Tektronix 2445 Oscilloscope Repair Revisited part 1 of 1
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- เผยแพร่เมื่อ 1 ต.ค. 2024
- My Tektronix 2445 oscilloscope slowly started failing until it finally stopped functioning altogether a few months ago... find out how I repair it in this video
Enjoy :)
I systematically replaced a number of old components rated for 85C° (17 electrolytic capacitors on the powersupply boards A2 & A3) , with equivalent capacitors rated for 105C°, as well as 3 paper capacitors and 1 (probably) mylar one by PP film capacitors rated for 1KV and 630V respectively.
I suspected that the replaced (failed/failing) components were either inferior in quality or just not rated properly (temperature-wise) for the job. The final outcome of the repair session seems to have confirmed the initial assessment was correct
Use of a desoldering gun and a dremel tool for the repair are recommended. Do use good quality solder + flux, since the PCB's are doublesided and require soldering on BOTH sides. Be meticulous and careful while soldering and check every solderpoint; retouch where necessary.
Be gentle when dis- or reconnecting PCB's and connectors, most are very sensitive to mechanical or heat stress. Make sure your hands and tools are properly grounded for static electricity, BEFORE touching IC-boards
Be careful when working on / testing the oscilloscope, there is DANGER(!) : Deadly High Voltage and possibly harmful chemicals !
Opening up the Tektronix 2445:
• Tektronix 2445 part 1 ...
Repairing the RCA Volt Ohmyst WV98-A part 1:
• RCA WV98-A Volt Ohmyst...
Repairing the RCA Volt Ohmyst WV98-A part 2:
• RCA WV98-A Volt Ohmyst...
Repairing the RCA Volt Ohmyst WV98-A part 3:
• RCA WV98-A Volt Ohmyst...
How to read capacitor values:
www.electronic...
Film capacitor theory and information:
en.wikipedia.o...
Voltage rating code quick reference:
www.google.com...
Always replace RIFA brand 'safety' capacitors on sight, with the appropriate X or Y rating. They have a poor record of reliability and always fail eventually, sometimes with catastrophic, or firey results.
You have been warned!!
I' m Marcelo from Brazil.
I have an Oscilloscope Tektronix 2445B and it presents a distortion on the channels 1 and 2.
My english is very poor, so I can not describe it well.
Could you please take a look on the video and maybe help me to find out how to solve the problem?
There are just 2 videos on my TH-cam Channel and both are demonstrating the distortion.
Thank you in advance.
Marcelo Silva.
TM very good explanation together with an interesting job to get to know these teams from the inside. I bought a similar one a few days ago and your video will serve as a guide for the replacement of the RIFA. I could see that the battery is not in the same location on each series of the 2445, 2445A, 2445B. Thanks for sharing your experience.
I love this oscilloscope, it's one of the very best analog ones around, and Tektronix is a leader in this kind of equipment. You bought quality for sure. Unfortunately, the power supply is replete with electrolytic capacitors which are graded for low temperature levels (85C°) instead of 105C°. This is unfortunate considering the Tek runs pretty hot after a while. One can replace those caps (I replaced all those rated for the lower temp range) but since the PCB's are double sided one needs to take appropriate action to solder new caps to the boards. Thank you for your very nice comment and I hope my videos on the Tektronix will be helpful to you :) Good luck !
Good evening, I know this is probably a little late, but your removal procedures for the A1/2 A3 assemblies are not necessary. The A1/2 and A3 board is removed as ONE assembly and not individually. The pass transistors you see on the A2 are mounted to a plate that is mounted to the chassis by three screws. It is a simple matter to disconnect the voltage selector wires, the ac power wires, remove the fastening screws from the rear top and bottom and the three screws holding the heatsink to the chassis. Unplug the two connectors on the A2 and lift the entire ASSY out of the scope. The removal procedure for these boards begins on page 6-24 of your service manual. I hope this helps in the future. It will definitely save you a ton of tine and aggavation.
