Repair/Restoration of a Tek Type 561B - Page 1
Forum section: electronics / repair

author: med6753
author_rank: Super Contributor
timestamp: April 30, 2020, 07:18:59 pm
content: The latest project here is this basket case Tek Type 561B. If I didn't get it REAL cheap I would have passed it by. It came with Type 3A72 Vertical plug-in and Type 2B67 Time Base plug-in.Front panel. It's all there just needs a good cleaning and sticker residue removed.Handle missing. I have leather strapping plus leather tools. Used them to successfully make new handles for a Type 535A. Both cabinet halfs are banged up and scratched. Will hammer out the dents and repaint.A look inside. It's complete but absolutely filthy. Before any testing will give it a complete dry clean.Front view of the plug-in's. Not too bad but inside tells a different story. Tube raiders struck. Both plug-in's stripped of all their tubes. I knew this when I went to look at it and decided to go forward anyway. The Type 3A72 has a B/W of only 650Khz. Pathetic. So I'll go out on Ebay for a better Vertical plug-in. The Type 2B67 Time Base plug-in is a decent unit but it would cost hundred's to re-tube it. So I'll also look for another Time Base plug-in.So once cleaned up next step is to check the filter caps for shorts. The Type 561B mainframe is actually pretty simple compared to other Tek's. It's basically a power supply, HV supply, and CRT. The vertical and time base circuits are all in the plug-in's. So I'm going to concentrate on getting the mainframe complete before investing in plug-in's.I'll update this thread as I make progress.

author: jxjbsd
author_rank: Regular Contributor
timestamp: May 01, 2020, 10:05:31 am
content: Thank you very much. I can see the wonderful repair process. I saw a 3a75 plug-in for $90, and the seller said it was an electronic tube hifi amplifier. But there is only 4m bandwidth.

author: med6753
author_rank: Super Contributor
timestamp: May 01, 2020, 01:55:12 pm
content: The cleaning process completed.The front panel came clean with all sticker residue removed except for a few scuffs. There was a clear plastic lens between the CRT face plate and the bezel that had deep scratches so I removed it. It may affect the light distribution of the scale illumination but that's no big deal.The covers have been removed and cleaned. Currently out for dent removal and repaint. The interior is now clean. Compare that with yesterday.This is the power supply/calibrator board. In order to gain access to the filter capacitors this board and all that perimeter wiring has to be removed. So I've decided rather than pulling it out and checking for shorts I'm going to do a mass replace. I am not an advocate of “re-forming” capacitors, especially ones 50 years old. It's false economy. Better to replace.I did some quickie checking and both the line fuse and the HV fuse are good. So that is very encouraging. I am also going to check the four TO-3 transistors on the rear heatsink. Next installment should have the covers painted and replaced.

author: Specmaster
author_rank: Super Contributor
timestamp: May 01, 2020, 02:13:46 pm
content: Thats a great transformation, almost as good as new

author: med6753
author_rank: Super Contributor
timestamp: May 02, 2020, 05:13:40 pm
content: Mechanical restoration essentially complete. The original remnants of the broken handle assembly were damaged beyond repair so it was removed. I have other alternatives in mind for a replacement. And the line cord needs a new strain relief.Next step is the electrical repair/restoration. The replacement capacitors have been ordered and should arrive Tuesday. Will provide an update when that process begins.

author: Specmaster
author_rank: Super Contributor
timestamp: May 02, 2020, 10:18:24 pm
content: What a difference a nice coat of paint makes

author: Kosmic
author_rank: Super Contributor
timestamp: May 03, 2020, 12:41:35 pm
content: Yep, looking goodI need to do the some thing on my Power designs PSU. They used also the same color as Tek on their casing.

author: Cubdriver
author_rank: Unknown
timestamp: May 03, 2020, 04:55:30 pm
content: Nice work, Mike. Shame that the tube vultures picked it clean. Mostly 6DJ8s missing?-Pat

author: med6753
author_rank: Super Contributor
timestamp: May 03, 2020, 07:34:44 pm
content: Quote from: Cubdriver on May 03, 2020, 04:55:30 pmYep, between the 2 plug-in's at least 10 of the tubes were 6DJ8 "Bugle Boys" which drive the audiophools rabid with delight. Along with several 6BL8's and 6AU6's. And I'm finding plug-in's going for stupid money on Ebay that have been raped too.

