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Hello:

I am checking out my 2235 (US/AN version), and apart from some other idiosyncrasies, that I will leave for later, the unit is making a quiet, but very unpleasant high pitch "whine" after about 5-10 min of warm-up. The best I can say it is coming out of the power supply portion, but the source of the sound is difficult to pinpoint for certain...

What would be you suspicion? Is it a PSU showing signs of fatigue? Recommended steps? Time to recap?

Not sure if this is relevant, but 2 out of 3 small neon bulbs close to the PSU are briefly flashing, when the power is being turned off... Switch-off voltage spike protection possibly?

Advices would be appreciated.

DS

The link I had for the SR 760 manual seems to be dead. I have it in PDF form so I'll have to figure out where to post it. Doesn't seem appropriate to put in on a Tek dedicated website... Suggestions?

SR 780 manual:

In case it isn't apparent from the information below, I created a small
PDF that outlines the procedure I used to replace the electrolytics in my
465B using an auxiliary PC board and snap-in caps. I've shared the
pictures in the photo album but this makes it a little more organized.

Note that I'm going to order another batch of boards as I'm pretty much
sold out. Should take about a week before they get here.

Thanks,
Barry - N4BUQ

----- Original Message -----

From: "[email protected] Notification" <TekScopes+notification@

groups.io>

To: [email protected]
Sent: Sunday, July 29, 2018 2:44:43 PM
Subject: [TekScopes] New file uploaded to [email protected]

Hello,

This email message is a notification to let you know that a file has been
uploaded to the Files area of the [email protected] group.

*File:* Replacing Electrolytic Filter Capacitors in a Tektronix 465.pdf

*Uploaded By:* n4buq

*Description:*
Step by step procedure for replacing the electrolytic capacitors in a

465B

using an auxiliary board with snap-in capacitors.

You can access this file at the URL:
/g/TekScopes/files/Replacing%20Electrolytic%20Filter%

20Capacitors%20in%20a%20Tektronix%20465.pdf

Cheers,
The Groups.io Team

From: Adrian <Adrian@...>
Sent: Jul 29, 2018 5:50 PM
To: [email protected]
Subject: Re: [TekScopes] Slightly OT - Bourns trimmer pot failure

Hi Michael,
Did that and not a trace of anything, just a ‘bruise’ where a dimple in the stake has been pushed hard against the surface as if to make contact. I am really beginning to think this has been faulty from day one.
Adrian

Adrian
Sent from an I-thingy

On 29 Jul 2018, at 10:39, Michael A. Terrell <mike.terrell@...> wrote:

The failures I saw with the Beckman pots were in telemetry receivers being built for NASA. They were the ones in use when we lost that last shuttle. The media was waiting for information, but when you had built the equipment for the earth stations, with dual diversity at every tracking site I knew as soon as they stated, We have a loss of telemetry' that we had lost another shuttle. It was like a kick in the gut, hoping for the impossible in that six complete systems had failed at the same instant instead of the loss of the shuttle.

We couldn't wait for Beckman to decide that we were right, because our products were used by many Aerospace companies where failures could cost hundreds or thousands of lives. They forced us to make the change, and only by removing a company from the master Approved Vendor List could we make sure that no one substituted anything else. Purchasing was then forced to state 'NO SUBSTITUTIONS ALLOWED ON THIS ORDER'.

As an example, a distributor offered purchasing some tighter tolerance molded inductors for a lower price than the approved part. Purchasing bought them and patted themselves on the back for sving almost 50%, but the new 5% parts caused problems that we had never had with the specified 10% parts. No one bothered to compare the SRF, and the new, unapproved vendor line was about 20% lower, across the range that we needed. Purchasing got their asses chewed out by the head of engineering and one of the Corporate VPs, over that blunder.


Michael A. Terrell

On 29 Jul 2018, at 10:39, Michael A. Terrell <mike.terrell@...> wrote:

The failures I saw with the Beckman pots were in telemetry receivers being built for NASA. They were the ones in use when we lost that last shuttle. The media was waiting for information, but when you had built the equipment for the earth stations, with dual diversity at every tracking site I knew as soon as they stated, We have a loss of telemetry' that we had lost another shuttle. It was like a kick in the gut, hoping for the impossible in that six complete systems had failed at the same instant instead of the loss of the shuttle.

We couldn't wait for Beckman to decide that we were right, because our products were used by many Aerospace companies where failures could cost hundreds or thousands of lives. They forced us to make the change, and only by removing a company from the master Approved Vendor List could we make sure that no one substituted anything else. Purchasing was then forced to state 'NO SUBSTITUTIONS ALLOWED ON THIS ORDER'.

As an example, a distributor offered purchasing some tighter tolerance molded inductors for a lower price than the approved part. Purchasing bought them and patted themselves on the back for sving almost 50%, but the new 5% parts caused problems that we had never had with the specified 10% parts. No one bothered to compare the SRF, and the new, unapproved vendor line was about 20% lower, across the range that we needed. Purchasing got their asses chewed out by the head of engineering and one of the Corporate VPs, over that blunder.


Michael A. Terrell


-----Original Message-----

From: Adrian <Adrian@...>
Sent: Jul 29, 2018 4:54 AM
To: [email protected]
Subject: Re: [TekScopes] Slightly OT - Bourns trimmer pot failure

Yup, you could be right, I just looked at a copy of the datasheet I
found on the web. The strap line in the sheet is "Now you can specify
Bourns for cost-sensitive applications" the sheet is marked 1977 but it
is over-stamped with "Obsolete" dated 79 so this design wasn't around
long, that may say something about the design? Certainly compared with
the lifetime of products like the 3386 which I also used in large
numbers at one point in my life with no issues.

I agree, why do people have such an issue with owning up to a problem? I
spent a fair part of my life in aerospace world and there the culture is
different - Problem? 'share early, share often' - was the mantra in
Boeing and it worked, genuine 'no blame' culture. S**t happens, what
matters is you truly understand root cause and fix it, that way we don't
kill a bunch of folks (which could include our family members, as we
were oft reminded) sitting in a tube at 35,000 ft!

On 7/29/2018 8:47 AM, M Yachad wrote:
So, crap like that happens every so often - I haven't boycotted Bourns over that - their quality is usually excellent - and it would be nice if the manufacturer would 'fess up, without dancing around an issue which is plain as day for anyone to see.