Tek 2232 just before the repair attempt - Page 1
Forum section: electronics / repair

author: Wh1sper
author_rank: Regular Contributor
timestamp: September 01, 2014, 11:33:12 am
content: My 2232 seems to begin to fail.It is starting well, no error messages.In Storage mode the Display is showing the Wave and Information correctly for a half of second. After that there is a approx. 5 sec. pause while only the no store mode waveform is visible without any character generator sign, no text at all.Then the Display loops again with showing all for about a half second.When disabling the Digital Store mode everything is normal again.My guess is, that the power supply is getting worse and I would measure the output of the 5Volts and the other voltage.I do have a service manual in PDF. On 5-4 there is the speak about "Adjustments Locations 1 at the back of this Manual for location of test points and adjustments."Unfortunately this is missing.So before I begin to open the device I would like to know where to find the Test points mentioned at Page 5-4 Table 5-2 and 6-13 Table 6-8FYI: I do have a spare simple DSO to watch the ripple as well.

author: David Hess
author_rank: Super Contributor
timestamp: September 01, 2014, 12:48:37 pm
content: Figure 9-10 which is at the beginning of the diagrams and circuit board illustrations shows these test points on the bottom of the main board. They are not well marked in the diagram.The 2235 service manual has a much better diagram showing the power supply measurement test points along with the adjustment locations on the main board.

author: Wh1sper
author_rank: Regular Contributor
timestamp: September 01, 2014, 01:13:30 pm
content: Thanks, found them!Now, after repairing the dishwasher -- HIGH Priority!-- I will look at this.

author: David Hess
author_rank: Super Contributor
timestamp: September 01, 2014, 04:26:01 pm
content: I think you are on the right track and have the right tools for the job. The first thing I would check is the power supply levels and ripple with a voltmeter and oscilloscope.

author: Wh1sper
author_rank: Regular Contributor
timestamp: September 02, 2014, 08:13:39 am
content: Couldn't resist and took a first look.I'm surprised The Manual say + 5.0V W9068 Range (+5.75V to +5.25V )I see two choices. They mean 5.5V then the Range is ok, or the Range is wrong and should be 5.25V to 4.75VHere we speak from normal TTL ICs they take 5.0V so the Range is an Error, isn't it?I measure 5.1V btw.Ripple measuring is pending

author: tautech
author_rank: Super Contributor
timestamp: September 02, 2014, 08:20:26 am
content: Yes, I would definitely read that as a mis-print. As you say it should read: +4.75 to 5.25.They put it like that to test you.You passed.

author: David Hess
author_rank: Super Contributor
timestamp: September 02, 2014, 10:13:45 am
content: Table 5-2 on page 5-4 says +4.75 to +5.25 and shows different limits for the +102 volt supply also.I wonder if the difference is because table 6-8 assumes that the storage board which provides most of the +5 volt load is disconnected during the measurement.The 2230 service manual has the same difference between table 5-2 and table 6-7.You could ask about it over on the TekScopes@yahoogroups.com discussion list.

author: Wh1sper
author_rank: Regular Contributor
timestamp: September 02, 2014, 06:54:54 pm
content: Quote from: David Hess on September 02, 2014, 10:13:45 amYou may right.This evening I checked the Values again and measured the ripple with the Scope itself.But I have to say, the failure is gone! Hhm.The ripple is a way more than it should be. about 6mV @5Volts and 100mV@30V.But when I see so much stuff to take apart just to see the powersupply Board my braveness is vanishing, I really have the faer not to get everything inplace correctly after that

author: David Hess
author_rank: Super Contributor
timestamp: September 02, 2014, 10:04:45 pm
content: Quote from: Wh1sper on September 02, 2014, 06:54:54 pmGetting to the power supply on these oscilloscopes is not much fun. It is easier on the models without a storage board because the power supply is exposed.

author: jlmoon
author_rank: Unknown
timestamp: September 03, 2014, 03:29:39 pm
content: Quote from: David Hess on September 02, 2014, 10:04:45 pmThat's where your smart phone camera becomes your best friend, or a small digital camera. Never venture into something that is stacked like cord-wood before taking many photos for restore documentation.

author: David Hess
author_rank: Super Contributor
timestamp: September 03, 2014, 05:36:14 pm
content: Quote from: jlmoon on September 03, 2014, 03:29:39 pmI have a small point and shoot camera for documenting disassembly processes if necessarily.The Tektronix service manuals are pretty good about going over access procedures and on the 2232, they changed the design making it a lot easier to tilt the storage board out of the way. On the 2230, it is much more difficult to do.

