Date   

Re: Dennis Tillman

Dave Daniel
 

I have communicated very recently with Dennis. I did not sense that anything is wrong.

DaveD

On 11/7/2020 1:12 PM, Colin Herbert via groups.io wrote:
Does anyone have any idea if Dennis Tillman is still ok? I was having some conversation with him a little while ago, but he has gone quiet since I gave him another email address for me in a PM.He doesn't seem to have posted much over the last few days, which is a little unusual, especially since the topic of WD-40 has come up again....
Colin.



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Dennis Tillman

Colin Herbert
 

Does anyone have any idea if Dennis Tillman is still ok? I was having some conversation with him a little while ago, but he has gone quiet since I gave him another email address for me in a PM.He doesn't seem to have posted much over the last few days, which is a little unusual, especially since the topic of WD-40 has come up again....
Colin.


Re: Clean and Lubricate Pots in Tek 475

 

Jeff:
Don't be mislead slightly by the removal of the 465 vertical preamp board in the eevblog tear down. The 475 vertical board differs in that the attenuator switches and BNC front panel connectors do NOT come out with the vertical board. The vertical board is separated from the attenuators by unsoldering the connection between the attenuators and the vertical board. There is a difference in what components are involved here depending upon S/N. This makes the removal a little easier than in the 465. Follow the instructions in the manual section on Vertical Preamp Circuit Board Removal. Make sure you have the correct manual for your S/N. Both of mine are S/N 250000 and up. Also be careful when removing the Delay Line connection to the vertical board as there is a solder connection here. I guess I should have photographed and documented my removal of the vertical preamp board in the 475. My bad! Some day Real Soon Now.
I have always used the Caig Laboratories line of contact cleaners and contact restorers. Cramolin and then the Deoxid line of contact cleaners. I have used the WD40 Cleaner for some applications. The WD40 brand seems to have a line of different products now. I have seen one other reference to using the original WD40, used for loosening corroded bolts, for contact cleaning/restoring. This was in a GR 1432 instruction manual dated 1956. I was surprised to see this and didn't understand exactly why. But I guess GR had some reasons for doing this. I don't think that TEK intended for WD40 to be used on the pots, nor did they expect the pots to need cleaning. But 50 years does take it toll. I am not as good 50 years later either at the ripe old age of 80.
Bill


Re: Clean and Lubricate Pots in Tek 475

Tom Phillips
 

I was able to free up a frozen intensity pot in my 465B. The 465B intensity pot is located near the rear of the interface circuit board. A long thin epoxy extension shaft connects the pot shaft to the front panel control knob. The pot shaft was so stiff that the long shaft just flexed rotationally when I turned the front panel knob as the pot refused to move. After removing the case, I set the scope vertically on the rear feet and removed the high voltage shield to access the intensity pot. I put a couple of drops of Deoxit D5 on the metal pot shaft and left it to soak. Over a day’s time I periodically added another drop of D5 when the previous drop had evaporated/penetrated down the shaft. The long epoxy shaft continued to flex and the pot shaft didn’t budge. I then used pliers applied to the metal coupling at the pot shaft to gently get rotation started. Once the pot shaft started to move things improved quickly over the next few hours because, I believe, the D5 could now better penetrate down the pot shaft.

This process took a day but it didn’t require much of my hands-on time. Eventually, I’d still like to disassemble the pot for complete internal cleaning because the intensity adjustment is a little jumpy. However, the process I described solved the main problem of a totally unusable intensity control.

Tom


Re: OT - RIFA caps & 'transformerless' PSU

Carsten Bormann
 

On 2020-11-07, at 14:31, Lawrance A. Schneider <llaassllaaass@gmail.com> wrote:

At the present time, I can get to my equipment - so, I was wondering did HP put this type of capacitor on their equipment?
I’m not sure I understand this sentence, but I’m sure at the time HP (or the supplier HP relied on, e.g., Schaffner) speced these, the failure mode was not known. Other manufacturers did the same. I haven’t been able to precisely delimit the time frame over which this was a problem, but, e.g., a Schaffner filter from this century won’t have these types of caps any more.

If so, should each and everyone be replaced?

In general, should these be replaced anytime you encounter one?
Anything that is potentially connected to high-energy sources (line filters, snubbers etc.): Yes.
(You’d need good knowledge of the circuit to rule this out, so maybe the answer is a “Yes” in general.)
Note that these may be buried in high-quality line filters (e.g., from Schaffner), so any line filter from that period is suspect.

