Tektronix 465b oscilloscope CH1 & 2 issues

[Radio Surfer]

Hi Mr B and Alan, I didn't have a torx bit that small and no shops on Tiree other than a Co-Op and that's not in their current stock range (I must complain about that).

Managed to try your approach Alan and first one removed, obviously screws are "shot" now.

Anyone any idea of the thread size so I can order something?

I'm now going to have a drink or 2 , what a game.

Regards Richard

[ajgriff]

Glad you've managed to remove at least one screw Richard. I'm fairly sure that the thread will be UNF. The attached chart might help.

Alan

[Radio Surfer]

Hi,

My last post hasn't loaded for some reason?

Anyway, what a game, Volt/Div knobs removed, screws "shot" as I had to use Alan's suggestion. So I'll need to order some replacements. Any idea of the thread/size for these?

Whole of the cam and Attenuator board out and I can actually see to clean it properly now.

Time for a lie down in a darkened room.....

Regards, Richard

[Radio Surfer]

Sorry Alan,

I was writing as you loaded the attachment. I'll take a look,

Cheers

[MrBungle]

UNF sounds sensible. I've usually nicked the grubs out of a parts mule so never measured them myself!

[ColinTheAmpMan1]

According to my 465B Service Manual (B060000 and up), the setscrews are:

Red, Variable knob - Tek# 213-0153-00 5-40 x 0.125
Grey knob - Tek# 213-0153-00 5-40 x 0.125.

So they are, fortunately, identical and the 5-40 is an UNF designation. Tek specified "steel, black oxide, hex socket", but I doubt that is essential, except perhaps the "hex socket" part. I would hazard a guess that these setscrews are common to the whole 4xx range of scopes.

You really should get yourself a good manual, preferably an original paper one, if you can, or maybe one from Artek Manuals. The parts-lists are in the back.

Colin.

I usually get my manuals from Marc Christian at Telford Electronics - his prices are pretty good and he has only failed to find about two of the manuals that I have been looking for. Incidentally, I live in London and have tool-shops fairly close. If you want something that I could get easily and then post to you, I could do that. There are such things as left-hand drill bits (I kid you not! I have a few) of various sizes which can be handy getting screws out, especially when the head has been truly mangled. There are also screw-extractors which can do the same job, but I have found that the small ones snap easily. Another trick with rounded hexagon-head screws is to take an Allen key which is the next size up and grind the end to make it smaller on all the sides. Tapping this in with a small hammer could achieve what MrBungle was suggesting with a torx bit, but would involve sacrificing the Allen key. It is likely, if your grinding is reasonably accurate, to mean that more contact with the socket is achieved and would be better than using a torx bit.

[Andrewausfa]

Richard,

You may want to try this manufacturer. 5-40 UNF isn't listed but they might have some.

Andrew

http://www.ba-bolts.co.uk/index.html

[Radio Surfer]

Thanks for the information Colin,

I do have a the manual, but admit couldn't find the part. "Must try harder" , came the report! I'm still finding my way round it as its so extensive.

I've just stripped down the first switch contacts, cam, attenuator boards etc. for channel 2, and cleaned it thouroughly. No way could you get at the 2 contacts causing me problems without dismantling. Not only were they under the board, but surrounded by a thin metal casing which seems to make another contact when they are apparently in the "off position". It was quite difficult cleaning these 2 even when removed. At least they work on my multimeter and I get the correct 1X reading Mr Bungle noted way back at the start of this thread. I had a minor panic as the cam fell in 2 halves as I removed the last screw securing it to the board, but no problems, easier to clean the cam!

So far, so good. Incidentally, I ended up using methylated spirits to move some stubborn white marks in a few seconds where the contacts touch the pcb copper tracks. IPA wouldn't touch it after an hour of polishing with IPA soaked paper. I've then cleaned again with IPA.

Now we seem to be moving again.

Thank you again for all the advice, first time on something like this.

Regards, Richard

[Radio Surfer]

Thanks Andrew, I'll take a look and ask the question.

Regards, Richard

[ColinTheAmpMan1]

Originally Posted by Radio Surfer

I do have a the manual, but admit couldn't find the part. "Must try harder" , came the report! I'm still finding my way round it as its so extensive.

For the record, Section 10-1 is where the "Replaceable Mechanical Parts" starts. Section 8-1 is "Replaceable Electrical Parts". Both of these contain comprehensive information of the parts and where they were originally sourced from (in the case of those setscrews, it was Northwest Fastener Sales Inc., Beaverton, Oregon). The Mechanical Parts Section contains two exploded diagrams, too.

Incidentally, I ended up using methylated spirits to move some stubborn white marks in a few seconds where the contacts touch the pcb copper tracks. IPA wouldn't touch it after an hour of polishing with IPA soaked paper. I've then cleaned again with IPA.

