Date   

Tek 2246A

leesbreeze@...
 

I'm retired and a bit of a newbie to electronics. I just got my first scope a tek 2246A from eBay. Said it was manufacture refurbished. When it arrived the shipping box was in pretty bad shape and the scope wasn't packed very well. When I turned the scope on all the front panel lights come on okay but the display does not power on. The seller adjusted the price and I kept the scope.
So far I've just been trying to find information on forms and YouTube. But not making much headway. I've been looking for a good schematic but I'm not sure if I'm far alone enough with this hobby to attempt the repair.
Any thoughts or guidance would be appreciated!


Lee


Re: 7704 issues

Dave / NR1DX
 

OK

For starters what is the serial number of your unit? Bxxxxxx ?
What manual are you using 070-xxxx-yy? and what release date is on the
bottom of the title page

What board are you struggling with in particular A?? there are some
18-20 different ckt boards in the 7704A, some of them were released with
4 different versions of the board over the years, some never changed?

If you can tell what is the part number of the board in particular you
are struggling with? This may or may not be printed on the board itself,
some are some are not. For the 7704A most likely the part number is
something like 070-18xx-yy

Figure 6-30 in my manual is a photo of the HV test point and doesn't
show any board?

Dave
manuals@artekmanuals.com

On 8/30/2017 1:57 PM, regman10@comcast.net [TekScopes] wrote:

I've been pondering the schematic for 2 days now and its really poorly
documented and kind of surprising compared to the rest of the scope.
None of the schematics match up with the what I've got, maybe theres
an older (or newer service manual). I pulled together a manual from 2
different sources for the 7704A as the schematics were fragmented over
several pages on the link provided and added to the manual, schematics
that either fit the pager, or are simply taped together to create the
foldout.

My supply voltages are fine and I'm not seeing any shorts. My theory
is that for one reason to another those harmonica connectors were
unplugged from the green connector and since there are no clear
indications of where they go. The pin outs alone are enough to drive
you crazy. Every connector has a different number of pins so that part
of it is pretty easy, determining where exactly they plug into the
host connector that plugs into A20. So the Navy tech working on it
gave up.


The scope is fully functional, readouts work fine, analog, no issues,
was last calibrated on 2009.


Once again, if someone could snap a photo like the one in fig 6-30 but
with a close up of the harmonica connectors, I would be eternally
grateful. email to ga4blues@gmail.com

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

--
Dave
Manuals@ArtekManuals.com
www.ArtekManuals.com


New, Expanded, VintageTEK Museum On-Line Content

 

Hi Dave,

This was a bug. It has been fixed.

Thanks for catching that.

Dennis Tillman W7PF





From: Dave Daniel [mailto:kc0wjn@gmail.com]
Sent: Tuesday, August 29, 2017 3:01 PM
To: dennis@ridesoft.com <mailto:dennis@ridesoft.com>
Subject: Fwd: [TekScopes] New, Expanded, VintageTEK Museum On-Line Content



Hey, Dennis.

Thanks for the heads up. It looks nice.

One question - why, after I've been browsing a bit on the website, and I
click on the vintageTEK logo in the upper LH corner of the page, does it not
take me back to the home page?

Cheers,
DaveD



-------- Forwarded Message --------


Subject:

[TekScopes] New, Expanded, VintageTEK Museum On-Line Content


Date:

Tue, 29 Aug 2017 12:26:09 -0700


From:

'Dennis Tillman' dennis@ridesoft.com <mailto:dennis@ridesoft.com>
[TekScopes] <mailto:TekScopes@yahoogroups.com> <TekScopes@yahoogroups.com>


Reply-To:

TekScopes@yahoogroups.com <mailto:TekScopes@yahoogroups.com>


Organization:

Ridesoft, LLC


To:

TekScopes@yahoogroups.com <mailto:TekScopes@yahoogroups.com>


CC:

'Dave Brown' <mailto:davebr@modularsynthesis.com>
<davebr@modularsynthesis.com>





If you haven't been to the vintagetek.org website lately I would suggest you
take a look. They have added a number of scanned articles, scanned
publications, on-line exhibits, locations, STEM, employee stories,
schematic cartoons, patents, hams, some repair information, and a couple of
audio files. The locations pages include history/photos/videos for Grass
Valley, Heerenveen, Guernsey, Hoddesdon, Wilsonville, Sunset, and Beaverton.