You're probably right (I haven't tried your procedure myself) but, the point of my videos is to find ways to restore old equipment(s) even when one doesn't have all the available information or specialized tools to do so.
After all, many seem to think there's nothing "adventurous" about restoring old equipment.
To "think" yourself through a labyrinth of connections and electronic circuits, however, to finally solve a problem and bring the equipment back to life, is one of the ultimate "kicks" one can get, in my opinion :)
Nevertheless, I thank you for your kind advice and considering subscribing to my channel !
@@TechneMoira You are of course, 100% correct in your statement "To "think" yourself through a labyrinth of connections ......""is one of the ultimate "kicks""..... I couldn't agree more wholeheartedly . You pump out your chest and think "I fixed it with no external help" it is truly satisfying. I was not trying to be critical of your procedure, I was only trying to suggest there is a much easier and less damage risk of removing those two boards. After watching your first video on this scope, I felt bad because of all the hardships you encountered resolving the capacitor issues. BTW, I have totally re-capped 4 of the A!,2 &A3 boards with 100% success. TEK really used some cheap undertemp and marginal electrical components Most of the stuff that is on these boards are 85C items and most definitely will fail in a few hundred hours. I have a spreadsheet that I made up with current clickable DigiKey part numbers using all 105C top quality long life components. I am ready the next time I have to do this. My own 2445B is my absolute favorite instrument and I will never let it go. Lastly, thank you for your videos. No matter how much you know about any one subject there is always new things to be learned. My best to you and yours. Joe
Thank you for the information. But you really need to use a mini tripod to prevent shaking of the video plus to center it on the topic being discussed.
Thank you for the tip. Yes I know, I should use a tripod more often, but the real estate in my lab is minimal and depending on the device under scrutiny I sometimes run out of space for a full grown tripod :) Either way, thanks for watching, giving me a thumb's up and considering subscribing
Tomorrow I hope to get the same type oscilloscope for cheap, hence I was watching your elaborate step-by-step description. Thanx for that! This particular scoop gave some smoke signals from its rear today 😁 as I was told from the seller. It's no easy repair to find your way inside, but I suppose it is doable if you have enough patience. I hope there is no too big of a damage inside. ...
Yes, unfortunately Tektronix made the very unwise decision to source RIFA capacitors to populate the Tek Scopes many years ago, and those are now "exploding" in ever-increasing numbers as the years go by.
If you replace low temperature spec electrolytic capacitors on the power supply boards for high temperature ones and the occasional RIFA (paper) caps for poly caps you should be fine.... unless the PCB's got damaged in that power-up.
Either way, I wish you success and a lot of fun getting the scope to work... a 2445 is a great machine to own (if it works :) ) Thanks for your nice comment and considering subscribing
@@TechneMoira Yes, those are now ticking time-bombs, as it seems... Everybody is talking about those cracking RIFA's. Thanks for all the tips and tricks. It will need some repair/restauration time and small financial investment, but if you not do some preventive replacements the bomb keeps ticking. I don't know how big is the chance of electrolite capacitor leakage? Because those damage the PCB, and you are then even further from the home... But for sure I will use your elaborate video as the guide once I am in there 😀
Hello Ernest. If memory serves, I did not find a lot of leaking electrolytics on either power supply board or anywhere else in my oscilloscope. However, I DID find a "fine" mix of low temperature electrolytics (85C°) among high temperature (105C°) ones.
I would advise you to replace the 85° ones for sure and any stray RIFA's anywhere you find them (there are less than ten of them in all I recall).
Remember the PCB's are DOUBLE-sided which means the leads of the replacement capacitors need to be soldered on BOTH sides.
The way I did it, was by carefully (de-)soldering respectively the original and new capacitors... you should always take care NEVER to OVERHEAT the PCB traces, of course.