author: Cubdriver
author_rank: Unknown
timestamp: May 03, 2020, 08:45:40 pm
content: Yep. I accidentally bought some from a tube rapist. Was searching for a 3-series time base and found two plus a vertical one for pretty cheap as a buy it now. They'd been stripped, of course, but I snagged them anyway figuring that ultimately I'll re-tube them. After placing the order, I did a "see seller's other auctions" search only to discover he was also selling tubes from various Tek scopes.Part of me feels bad for in effect 'encouraging' him, but at the same time I may have saved those plug ins from the landfill. I dunno. I'm not looking forward to buying the tubes though, because yeah, it needs a bunch of them!-Pat

author: jxjbsd
author_rank: Regular Contributor
timestamp: May 04, 2020, 01:38:16 am
content: If you can buy electronic tubes made in China, you can replace them. Replace 6dj8 with 6n11, about $5-10 each, the performance is the same. Other types of electronic tubes should be inexpensive.

author: mnementh
author_rank: Super Contributor
timestamp: May 05, 2020, 11:56:23 pm
content: mnemsssh. I'm not really here.

author: coromonadalix
author_rank: Super Contributor
timestamp: May 06, 2020, 12:01:46 am
content: Nice to see dedicated people

author: jdragoset
author_rank: Frequent Contributor
timestamp: May 06, 2020, 02:02:17 am
content: Very nice work.Don't toss the CRT face plate.It can be buffed out or even plastic headlamp-lens restored.

author: nixiefreqq
author_rank: Super Contributor
timestamp: May 07, 2020, 08:39:00 pm
content: ahhhhhhh. that's the stuff.

author: med6753
author_rank: Super Contributor
timestamp: May 11, 2020, 05:58:14 pm
content: More work on this Type 561B.Got the power supply board removed. A chart and lots of pictures for the approx 40 wires that had to come off. Once removed and cleaned with IPA issues reared their ugly head. Evidence of some capacitor leakage corrosion. Evidence of some prior repairs. And in the lower left a burn and bodge repair. It looks like a resistor burned and rather than replaced was bypassed. I'll investigate further after completing the re-cap of the board.Here are the capacitor cans that were hidden behind the power supply board. They will all be removed and replaced with new on terminal strips on opposite side. I used this technique on the Type 535A restore and it worked well.I found reasonably priced (and complete) Type 3A6 Vertical plug-in on Ebay that should arrive this week. Still looking for a Time Base that is complete and reasonably priced.

author: Specmaster
author_rank: Super Contributor
timestamp: May 11, 2020, 06:17:08 pm
content: Oh dear that looks nasty, I hope that the board is not a multilayer otherwise you could be wasting your time and money recapping it. I'd check the board out first and see how many layers it is, keeping my fingers crossed that is repairable.

author: med6753
author_rank: Super Contributor
timestamp: May 11, 2020, 06:28:04 pm
content: Quote from: Specmaster on May 11, 2020, 06:17:08 pmIt's only 2 layer. Top side and bottom side. I checked out the circuit. It's for the -100VDC supply and it also supplies voltage to HV oscillator. The resistor was a 1.2 ohm in series between the transformer and the rectifier stack. Those 2 smaller diodes are replacements. I am going to assume the repair worked and for now I'll leave it. When I get it all back together I'll pull the fuse for the HV oscillator and make sure the -100V is OK. Then install the fuse and give it full beans and see what happens.

author: Cubdriver
author_rank: Unknown
timestamp: May 11, 2020, 06:35:24 pm
content: Damn!! There's something to be said for multi-pole connectors, huh? Nice work, Mike.-Pat

author: David Hess
author_rank: Super Contributor
timestamp: May 11, 2020, 06:46:43 pm
content: Quote from: jxjbsd on May 04, 2020, 01:38:16 amThe performance may not be the same if Tektronix was grading the tubes. Details would be in their common parts design catalog but I do not have the one for tubes.

author: m2circuits
author_rank: Newbie
timestamp: May 11, 2020, 06:58:57 pm
content: The 561 is a great scope. I have the original 561 with the tube PSU, and use it regularly. It's particularly useful for tube audio applications.If you're looking for an easier way to replace the multican caps I designed these PCBs a few years ago. They are available here:https://www.thetubestore.com/Multi-Capacitor-PC-BoardI restored a 561 with them and it was way easier than restuffing or using terminal strips. Here's a link to a blog I wrote about the project:https://m2sbench.wordpress.com/2019/06/02/tektronix-561-oscilloscope-repair/Cheers

author: Specmaster
author_rank: Super Contributor
timestamp: May 11, 2020, 07:02:54 pm
content: Quote from: med6753 on May 11, 2020, 06:28:04 pmWell t seems that you have it well under control so no need to be scared now that you've done your homework it'll be fine you'll see.