author: Wh1sper
author_rank: Regular Contributor
timestamp: September 03, 2014, 06:00:47 pm
content: Quote from: David Hess on September 03, 2014, 05:36:14 pmThis point goes to you, of course I didn't :-( I must become better with thisQuote from: David Hess on September 03, 2014, 05:36:14 pmYes, behind the shield I've found the Lithium Battery, 3.06V after 11 Years, with 1K Ohm load down to 2.86V so this must be replaced.The Error behavior is gone. I'm surprised that there is absolutely no dust at all!I think I wait for the battery delivering and put it together and give the scope a try.Never change a running system :-)After thinking and trying a lot of times I think it was the switch for the storemode, maybe a contact was a bit noisy or so

author: jlmoon
author_rank: Unknown
timestamp: September 03, 2014, 06:09:20 pm
content: Quote from: Wh1sper on September 03, 2014, 06:00:47 pmI don't know that model, but does that battery keep the memory for the cal constants alive? Just a thought.

author: Wh1sper
author_rank: Regular Contributor
timestamp: September 03, 2014, 07:55:30 pm
content: Quote from: jlmoon on September 03, 2014, 06:09:20 pmNo, only user definitions and saved "screenshots"So, no Problem at all.But if empty the 2232 claims at every switch in a power fail error which is annoying.

author: Wh1sper
author_rank: Regular Contributor
timestamp: September 06, 2014, 06:57:05 am
content: To end this thread:I renewed the battery and put all together again... working.And... Don't laugh. I discovered a menu setting which allow to display the frequency of the cursor setting instead of tMan ..--.. so much things to learn about this fine gear.

author: David Hess
author_rank: Super Contributor
timestamp: September 06, 2014, 02:18:19 pm
content: There are some other obscure features these oscilloscopes have besides reciprocal time measurement:1. Voltage measurements can be made to either ground or between cursors if you leave one cursor at the left most point.2. Peak detect mode normally use a threshold algorithm to reduce low level noise. Display - Smooth can turn this off.3. Press Advanced - 3 twice and then turn the cursor control to bring up the secret menu.

author: Wh1sper
author_rank: Regular Contributor
timestamp: September 06, 2014, 05:52:30 pm
content: Quote from: David Hess on September 06, 2014, 02:18:19 pmThanks David.1 and 3 are already known. It had knocks my socks off, as I tried it.What a complex vector graphic game! The software engineers are have had a lot of spare time ;-)2 needs to check :-)

author: David Hess
author_rank: Super Contributor
timestamp: September 06, 2014, 06:47:57 pm
content: Quote from: Wh1sper on September 06, 2014, 05:52:30 pmI only mentioned 2 because the 2230 and the 2440 series oscilloscopes lack it (although the 2440 series has a different noise reduction technique which does not operate during peak detection anyway) and because the 2232 smooth peak detect mode is sometimes misleading because it covers up peak-to-peak noise *and* signal at low magnitudes which is not always desirable.A true index graded display would be superior but even modern DSOs usually fail in delivering this so I do not find the lack of index grading on these old DSOs to be particularly disadvantageous. I prefer limited and understandable to obscure and broken.You can sort of see the results in this 2232 photo (*) where smooth mode showed the peak detected noise in divisions 2 and 3 but removed it everywhere else. It makes for a great visual display but it is important to know how it was produced. The second photo from a 2440 shows the same waveform also acquired with peak detection but no smoothing. Most of the noise outside of divisions 2 and 3 is background noise which is always present and the 2232 smooth mode effectively removed. As to which is preferable, it depends on what you want to look at.(*) These photos were taken with a Sony DSC-S70 camera which I borrowed. It just added more reasons that I hope to never have to use another Sony product for as long as I live. Sony can DIAF.

author: Wh1sper
author_rank: Regular Contributor
timestamp: September 07, 2014, 06:47:03 am
content: Uhh, amazing difference. I will definitely look at this deeper.btw. I don't use or sony at all. Not only for their rootkit in CD, their proprietary interfaces and more.

author: GeorgeOfTheJungle
author_rank: Super Contributor
timestamp: September 07, 2014, 08:51:08 am
content: Quote from: Wh1sper on September 03, 2014, 06:00:47 pmThat's very likely, in these scopes it's quite common. Not sure how easy to fix is that in a 2232 though. But I'm going to learn soon as I have one that's starting to develop the disease.

author: GeorgeOfTheJungle
author_rank: Super Contributor
timestamp: September 07, 2014, 08:56:24 am
content: Quote from: David Hess on September 06, 2014, 06:47:57 pmThe 2232, what a wonderful scope!