Also, it helped to "wet" the replacement capacitors' leads with a THIN layer of fresh solder and a bit of flux to have a nice solder flow at minimal heat on both sides of the PCB at once. Shortening the leads to just necessary length helps too (since less heat is leeched off into the long leads) and leaving about 4mm (or less) of space (not much more !) between the capacitors and the PCB helps too.
When you're done, ALWAYS CHECK your soldering on both sides and retouch with some flux and a tiny bit of fresh solder to make sure the solder does flow out nicely.
There, you're all set now for a succesful restoration :) Good luck !
@@TechneMoira thanks again for the heads up and valuable tips 👍I hope also that the scope will survive the transport 🙈 I don't know how good it is packed. We will see tomorrow...
Hello TM. Great to see you back. Very complicated Scope. That company is know to be, bad, for using in-house parts. Almost impossible to get. I own a lower cost digital scope. So far so good. America is in a mess now. My own humble opinion and mine alone. Has always Liked,shared. All my very best.
yeah, there are a lot of proprietary parts in this oscilloscope. I guess eventually I'll have to move on to a new digital scope someday... but not today :) thanks for your nice comment... and countries are like people in my opinion, they do have ups and downs. see you soon Bobby
Dear Sir, would not fit a vintage condenser checker with an eye tube perfectly to your portfolio? Like other old stuff repair guys you quite often would like to actually see a condensers leakage at higher voltages. IMHO I do not regret to have purchased one from the other side of the pond. A modern cheap alternative would be a vc60b+ generic isolation tester (of course not suitable for electrolytics). Also the self-made checker by mcaldera from the island Madeira is great (Electronics old and new). Greetings from Frankfurt.
Certainly. An affordable capacitor leakage meter could be useful if combined to an ESR and capacitance readout. But as far as I know I haven't found one yet. Even oldfashioned Capacitor meters (except perhaps very expensive and very rare military models from the 50's or 60's) do not combine leakage + ESR + capacitance measurements. But it's on my wish list :) As it is, there are still a number of tools I'd love to have... unfortunately I'm just an electronics enthusiast with a limited budget (unless my channel suddenly had 100K+ subscribers :) )
Thanks for your nice comment, giving me a thumb's up and considering subscribing
Always welcome to my channel
Nice one, at least it works again now. I watched for entertainment only as it's
out of my depth. Maybe you could do tests with other equipment and compare
results, to check that it still has reasonable values. Thanks for sharing.
That's a good suggestion, although I have to confess there are already quite a few TH-cam channels doing just that. To be interesting enough for my viewers it would need to have a radically different "angle" that would be relevant and entertaining... that's a tall order :) Thanks for your nice comment and the thumb's up
Nice work TM, I have the same Tektronix 2445 and have repaired once so far and would not look forward to doing it again....................................Berni
I'm with you, Berni. Repairing this oscilloscope could easily have turned into a nightmare but, that being said, it was also interesting. Having the service manual did help though. Thanks for watching and giving me a thumb's up :)
I'm still having some issues with mine, no power but, would you be able to tell me where did you get the "Power Supply Troubleshooting schematic"? I have the service manual but it doesn't give the same flow chart that you have on your video. I would greatly appreciate your help! Thank you for this video, it's has helped so much!
Hello Alfonso. Thank you for your nice comment and considering subscribing and giving me a thumb's up.
As for the flow chart, it is part of the paper service manual I got when I bought my oscilloscope a few years ago. I could send you a couple of pictures I could take with my camera of the flowchart and send that up to you... not the whole service manual though, I'm sure you understand :)
If you give me your email I think I can do that the next few days. Alternatively you can find my email (somewhat disguised) in the about section of my channel (it's a gmail address)
Thanks again for watching and good luck with your repair.
P.S.: The repair of my scope was relatively painless since the voltages were out of spec due to a few bad electrolytics on the supply boards A2 & A3, so all it took was replacing those (as you'll read in the comment section under the video)
@@TechneMoira Thank you so much. I would really appreciate help. I will send you my e-mail at your address. The flow chart would be helpful. Once again thank you so much!!