author: med6753
author_rank: Super Contributor
timestamp: May 12, 2020, 12:20:13 am
content: Quick update. The re-cap of the supply board is complete. There were only 4 electrolytics to change.But I discovered an interesting flaw and a clue as to why that 1.2 ohm resistor was burnt. C31 is specified as a 6.8uf/100V. But it's installed across the -100VDC bus. Now granted, older electrolytic capacitors had a wide voltage tolerance but that's cutting it damn close.And apparently the original did fail as evidenced by corrosion in that section of the board. And what was installed was a 7uf/250V as a replacement. That makes sense and I think it explains the cooked and bodged rectifier stack for the -100VDC supply. And of course my replacement capacitor is 6.8uf/100V as specified in the parts list. I installed it for now but it can't stay there. New electrolytics do NOT like over voltage in the least. I'll order a higher rated cap and I may in fact pull that one and install a 10uf/150V + as a temporary measure.Tomorrow I'll start on the cans.

author: Specmaster
author_rank: Super Contributor
timestamp: May 12, 2020, 12:31:51 am
content: You could always leave the 10uF 150V cap there once you swap it out for 100V 6.8uF cap. going up in value slightly is perfectly OK and a 50% headroom in voltage is adequate I'm sure.

author: med6753
author_rank: Super Contributor
timestamp: May 12, 2020, 12:38:46 am
content: Quote from: Specmaster on May 12, 2020, 12:31:51 amYep, I know. I do that quite often. These old Tek's have some odd ball capacitor values in them that can be hard or impossible to source.For example: 180uf/250V. If you can find them they are super expensive. 220uf/250V standard value works a treat.

author: med6753
author_rank: Super Contributor
timestamp: May 13, 2020, 11:10:29 pm
content: Received the 3A6 Vertical Plug-in. Not too dirty and complete but there was some shipping damage.The front panel. The detent for the Channel 1 variable is broken at the pot. I have the broken piece and it should be repairable.View inside. This is a true “hybrid” plug-in and represents the revolution in electronics packaging that was taking place in 1960's. First we have two sub-minature 7586 high frequency vacuum tubes called “nuvistors”. When FET's appeared around the same time they became obsolete. In between the nuvistors are discrete transistors. And in the background conventional 7 and 9 pin minature vacuum tubes. I believe the Tek 500 series and plug-ins were the last designs to incorporate vacuum tubes in their design. Everything beyond that went either discrete solid state or starting in the early 1970's to IC's.Damage. Both output peaking coils have broken posts on the top. One looks like it happen before and was glued. It appears all the coil wire is there and in tact. So I will remove the coils and carefully glue the wires and use emory paper on the wire ends to solder additional wire and reattach them to those large resistors. It will take time and careful prep but it should work.

author: med6753
author_rank: Super Contributor
timestamp: May 14, 2020, 04:15:25 pm
content: Started on the can replacement. Three done so far. 2 more to go.The vanquished.With those cans removed there are more areas accessible to clean out the remaining dirt.

author: Cubdriver
author_rank: Unknown
timestamp: May 14, 2020, 04:58:52 pm
content: Mike, if your inclination is to shitecan the cans, perhaps I could prevail upon you to save them and at some point I'll send you what it should cost and you could to mail them to me. I'll then restuff them and keep them ready to swap out on mine to save time, as I like to do things the hard way.-Pat

author: med6753
author_rank: Super Contributor
timestamp: May 14, 2020, 05:18:23 pm
content: Quote from: Cubdriver on May 14, 2020, 04:58:52 pmIt wasn't just an inclination....it was an absolute intention to shit can them.But if want them I'll save them and send them to you. I should finish with the other two by tomorrow so next week if you want them that soon. Contact me via PM.

author: Cubdriver
author_rank: Unknown
timestamp: May 15, 2020, 07:01:46 am
content: Quote from: med6753 on May 14, 2020, 05:18:23 pmYes, please save them for me. I'll be in touch via PM; hitting the sack now.-Pat

author: med6753
author_rank: Super Contributor
timestamp: May 15, 2020, 06:05:22 pm
content: Re-cap of the cans finally complete. Took longer than anticipated because of the tight area.Backside view of the new capacitors on terminal strips.Front view. The power supply board can now be reinstalled then will apply power. That will be next installment.Pat, send me a PM and I'll get the old caps on their way to you early next week.