The link is http://vintagetek.org/

Dennis Tillman W7PF


Re: 7704 issues

regman10
 

I've been pondering the schematic for 2 days now and its really poorly documented and kind of surprising compared to the rest of the scope. None of the schematics match up with the what I've got, maybe theres an older (or newer service manual). I pulled together a manual from 2 different sources for the 7704A as the schematics were fragmented over several pages on the link provided and added to the manual, schematics that either fit the pager, or are simply taped together to create the foldout.

My supply voltages are fine and I'm not seeing any shorts. My theory is that for one reason to another those harmonica connectors were unplugged from the green connector and since there are no clear indications of where they go. The pin outs alone are enough to drive you crazy. Every connector has a different number of pins so that part of it is pretty easy, determining where exactly they plug into the host connector that plugs into A20. So the Navy tech working on it gave up.


The scope is fully functional, readouts work fine, analog, no issues, was last calibrated on 2009.


Once again, if someone could snap a photo like the one in fig 6-30 but with a close up of the harmonica connectors, I would be eternally grateful. email to ga4blues@gmail.com


Re: Intensity not working on 2465A

Chuck Harris <cfharris@...>
 

If you stop a calibration routine part way through, when
you find it asks for something you don't have, the NVRAM
will void the calibration, and give you the "......"
display.

There are sellers that make available pre programmed NVRAM
parts... they are intended for test and evaluation of a
scope, but don't make the mistake of thinking they will
give you a calibrated scope. They will be as much as
5 to 10% off, at best.

The only way to get rid of the "...." display, that is
meaningful, is to totally recalibrate the scope.

The 2465 family needs about $1000 worth of test equipment
to do a proper calibration... even at today's fire sale
prices. The calibration equipment needs to be calibrated
before using, and every 6 months thereafter to remain usable.

The 2465A can be modified to take either the Dallas/maxim
NVRAM used in the "B" models, or a FRAM. You have to fool
the battery testing circuitry into thinking that the non
existent battery is good.

Note:
You often see "Disclaimer's" put in posts, I feel obliged
to put a "Claimer" in this post, as I sell discounted
calibration and repair services for the 2465 family. As
a result, I definitely am biased in my opinions.

-Chuck Harris

ti8jlh ti8jlh@gmail.com [TekScopes] wrote:

Hello Siggi,Thanks, I will calibrate and adjust what I can and tell you what
happened.I'm little afraid because of the resistors that are changing their value.
They seemed to be ok. And there are thousends .Joachim ti8jlh

-------- Ursprüngliche Nachricht -------- Von: "Sigurður Ásgeirsson siggi@undo.com
[TekScopes]" <TekScopes@yahoogroups.com> Datum: 30.08.2017 07:48 (GMT-06:00) An:
TekScopes@yahoogroups.com Betreff: Re: Re: [TekScopes] Intensity not working on
2465A


Re: Intensity not working on 2465A

ti8jlh
 

Hello Siggi,Thanks, I will calibrate and adjust what I can and tell you what happened.I'm little afraid because of the resistors that are changing their value. They seemed to be ok. And there are thousends .Joachim ti8jlh

-------- Ursprüngliche Nachricht --------
Von: "Sigurður Ásgeirsson siggi@undo.com [TekScopes]" <TekScopes@yahoogroups.com>
Datum: 30.08.2017 07:48 (GMT-06:00)
An: TekScopes@yahoogroups.com
Betreff: Re: Re: [TekScopes] Intensity not working on 2465A


 









On Wed, 30 Aug 2017 at 01:21 ti8jlh ti8jlh@gmail.com [TekScopes] <

TekScopes@yahoogroups.com> wrote:



Hello SiggiI changed R2013 to 10,02 k and now the situation changed: the
voltage on the two testpoints are ok.There are still blinking dots on the
top and bottom of the screen but the intensity I can adjust it a bit more
but not much.The focus works only on the readout and a little on the
signal.Joachim
Hey Joachim,



I missed the fact that you noted dots on the screen in your initial email.

