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On Thu, Jan 9, 2025 at 09:12 AM, jason neumann-grable wrote:

I have a Tek 321A scope that I am very anxious to get working. However, it
has the "legendary" 2N2207 transistors (lots of 'em) that grow crystals
inside and short themselves out.

I ran into this same problem with several Tek 3S76 plugins. I had the same experience that you had when buying replacements; it's clear that the zinc whiskers grow just as well in storage as in use. I tried the mechanical shock method with little success, but blowing the shorts away electrically worked. Eventually I worked out a method that almost always worked, but the whiskers sometimes returned. The new shorts could be blown away again and the MTBF (Mean Time Between Failure) always seemed to get longer.

I wrote up my experience and method here:



In the 3S76, I found that Tek used Si NPN/Ge PNPs in pairs to make amplifiers that could be analyzed just like an Op-Amp: the gain was solely dependent on the ratio of an input and feedback resistor, plus the biasing of the Ge PNP was "long tailed" so the circuit readily accepted a Si PNP as a replacement with no other component changes. In the case of the 3S76, I found that 2N3906s worked perfectly.

While I started out hoping to maintain the originality of my 3S76s, I slowly realized that any transistor in a whisker-prone TO-7 case was too unreliable in the long term.

--
Jim Adney
Madison, WI USA

Dear all.

The problem has been solved by replacing the burned diode by a (rather over-dimensioned) fast recovery diode (SURF1560). Now image intensity, gray scale and color can be nicely set according to the provided calibration scheme. Fortunately, the flyback transformer was not damaged by the failing diode.

With kind regards,
Gerard

Hi Gianni,
Usage of FAST LEVEL CENTER is described at page 5.66, section 13, steps h-j.
I also own a 7633 :-)
Max

Thanks for your answer. Last year I went through the alignment of the 7834 and I didn’t remember that; but ….the 7834 has not this control!

However they added this trimmer in the 7633 without telling the user how to set it - probably there was a way to set it without the general adjustment.

Even at page 5.64 the simply say to set it fully CCW, but then they don’t say anything more.

I set it empirically….

These are wonderful instruments, I have a 7623A too and wors like a charm.

Thanks again

Gianni

--
Roy Thistle

Hi Jason. I am glad to hear you are going for a 321 restoration. They are wonderful little scopes. I have about 12 of them, 7 restored, two in progress, and a couple of parts scopes. So I have a large selection of parts, let me know if you need something.

As far as the transistors go, I would encourage you to ignore whatever you have heard about them. In my restorations I have only had to replace one of the little buggers. I would suggest that you approach this like any other, that is, fix what is wrong and leave well enough alone if something works. I always start with the power supplies. I have replaced some electrolytic capacitors in the 10 volt primary side. Once the power supply is checked out then you can approach each section in turn and get that working. The order I usually follow is vertical, horizontal, and sweep. Hope this is of value, please let me know if you have any questions.

/g/TekScopes/photo/299466/3866337?p=Created%2C%2C%2C20%2C2%2C0%2C0

Bill,

See if CR1499 is shorted. Check voltages on the regulator board for the -15V supply. Dirty contacts in the sockets of the transistors could be a problem. If a ribbon connector is not fully seated or is off by a pin, that will cause the problem. The plastic ends on the ribbon cables will degrade due to age - especially the blue ones. Mouser has the black replacements. The scope should not tic with no plugins. That says something else is wrong. If the replacement transistor is shorted to the heatsink, that could be a problem. The insulator could be broken.

You can disconnect boards to see if the problem is on a particular board. Tantalums will not always show leakage or short by a DMM. I prefer to use my VTVM for testing and a DMM for exact measurements such as B+ adjusting.

In my 7000 series scopes, I replaced the condensers with higher capacitance in voltage and raised the wattage of some resistors. If the beta of the TO-3s in the power supply are low, use BUX48A. Low beta will cause problems or hard to start.

Mark

Are there any options for the slots that seem to be present on the rear of the scope?

I did? a search for documentation for one I received recently, and found user, maintenance, etc., but didn't see what I'd expect listing what options might go in those slots if anything.

thanks
jim

Eric,

You were first to ask! It's yours for the shipping and packing materials send me an address and I'll put a bill in it for the postage and packing materials and you can mail it back to me.

Mark

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Like other PCB card edge connectors, the recepticle has bifurcated gold plated pins.

See Tek 7000 test fixture extenders.




Connectors are Tektronix made.

Plug-ins and PS current limits are set to a safe short circuit, probably 2-5A.

Jon

I'd be interested. what are you asking for it + shipping to 97034



On Thu, Jan 9, 2025 at 1:41?PM W7HPW Radio via groups.io <t265frc10=
[email protected]> wrote:

Calibration Fixture Flexible Extender for 11000 series scopes, excess to
my needs, like new I don't think it has ever been used, anybody want it?

