Tektronix 2445 Oscilloscope Repair

[@makaryawadalla5547]

Great video, thank you. I have Tektronix 2432 digital scope and it started to misbehave. I get a trance on channels 1 and 2, but cannot display a signal. My suspicion so far is that the issue is in the attenuators at the input. This is mainly because self diagnostics all pass. Do you have a video on removing and repairing the attenuators or can you have one in the future? I especially find your videos and your style to be very informative, you hit the useful stuff and don’t waste time showing the obvious or telling long stories. Keep up the good work!

[@t1d100]

Great score. Great video. Great repair. Sooo good to see you DIY repair the collet. A repaired fan action shot with audio would have been interesting.

[@NearFarMedia]

The fan is actually reallllly quiet, barely audible at all. These 'squirrel cage' fans are a lot quieter than standard axial computer style fans and move a lot of air, but they are a bit more bulky is size.

[@davidv1289]

Thanks for an excellent video. I have a 2445B on my bench that's my go-to analog scope - I need to check it for those pesky Rifa caps!

[@NearFarMedia]

Definitely a good idea, when I order X and Y class caps, I usually buy 10 at a time. That way I hit the price break and I'm building up a stock of them to keep on hand.

[@user-lp3cf5yn5b]

Hey, is it okay to replace rifa with kemet? Same manufacturer, different name

[@davidv1289]

​@@user-lp3cf5yn5b Yes, provided they are the same class, voltage rating and close to the original value. It is also okay to replace them with new Rifa capacitors. Rifas from the sixties and seventies are infamous for cracking open and burning up, releasing lots of smoke and a terrible smell. New Rifas don't seem to have that problem - yet.

[@user-lp3cf5yn5b]

Okay, so questions. I have one, no boot, but you can get dots on the CRT, just no sweeps, no creeps and no bleeps. The voltages are mostly on except for a few which are down. +5VD is 4.29 instead of 5. Went through troubleshooting flow charts and it leads me to either the feedback circuit or unregulated 5 and 15 volt circuits. U1040 input is dead, reads open both ways. S0C123 is unfindable. I'm hearing three different values to replace with. 4N35, TIL117 or TLP631 (obsolete) which according to Vishay is equivalent to CNY17-3. How critical is CTR value to the proper operation of feedback? Once I do that then I suppose I need to recap the LVPS. Does anyone have a good angle on which series of caps to replace those 672D caps with? If it doesn't work after all of what I plan to do idk.

[@davidv1289]

@@user-lp3cf5yn5b Sounds like you've been "jammed". The 5 volt digital supply of 4.29 volts is definitely too low. U1040 is a H11AX1 series optoisolator with a minimum CTR of 50, the 4N35 has a minimum CTR of 100. The H11A1 is available from Vishay ($0.72 each from Mouser, P/N 782-H11A1) in the 6 pin DIP package. Definitely check U1371 and the +10 volt reference after installing U1040. Good quality low ESR capacitors should be good for the SMPS section. Hope this helps. Regards, David

[@DarianCabot]

Good score 👍 nifty repair on that fan adaptor too

[@alfonsoincorvaia2595]

Great video! I have the same unit and one day I went turn it on and I smelled smoke. I noticed that the REFA caps are old and cracked. I also need to know if I should replace the two gas filled surge protector on the LV power supply? My other question is where can I find the RIFA caps? I would appreciate your help. Thank you so much!

[@NearFarMedia]

I buy my replacement X and Y class capacitors from Digikey and Mouser. I wouldn't worry about replacing the gas discharge devices unless they are physically broken.

[@alfonsoincorvaia2595]

@@NearFarMedia Thank you so much sir! Please continue with your video's, I enjoy them. I'm a retired electrical engineer and now I just enjoy working at projects at home. I miss my 2445 scope, it's one of the best!! Once again thank you!!! Alfonso

[@danishnative9555]

I have repaired the power supplies on both 2445 series and 2465A/B. I don't hedge to replace all the PS electrolytics anymore, with the possible exception of the two 390uf high voltage axials. Also the Rifa's and (2) 47 ohm 2 watt film resistors located in the ac mains near the ICL's. I use the shot gun approach. Beware those Green Nichicons & Sprague 672D's. Many times its just one shorted cap that has shut down an entire rail. Also, if that Siemens made fan motor fails, your screwed.

[@NearFarMedia]

Yeah, for a scope that's a keeper, best to replace all the caps on the power supply. Don't forget to replace the SMD tantalum caps on the A5 Processor board on the right side of the scope if they are there (On older units they are electrolytics), they ALWAYS leak and can kill the PCB. I went all out with my 2467B (featured in another video) as I'll be keeping that one so it got the royal treatment to ensure reliability.

