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Old 10th Jul 2019, 2:27 am   #121
Argus25
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Default Re: Tektronix 465b oscilloscope CH1 & 2 issues

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Originally Posted by Radio Surfer View Post

This afternoon, I'll make up a some sort of wave generator, depending on what I've got to hand, and test the scope out a bit more. Hopefully I can feedback results and any questions or issues later.

Regards, Richard
It is an interesting task to properly calibrate these Tek scopes. A sine wave generator is useful for final checking, very tedious for checking the response at all frequencies.

The ideal generator required for a proper calibration is the Tek PG506 (or similar), a plug in, which has fast rise square waves over a range of frequencies, these are excellent and can be a improved a tad with a tunnel diode pulser for a perfectly rectangular step, but the PG506 is so good that its hardly required, except perhaps for a 400MHz bandwidth scope such as a 2465B. The PG506 is also an amplitude calibrator.(Tek also make another timebase calibrator plug in the TG501)

I once knocked up a brief article on the principles of vertical amplifiers and their calibration in Tek scopes, it may be of some interest if you are planning a calibration of the vertical amplifiers:

http://worldphaco.com/uploads/TEKTRO...ILLOSCOPES.pdf

If you look at page 24 of this article you can see a photo of both the PG506 and TG501 in the one power supply housing (a TM503B). These are the two instruments required to perfectly calibrate Tek scopes (the Tek sinewave generator is not really needed). Although there are other equivalent generators, I have never found anything else as good for the task, especially since the PG506 has the correct high level output to trigger the tunnel diode pulse too:

http://worldphaco.com/uploads/TEKTRO...THE_DS1225.pdf

(Of note: if a sine wave generator is to be of any use calibrating a scope, it has to be a leveled type, Tek made at least two plug-ins for this purpose, SG503 and the SG504 this one covers frequencies up to 1GHz and it has a leveling head)

Last edited by Argus25; 10th Jul 2019 at 2:40 am.
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Old 10th Jul 2019, 2:56 am   #122
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Default Re: Tektronix 465b oscilloscope CH1 & 2 issues

Hi!

Regarding 465/465B original paper manuals, these have now fallen victim to the rotten U.S. "Tekfoolery" syndrome with vastly inflated postage charges in recent months, so I had to buy one of Artek's CDs for mine – a 465B with the DM44 on top – the fault it has is a very faint random blur of light on the screen and the DM44 shows "3.3.3.3!"

Incidentally there's not a single complete 465/465B download on the net – every one I've found is missing Diagram 9, Horizontal Amplifier, and I believe Members have said there's Trigger Circuit info gone astray as well!

It's buried at the bottom of my wardrobe at the moment awaiting it's turn on restoration until I can get a bench RCL meter after next week!
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It's an enigma, that's what it is! This thing's not fixed because it doesn't want to be fixed!
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Old 10th Jul 2019, 10:59 am   #123
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Default Re: Tektronix 465b oscilloscope CH1 & 2 issues

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Originally Posted by Chris55000 View Post
Incidentally there's not a single complete 465/465B download on the net – every one I've found is missing Diagram 9, Horizontal Amplifier, and I believe Members have said there's Trigger Circuit info gone astray as well!
For anyone interested in 465B manuals in general (including download versions) post #53 of this thread might be worth a read.

Alan
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Old 10th Jul 2019, 12:14 pm   #124
Radio Surfer
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Default Re: Tektronix 465b oscilloscope CH1 & 2 issues

Morning,

Thank you for all the comments and advice. I'll check out Mr B's (careful with his pennies) advice on probes. Thanks for the comment on the condition of the scope panel Alan, at least the barn and front cover kept it from being marked. I'm not sure how long it was in storage, but the previous owner said it was "years". Given the levels of dust and muck I'd agree with that.

Very interesting notes by Argus25 on calibration. I wish I could "knock" something up as comprehensive. At the moment, I'm breaking this process into 3 sections; Firstly, as per this thread, getting the scope back to a working condition and I think (hope) I'm close to acheiving that; Secondly, learning how to drive the thing and I'm just out of first gear now with a few "kangaroo hops" along the way; Finally, calibration if I ever have the knowledge and confidence to do this. I've printed the notes Argus attached and placed them in my manual. Am I the only one that reads something interesting and can never find it again?