Sadly that indicates that the scope has written off its calibration

information, and requires re-calibration. If your keeper battery is still

good it's a bit of a mystery why that would have happened, but there you

are.



Since you changed things in the DAC reference, you might want to verify and

perhaps adjust the 10.00V reference, and then go through the DAC ref

adjustment (p 5-10). This is relatively quick and painless, and also

verifies or adjusts the range of the DACs output.

Note also that the tempco and general stability of R2013 is critical to the

scope keeping cal over temperature and time. This may or may not be

critical to your needs, but I thought I'd mention again that this resistor

is specified with a low temperature coefficient.



As for the intensity and focus problem, since you twiddled the grid bias,

you may want to go through the CRT adjustment procedure (p 5-7) and see if

you can pull things into nominal. As far as I know the CRT adjustments are

all "hard" - e.g. done by potentiometer, rather than soft by cal constant.



Siggi



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














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


Re: Intensity not working on 2465A

Siggi
 

On Wed, 30 Aug 2017 at 01:21 ti8jlh ti8jlh@gmail.com [TekScopes] <
TekScopes@yahoogroups.com> wrote:



Hello SiggiI changed R2013 to 10,02 k and now the situation changed: the
voltage on the two testpoints are ok.There are still blinking dots on the
top and bottom of the screen but the intensity I can adjust it a bit more
but not much.The focus works only on the readout and a little on the
signal.Joachim
Hey Joachim,

I missed the fact that you noted dots on the screen in your initial email.
Sadly that indicates that the scope has written off its calibration
information, and requires re-calibration. If your keeper battery is still
good it's a bit of a mystery why that would have happened, but there you
are.

Since you changed things in the DAC reference, you might want to verify and
perhaps adjust the 10.00V reference, and then go through the DAC ref
adjustment (p 5-10). This is relatively quick and painless, and also
verifies or adjusts the range of the DACs output.
Note also that the tempco and general stability of R2013 is critical to the
scope keeping cal over temperature and time. This may or may not be
critical to your needs, but I thought I'd mention again that this resistor
is specified with a low temperature coefficient.

As for the intensity and focus problem, since you twiddled the grid bias,
you may want to go through the CRT adjustment procedure (p 5-7) and see if
you can pull things into nominal. As far as I know the CRT adjustments are
all "hard" - e.g. done by potentiometer, rather than soft by cal constant.

Siggi


Re: Intensity not working on 2465A

ti8jlh
 

Hello SiggiI changed R2013 to 10,02 k and now the situation changed: the voltage on the two testpoints are ok.There are still blinking dots on the top and bottom of the screen but the intensity I can adjust it a bit more but not much.The focus works only on the readout and a little on the signal.Joachim 

-------- Ursprüngliche Nachricht --------
Von: "Sigurður Ásgeirsson siggi@undo.com [TekScopes]" <TekScopes@yahoogroups.com>
Datum: 29.08.2017 07:08 (GMT-06:00)
An: TekScopes@yahoogroups.com
Betreff: Re: [TekScopes] Intensity not working on 2465A


 









On Tue, 29 Aug 2017 at 00:00 Joachim Lange ti8jlh@gmail.com [TekScopes] <

TekScopes@yahoogroups.com> wrote:



The scope is a through hole version. Ripple looks good but the voltage
on TP2420 is 1,019V and on TP2421 is -0,933V.


This is great news - it means that there's something up with your DAC, its

reference current, or the MUX & S&H. If these voltages are off, then all

bets are off for the functionality of the scope. The 1.36V is used as

centerpoint for the DACs output voltages, so all your analog controls are

going to be off and lopsided when that's off.