[@Masks_alot]

@nfm thanks for the video. Could you suggest me where I can get a schematic for agilent 54855A DSO 6GHZ scope. I accidentally shorted power connector (ATX style) then somehow it is not turning on. Seems like the power supply is OK, it is outputing all the voltages (there is a separate analod voltage generation board and when I disconnect from it and connect the power plug) I can measure all voltages within range on SPS. The front panel buttons are not working, but it power on itself and can boot wothout that connceter pluged in.

[@andymouse]

Am I right in thinking that Tektronix made there own ceramic CRT's for some models ? the reason I ask is, the shape of the tube in this lovely scope made me think it is...cheers.

[@NearFarMedia]

Tek made most of their own CRT's, they were a large manufacturer of CRT's back in the day. They have some interesting variants in some of their gear too.

[@felipechan9654]

Gd day sir, is there a way of measuring all the voltages of the low voltage power supply before disasembling the unit just like the tek 465

[@NearFarMedia]

I'm not sure of the process to check voltages off hand, but if you have a look in the service manual, it will tell you how to do it in the adjustment section: w140.com/tekwiki/wiki/2465

[@abeleski]

Great job but please show more of the actual work, like replacing caps etc... Cheers

[@nrcha]

“Have you got any pot, sir?” “yes, but it’s broken”. Nice vid! Awesome that all of the unobtainium ICs were intact. How do you polish the bnc connectors?

[@NearFarMedia]

To polish the BNC connectors I just use jewellery cleaning paper cloth from the dollar store. Brings them up nice and shiny.

[@tenminutetokyo2643]

That is nuts dood!

[@joehubler4965]

nice job

[@shariqkudcs]

Your videos are great, Can you also put digikey part numbers just like you did for 2235?

[@markgreco1962]

Fun to watch thanks

[@stevec5000]

My Tek scope is missing the Trigger knob and it's a weird setup with a plastic shaft on the knob that pushes down into a hole in the pot inside below the front panel so how can I replace that?

[@NearFarMedia]

Check the service manual (available via google) for the part number and check ebay, or try asking on the Tekscopes group on groups.io, or eevblog forums etc.

[@Sheevlord]

Speaking of the clip - I suspect it was a custom made part. You could try using narrow adhesive copper tape to tie transistors together. It's a bit of a ghetto solution but I don't see why it wouldn't work.

[@NearFarMedia]

I have been known to use a bit of superglue too. :)

[@eiichishiraishi9911]

プラスチックが脆性をおび、本体の驚愕な精度な部品達から守れなくなってきて

[@eiichishiraishi9911]

を

[@keithcoltron3171]

Q Electronics for Hybrids & Chips

[@user-lp3cf5yn5b]

Damn I feel like an idiot now for buying one for 80

[@NearFarMedia]

$80 isn't a bad price at all! I just got lucky at the junk store. 🙂

[@user-lp3cf5yn5b]

@@NearFarMedia lol! Yeah, that is a helluva deal. I just have to get out of my head and use the cap list from tekscopes group and change U1040 to see if there's anything actually wrong with the scope itself. All the lights come on, and there is a few dots, but no intensity control, none of the other controls work except for position of the different channels. Quite a few of the voltages are low at j119. I think I accidentally zapped the input of U1040 trying to get a probe onto the feedback pin because I didn't see any real variation at pin 1 of J232 when I turned R1292 following the troubleshooting flowchart and shorted FB to line up. I still don't have any good answers for why a good bit of the voltages are slightly low unless maybe it's bad caps. The only other thing I can think of is something loading the PS down.

[@NearFarMedia]

Yeah, a few of the caps do go bad on the PSU section. I believe there is one that is in maybe the 8V or thereabouts rail that is used to reference the other rails, maybe? I remember reading if that cap is bad, it can affect more than one voltage rail. Anyway, the tekscopes groups.io page and eevblog can get you up and running again I'm sure 🙂

[@user-lp3cf5yn5b]

I just wrote a whole long reply that died somewhere between my keyboard and KZbin servers, lol. Does anyone know a good sub for the high ripple current 672D caps? Tolerances and ratings have me bumfuzzled. The new caps you find are ±20% ,the 672D series were from -10 to +100% tolerance. Which tells me that I need to get slightly higher capacitance values. Also, can't find any caps with the original cap and voltage that has the same or higher ripple current ratings. So I'm losing my mind over here. On the U1040, can't find the original Motorola SOC123A. Supposedly the equivalent is TLP631. Vishay says CNY17-3 is the equivalent but the CTR is higher than the 631 or the other pn I found which was MOC1005. Any issues with using a "higher gain" higher CTR part for U1040?

[@NearFarMedia]

Don't worry too much about the tolerances. I like United Chemicon. Have a look at the KZE, KZH, KZM and KZN series (in order of increasing performance). If you like Rubycon, the ZL, ZLK, ZLH, ZLJ etc (in order of increasing performance) are very good too.