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Hakan,


Thank you for your help. I put my card in the 2a mode and edited the adj700.bat file.
I removed the NI drivers from config.sys I am now able to run the software.


Many thanks !!!


Regards,


John

Someone here may have mentioned the issue of TC-zeners already, but if not, you should be aware of the details. Is this zener spot used as the reference for the whole power supply, or is it elsewhere in the circuit? Do you have the Tek part number? If it's the reference, then you should use the Tek part number equivalent, which can be found easily.

With TC-zeners, they may on the surface look regular spec-wise, but the tempco spec is much tighter, compared to normal zeners.

Ed

Magnus,

Try accessing using dotted decimal notation your local DNS may be the culprit.


Regards,

Mike

Good Day,

wow, it *does* work when I tried it through a US-based VPN...

I have printed the content as PDF for my own reference.

It does *not* work when accessing it thru a German/EU ISP! Any comments would be appreciated.

Cheers,

Magnus

****

Magnus, Seems to be up and running fine this morning at 8:10 AM Eastern time. Mark

Hi Ed. Thanks for the email. That is a neat trick with the NPN transistor, but I only see this as a temporary fix. I ordered a 1n5234B zener as a replacement from Mouser and will install it next week after it arrives. The specs are comparable to the tek part listed in the service manual. The Tek part lists .4 w, 6.2 v, 5%. My part coming from Mouser is .5 w, 6.2, 5%. I believe that will be close enough. I posted a few pics of the temporary fix and the dual trace (haha) in the Tek 465 woes file in the files section.

I think you can consider the transistor B-E reverse breakdown to replace a zener diode as a permanent fix if necessary, if the circuit seems to work properly, but there are no specifications that you can rely on, as there would be with a normal, part-numbered zener. I used reversed B-E transistors as voltage references in some power supplies I built over forty years ago, and they still work just fine.

One thing you don't want to do, however, is to use a transistor in breakdown mode for a long time, and then use it as a regular transistor again. The normal characteristics can suffer from extended reverse breakdown. I have seen specs on certain low noise transistors and even opamps warning to avoid reverse breakdown - even once - because it may permanently degrade the performance.

Another thing to watch for is that transistors in this mode can be very noisy, and in fact are often used for generating noise, rather than a specific voltage drop. Some types are more susceptible than others - those ones I used many years ago came from a family of GE-brand transistors that were well-known for this characteristic. Some made nice zener-replacements, breaking around 7V, and others made great noise generators, producing relatively large noise levels. I still have some that I saved way back then, that could make hundreds of mVpp noise voltage in high-Z circuits.

One last thing - I haven't followed this discussion, so I don't know the circuit context, but I assume that this is just a voltage dropping or clamping type zener application, and not a voltage reference. If it's for a reference, then it's likely to require a temperature compensated zener, which is a whole different deal - a temporary zener can work, but it should be replaced by the proper type to maintain performance.

Ed

Ok. I uploaded the file of the Frankenstein zener. Please no comments on
the sloppy solder job. I had some trouble getting the original zener out of
the board. I plan to clean it all up when I install the new component.
Also, check out the image of the nice dual trace --- sweet.

Hello,


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


File : /TEK 465B woes/IMG_3867.JPG
Uploaded by : kevincrossett <kcrossett@...>
Description :


You can access this file at the URL:



To learn more about file sharing for your group, please visit:



Regards,


kevincrossett <kcrossett@...>

Hello,


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


File : /TEK 465B woes/IMG_3837.JPG
Uploaded by : kevincrossett <kcrossett@...>
Description :


You can access this file at the URL:



To learn more about file sharing for your group, please visit:



Regards,


kevincrossett <kcrossett@...>

Hello,


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


File : /TEK 465B woes/IMG_3868.JPG
Uploaded by : kevincrossett <kcrossett@...>
Description :


You can access this file at the URL:



To learn more about file sharing for your group, please visit:



Regards,


kevincrossett <kcrossett@...>

At Sphere Research, we are still digging through all the various lots of repair parts we bought, and I found two interesting things that may help somebody trying to do a repair:

Tek Fan Impellers (the flat ones that fit in the 465/475, etc on the siemens motors.) 369-0031-00. we have 4 new ones, US$10 each (black)

Tek temp probe sensing head element 206-0248-03 (long black tapered cylinder with 2 pins). we have 2 new ones, US$20 each.

also have a big 2 cu ft box filled with misc Tek repair parts of all kinds, lots new in bags, some assembly pulls, US$35 to anybody interested, will be a few bucks to ship, it's big and heavy. there's a 7603 rear heatsink cover, case trim, attenuator boards, 24xx series complete front control assembly with knobs and controls, cables, connectors,passives, etc.

also found a box of big non-inductive power resistor (brown cylindrical) marked for Tek 577, looks to be maybe a dozen of them, different values, US$20.

please reply OFF List to me at walter2 -at- sphere.bc.ca, so we don't make the nice people here crazy.

all the best for christmas & new years!
walter & susan
sphere research corp.
Sphere's Used Electronic Test Equipment



Sphere's Used Electronic Test Equipment Sphere's Canadian test equipment site contains an extensive inventory of all kinds of new and used electronic test equipment, service parts, bargains, ele...



View on www.sphere.bc.ca
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Hi Jim. On on Mouser now. Radio Shack didn't have anything close to what I
needed. I'm guessing the power at .4 w isn't critical so I am looking for
.5 w (500 mw) zeners now. I plan to purchase a lifetime supply...As soon as
the part arrives, it's out to the garage to install it in the scope.