I see that Chris55000 has a DM with default number 3.3.3.3, the time to worry is when that changes to 6.6.6. ,!!! I also smiled at the comment of having it stored at the bottom of the wardrobe. I bet test gear is stored all over the place in people's homes, I've just cleared out a space under the stairs for mine, dry and about as far from the sea air as I can get it.

Since my last post, I've managed to get another reluctant button and switch working, this time the ALT switch. Another squirt of Servisol, leaving to soak a bit longer and then pushing the button 30 or so times seems to have done the trick. As the attached image shows, I can highlight a signal and 'focus' in on it as per the trace below. I think this is why I was struggling the other day with my understanding when it was actually a faulty switch not behaving all along.

Regards, Richard
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Old 10th Jul 2019, 12:19 pm   #125
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Default Re: Tektronix 465b oscilloscope CH1 & 2 issues

Having the front cover for protection is a big plus and really helpful when removing the case. Mine's missing of course.

Alan
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Old 10th Jul 2019, 2:39 pm   #126
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Default Re: Tektronix 465b oscilloscope CH1 & 2 issues

I have a 7A26 dual-trace amplifier with a gain problem and I was noodling through Tekwiki to see if I could find any clues. Something that leapt out at me came as a bit of a surprise, it concerned the attenuator modules. By and large, these are the same part-numbers as those in the 4xx series of scopes - indeed, the attenuator I have sent off to Richard was taken from a parts-donor 7A18. It is mentioned that these attenuator modules have the resistors soldered to the pins with low-melting-point solder and that this can fail. Re-seating the module can effect a temporary repair, but a possible fix is to pop the clip-on top of the module and re-solder the joints, obviously being very careful not to use too much heat and not to melt anything else. Oddly enough, this isn't mentioned in regard to the 4xx scopes.

I have had a look inside these modules in the past and I might even have tried this fix at some time, but I can't remember. If anyone else has any definite experience of this, perhaps they could enlighten us? I can't see the suggestion of trying to clean the resistor elements with meths or IPA resulting in much joy, except in that it might remove conductive muck from the plates of the trimmer capacitors.

I, too am surprised at how good your 465B looks, Richard. That must have been a very kind barn.

With regard to possible calibration once you've got the scope functioning, you will need access to a PG506, TG501 and SG503 in a TM503. Rather than me describing what these do, have a look in TekWiki and the "Calibration" section of the Service Manual. I have all three of these items, as well as another TM503, a TM504, SC502, PS503A and a FG504 in need of attention. Unfortunately, I live in London, so I'm too far away to help. But don't discount the fact that there might be other Forum members who may be much closer to Tiree. You could also do a search of eBay to see if anyone is selling a set. Expect to pay about £300 for all four items, if they are all functioning correctly.

Colin.
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Old 10th Jul 2019, 2:47 pm   #127
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Default Re: Tektronix 465b oscilloscope CH1 & 2 issues

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Originally Posted by ajgriff View Post
Having the front cover for protection is a big plus and really helpful when removing the case. Mine's missing of course.

Alan
Keep looking, Alan. I recently got a front-cover with the "penthouse" to use with the 475A/DM44 that I "inherited" from MrB. It cost me a fair amount, as they are even rarer, but it is absolutely pristine. A lot of these are cracked, chipped, soldering-iron burned, marked with indelible ink or otherwise imperfect, but not this one! They are invaluable when storing the scope and removing the casing. Without one you are likely to damage knobs or even worse.

Colin.
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Old 10th Jul 2019, 4:05 pm   #128
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Default Re: Tektronix 465b oscilloscope CH1 & 2 issues

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Originally Posted by ColinTheAmpMan1 View Post

I, too am surprised at how good your 465B looks, Richard. That must have been a very kind barn.

Colin.
Hi Colin, I wish I'd taken some before pictures, I was just too keen to get started, but as you say, the covers are invaluable to help save delicate parts and for standing on end. So I'd encourage Alan as well to keep a look out. Fortunately, as I've noted it was just covered in dust and general muck (I sound like Larry Grayson at this point) which ear buds and soapy water soon removed. IPA or meths was used for stubborn stains, mainly residue glue from labels, oil and paint spray. The front cover and the top wallet helped save the scope from any real damage. They are quite faded, but are both in one piece with no cracks, tears or splits which is good. There was just one of the plastic nuts missing from the wallet where it bolts to the supporting metal plate, but I found a brass nut to fit. I've since treated the wallet with some leatherrette cleaner/conditioner that I used on an old classic car I once had. Helps to soften the material a bit to avoid splits. It smells less fusty now too.