author: med6753
author_rank: Super Contributor
timestamp: May 22, 2020, 07:19:54 pm
content: Update of this Type 561B restoration. Two major set backs and some progress.First major set back: Yes, I should have used a series lamp limiter upon first try at power up. I didn't and I paid the price. Even though I triple checked the perimeter wiring on the power supply board I did swap 2 wires with very similar color codes. The result was approx 300V applied to an area that should only see 125V. Yes, a lot of flames and magic smoke. The carnage was 4 blown transistors and 4 carbon comp resistors vaporized. 3 of the transistors are common types still available. But the TO-3 series regulator is Tek spec and unobtanium. I was able to cross reference a sub but thanks to forum member cycle_collector he had a stock in the vast stash of Tek parts he has for sale. Thanks to him I have an exact replacement. I hope to have all repairs completed in a few days.The next setback: One of the broken peaking coils on the 3A6 Vertical plug-in is open which makes the plug-in unusable. Replacement unobtanium. Looking for an alternative but what complicates matters is that it's a 3 wire center tapped adjustable coil. I haven't totally given up bodging some sort of fix but in the meantime I found a reasonably priced 3A3 that I should have in a few days.Some progress: The 2B67 Time Base plug-in which was stripped of all it's tubes will now be put into service. It's tube complement is one – 6BJ7, two – 6BL8, and six – 6DJ8. I had the 6BL8's on hand. The 6BJ7 cost $10 USD and will arrive early next week. But the score was I won an Ebay auction for five – 6DJ8 for the sum of $19.50. They are Sylvania marked non-Bugle Boy not matched but tested which is why they were cheap. Audiophools frown on anything other than Bugle Boys. As far as I'm concerned I'm sure they will work just fine. And I was able to scrounge one more 6DJ8 so all this plug-in needs is the 6BJ7.

author: Cubdriver
author_rank: Unknown
timestamp: May 22, 2020, 07:30:36 pm
content: Great score on those 6DJ8s, Mike!-Pat

author: med6753
author_rank: Super Contributor
timestamp: May 23, 2020, 05:35:17 pm
content: How quickly fortunes change. The Type 561B is repaired and now powers up. No drama, no magic smoke.The 4 voltages (+300V, +125V, -12.2V and -100V) are just about on the mark without any plug-ins installed. I will make final adjustments after both plug-ins are in place.I even have a spot of the CRT which says I have HV. (I turned the intensity down after the pix so as to not burn a spot in the phosphor)Next step. Awaiting delivery of the 3A3 Vertical plug-in and the 6BJ7 tube for the 2B67 Time Base plug-in.Sorry for the lousy focus. Camera phone doesn't do well on close ups.

author: Smoky
author_rank: Frequent Contributor
timestamp: May 23, 2020, 06:32:31 pm
content: These two plug-ins were included with an old 310 oscilloscope I bought at a garage sale.Parts are missing from both. One is a 3A1 and the other is 3B1. Both are corroded from the North Carolina humidity.I do see about six coils with three wires on them.I'll be happy to pull them and even measure them on my LC53 or LC102 if needed.

author: med6753
author_rank: Super Contributor
timestamp: May 23, 2020, 07:36:39 pm
content: Quote from: Smoky on May 23, 2020, 06:32:31 pmI just checked the 3A1 service manual and yes, peaking coils L361 and L371 on your plug-in are the same P/N as used on the 3A6. Tek P/N 114-151. I would greatly appreciate getting them from you. Hit me up with a PM and we'll talk.Thanks!

author: jxjbsd
author_rank: Regular Contributor
timestamp: May 24, 2020, 02:48:23 am
content: Quote from: Smoky on May 23, 2020, 06:32:31 pmIt seems that there are many friends who like old-fashioned Tektronix oscilloscopes. I need to save money, buy a bigger house, or stop collecting oscilloscopes

author: med6753
author_rank: Super Contributor
timestamp: May 24, 2020, 04:01:44 am
content: Quote from: jxjbsd on May 24, 2020, 02:48:23 amOnce you start collecting you can't stop. And the Type 561B is small compared with this monster.

author: jxjbsd
author_rank: Regular Contributor
timestamp: May 24, 2020, 04:01:21 pm
content: So I only collect things from the transistor era. The small size is one aspect, mainly because Tektronix oscilloscopes with electron tubes are hardly seen in China.

author: med6753
author_rank: Super Contributor
timestamp: May 24, 2020, 05:21:00 pm
content: More work on Type 561B mainframe....The original incandescent pilot lamp was burnt out. It uses miniature colored lamps that I didn't even bother to look for. Replaced it with this LED assembly. But the lamp operated on 6.3VAC so the LED required the addition of a diode, capacitor, and current limiting resistor. This is the result.The mainframe is now complete and the balance of the restoration is pending the arrival of the parts for the plug-ins.

