Tektronix 465b oscilloscope CH1 & 2 issues

[ColinTheAmpMan1]

Originally Posted by MrBungle

Bit of a failure on my part here. Went to hook out the 2x attenuator for Radio Surfer and found my 465, being an early model, doesn't have a 2x attenuator in it! It has 10x and 100x ones but the 2x and 5x are done using discrete circuitry to control the amplifier gain.

If anyone else has one available, please drop a post in.

I will sit in the corner and face the wall for a bit

I too, made a bit of a boo-boo. The spare that I have loose is a 10x module (and I'm not sure it is any good). It has P/N 307-1013-01.

Having perused both my 466 and 465B manuals, I think the P/N for the 2x attenuator module is 307-1010-01 on both scopes. It's a right pain finding these P/Ns, as they don't appear on the circuit diagram, only the internal trimmer capacitors do.

Richard, if your faulty 2x attenuator module has the P/N 307-1010-01 on it, I will go digging into both my 466s (parts-mule and functional) to see if I have the part and that it works as it should. Otherwise, that would be wasting my time. I am attaching a photo of my 10x attenuator module, showing the P/N clearly.

Failing all of this and possibly with more certainty of getting a good part, Qservice in Rhodes have 2x attenuator modules for $US6.

https://www.qservice.tv/vpasp/shopdi...&searchfields=

They are a good company to deal with.

Colin.

[MrBungle]

Qservice also trade on ebay as well if you want a click and buy approach:

https://www.ebay.co.uk/itm/233175943741

I've had a few things from them over the years.

[Radio Surfer]

Hello,

Thanks for the information , it is 307-1010-01. If no joy in the parts box Colin, I can always try the link from Mr B. No real problem at the moment as I have one channel working and I now know the other also works.

Regards, Richard

[ColinTheAmpMan1]

Originally Posted by ajgriff

Mine stops at 2 as well Richard which I think is 'normal'. Not pretending to know why - I'll leave that to someone with more knowledge.

Alan

Aha, you've both found Tektronix's little mystery!
Delay Time Multiplier ten-turn pot fully counter-clockwise settings differ between scopes. I think this is so that delay times can be accurately read off the knob setting and if you get it wrong, some silly stuff can happen. I am attaching a copy of a document listing the proper settings. I think I got it from Zenith aka Hakanh:

http://hakanh.com/dl/docs/hardtofind/dtmsettings.pdf

With regard to the small knobs that have a white spot index (if it hasn't worn off): you can pretty much ignore the inten., focus and scale illum. indexes, or adjust them to wherever suits you. The Trigger Level knobs can be adjusted by setting the knob so that the triggered trace is starting at zero volts on the properly adjusted vertical zero, then undo the set screw in the knob and place the index at zero volts. This can be fiddly as the shaft is likely going to turn a little when you loosen the knob. A few iterations may be necessary, but it's probably easier than outdoors painting on Tiree! The position knobs for both horizontal and vertical can be similarly adjusted, bearing in mind that the horizontal position has both coarse and fine knobs. I adjust the fine knob to the centre of its travel and then do whatever is necessary with the coarse control to make sure that it will adjust the start of the trace before the left-hand graticule line. There may be something in the manual about adjusting the position knobs' range. There are some other knobs which have detent positions and they are easily set by making sure that the knob index is in the right place when the pot is in the detent position. Notice that some of these detent positions are fully counter-clockwise and some are fully clockwise (A Trig Holdoff; View Time on storage scopes). I also like to make sure the "VAR" lettering is horizontal in the "CAL" detent on those variable controls which have a such a detent position.

Colin.

[Radio Surfer]

Hi Colin,

Amazing what bits of information people have tucked away. So I see the correct zero setting for a 465b is + 0.2, at least one knob was correct then. Also, relieved I didn't mess about with it, now I just need to work out what it does !! More reading and videos.

By the way, the fan on mine is so quiet I wondered if it was working, but I can just see it starting to spin and stop when unit is turned off with a torch. I've cleaned a lot of dust from within that area. I assume its not had any filter attached for a long time, so definitely worth doing especially after cleaning all those contacts. Any dust is bound to settle on the most inaccessible one.