Regards, Richard
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Old 10th Jul 2019, 5:32 pm   #129
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Default Re: Tektronix 465b oscilloscope CH1 & 2 issues

With regard to Colin's post #126 paragraph 2, I managed to repair a Tek thick film 5x attenuator module that had one leg dry jointed where it joined the thick film network. I used my smallest temperature controlled iron (a Weller MCP) and worked very quickly, adding a very little 24swg 60/40 solder. It was a while ago, (2011) but I think the faulty joint was the leg in the middle of the left-hand side in the photo.

Ron
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Old 10th Jul 2019, 5:44 pm   #130
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Default Re: Tektronix 465b oscilloscope CH1 & 2 issues

That was a bit of a nifty repair that one.

Usually when I have found them it's the 100x attenuator has a burned thin film resistor in it
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Old 10th Jul 2019, 6:04 pm   #131
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Default Re: Tektronix 465b oscilloscope CH1 & 2 issues

Ron, Thanks for that info and photo. I think I probably did do one of those repairs once. Plenty of light, magnifying-glass, something to hold the module nice and firmly and the tiniest tip on a soldering-iron that you can imagine.....

Colin.
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Old 10th Jul 2019, 9:04 pm   #132
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Default Re: Tektronix 465b oscilloscope CH1 & 2 issues

I agree with Colin about sourcing a front cover but no luck thus far. For now a rudimentary wooden stand does the job for case removal and servicing. The dust cover (aka old tea towel) helps protect the scope from the elements when it's not on active duty. Not very elegant I'm afraid.

Seeing the photo of the attenuator module makes me think that my once faulty attenuator suffers from a poor pin connection which was 'cured' by re-seatng. The meths might have helped to clean the dodgy solder joint. Not ideal but it's working for the moment so I'll leave well alone.

Off topic but I'm jealous of Ron's Weller MCP iron as I acquired one a while ago with the remains of an old tip firmly stuck in the element casing. Impossible to remove without destroying the element and I've never managed to find a replacement. I have a spare tip though which is really not much use as things stand.

Alan
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Old 10th Jul 2019, 11:51 pm   #133
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Default Re: Tektronix 465b oscilloscope CH1 & 2 issues

One thing about the TEk SG503 sine wave generator, its amplitude leveling is internal with a detector and a feedback loop as a servo which controls the emitter current of the oscillator transistor.

The tank circuit is formed from a V/C (that looks like it was a radio part) and it has continuous and stable tuning over the set ranges with the digital frequency meter, quite nice. They also have a single ceramic bolt down RF output transistor and can deliver a modest power output.

In an experiment I opened the control loop and applied a control signal to the oscillator and it makes for a very linear amplitude modulator. So it is very easy to convert the SG503 into a darling of a Pantry transmitter where you can set the carrier frequency where you like. So the SG503 can have more than one use. I use one of mine for this application.
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Old 11th Jul 2019, 11:21 am   #134
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Default Re: Tektronix 465b oscilloscope CH1 & 2 issues

I've got a half built W7ZOI 8640jr signal generator[1] here which I was going to do something similar with. It needs ALC so was going to use a diode detector, opamp and 2N7000 to control the final amplifier gain.

[1] https://www.cwtd.org/AnalyzeThis/8640jr.pdf
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Old 11th Jul 2019, 1:34 pm   #135
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Default Re: Tektronix 465b oscilloscope CH1 & 2 issues

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Last night I found a better set of allen keys that my Grandfather had, they are the ones with the "ball" at the end of the long shaft. What a difference they made in adjusting the little grub screws. Just shows how well made old tools were when 1/16" really was 1/16", they fit snugly into the grub screws, no slippage and the ball end gives that little bit of play for getting between knobs.
Richard
I knew there was something else that I wanted to mention. I have a set of ball-ended Imperial Allen-keys, too. They are useful when getting to grub screws that are buried in the guts of scopes and long-handled ones are equally useful. The problem with the ball-ended ones is that unless they are really good quality, the ball-ends can easily slip in the sockets and round-off. They certainly won't take as much torque as the plain types.
Colin.
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Old 11th Jul 2019, 4:55 pm   #136
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Default Re: Tektronix 465b oscilloscope CH1 & 2 issues

Hello Colin,

I've still got quite a lot of my grandfather's tools, nearly all stamped with a well known aero engine manufacturer where he worked during and after the war. So, I suspect they are all good old makes long since gone. Most are still wrapped in a thick waxed paper which is how we found them when my father inherited them. Very good for here with a salty atmosphere.