For information, My 475A Service Manual says of the attenuators that the substrate is made of polyphenylene oxide, which is easily damaged by the use of carbon-based solvents (unfortunately poor chemical knowledge, as IPA contains carbon). The use of acetone, benzene, toluene, xylene, petroleum ether, white kerosene, carbon tetrachloride, methylene chloride, trichloroethane, trichlorotrifluoroethane and trichloroethylene should be avoided. I would add "like the plague". The use of methylated spirits, as you have done, is probably ok, as it is a mixture mainly of ethanol and methanol but unfortunately it contains pyridine and a dye to make it unpalatable. I don't think that the ethanol and methanol would be damaging, but the pyridine might be and the dye could certainly deposit on the contacts. You might have preferably used IMS (Industrial Methylated Spirit) which doesn't contain pyridine or the dye, but cleaning with IPA afterwards was almost certainly a good idea. You might be able to find IMS somewhere, such as a pharmacy, but be prepared for funny questions as to what you want it for, as apart from the methanol, which sends you blind, crazy and dead in that order, it is drinkable.

Again for your information, those attenuator contacts are all gold-plated, not only the springy contacts, but also the pads on the PCB, not just copper.

Keep up the good work, Richard!

Colin.

[Radio Surfer]

Hi Colin,

Thanks for comment on cleaning chemicals etc. I read the bit in the manual about IPA and there are plenty of warnings of not using anything else upon risk of catastrophe, hence I've only used the methylated spirits on this one mark, not sure what it was but it was a trade off between rubbing the life out of the plating or trying something else then quickly cleaning off with IPA. I hope I don't regret the calculated risk.

The barn storage it's been through is certainly not to be rcommended for these things, it's played havoc with the contacts, but it was a "freebie" . I'll have to be careful in the future , as mentioned in your note the other day, about salty sea air as well !

The section on dismantling in section 5.14 is a guide but most of the key steps and hidden bolts are not referred to which was fun (and it is the original manual) but I got there with plenty of handwritten notes and photos with stickers on cables so I know where them plug them back in.

Just got to clean up the other switch now and put it back together, so another day of gentle cleaning. Sometimes feel like getting the sander on it - only joking ��

Regards, Richard

[factory]

Originally Posted by ColinTheAmpMan1

According to my 465B Service Manual (B060000 and up), the setscrews are:

Red, Variable knob - Tek# 213-0153-00 5-40 x 0.125
Grey knob - Tek# 213-0153-00 5-40 x 0.125.

So they are, fortunately, identical and the 5-40 is an UNF designation. Tek specified "steel, black oxide, hex socket", but I doubt that is essential, except perhaps the "hex socket" part. I would hazard a guess that these setscrews are common to the whole 4xx range of scopes.

Actually 5-40 is a coarse thread (UNC) not fine (UNF), the chart that Alan posted is the one I created (for use in the shed) by editing the relevant info from several pages of the 11th edition of Machinery's Screw Thread Book.

This company which I've used before has 5-40 grub screws, other places probably have them too:
https://www.accu.co.uk/search?query=5-40+unc+grub

David

[ajgriff]

In an earlier post Colin raises some interesting points regarding 465B manuals. A couple of years ago when I researched the subject it seemed almost as challenging as dismantling and cleaning attenuator boards. Things may have changed but I'll detail my thoughts at the time.

Fundamentally there are two manuals relating to serial numbers above and below B060000. This is fine if you have a US made scope. However, here in the UK you are much more likely to own a machine made in Guernsey and the serial numbering system used by the Guernsey factory was completely different. So far I haven't found anything or anyone able to explain how the different number ranges correspond, if indeed they do. Very happy to be enlightened. Even if you have the correct manual this problem is made worse by the fact that any reference to the serial number in the form of change information is meaningless for a Guernsey scope. There may have been Guernsey versions of the manuals, as there were for 500 series scopes, but I've never seen one in any format.

Whilst a paper manual is ideal, mainly because of the pull-out circuit diagrams, they are not so easy to come by at the local flea market in the UK generally, let alone in Tiree. Although I didn't get my scope for nothing like Richard I acquired it for a very reasonable price and wasn't keen to double the cost by buying a manual from one of the usual sources so inevitably I went for the free download option.

Aside from the stupidly large file sizes of some downloads I've yet to find one that is actually complete. This includes the one from the Tek website and I did use the feedback service at the time to highlight the issue but didn't get a response. In view of the length and complexity of the manual the missing information is less than apparent until you need it or unless you enjoy long nights of bedtime reading. I did eventually manage to download most of the missing sheets from various obscure sources with the exception of the diagnostic waveforms for Diagram 7 (Sweep and Z-Axis Logic). For this I have an extract from the 465 (not B) manual which is close enough to give some clues.