Regards, Richard

[Radio Surfer]

Afternoon,

I've finished cleaning for today and just put the aluminium covers back over the attenuator board. The unit can now go back in its case so I don't touch or damage anything whilst I experiment with various settings.

The jitters (scopes not mine) appear to be much reduced (I daren't say eliminated just yet) and as far as I can tell, all buttons, switches and rotary knobs seem to behave, at least those I vaguely understand. Several I have no idea yet how to use, but for the time being I've enough to work with.

So, successes for today, no initial evidence of jitters, focus button will turn but still stiff, screen illumination now works without cutting out and slope trigger +/- works on a test signal and my Delay Time Position is confirmed in the correct zero position.

Next jobs are to sort out filter, clean Time/Div cam switches, although they seem ok at the moment or should I leave alone on the basis "if it ain't broke...."? Finish interior cleaning, read through user manual and watch some more of the videos in the range from Andrew's link - great the scope in that is a 465b. Sort out mains cable as its looking a bit weak at the entry point to the unit.

The forecast is for sun over the weekend with only a moderate breeze, so the paint might stay on my brush. I daren't spend another day tinkering or I'll be in trouble. Hopefully, I'll get a few hours in the evening to progress things.

All the best, Richard

[ColinTheAmpMan1]

Hi Richard,

I've checked the 2x attenuator module by trying it in my (mainly) working 466 and it does what it should do. I don't know if you are aware, but there are two trimmer capacitors in these attenuator modules, which can be set to the particular scope during the calibration procedure. There is a possibility that you might need to adjust them in this module, since it hasn't been in your 465B as yet. If you notice a square-wave looking a bit under- or over-shot on the 2 and 5 positions of the attenuator switch (that's when the 2x attenuator is switched in, if I have read it correctly), then there is a possibility. I should add that it hadn't been in my 466 before now, but it looked pretty good to me, so maybe no futzing will be needed.

If you let me know your postal address, I'll shove it in a jiffy-bag with a bit of antistatic foam or something to protect the pins from bending/picking up static. I just hope that the postage to Tiree isn't too expensive. I know that MrB has a load of stamps, but I don't!

Colin.

PS: isn't there a nearby island called Coll? Because of my first name, my family shorten it to "Col". I've only been to Skye and Iona and seen Staffa and Mull from a boat (MacBrayne, of course).

[Radio Surfer]

Hello Colin,

Great news, thank you and I'll PM my address.

Yes, Coll is Tiree's sister island. Very close but very different. The CalMac boat calls into Coll on the way over. You tend to get a lot of youngsters (sixth form and university age) going there to train for voluntary work under the Project Trust scheme.

Regards, Richard

[ColinTheAmpMan1]

Originally Posted by Radio Surfer

I've finished cleaning for today and just put the aluminium covers back over the attenuator board.

Just a thought, but did you make sure that the springy metal fingers on one side of the ally covers are making the right contact? They are there for correct earthing and can be easily forgotten and left outside the attenuator assembly, rather than inside and contacting the other metalwork. There are also other bits of the covers which should be aligned correctly for proper earthing and alignment, too. I will assume that you took lots of photographs and got it all together properly, but they can be surprisingly fiddly to get right....

Some attenuator assembly boxes have plastic covers over the ally covers, but not all. I don't know why this is so on some attenuator assemblies and not all, but I'm pretty sure that its to prevent the irrepressible twiddlers from screwing things up too easily.

Colin.

[Radio Surfer]

Hi Colin,

Yes I've got plenty of very interesting photos on my phone and I made sure those tongue type springs were in the correct contact position. The wider section nearest the front was more of a fiddle where the aluminium overlaps one side then the other to "grip' the metal base below. So all should be well earthed and shielded.

Mine didn't have any plastic anti-fiddling type cover over the holes.

Regards, Richard

[6AL5W-Martin]

I have nos in stock:

1011-00 (4x) a lot
1012-00 (5x) one

Martin

[ajgriff]

A few idle musings regarding Richard’s scope while he’s outside fighting to apply paint to the walls.