Anyway, where was I? When I replace the faulty attenuator module I'm also going to take a look at the old one and see if I can spot a dry joint as in Ron's photo. Useful to know if ever I have a problem in the future, looks like a potential weakness in these devices. Whether I can repair it is a different matter.

I'm still experimenting and testing and so far (touch wood) looking good.

Regards, Richard
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Old 13th Jul 2019, 1:40 pm   #137
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Default Re: Tektronix 465b oscilloscope CH1 & 2 issues

Postie has delivered the replacement attenuator module in one piece, so thank you Colin for sorting this out and packing well to ensure the delicate pins weren't damaged.

Its the Music Festival on the Isle this weekend so I won't be fitting it until Monday. I don't think I'll be in a fit state for delicate electronics work!

Regards, Richard
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Old 13th Jul 2019, 8:21 pm   #138
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Default Re: Tektronix 465b oscilloscope CH1 & 2 issues

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Hi Colin,
Amazing what bits of information people have tucked away.
Regards, Richard
There is more good stuff at Zenith/Hakanh's site.
See here: http://hakanh.com/dl/

Colin.
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Old 14th Jul 2019, 10:22 pm   #139
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Default Re: Tektronix 465b oscilloscope CH1 & 2 issues

Just a heads up for the Tek users here, I've given up on my remaining 465 and 475 units and put them up in the for sale section: https://www.vintage-radio.net/forum/....php?p=1160472
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Old 16th Jul 2019, 4:36 pm   #140
Radio Surfer
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Default Re: Tektronix 465b oscilloscope CH1 & 2 issues

Hello,

Well, the music festival is over, and today I felt safe to tackle the final (hopefully) minor repair to the oscilloscope!

Attached are some photos of the replacement 2X attenuator module kindly sent by ColinTheAmpMan1. The first photo is the module sitting in its protective foam base to ensure the delicate pins survived the postal service trip to Tiree. The second is the module in place. The third is a view of scope generated square wave showing a slight curve to the trace and the final photo showing a "squared off" edge to the wave having adjusted the left hand of the 2 small trimmers within the module (the probe had aleady been adjusted).

So, there we are - a fully working oscilloscope and the successful completion of the first of my 3 stages. If you recall, stage 1 was to see if I could bring this non working, very dusty and cosmetically dirty "barn find" scope back to life. Stage 2 was to be about learning how to use it, and thanks to the advice and links to various videos the see mist is clearing and I'm getting there slowly. Stage 3, when I eventually get there will be about calibration, but that bit scares me at the moment. Nevertheless, I've learnt so much over the past 3 weeks, that is way in excess of my initial expectations, anything is possible. When the time comes at least I know I'll receive sound advice from those that have "been there, done it, succeeded and got the T-shirt".

The main challenge in this restoration was cleaning the very delicate attenuator board contacts, some of which were very well hidden and totally inaccesible without dismantling. With hindsight, I should have stripped the board straight away and saved myself 4 days of cleaning fresh air. Once stripped down the cleaning, although still fiddly went smoothly and relatively quickly. The rest of the repairs were simple enough; a replacement 2X module from ColinTheAmpMan1, some filters from Nymrod121, a set of new stainless steel grub screws, the removal and cleaning of dozens of transistor push-fit connections and Servisol applied to some scratchy and reluctant-to-turn pots. The rest was just general cleaning and vacuuming of dust, dead spiders etc. from within the unit.

So, finally I'd just like to say a big thank you to all those that contributed spares and/or advice so readily and helped guide me through this process. It certainly gave me a lot of confidence to tackle quite a daunting piece of kit.

Here's to stages 2 and 3.

Kind regards, Richard
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