Grüße, Carsten


Re: Another A5 board repair attemp - help needed

tekscopegroup@...
 

On Fri, Nov 6, 2020 at 09:03 AM, Rogerio O wrote:


This time I got the error message test 4 fail2 (but still no trace), but I
guess it is not the main problem for the moment.
I tried to check the +1.36V and the -1.25V as suggested in other trend, and
they are VERY off.
From my own experience fixing a 2465B by dealing with the A5 board issues, if the DAC voltages are way off or not even present you will most likely not get a visible trace at all because for one the brightness setting depends on the DAC voltage references. I ended up having to replace several resistors, notably both of the 10K 0.1% ones and a few others, this aside from the obvious leaking caps. I used common leaded 1/4w 5% resistors tack soldered in place of the damaged SMD ones as a temporary test and managed to get the DAC voltages back in the ballpark and so the trace came back as well. And if you are lucky you might be greeted by a error free screen as well. Calibration will obviously still be off with those temporary resistors but at least you can get things working again and make sure the incorrect DAC voltages where your main problem related to the no trace condition. After getting these results only then went ahead and ordered all the required correct parts from Mouser. In some extreme cases the adjustment trimmer next to the DAC chip will also be damaged, but leave that for last and if possible try not to mess with it. The idea is to leave the current adjustment values to whatever they where, and BTW they are not supposed to be EXACTLY at +1.36 or -1.25 but rather show the values to whatever they where adjusted to during the last cal, usually close to those reference values, but not necessarily exactly that.

In my case the faulty resistors where either totally open or way off value (usually up) , so almost all the faulty ones where easy to find without desoldering them. And again if at all possible refrain from making any adjustments to the DAC as you might loose whatever little calibration is left. If you mess with the DAC voltage adjustment trimmer all bets are off and a full cal will indeed be required. Of course the best action would be to fully cal the scope once its back to fully working, but some of us don't have the necessary instrumentation or just don't want to bother with it, or have access to a qualified workshop that can do this, or simply do not need our scope to be absolutely on the money as we are only hobbyist and able to tolerate slight variances.

Also worth mentioning in case you did not yet do so, to ensure that you got all the leaked electrolyte off the board, make sure to wash and gently scrub off the complete top side with water and -dish soap- and use a soft toothbrush. This is the only sure way of getting rid of all the electrolyte still left on the board (IP Alcohol will not work). If you still have any hidden electrolyte left it might cause unwanted conductive paths around affected components and throwing off voltages and lead you to a merry go round while trying to troubleshoot the components. So making sure to start diagnostics and troubleshooting with an absolutely clean board is paramount.


Re: OT - RIFA caps & 'transformerless' PSU

Lawrance A. Schneider
 

At the present time, I can get to my equipment - so, I was wondering did HP put this type of capacitor on their equipment? If so, should each and everyone be replaced?

In general, should these be replaced anytime you encounter one?

Thanks, larry


Re: Clean and Lubricate Pots in Tek 475

Colin Herbert
 

There has been (and I suspect always will be) much discussion on the pros and cons in the use of WD-40. The current opinion generally is not to use it anywhere in an electronic device. There has been some mention of two differing products, WD-40 and a contact-cleaner, by the same company. It is generally understood that the common "WD-40" that you can buy from a hardware store contains a solvent which evaporates and a light oil which does not. If you want a light oil on your contacts an pot tracks, go ahead, but I wouldn't.

I don't have a Manual for the 475, nor do I have a 475, but I do have two 475As and a paper manual. In the Maintenance section of that Manual and under "Lubrication", it states that switches, potentiometers and the fan motor are permanently sealed and "generally do not require periodic lubrication". It does not mention _any_ recommended lubricants that I can see. We are all aware, I think, that the cam-operated switches can be carefully cleaned with IPA and this is indeed mentioned under "Preventive Maintenance". I appreciate that this information is a little paradoxical, but there it is. If you must attempt to clean the interiors of pots and switches, use an accredited contact cleaner, not the bog-standard WD-40.

Colin.