author: med6753
author_rank: Super Contributor
timestamp: May 25, 2020, 04:38:18 pm
content: The new carrying handle. Forgot all about it. Replaces the original which was damaged beyond repair. I have to notch the covers to clear the mounting screws.No deliveries today because of our National Memorial Day.

author: med6753
author_rank: Super Contributor
timestamp: May 26, 2020, 07:57:16 pm
content: The Type 3A3 Vertical Plug-in arrived as well as the 6BJ7 tube for the Type 2B67 Time Base Plug-in.The Type 3A3 is very clean and appears complete. Deoxit'ed the switches and controls.Time to install and power up as a complete unit.

author: med6753
author_rank: Super Contributor
timestamp: May 26, 2020, 08:02:45 pm
content: Close but no cigar. The PSU voltages are set. The -100VDC is the only adjustment and it serves as a reference for the other PSU voltages and they are in spec.With both plug-in's installed there is no trace. If I pull the Type 3A3 I get a trace. The Type 2B67 is sweeping but that is also intermittent. So progress but additional troubleshooting is needed.At least there's no magic smoke.

author: med6753
author_rank: Super Contributor
timestamp: May 27, 2020, 12:08:24 am
content: Troubleshooting the Type 3A3 Vertical Plug-in and found the issue.One vertical deflection plate had +165V on it (normal). The other vertical deflection plate had -76V on it (definitely not normal).See schematic. R679 (8K/3W) is open killing the B+ to pin 9 of V674.The open resistor is top far left. I'll have to see if I can cobble something together from my parts stash.

author: med6753
author_rank: Super Contributor
timestamp: May 27, 2020, 03:37:26 pm
content: Progress and more issues have shown up.Replacement of the 8K/3W resistor in the Type 3A3 Vertical Plug-in fixed the no trace issue. Now have full control of a base line trace both vertically and horizontally.The Type 2B67 Time Base refuses to have trigger lock. Comes close but then drifts. Extremely touchy adjustment of the Stability and Trigger Level. In order to troubleshoot this I may have to build up an extension cable so the plug-in can be operated outside the scope to gain access to the component side. But I'm going to hold off until the Type 3A6 plug-in is repaired in case there is a compatibility issue with this Type 3A3.Other issues:The Calibrator is totally dead. I suspect it might have gotten fried when there was the fireworks. That's low priority right now.Bigger concern is the CRT. It's not as bright as it should be and it is displaying what is called “double peaking”. As you turn up the intensity it gets brighter, then darker, then brighter. That is a sure sign of a worn out CRT with many hours on it. I will be checking the CRT bias and HV but I doubt that's the problem. The CRT is near end of life but right now still usable with a sharp, if someone dull, trace.

author: med6753
author_rank: Super Contributor
timestamp: May 29, 2020, 03:30:42 pm
content: A public thank you to fellow forum member Smoky. He generously sent me 2 new peaking coils for the Type 3A6 Vertical plug-in. Now installed and this plug-in is ready for testing.But unfortunately the Type 561B mainframe has a new issue that must be worked out first. More later.

author: med6753
author_rank: Super Contributor
timestamp: May 29, 2020, 05:58:03 pm
content: One step forward, 2 steps back. Another setback on this restoration.The CRT may not be defective. Measured the HV and it's -1.6KV. It should be -3.3KV. Adjustment of the HV control yielded no difference. Decided to check the primary side of the HV oscillator and I accidentally shorted the collector of the TO-66 output transistor to ground. The 125ma HV fuse blew and I was hopeful that's all that went out. Not the case. Lost that transistor. Got one coming from Ebay but this project is on hold until it's replaced.I suspect the low HV is due to an open resistor in the focus divider. It's a very common issue. So while I'm waiting for the replacement transistor I'm going to pull the entire HV assembly and check all the resistors.

author: Cubdriver
author_rank: Unknown
timestamp: May 29, 2020, 06:37:04 pm
content: Damn. We need to get you some test prods with everything but the very tip insulated! I hope that the transistor was all that it took out and you can get back to business once the replacement arrives. That's gotta be frustrating!-Pat

author: med6753
author_rank: Super Contributor
timestamp: May 29, 2020, 07:09:37 pm
content: It wasn't the test lead. I was going to scope the oscillator signal after verifying all the DC voltages were correct. I went to clip the ground lead on the chassis not realizing I was right near where the transistor was mounted. Saw a little spark and had an "aw shit" moment. The ground clip also contacted the collector of the TO-66 transistor. HV fuse blew but it was too late.