Mark

--
--Eric
_________________________________________
Eric Garner

Calibration Fixture Flexible Extender for 11000 series scopes, excess to my needs, like new I don't think it has ever been used, anybody want it?

Mark

Yep, in particular C60 as thats the one on the -15. sadly it was fine.

Make sure you read the topic all the way to the end, I updated old posts three or more times as better recipes were discovered.

Dave Wise

________________________________
From: [email protected] <[email protected]> on behalf of Sigur?ur ?sgeirsson via groups.io <siggi@...>
Sent: Thursday, January 9, 2025 7:51 AM
To: [email protected] <[email protected]>
Subject: Re: [TekScopes] TEK 321A

Hey Jason,

I don't know anything about Ge transistor replacement. I did, however, find
this thread (/g/TekScopes/topic/7640286#msg35340)
apparently written by people who've worked on the 321A and replaced some of
the 2N2207s with modern-ish Si transistors. Maybe this will help?

Good luck,
Siggi

On Thu, Jan 9, 2025 at 10:12?AM jason neumann-grable via groups.io
<magrepha1@...> wrote:

Hi: I'm a new subscriber and somewhat of a computer-illiterate, so I hope
this is the right place to ask questions.
I have a Tek 321A scope that I am very anxious to get working. However, it
has the "legendary" 2N2207 transistors (lots of 'em) that grow crystals
inside and short themselves out. I recently acquired (at considerable
cost) 10 more of the little jewels - - every *$&%^# one of them was bad !
Does anyone out there know of a substitute device or a fix that would
enable me to get this scope working ? I worked at Tek when the 321 was
first introduced and this scope has considerable sentimental value.
Thanks for whatever help y'all can give !?
Jason Neumann-Grable
KF7JEI

Hey Jason,

I don't know anything about Ge transistor replacement. I did, however, find
this thread (/g/TekScopes/topic/7640286#msg35340)
apparently written by people who've worked on the 321A and replaced some of
the 2N2207s with modern-ish Si transistors. Maybe this will help?

Good luck,
Siggi

On Thu, Jan 9, 2025 at 10:12?AM jason neumann-grable via groups.io
<magrepha1@...> wrote:

Hi: I'm a new subscriber and somewhat of a computer-illiterate, so I hope
this is the right place to ask questions.
I have a Tek 321A scope that I am very anxious to get working. However, it
has the "legendary" 2N2207 transistors (lots of 'em) that grow crystals
inside and short themselves out. I recently acquired (at considerable
cost) 10 more of the little jewels - - every *$&%^# one of them was bad !
Does anyone out there know of a substitute device or a fix that would
enable me to get this scope working ? I worked at Tek when the 321 was
first introduced and this scope has considerable sentimental value.
Thanks for whatever help y'all can give !?
Jason Neumann-Grable
KF7JEI

Ron,
I second that - great to hear this is all legit and then quite a bit more.
Thank you for clarifying.
Radu.

On Thu, Jan 9, 2025 at 6:13?AM Wayne via groups.io <WAYNECL=
[email protected]> wrote:

Ron,
Thank you for posting, and for your willingness to help to carry on Dave's
legacy through this assistance to Linda. The value of Dave's dedication to
those of us who need these manuals is unsurpassed, so far as I know, and it
is wonderful that his work can continue even after his untimely and
unfortunate passing. Many will find Artek products on ebay that perhaps
would not know of their service otherwise.
Thanks again,
Wayne

Hi: I'm a new subscriber and somewhat of a computer-illiterate, so I hope
this is the right place to ask questions.
I have a Tek 321A scope that I am very anxious to get working. However, it
has the "legendary" 2N2207 transistors (lots of 'em) that grow crystals
inside and short themselves out. I recently acquired (at considerable
cost) 10 more of the little jewels - - every *$&%^# one of them was bad !
Does anyone out there know of a substitute device or a fix that would
enable me to get this scope working ? I worked at Tek when the 321 was
first introduced and this scope has considerable sentimental value.
Thanks for whatever help y'all can give !?
Jason Neumann-Grable
KF7JEI

I have a Tek 321A that is loaded with these transistors. They have a reputation for failure, due to growing crystals inside that short them out. I recently acquired 10 more and every one of the #&$%# things was bad.
Is there a "fix" for this problem that uses another device? I'd really like to get this little jewel going again. It has great sentimental value to me, as I worked at Tek when the 321 was first introduced.
Any help would be greatly appreciated.

Jason Neumann-Grable

This group doesn't permit attachments. Please write an off-list email to
me. I'll the pdf to you

WBR

чт, 9 янв. 2025?г. в 17:36, Night Walker <walkerru@...>:

Ron,
Thank you for posting, and for your willingness to help to carry on Dave's legacy through this assistance to Linda. The value of Dave's dedication to those of us who need these manuals is unsurpassed, so far as I know, and it is wonderful that his work can continue even after his untimely and unfortunate passing. Many will find Artek products on ebay that perhaps would not know of their service otherwise.
Thanks again,
Wayne