-----Original Message-----
From: TekScopes@groups.io [mailto:TekScopes@groups.io] On Behalf Of Jeff Dutky
Sent: 07 November 2020 10:36
To: TekScopes@groups.io
Subject: Re: [TekScopes] Clean and Lubricate Pots in Tek 475

Eric and Greg,

The recommendation for WD-40 comes directly from the 475 Oscilloscope Service Manual, page 4-2 under Maintenance, Cleaning, Switch Contacts, the exact passage reads "There are three recommended switch lubricants. They are Silicone Versilube (General Electric Co.), Rykon R (Standard Oil), and WD-40 (Rocket Chemical Co.)." So, while Tektronix DOES specifically recommend WD-40, it is not recommended for this use. The manual specifically says of the potentiometers in the unit "most of the potentiometers used in the 475 are permanently sealed and generally do not require periodic lubrication." Of course the period that they were considering was presumably much shorter than 50 years.

I've ordered a set of syringes and industrial needles to try either forcing some lubricant down the shaft, or into a the partially opened back end of the modular pots. I would like to order some DeoxIT to use in place of WD-40, but the range of options, and CAIG's claims for the product, give me pause.

I'm not too worried about using WD-40 on the unit in general, and I'm not terribly concerned with preserving these specific three pots, as there appear to be readily available replacement units at reasonable prices (I am going to order a full set of replacements for these three pots under any circumstance. The channel #1 vertical position pot can be easily replaced without even removing the vertical input board from the unit, and that is the one that is giving me the most trouble. The channel #2 vertical position pot is not as troublesome, and I don't use the beam intensity adjustment, which is the one with most serious problems, nearly as often as I do the vertical position adjustments).


Re: Troubleshooting an old Tek 475

Göran Krusell
 

Hi, the R1059 and C1059 low pass filter is filtering the +110V voltage, the values are not critical.
Göran


Re: Clean and Lubricate Pots in Tek 475

 

You should be aware that the WD-40 of 50 years ago is not the same stuff you get these days - I believe for example that it used to contain "duck oil" and that the formulation has changed at least twice since then.

Personally I wouldn't let it near a potentiometer.

David


Re: Clean and Lubricate Pots in Tek 475

 

Eric and Greg,

The recommendation for WD-40 comes directly from the 475 Oscilloscope Service Manual, page 4-2 under Maintenance, Cleaning, Switch Contacts, the exact passage reads "There are three recommended switch lubricants. They are Silicone Versilube (General Electric Co.), Rykon R (Standard Oil), and WD-40 (Rocket Chemical Co.)." So, while Tektronix DOES specifically recommend WD-40, it is not recommended for this use. The manual specifically says of the potentiometers in the unit "most of the potentiometers used in the 475 are permanently sealed and generally do not require periodic lubrication." Of course the period that they were considering was presumably much shorter than 50 years.

I've ordered a set of syringes and industrial needles to try either forcing some lubricant down the shaft, or into a the partially opened back end of the modular pots. I would like to order some DeoxIT to use in place of WD-40, but the range of options, and CAIG's claims for the product, give me pause.

I'm not too worried about using WD-40 on the unit in general, and I'm not terribly concerned with preserving these specific three pots, as there appear to be readily available replacement units at reasonable prices (I am going to order a full set of replacements for these three pots under any circumstance. The channel #1 vertical position pot can be easily replaced without even removing the vertical input board from the unit, and that is the one that is giving me the most trouble. The channel #2 vertical position pot is not as troublesome, and I don't use the beam intensity adjustment, which is the one with most serious problems, nearly as often as I do the vertical position adjustments).


Re: Troubleshooting an old Tek 475

 

Okay, I'm not nearly qualified to understand what C1059 was doing in the sweep generation circuit, I mean I can trace out what it's connected to, but my EE fluency ends with "which way to Kirchoff Cafe" and "My hovercraft is full of eels." The failed part still appears to act like a capacitor (in the 200nF range), at least from what my multimeter can tell (I don't have an ECR meter or a working comparator bridge to check it any real way). Whatever the case, it was clearly the culprit in disabling the horizontal sweep. I suppose it also may have been distorting the timebase, but even before this failure the timebase wasn't off by more than a few percent (if that, as I was judging the timebase by comparison to the built-in calibrator signal, which appears to be off by 5% or more), and if C1059 played any significant part in the timebase itself then I would expect a change of an order of magnitude in C1059's value to have more than a 1% effect on the timebase.