author: Cubdriver
author_rank: Unknown
timestamp: May 29, 2020, 07:36:42 pm
content: Quote from: med6753 on May 29, 2020, 07:09:37 pmThe protection circuit obviously failed, then. Normally the semiconductor blows to protect the fuse!-Pat

author: bitseeker
author_rank: Super Contributor
timestamp: May 30, 2020, 02:16:33 am
content: Condolences, med.Hang in there!

author: med6753
author_rank: Super Contributor
timestamp: May 30, 2020, 02:18:12 am
content: I (almost) never give up.

author: jxjbsd
author_rank: Regular Contributor
timestamp: May 30, 2020, 02:51:45 am
content: I like stubborn people, you will not be defeated by difficulties.However, IMHO, there are many accidents caused by humans.

author: Mr. Scram
author_rank: Super Contributor
timestamp: May 30, 2020, 12:34:56 pm
content: Quote from: Cubdriver on May 14, 2020, 04:58:52 pmI understand why people don't want to bother with restuffing old cans but their look can't be beat.

author: med6753
author_rank: Super Contributor
timestamp: May 30, 2020, 02:48:46 pm
content: Starting to disassemble the HV supply boards. I definitely have my work cut out for me. In order to get those 2 boards out all that cabling plus the two HV diodes from the HV transformer have to be completely unsoldered. Yikes!To the left is the TO-66 HV Oscillator transistor that I FUBAR'ed. Luckily the replacement is also the obsolete TO-66 case so it should go in place without any hassle. I'll have the replacement on Tuesday.

author: David Hess
author_rank: Super Contributor
timestamp: May 31, 2020, 06:13:16 pm
content: Those little ones are hermetically sealed solid tantalum capacitors; I have never seen one fail.

author: med6753
author_rank: Super Contributor
timestamp: May 31, 2020, 06:57:52 pm
content: Quote from: David Hess on May 31, 2020, 06:13:16 pmDavid, where do you see tantalum capacitors? Trust me, I know tants quite intimately from working on later Tek's. This guy doesn't have any.

author: David Hess
author_rank: Super Contributor
timestamp: June 01, 2020, 09:17:33 pm
content: Quote from: med6753 on May 31, 2020, 06:57:52 pmThe photograph here:https://www.eevblog.com/forum/repair/repairrestoration-of-a-tek-type-561b/msg3062698/#msg3062698

author: med6753
author_rank: Super Contributor
timestamp: June 01, 2020, 09:44:13 pm
content: Quote from: David Hess on June 01, 2020, 09:17:33 pmIf they are tantalums the parts list is mum on that fact and I replaced them with standard aluminum caps. No issues that I can see.

author: Specmaster
author_rank: Super Contributor
timestamp: June 02, 2020, 07:18:50 am
content: For a minute there, I thought David meant those big arse metal canned diodes

author: med6753
author_rank: Super Contributor
timestamp: June 02, 2020, 12:04:33 pm
content: I think David is correct. They could possibly early versions of "wet" tubular tantalums. His observations is that he has never seen one fail. Well I have, one than once. These same variety of tubular tants are used on 465/475 scopes on the input to the HV Oscillator. Either two 22uf in parallel or one single 47uf. They have a nasty habit of shorting out and taking the HV fuse with them.

author: David Hess
author_rank: Super Contributor
timestamp: June 03, 2020, 04:11:39 pm
content: Quote from: med6753 on June 02, 2020, 12:04:33 pmThey are still made for the highest reliability and performance applications and you can buy them from Mouser or Digi-key or whoever if you can accept the high price and you know what to look for like the T110 series from Kemet or the Sprague 150D series (1) found in the 465/475 series of oscilloscope. They are distinct from the even better wet tantalum parts and in an entirely different class compared to the common epoxy molded solid tantalum capacitors.The input decoupling capacitor for the high voltage inverter in the Tektronix 465/475 is a particularly demanding application explaining why Tektronix used that part. Their early switching power supplies also used them. An aluminum electrolytic or epoxy packaged solid tantalum would have to be much larger and would still have lower reliability or operating life. A modern polymer aluminum electrolytic or polymer tantalum might be a good replacement.(1)https://www.mouser.com/Passive-Components/Capacitors/Tantalum-Capacitors/Tantalum-Capacitors-Solid-Leaded/150D-Series/_/N-75hr3?P=1z0z819Z1yzvd7x

author: SeanB
author_rank: Super Contributor
timestamp: June 03, 2020, 05:32:36 pm
content: The small ones are CTS13 series wet slug tantalum’s, usually ultra reliable, at least till the case corrodes through, or you reverse bias it, and it turns into a pretty good popgun. The rubber sealed ones are in general pure crap as they age, and replacing with the same value, or the next value up, as they have odd values like 82uF, 150uF, 330uF and such, and next voltage up in a low ESR good quality electrolytic is worth it, though you will probably only find the replacement units as radial capacitor, and will need to sleeve the one lead to fit the board.Wet slug is available up to around 10000uF 100V though the price is in the stratosphere for them, and you special order them from Vishay. But they do come with a really good guarantee, and a per unit certification.