1. The Jitters - I suspect that plenty of exercise will do the scope a power of good after it’s long period of hibernation in less than ideal conditions. If the exercise regime is combined with self-administered driving lessons both Richard and the scope will benefit. It took me a while to reach a reasonable level of proficiency in using my 465B and I still refer back to the operating instructions occasionally. Also, it it is surprising how turning knobs and pushing buttons with current flowing cleans up poor contacts. Ultimately in this instance it may not even be necessary to dive inside again and start dismantling things.

2. Stiff Focus Pot - On arrival a couple of the pots along the lower edge of my machine were very stiff and I think this was caused by slight corrosion around the entry point of the shafts into their housings. Anyway this was resolved by standing the scope upright and applying a few drops of light oil to the shafts and leaving overnight to allow the oil to penetrate followed by lots of back & forth rotation. In severe cases penetrating oil might be best or even, dare I say it, WD40 ( ) but only if applied with a brush or similar and not sprayed.

3. Faulty Attenuator Module - Since I’ve already sinned by advocating the use of WD40 I might as well go a step further regarding the faulty X2 attenuator. I had exactly this problem with one of mine and in desperation brushed meths into the screw adjustment entry points and left it overnight (a favourite habit in my case). Amazingly the attenuator worked fine after this treatment. I’m sure this is a risky strategy but there’s not much to lose if the module is proven to be faulty already. Luckily for Richard he has a working module on its way in any event.

4. Delayed Sweep Vernier - Tektronix obviously decided that zero equals two in the case of the 465B and I’m grateful to Colin for sharing his copy of the chart. I’d still love to understand why this adjustment was necessary and, indeed, why the amount of shift is different for different scopes. However, it’s good to know that my 545B is correct in believing that zero really does equal zero!

5. Cord Wrap Feet - Don’t know what these are like on Richard’s scope but they are often broken or damaged in some way. A flawed design in my view especially when coupled with the UK’s cumbersome mains plug.

Alan

[Radio Surfer]

Evening,

Well most of the paint is washed off me and a good job started. Although painting is not my favourite pastime, on a sunny day with views of the sea behind the house, its not that bad.

Looking at Alan's musings from earlier:

1) - the jitters, I'm inclined to agree, lack of use in anything is not good. Hopefully, making adjustment with settings as I experiment should not only improve my understanding but help clean the contacts and steady the jitters. I note that the manual says the occasional application of IPA to the contacts with a camel haired brush can be done. These are in short supply on Tiree (both camels and brushes !) but I do have some long thin artist brushes to apply IPA to the Time/Div contacts. These contacts look much more robust than the attenuator contacts, so hopefully won't be so sensitive to any dust/oxide layer that may have built up.

2) - Stiff focus pot, as I commented before I assume this one is unusually stiff as its probably the least used of the knobs. If I recall, that pot is difficult to get at as its somewhat buried deep in the unit. I taped 2 red tubes from a couple of WD-40 cans to make a longer tube that just reached the entry into the pot and got some Servisol around the shaft entry point and then left the unit standing on end. It eased off a bit, so at least it turns. Maybe some light oil round the shaft may help if there is some corrosion and then wipe off any that has not soaked in?

3) - Faulty attenuator module, interesting thoughts on cleaning/soaking in meths, nothing to lose?

4) - Sweep vernier, I just need to work out how this works. I've not found any videos on the delayed B sweep type settings and use. If anyone is aware of one, please let me know.

5) - Flex feet. I've not put those back yet, they just need a good soak and clean and only one has a small section missing where the flex clicks into. I suspect they are quite brittle now so won't be using them to hold the cable. I've noticed that the power cable is worn at the exit point from the unit, not surprising really. But the cable in general is not very flexible. It needs attention, so I might just replace with some new twisted copper cable, the current one seems to be twisted steel core.

Finally, here are some of my own musings/activities from today.

When I was putting everything back together yesterday I noticed a "checked by" sticker and signature on a Tektronix logo'd sticker and next to it a Guernsey sticker. Although all the parts seem to have "made in USA" stamped on them, I assume Guernsey was an assembly plant for the European markets?

I've just cleaned the plastic wallet that bolts to the top of the scope. I've lobbed the contents into a box for the time being and will look at what I've got later.