As it is, I checked the value of the replacement capacitor to make sure that it was within 10% of the specified value. I even ordered several replacement parts so I could select the one that was closest to 3.6uF, and both the candidates were right about 3.5uF, so I feel pretty good about the transplant not screwing up the host circuit.


Re: Clean and Lubricate Pots in Tek 475

Greg Muir
 

Eric,

I am aware that there are various camps regarding the use/not use of WD40 as a cleaner & lubricant for potentiometers. I myself shy away from it given past experiences with the behavior of this penetrant/lubricant and it’s properties over time.

There has been much said about the combination of the carrier and lubricant used in this product and its propensity to leave behind residue after the carrier evaporates. In my experience I have witness a very heavy and sticky form of oil that forms after extended periods of time.

Aside from that I adhere to products listed as being specifically formulated for electronic purposes. In many respects it is better to be safe than sorry especially if the target item is non-replaceable as those things used in legacy equipment. Granted Tek did specify (or recommend) WD40 in a couple of their documents but it was not widespread. This was possibly due to a recommendation made by one or a few individuals. Although I do not know where these recommendations were made I feel that the factory designed service lifetime has past some considerable time ago.

I am sure that if the WD40 company felt safe with recommending its use on potentiometers they would have included that in their promotional literature. But when they state that it is useful on “larger electric motors, armatures, relays, electric panels, and generators” I feel a little unsure about committing it to sensitive electronic purposes other than those that are stated.

There are plenty of good products out there on the market targeted at applications like that in this discussion. Why not use them?

Greg


Eric wrote:

“Greg I have to disagree with you on this one…..”


Re: 475M metal can caps

greenboxmaven
 

One thing Tektronix did a great deal was to only have one voltage supply with a zener reference, it's output was the reference for other voltage supplies. Sometimes there would be a cascade of supplies giving reference to others. Needless to say, if any one of them is not accurate and clean, the following ones won't be either. The absolute worst examples I ever dealt with were some Yamaha stereo receivers where one zener ultimately controlled cascaded power supplies producing nine different voltages.

Bruce Gentry, KA2IVY

On 11/6/20 5:27 PM, Paul Amaranth wrote:
I will second Michael's recommendation. The little adapter boards make
for a very neat and professional looking repair. In a pinch I've used
PNP blue to etch my own, but it's easier to buy them ready made.

Use 105C caps if you can.

On these scopes if the power supplies are not right, nothing works right.
Always ensure the power supplies are correct before looking at anything
else.

Paul

On Fri, Nov 06, 2020 at 10:15:53AM -0800, Michael W. Lynch via groups.io wrote:
I have restored several of this family of scopes. Finding OEM style caps that are good is not a really viable option.

I use Modern radial lead caps and these adapters:

www.ebay.com/itm/Capacitor-Adapter-15-5mm-triangle-recapping-vintage-equipment-Tek-465-kit-x5/273254508468

I would say that you have issues with you -15 and -8V Supply. Caps may help rectify some of those issues. A Good place to start in any case. Get you supplies back in spec and you will go a long way to fixing the scope.

Good Luck!
--
Michael Lynch
Dardanelle, AR


Re: 475M metal can caps

Bill Perkins <sales@...>
 

Here's some work I did 20 years ago on a Tek 570 S/N 215:

https://www.pearl-hifi.com/07_Facility_Tour/Tek_570_215/Internal.jpg

I made the parts from FR-4 and used stake-in solder terminals from Keystone.

Bill

I will second Michael's recommendation. The little adapter boards make
for a very neat and professional looking repair. In a pinch I've used
PNP blue to etch my own, but it's easier to buy them ready made.
Use 105C caps if you can.
On these scopes if the power supplies are not right, nothing works right.
Always ensure the power supplies are correct before looking at anything
else.
Paul
On Fri, Nov 06, 2020 at 10:15:53AM -0800, Michael W. Lynch via groups.io wrote:
I have restored several of this family of scopes. Finding OEM style caps that are good is not a really viable option.

I use Modern radial lead caps and these adapters:

www.ebay.com/itm/Capacitor-Adapter-15-5mm-triangle-recapping-vintage-equipment-Tek-465-kit-x5/273254508468

I would say that you have issues with you -15 and -8V Supply. Caps may help rectify some of those issues. A Good place to start in any case. Get you supplies back in spec and you will go a long way to fixing the scope.