The voltage of the Keeper Battery is 3,7V and the voltage over R2770 is
ca 0,2mV. But this is not very correct because sometimes it 0,0mV and
then it is 0,4 mV on the mV scale.
This sounds good - the main thing is that you're not observing excessive

current draw.



Maybe if I pull out one side of R2770 it is possible to get the mA
drain. But then the scope would not have a battery.
No don't do that - it looks like the keeper's doing fine. What's the date

code on it - out of curiosity?



Where are these voltages on the test points come from? Maybe there is
again a resistor that changed the value.
BTW: If you don't yet have a service manual, I can recommend the Artek

Manual scan - I have both the 2465 and the 2467 scans, and they're off

excellent quality.



The way these voltages come about is fairly convoluted. Let's walk through

it.



The DAC, U2101, is a current-mode device, and it takes an input reference

current.

The reference current is derived from the 10V REF input, and from R2013 -

which is a 0.1%, low TC resistor. The reference current can then be trimmed

by way of R2010 and the network around that trimmer. If the reference

current is low, the DACs outputs will be low also.



Start by measuring the voltage between pins 14 and 15 on U2101. As these

are the inputs of an opamp in negative feedback, the voltage difference

between those pins should be effectively zero. A visual inspection of the

circuit around R2013 would be in order, and maybe you can measure them

in-circuit, or at least measure the resistance from pins 14/15 to the 10V

rail (<=10k), to ground (<=10k) and to each other (<=5k), just to verify

that the network is connected and sound.



Now, the output of the DAC is a current that's converted to voltage by the

two load resistors R2520/R2521. Unfortunately the service manual I have

doesn't have the waveform you should see across those resistors, but if you

can measure that differentially with a scope, there is a spec somewhere for

the peak-to-peak values you should be seeing. We know the DC offset is

going to be wrong already, because TP2420 sets that.



The way the -1.25 reference voltage is derived, is that the DACs input is

set to a predefined code. The resultant output is sampled through U2521,

held by C2320, and buffered by U2420D. U2420A then creates the +1.36V

reference by ratio across the ground. The ratio of your voltages is right,

so we can assume that U2420A is good, I think.



Assuming you find nothing off in the DACs reference, your most likely

suspects would be



- U2521, a 4051 analog MUX.

These have been known to fail sometimes. The way to check is to probe

pin 3 and pin 13 at the same time. You should see a repeating waveform at

pin 3, and on pin 13 you should see one of the values from that waveform

held at DC. If the switch is leaky, you'll see the input waveform bleed

through it.

- A leaky C2321 or C2322.

You'll see droop in the DC value on pin 13 of U2521 and/or pin 12 of

U2420(D) that's periodic with the refresh rate of the voltage (I think I

remember 15ms period, but don't quote me on that).



If none of those are the culprit, then either U2420 is bad or struggling

because something is loading down the -1.25V. Let's eliminate the lot above

first, but on my 2467, VR2420 had gone short, and was pinning the -1.25V

reference to ground. This lead to no trace and a bunch of other symptoms

that led me around the merry go-around for a while :).



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














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


Re: Hi I'm Lennart

Lennart Jansson
 

Thanks I will try ;)
Lennart


Re: Tektronix 24xx Blue filter and Implosion Shield replacements

mosaicmerc
 

Hmm...

If you can supply the dimensions (accurate to 0.1mm) required for the 465 and 475 filter and shield I can factor it in.


Re: Tektronix 24xx Blue filter and Implosion Shield replacements

mosaicmerc
 

Well, it's an effort to do a group buy so batching reduces costs. Usually costs are higher for smaller runs.


Re: Hi I'm Lennart

Jon Batters
 

HI LENNART, WELCOME, YOU’LL HAVE A GOOD TIME WITH GREAT PEOPLE !

MY PEOPLE CAME FROM NORWAY A COUPLA’ GENERATIONS AGO. THE ONLY THING,…..THEY MOVED TO MINNESOTA. MAKES NORWAY LOOK LIKE A SUMMER VACATION LAND….