author: Specmaster
author_rank: Super Contributor
timestamp: June 04, 2020, 08:34:40 am
content: Those wet tants are quite common in Russian radios.

author: David Hess
author_rank: Super Contributor
timestamp: June 04, 2020, 09:48:17 pm
content: I could not tell if they were wet or dry from the photograph so I said "sealed solid tantalum capacitors".I have had a couple of the wet ones leak, and of course they lasted decades, but never a failure of the solid ones yet.I am not exactly sure how these capacitors perform as far as ripple current rating and high frequency ESR because no datasheets say but Tektronix seems to use them where these were important.

author: mnementh
author_rank: Super Contributor
timestamp: June 08, 2020, 07:00:07 pm
content: *pokes the thread*Any news,med?mnem

author: med6753
author_rank: Super Contributor
timestamp: June 08, 2020, 07:47:12 pm
content: Not yet, still waiting on the last part to be delivered. Should be by Wednesday.

author: med6753
author_rank: Super Contributor
timestamp: June 11, 2020, 05:22:48 pm
content: Update. Making headway. Several items resolved.First, The HV has been restored after my FUBAR in destroying Q219 and D217. (See schematic) It was suggested in one of our Discord sessions in the TEA Thread that it appeared that the upper HV rectifier (D221) was replaced and might be the wrong P/N. I replaced it with an OEM part and now the HV adjusts to -3.3KV spec. But the CRT is still not as bright as it should be which seems indicate it's near end of life. I'm going to check the bias but I doubt it's going to make much difference. But we'll see. It's usable as is as long as you don't shine a light directly on the screen.The Trigger issue with the Type 2B67 Time Base is fixed. Needed additional deoxit of the controls. It now has rock steady trigger. I inserted the Type 3A6 Vertical plug-in and I get a trace on both channels but doesn't pass a signal. So that will need some additional troubleshooting. For now will use the Type 3A3 Vertical plug-in.Left to do:Adjust CRT biasTroubleshoot the Type 3A6 plug-inTroubleshoot the calibrator

author: madao
author_rank: Frequent Contributor
timestamp: June 11, 2020, 05:50:11 pm
content: Did runs guy without problem over few hours ?This transformer with brown potting has common failure: thermal runaway after bad storaging by high humidity. (Same as Tek 547 HV Transformer)My Tek 568 has this problem and is replaced by improved transformer with "glibber"-potting.http://w140.com/tekwiki/wiki/HV_transformersGreetingsmatt

author: mnementh
author_rank: Super Contributor
timestamp: June 11, 2020, 06:20:41 pm
content: Looking goodmed!I guess I'm just not seeing it; that trace looks beautiful from here. Especially for 60-year-old photons!mnem

author: med6753
author_rank: Super Contributor
timestamp: June 11, 2020, 06:24:04 pm
content: Quote from: madao on June 11, 2020, 05:50:11 pmThe HV transformer in the 561B is not potted like the 547 or the 568. Much lower HV. -3.3KV vs -10KV.

author: med6753
author_rank: Super Contributor
timestamp: June 11, 2020, 06:26:36 pm
content: Quote from: mnementh on June 11, 2020, 06:20:41 pmIt does look good. Nice and sharp. But that is maximum intensity. At that level you should have some blooming. There is none. And if you shine a light on the screen it washes right out.I tried adjusting the bias and it really made no difference.

author: madao
author_rank: Frequent Contributor
timestamp: June 11, 2020, 07:23:09 pm
content: Quote from: med6753 on June 11, 2020, 06:24:04 pmIt doesn't look same, but share same problem (!), sad. Not often as 547 hv transformer. I have two case with this problem. 568 got NOS improved transformer (120-0466-01), other 561B is picked up for free.

author: med6753
author_rank: Super Contributor
timestamp: June 11, 2020, 08:11:20 pm
content: Quote from: madao on June 11, 2020, 07:23:09 pmIt has been on for several hours now and no issues. There is another failure point to watch for with these scopes. The 6.3VAC CRT filament is raised to HV through a resistor to prevent arcing between the filament and the cathode. Sometimes the power transformer develops a leakage path which shorts out the HV. The solution is to mount a separate filament transformer that is Hi-Pot certified inside the case.