I'm fortunate enough to have an inexpensive black & white laser printer which I used to print (double sided) the manual sections I need ie, excluding the options I don't have. These are slide bound by section which works well for me anyway. Exploded view portions of circuit diagrams can be printed when required which helps to overcome the problem of image size reduction in downloads. The Artek PDF manuals mentioned by Colin might be worth considering if they are complete, as Artek seems to have a good reputation amongst enthusiasts and its prices are competitive.

Changing the subject for a moment and referring to Colin's comments about solvents, it is aromatic hydrocarbon based solvents that must be avoided. Alcohol, methanol and IPA (iso-propyl alcohol) are all fine. I must admit that I have used meths a lot over the years for contact cleaning including Tek attenuator switches as I find it's more effective than IPA. It evaporates quicker too which helps to reduce the effects of accidental peripheral contamination. Have never found the tiny quantities of pyridine to be a problem. Controversial I know so I hope not to have opened a can of worms.

Alan

PS Thank you to David for clarifying the thread type as UNC. Hope you didn't mind me borrowing your very useful shed chart!

[Radio Surfer]

Hi David,

I took the grub screws out and thought they were UNC and checked in an old ZEUS chart I had. I've just created an account and bought 20 stainless steel from, of all places Accu. Then looged and and saw your email, so thanks for the confirmation, you've taken any doubt away.

Regards, Richard

[Argus25]

Originally Posted by Radio Surfer

The small grub screws in VAR/DIV are so rounded that there is no way they are coming out. I have used the correct allen key as per the manual (1/16") and the set I have are good quality barely used.

I have had this issue with some of my Tek 466 scopes. Although they get rounded they are often never 100 % round, right into the base of the hole. What I did was to get an over sized key ,just a little bigger and file the 6 faces with a very small taper with a diamond file at the long end. Cut the key and mount it in a small chuck with a large handle attached. That way it can be pushed (forced) into the damaged grub screw hole, with more force on that axis that the rotational force applied. I was able get all the damaged grub screws out this way. To replace them I had to buy knobs on ebay to get ones the correct thread.

(One thing I have found with Tek scopes, the worst damage appears to have been done at "Calibration Houses" where the wrong tools are often used, screws over-tightened, stickers scraped off with screwdrivers damaging surfaces etc. I once said it should be a Federal offence to damage a Tek scope. A pet dislike of mine is damaged screw heads and I get obsessed and have to replace them).

[MrBungle]

On the 465B manuals, there was one at the newbury radio rally but I didn't grab it as I didn't have a 465B. I still have a 465 and a 475 lying around I grabbed one each of them for a fiver a go though! I should have got the 465B one as well at that price and redistributed it on the forum.

I'll keep an eye out if the seller is at the McMichael Radio Rally.

[Radio Surfer]

Hi Alan,

Thanks for the reassurance on the meths, I only used a bit on one stubborn spot, as you say it did seem remarkably effective compared with IPA, the spot went in a few seconds. Anyway, Ill behave in future and stick to IPA.

As far as manuals go, it is a tomb of a document and you have clearly done a lot of research on them. I'm just happy to have one and supposedly the right one, although they take some getting around. I'm getting there, things aren't always where I'd expect it, but its good. Not surprisingly, you can't rely on it as gospel, its too big and as you say probably too many variants to keep it accurate. Much of the cross referencing and cabling numbers used to identify cables linking one board to another/component are invariably 1 digit out. Maybe US numbers v Guernsey conventions, who knows. But, some common sense and I'm working round it. Having written many training manuals and materials in my time I have sympathy with the author(s).

Regards, Richard

[Radio Surfer]

Hello Argus25,

I'll try that technique in future. One of my other hobbies is vintage Meccano and almost every wheel, pulley or brass coupling I buy has a broken grub buried within. I always approach undoing these type of screws wondering how many hours it will take and occasionally it just works and I'm so pleased. Little things in life......

Regards, Richard

[ajgriff]

If anyone is interested in verifying the US serial number range covered by a particular copy of the 465B service manual then check the part number printed in the bottom left corner of the front sheet. Part number 070-2757-00 covers serial numbers up to B059999 and 070-4273-00 is for B060000 and above. Doesn't help with the Guernsey numbering anomaly referred to previously but nothing in life is perfect, not even the classic Tektronix 465B oscilloscope.

Hope Richard makes good progress with the attenuator boards today subject to power interruptions of course.

Alan

PS If you do come across an original manual for a fiver Mr B please remember me!

[Alistair D]

Re the damaged Allen screws, I have had some success loosening them when I managed to find a Torx driver that is a tight fit in the hole. I reckon the sharper angle on the corners helps them dig into the screw increasing the bite.

Al