On Sat, Dec 6, 2014 at 10:04 AM, Jim Popwell jpopwell@... [TekScopes]
<TekScopes@...> wrote:

Hi Kevin,
be sure to get a real zener in before long, i have no idea how long the
“transistor fix will last”, I’ve used it a few times when i had no zener.
but it does have to be reversed biased to work… let me know how you do,
just be sure to check the real on’s polarity when you install it!
jim

On Dec 6, 2014, at 6:17 AM, Kevin Crossett kcrossett@...

[TekScopes] <TekScopes@...> wrote:

Thanks everyone for the support on this problem. I have one final

question.

When I placed the 2n3904 transistor as Jim suggested with the base at the
cathode end, the circuit did not work. When I turned it around, basically
because I thought maybe I hooked it up wrong, it worked fine. In other
words, the Base of the transistor is connected to the 27 kohm resistor in
the circuit. If the base is the cathode, isn't that wrong. I believe I

have

a standard transistor with the EBC configuration when looking at the flat
side of the TO-92 package. The B is connected to the same side as the
resistor and the E is connected to the other point. Am I missing

something

or is that backwards?

On Sat, Dec 6, 2014 at 4:22 AM, raymonddf@... <mailto:

raymonddf@...> [TekScopes] <

TekScopes@... <mailto:TekScopes@...>> wrote:

Congrats Kevin, I'm sure you'll enjoy your "new" 'scope. Don't forget:
You'll need at least two!


Raymond

Thank you very much for your support!
-> Alignment tool is ordered

But: You scared me a bit - Hopefully, I didn't demaged the core already ...
Maybe I find another CRT driver board on eBay so I have some spare parts?!

Best, Simon

Hi Kevin,
be sure to get a real zener in before long, i have no idea how long the “transistor fix will last”, I’ve used it a few times when i had no zener. but it does have to be reversed biased to work… let me know how you do, just be sure to check the real on’s polarity when you install it!
jim

On Dec 6, 2014, at 6:17 AM, Kevin Crossett kcrossett@... [TekScopes] <TekScopes@...> wrote:

Thanks everyone for the support on this problem. I have one final question.
When I placed the 2n3904 transistor as Jim suggested with the base at the
cathode end, the circuit did not work. When I turned it around, basically
because I thought maybe I hooked it up wrong, it worked fine. In other
words, the Base of the transistor is connected to the 27 kohm resistor in
the circuit. If the base is the cathode, isn't that wrong. I believe I have
a standard transistor with the EBC configuration when looking at the flat
side of the TO-92 package. The B is connected to the same side as the
resistor and the E is connected to the other point. Am I missing something
or is that backwards?

On Sat, Dec 6, 2014 at 4:22 AM, raymonddf@... <mailto:raymonddf@...> [TekScopes] <
TekScopes@... <mailto:TekScopes@...>> wrote:

Congrats Kevin, I'm sure you'll enjoy your "new" 'scope. Don't forget:
You'll need at least two!


Raymond

[Non-text portions of this message have been removed]

[Non-text portions of this message have been removed]

[Non-text portions of this message have been removed]

Hi Simon,

Absolutely you want a plastic tool. Use of a metal hex tool will crack the core.

Something like this:

From my experience with radios, TS-520, etc, please don't proceed till you have the right tool. ? Likely one of the other members here can give you an exact size/part number, but you are looking for plastic alignment tools. ?They are made with flathead, hex, and other patterns, and available quite cheaply. ?Those cores are quite fragile, and the tool that makes full contact with all surfaces of the slug is critical to avoid cracking. ?Original replacements for the slug or whole inductor are made of unobtainium for nearly all tuned inductors, leaving you to try to re-engineer the circuit to use a modern part that is hopefully "close enough". ? Sorry I don't have the sizes/part numbers myself, but either the manual or someone else here should.


Nathan

KK4REY


—
Sent from Mailbox

On Sat, Dec 6, 2014 at 11:17 AM, Simon evlab23@... [TekScopes]
<TekScopes@...> wrote:

Hi Tom.
Of cause - no I don't have the correct tool.
It seemed to me like a hexagonal insert. I have some hex screwdrivers,
but since the 16kV are not far away, I would like to use a
non-conductive material. Also, the metal of the screwdriver may
influence the inductor to be adjusted.
What kind of is the "correct tool"? Made of plastic? It should be six
inches long, so it can reach down to the inductor when the scope is opened.
Best regards, Simon
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[Non-text portions of this message have been removed]

Hi Tom.

Of cause - no I don't have the correct tool.
It seemed to me like a hexagonal insert. I have some hex screwdrivers,
but since the 16kV are not far away, I would like to use a
non-conductive material. Also, the metal of the screwdriver may
influence the inductor to be adjusted.

What kind of is the "correct tool"? Made of plastic? It should be six
inches long, so it can reach down to the inductor when the scope is opened.

Best regards, Simon

Hi,
I'm just getting started on a 7704A that has a few problems. There will
probably be a few more questions to follow but first off I need to know if
I can safely power it up with the top half disconnected and removed. I
don't want to cook anything!

The plugins (7A26, 7A16A, 7B85 & 7B53A) all appear to work fine in my 7603.
In the 7740A I'm not getting good vertical signal throughput, the vertical
position controls do nothing and the calibrator signals are badly
attenuated. PS looks good for voltage (will check ripple tonight). It was
full of prairie dust (Calgary). I'm hoping the worst of the problems will
be dirty board inter-connects.

Thanks!
Keith

Sometimes when the core seems to be stuck, it is cracked. Do you have the correct tuning tool?

Tom

Hi group.

I would like to adjust the screen setting of the CRT according to the
service manual.
To adjust the screen image size, the manual states to adjust using L321
on the CRT driver board to do so.
L321 is an inductor with some kind of ferrite core one has to turn /
adjust. I tried that, but the core seems to be stuck inside.

Am I doing something wrong? I don't want to damage L321. Can someone
give me an advise?

Best regards, Simon