened calling the authorities several times. But it continues. About a month ago, I went over there and had a pleasant conversation (no hostility) and you know what? The barking situation has improved 10x.

author: tggzzz
author_rank: Super Contributor
timestamp: September 04, 2022, 04:07:20 pm
content: Quote from: wn1fju on September 04, 2022, 02:21:03 pmI entirely agree.My general philosophy is turns out to be similar to the best strategy for the iterated Prisoner's Dilemma problem: tit for tat. Start by cooperating, and only change if the other party isn't cooperating.https://en.wikipedia.org/wiki/Prisoner's_dilemma#The_iterated_prisoner%27s_dilemmaPlus "Trust, but Verify", of course.QuoteI've seen similar, with a neighbour that "came on" tough and belligerent. He backed down when he realised that wouldn't frighten me, but asking nicely would help him get the result he wanted.Unfortunately modern Human Resources (i.e. not Personnel) diktats are that problems should go through your manager rather than having a quick chat. I'm not sure of the reason for that, other than to give HR ammunition against employees.

author: WattsThat
author_rank: Frequent Contributor
timestamp: September 04, 2022, 04:36:59 pm
content: Quote from: powerstroke7.3 on September 01, 2022, 07:41:14 amYup, that’s a broken one. Timebase issues, all on that really big bottom board. Shame you didn’t fix it before parting with the other two units.