Meths came to the rescue cleaning multiple stickers off the metal casing, it was the only thing that quickly removed the gum residue. There were quite a few long gone airline stickers on it including Anglia Air (based at Norwich airport in the 70's) so its been well travelled before its barn retirement

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.

Well tomorrow looks like wall to wall sunshine before the rain returns. So Monday looks the perfect oscilloscope day.

All the best, Richard

[MrBungle]

Thing to watch out for. The legends on the knob skirts are probably water soluble. Be careful when cleaning!

The attenuator is probably toast so not sure cleaning it will work. There is a bit of ceramic with thin film resistors on them. Sometimes they bubble up and it’s had it.

[ajgriff]

US scopes made at the Beaverton factory have serial numbers (bottom right of front panel) starting with 'B' followed by five digits. Guernsey scopes have six digits starting with '1'.

These two short videos demonstrate basic use of the delayed timebase:

https://www.youtube.com/watch?v=0enuruGWYk8

https://www.youtube.com/watch?v=J-7MycqHPOs

The legends on the Volt/Div skirts are particularly vulnerable when cleaning and tend to wear away if the knob is pushed in too firmly when fitted. One of mine has lost some of its lettering.

Think I just got lucky with the attenuator module.

Alan

[Radio Surfer]

Morning,

Thanks for the advice/reminders. I did almost have a disaster a few years ago with the glass markings on a barometer. It was knocked off the wall and the brass bezel fell off causing the glass to fall out. Fortunately nothing broken. But I decided to clean the glass before refitting and managed to clean off the "made in England" marking. So not too major disaster but since then I'm ultra careful.

The point of not fitting the knobs to close to the frame is true, I used a thin card spacer behind the knobs to give me a small but clear uniform space behind all the knobs as I tightened them up.

I'll take a look at the videos tonight, thank you.

One final question for now which may be obvious but not to me, so dunce cap at the ready. There are 2 slots behind the Volts\Div knob to presumably differentiate 1X and 10X probes. Does the one one on the right ever light up that shows the higher volts reading setting? I only ever see the left slot illuminated. I don't recall an led behind it, so I assume it doesn't.

Now, back up my ladder for the day. Sun cream applied too.

Regards, Richard

[MrBungle]

If you have a tektronix 10x probe there’s a shorting pin on it which actually activates that. Have a close look at the BNC connector on the front of the channel input. There’s a ring around the base insulated from the shell. If you short the shell to ring out it’ll light up the other one.

Probemaster sell replacement probes that have those pins.

[ajgriff]

This link provides a good overview of how a Tek scope knows which bulb to turn on and it's definitely not a dumb question.

https://www.jmargolin.com/projects/TekReadout.htm

From memory the 465B uses incandescent bulbs rather than LEDs. The manual will confirm.

Alan

[Craig Sawyers]

Yes - incandescent. I'm not sure what sort are used in the 465/475 without looking at the manual, but on 7000-series they are wire ended tiny things soldered in. If you know the rating you can get them still from Farnell or RS.

Craig

[ColinTheAmpMan1]

Originally Posted by MrBungle

If you have a tektronix 10x probe there’s a shorting pin on it which actually activates that. Have a close look at the BNC connector on the front of the channel input. There’s a ring around the base insulated from the shell. If you short the shell to ring out it’ll light up the other one.

Probemaster sell replacement probes that have those pins.

MrB is correct, to some extent. The correct resistance to go between the probe sensing ring and chassis earth is 11k, but a dead short will work on 4xx-series scopes. If you ever get a 1x/10x probe with the sensing pin on it, you can switch between the attenuation options and see the lamps change over.
With 7000-series plug-in vertical amplifiers, you have to use an 11k resistor, as there are IDENTITY push-buttons in the centre of the POSITION knobs and a dead short to chassis ground activates this.
If I remember correctly, some scopes can use a 100x probe and have the ability to light yet another lamp to indicate this.
Colin.

PS: I have the attenuator module packaged up and the address label stuck on. You didn't tell me your surname, though. If you need one, I could put an 11k resistor in there, too. We only have one Post Office which is about 12 mins walk away (and this is London, the capital city), so I will have to go there on Monday to post the package. I bet you have better postal service on Tiree and the other Scottish islands.