Good Luck!
--
Michael Lynch
Dardanelle, AR


Re: Troubleshooting an old Tek 475

 

Raymond wrote:
My memory urges me to write the following:
If you replaced one of the physically larger timing capacitors (metal cylinders, the smallest about 2cm length),
be aware that these are matched sets (I think 3 pcs, marked by a single letter, like "J", "K" or the like, the same
for each set). At calibration time, you can't adjust their timings individually.
The cap that I replaced is labeled C1059 and is the smallest capacitor on the Timing Circuit Board. In the parts list it is indicated simply as "3.6 uF, Elect., 125 V, 10%" so I don't think it's part of the matched set. There are two sets of capacitors on that same board (C1071,72,73 and C1082,83,85 that are specifically marked in the parts list as matched capacitors of 10uF/0.1uF/0.001uF) but this is not one of them.

Thank you for the warning, though; it is well taken.


Re: Clean and Lubricate Pots in Tek 475

 

Here is the link that says that removing the vertical amplifier board is not as involved as you would expect it to be (though I'm not sure I understand exactly what he is saying is involved in removing the attenuator switch assembly): https://entertaininghacks.wordpress.com/2018/02/27/renovating-a-tektronix-475-timebase-switches-potentiometers-and-hf-response/

This also covers most of the problems I've been seeing. It's an excellent post.


Re: 475M metal can caps

Bob Isselhard
 

Thanks Paul, Michael and Leon.   I told Michael in a PM I ordered five of the spacers off Ebay immediately after following his link.  Yeah, I know, power supply problems can doom the best of efforts.  That’s why I ordered the hard copy manual as soon as I saw the problem with the trigger. I wanted to see exactly where all the test points were and exactly what they should read.  I don’t have a second scope to check ripple  but getting the voltages correct on the -15 and -8 volt rails may solve this.  If not, I’ll no longer be a TEKSCOPE beginner, but a “veteran” with solder splashes and flux odor to boot.  When I pulled the -15 volt electrolytic, I checked it and it shows 3700 uf and .47 ESR.  But I’m not about to put a 10 + year old cap back in.

Thanks to all for the assistance so far.

Bob

Sent from Mail ( https://go.microsoft.com/fwlink/?LinkId=550986 ) for Windows 10


Re: Clean and Lubricate Pots in Tek 475

 

Bill,

I had a closer look at the vertical input board and it looks like it might come out with less work than I thought. I haven't verified this, but it looks like the BNC connectors might not be mounted to the front panel (I thought I read a blog entry about repairing a 475 that said something about this, but I can't it now, however this post of EEVBlog shows a full teardown, which seem to support my hypothesis <https://www.eevblog.com/forum/projects/tektronix-465-repair-and-restoration/>). If that's true, then getting at the two vertical position pots is much easier (if not quite trivial). I also noticed that the only pots that got stiff are the "double stack" ones. The single stack, which appear to be from the same manufacturer, are all easy to turn.

It looks like I can buy replacements for between $10-$20 per pot, which I think is a fine price. If I can get the vertical input and main boards out without too much fuss, and if just lubricating them doesn't help, then I will just replace them.

I'm not sure who made these pots, but all of them (with the possible exception of the two trigger level pots, which are metal cans rather than plastic blocks) are brown/black plastic with dark red inserts. The replacements I've found online (from talonelectronic.com and rshopboss.com) are blue, and my scope was assembled in late 1974, so I'm assuming that it has A&B pots.

I have been very happy with the results I've gotten so far with what I consider fairly minimal effort: I only had to break out the soldering iron ONCE on this old thing, and that was completely unavoidable; to replace a obviously very dead electrolytic capacitor on the sweep board.


Re: 475M metal can caps

Leon Robinson
 

Or herd cats.  Electronic equipment is like a house, the power supply is the foundation, 
If it,s not right nothing else is.


Leon Robinson  K5JLR

-------- Original message --------
From: "Michael W. Lynch via groups.io" <mlynch003=yahoo.com@groups.io>
Date: 11/06/2020 4:41 PM (GMT-06:00)
To: TekScopes@groups.io
Subject: Re: [TekScopes] 475M metal can caps

Trying to "fix" a TEK scope that has faulty power supplies is almost like trying to push a rope.

--
Michael Lynch
Dardanelle, AR

11981 - 12000 of 184726