[GreenKeys] OT: Need help to T-Shoot this Tek 485 scope

Thu May 11 07:16:29 EDT 2017

Cripes, well now I put my foot in it..

I pulled the A15 module, which was an absolute nightmare, and I'm not sure
how I'll ever get it properly re-installed without some additional major
disassembly. As this job progressed, I was trying my utmost to respect the
mechanical design, accepting the 'fact' that the Tek engineers were Very
Smart People - oh so much smarter than I.

In fact, that may not be the case. Thing is a real turd to work with, at
this level..

So I got the A15 transformer module out and, and here's where I really
might have blown it. There are two diodes on the A15 board, which look very
 much like the 600V silicon diodes used elsewhere in the machine. I tested
them, and found both wide open - hard to believe, but that's what I found.
But it was only after I pulled them that I found they were 12kV / 5mA
devices and most likely would never show as good on a typical meter. Ugh!

 And the resistors also measured out fine as well. So it's a big fat "no
trouble found", aside from the failure. I'm starting to worry that the g1
connection may have broken within the CRT. This was found and noted in a
similar case (look it up) and it's giving me the willies.

On Wed, May 10, 2017 at 7:35 PM, drlegendre . <drlegendre at gmail.com> wrote:

> @Bruce
>
> Hey, thanks for those photos - I hadn't come across those. But it's as I
> surmised, A15 is the one buried down in the midst of it all.. ugh. Not like
> it's all that easy to t-shoot it when active.. if that's even possible!
>
> Thing is, I still cannot find any illustration of it in the manual. No
> pictorials, no schematics, no graphics, nothing.. only partial schematics
> spread across several different drawings. This is really confounding, as
> the manual is so thorough. And even if it +is+ fully documented, I'm unable
> to determine this from the docs, and there's no procedure to R&R the module
> - which is very surprising.
>
> Anyway, I'm going to try removing A15. We'll see what that yields, and
> I'll report back in short order. Thanks again, to all of you for your
> support.
>
> (BTW - Just WTF Did Tek use primarily pozidriv screws, yet also used
> phillips in some areas?!)
>
> On Wed, May 10, 2017 at 7:21 PM, Nick <creativegardening at hotmail.com>
> wrote:
>
>> I totally agree and that's what I am doing. But it is not easy sometimes
>> to find your way through the Internet jungle. You can't see the forest
>> because of too many trees around.
>>
>> Rookies also face another challenge  - elmers are not elmers anymore like
>> in the old days. I  consider myself very lucky to have one of the best
>> living right around the corner from my location.
>>
>> And then you have the miserable guys who are jealous sometimes of the
>> rookies enthusiasm and accomplishments.
>>
>> Trust me, I speak from experience!
>>
>> Nick  -  N0NCQ
>>
>>
>>
>> Sent from my T-Mobile 4G LTE Device
>>
>>
>> -------- Original message --------
>> From: Paul Heller <paul0926 at comcast.net>
>> Date: 5/10/17 5:51 PM (GMT-05:00)
>> To: Nick <creativegardening at hotmail.com>
>> Cc: GreenKeys at mailman.qth.net
>> Subject: Re: [GreenKeys] OT: Need help to T-Shoot this Tek 485 scope
>>
>> I'm not against what is being proposed, but we are seeing a sudden influx
>> of repeat questions, some as recent as a few months ago (sprocket feed
>> paper). I would prefer people do some research first before asking
>> redundant topics.  The footer of every Greenkeys message has links to
>> archives.
>>
>> Paul
>>
>> On May 10, 2017, at 3:06 PM, Nick <creativegardening at hotmail.com> wrote:
>>
>> I am the rookie here and have to agree with Ray. There are so many things
>> I like to learn but I am afraid to flood this room with rookie questions.
>> So, I wait until the material pops up.
>>
>> On the other hand, not every subject is everybody's subject - so, what do
>> you do? What is right and what is wrong? Do you flood or do you play
>> conservative with your posts?
>> I don't know the answer.
>>
>> Nick  -  N0NCQ
>>
>>
>>
>> Sent from my T-Mobile 4G LTE Device
>>
>>
>> -------- Original message --------
>> From: Raymond Cote <bluegrassdakine at hotmail.com>
>> Date: 5/10/17 1:40 PM (GMT-05:00)
>> To: Gil Smith <gil at baudot.net>
>> Cc: Green Keys <GreenKeys at mailman.qth.net>
>> Subject: Re: [GreenKeys] OT: Need help to T-Shoot this Tek 485 scope
>>
>> Replies ON LIST would be preferred. I suspect we would all prefer to
>> learn by other technicians methods. Replying only to the originator does
>> not help the trst of us learn.
>> There have been many messages that i have been interested in learning
>> about only to see a message that states "thanks for the help in solving my
>> problem".
>>
>> Please, OM's. Consider sharing you methods of tracking and applying your
>> fixes with the rest if us. Many if us are hoarders (collectors) and have a
>> plethora if gear that trouble shooting practices of one item would apply to
>> other gear
>>
>> Thanks fir reading and joining this method if teaching us
>>
>> Bench technician for 50plus years and have a commercial radio phone snd
>> general ham ticket. Every time i open up something to investigate its
>> innards, i still learn  something new.
>>
>> Ray Côté
>> KD9CCZ
>>
>> Sent using Jedi Mind Trick!!
>> By
>> Raymond Côté
>> KD9CCZ
>>
>> On May 9, 2017, at 00:58, Gil Smith <gil at baudot.net> wrote:
>>
>> I found a wealth of info on tek scope repair on a yahoo group:
>> https://groups.yahoo.com/neo/groups/TekScopes/info
>>
>> Yahoo groups is a pain, but that is where they are.  I found lots of
>> folks to help when I wanted to re-cap my trusty 300 MHz 2465 and 150 Mhz
>> 2445.  I started with the 2445.  I replaced all of the caps with new/better
>> spec units.  When I got it back together, the trace had some jittering that
>> was not there originally.  F-me.  Also, the power switch was now stuck in
>> the on position, so I need to plug the power cord in to turn it on.  Very
>> disappointing outcome for a couple of days of work, plus parts cost.  I am
>> really pretty careful/anal and not generally a hack, but I guess I missed
>> something.  I bought a replacement power switch for the 2445, but I really
>> have no interest in spending hours to do the R&R.
>>
>> As for my prized 300 MHz 2465, I now have no interest in screwing with
>> it, as it still works perfectly.  It has great resolution for seeing things
>> like undershoot, which my DSOs cannot resolve.  If it craps out some day, I
>> will re-visit the re-cap (I have the bag of parts), but my original plan to
>> re-cap is on hold unless needed.
>>
>> fyi, gil
>>
>>
>> gil smith, AF7EZ
>> greenkeys moderator
>> gil at baudot.net
>>
>>
>>
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