author: med6753
author_rank: Super Contributor
timestamp: June 12, 2020, 08:27:43 am
content: This project is like a see-saw. Two steps forward and one step backward.The Amplitude Calibrator is fixed. Turned out to be a dirty switch. Deoxit took care of it. This is surprising because the calibrator uses the +125V supply as it's source and that's the section of the PSU that had the spectacular flames and smoke the first time I installed the PSU board and accidentally swapped 2 wires and applied +300V to that area.The 3A3 plug-in has successfully had it's gain and DC balance adjusted on both channels. The gain on both channels needed to be increased an equal amount apparently due to the decreased sensitivity of the weak CRT.I made an offer on Ebay for a Type 3B3 Time Base plug-in that was accepted because.......The Type 2B67 Time Base has gone out to lunch again and now refuses to trigger as before.Was working fine and suddenly quit. I also have the Type 3A6 Vertical plug-in which has a trace on each channel that I can move vertically up and down but if you apply a signal it's a flat line. In order to troubleshoot these plug-in's I need an extender cable so I can access the component sides of each. I can fairly easily make one but the issue is the connectors. They are Amphenol 24 pin connectors but I have no idea what the Amphenol P/N is. I can salvage a male off a junker plug-in but the female side is the issue. Google search on the Tek P/N revealed a source but rather than list a price they want you to submit an RFQ. Oh goody, I wonder how far I'll have to bend over and spread them when I submit it.Speaking of the CRT. There's one on Ebay right now. Supposedly brand new. They want $100 USD plus shipping. They're nuts.That's more than I paid last year for a CRT for the 7904. Granted, that one was used but still...I think a 561B CRT is worth maybe $50 USD at most. But this project has already turned into a semi money pit and unless the old CRT takes a complete dump it's staying in place. I got this entire Type 561B real cheap but it certainly ain't cheap now. But I'm a sucker for old Tek's.

author: tautech
author_rank: Super Contributor
timestamp: June 12, 2020, 08:33:25 am
content: Keep those knees firmly together mate !

author: David Hess
author_rank: Super Contributor
timestamp: June 12, 2020, 08:59:42 pm
content: Quote from: med6753 on June 12, 2020, 08:27:43 amCRT deflection does not change with age or use but acceleration voltage directly affects it.CRT deflection sensitivity varies between units and 560 series plug-ins directly drive the CRT so the plug-ins need to be calibrated for each mainframe. In most other Tektronix mainframes, the plug-ins drive internal amplifiers which are standardized for a specific sensitivity.

author: med6753
author_rank: Super Contributor
timestamp: June 12, 2020, 09:18:38 pm
content: Quote from: David Hess on June 12, 2020, 08:59:42 pmI realize 560 series plug-in's directly drive the CRT. And that's why the gain adjustment is on the front panel. Except this 3A3. For some reason I guess driven by it's design the gain adjustments are inside. Not convenient if you need to move this plug-in to another scope.But even the 500 series as well as the 7000 series plug-in's had gain adjustments on the front panel even though they drove an internal amplifier rather than the CRT directly.

author: David Hess
author_rank: Super Contributor
timestamp: June 12, 2020, 10:00:28 pm
content: Quote from: med6753 on June 12, 2020, 09:18:38 pmBut the variation in gain for the 500 and 7000 series is much less. In practice the gain does not need to be adjusted between mainframes if they are standardized.

author: med6753
author_rank: Super Contributor
timestamp: July 25, 2020, 04:52:41 pm
content: Been a while since I updated this thread and this repair/restoration is pretty much complete. There's still a few plug-in's that need repair but my immediate objective was to get the mainframe fully functional with functional vertical and time base plug-in's. That has been accomplished and as a bonus it also has a replacement CRT which is at least 2x brighter than the original which suffered from low emission.Thanks to fellow blog member nixiefreqq I was able to get another Type 561B with Type's 3A74 and 3B4 plug-in's. This scope was from his local CL and he picked it up for me. It had been stored in a very damp environment for years and was in fair to poor condition. The Type 561B and 3B4 will be for parts. In fact, the 561B has already given up it's CRT which is in excellent condition and as mentioned above is nice and bright, and sharp. The Type 3A74 Vertical plug-in appears to be in decent shape and will eventually be checked out.The scope has gone through several burn-in cycles with no issues. So this one is a wrap.

author: bitseeker
author_rank: Super Contributor
timestamp: August 02, 2020, 06:41:31 am
content: Congrats, med! Such a cool scope.