JON BATTERS, GRANTS PASS, OR. 2 of mine are; a 466 storage that I love and a 2213A .


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


Re: Intensity not working on 2465A

ti8jlh
 

El 29/08/2017 a las 07:08 a.m., Sigurur sgeirsson siggi@undo.com
[TekScopes] escribi:

On Tue, 29 Aug 2017 at 00:00 Joachim Lange ti8jlh@gmail.com [TekScopes] <
TekScopes@yahoogroups.com> wrote:



The scope is a through hole version. Ripple looks good but the voltage

on TP2420 is 1,019V and on TP2421 is -0,933V.
This is great news - it means that there's something up with your DAC, its
reference current, or the MUX & S&H. If these voltages are off, then all
bets are off for the functionality of the scope. The 1.36V is used as
centerpoint for the DACs output voltages, so all your analog controls are
going to be off and lopsided when that's off.

The voltage of the Keeper Battery is 3,7V and the voltage over R2770 is
ca 0,2mV. But this is not very correct because sometimes it 0,0mV and
then it is 0,4 mV on the mV scale.
This sounds good - the main thing is that you're not observing excessive
current draw.

Maybe if I pull out one side of R2770 it is possible to get the mA
drain. But then the scope would not have a battery.
No don't do that - it looks like the keeper's doing fine. What's the date
code on it - out of curiosity?

Where are these voltages on the test points come from? Maybe there is
again a resistor that changed the value.
BTW: If you don't yet have a service manual, I can recommend the Artek
Manual scan - I have both the 2465 and the 2467 scans, and they're off
excellent quality.

The way these voltages come about is fairly convoluted. Let's walk through
it.

The DAC, U2101, is a current-mode device, and it takes an input reference
current.
The reference current is derived from the 10V REF input, and from R2013 -
which is a 0.1%, low TC resistor. The reference current can then be
trimmed
by way of R2010 and the network around that trimmer. If the reference
current is low, the DACs outputs will be low also.

Start by measuring the voltage between pins 14 and 15 on U2101. As these
are the inputs of an opamp in negative feedback, the voltage difference
between those pins should be effectively zero. A visual inspection of the
circuit around R2013 would be in order, and maybe you can measure them
in-circuit, or at least measure the resistance from pins 14/15 to the 10V
rail (<=10k), to ground (<=10k) and to each other (<=5k), just to verify
that the network is connected and sound.

Now, the output of the DAC is a current that's converted to voltage by the
two load resistors R2520/R2521. Unfortunately the service manual I have
doesn't have the waveform you should see across those resistors, but
if you
can measure that differentially with a scope, there is a spec
somewhere for
the peak-to-peak values you should be seeing. We know the DC offset is
going to be wrong already, because TP2420 sets that.

The way the -1.25 reference voltage is derived, is that the DACs input is
set to a predefined code. The resultant output is sampled through U2521,
held by C2320, and buffered by U2420D. U2420A then creates the +1.36V
reference by ratio across the ground. The ratio of your voltages is right,
so we can assume that U2420A is good, I think.

Assuming you find nothing off in the DACs reference, your most likely
suspects would be

- U2521, a 4051 analog MUX.
These have been known to fail sometimes. The way to check is to probe
pin 3 and pin 13 at the same time. You should see a repeating waveform at
pin 3, and on pin 13 you should see one of the values from that waveform
held at DC. If the switch is leaky, you'll see the input waveform bleed
through it.
- A leaky C2321 or C2322.
You'll see droop in the DC value on pin 13 of U2521 and/or pin 12 of
U2420(D) that's periodic with the refresh rate of the voltage (I think I
remember 15ms period, but don't quote me on that).

If none of those are the culprit, then either U2420 is bad or struggling
because something is loading down the -1.25V. Let's eliminate the lot
above
first, but on my 2467, VR2420 had gone short, and was pinning the -1.25V
reference to ground. This lead to no trace and a bunch of other symptoms
that led me around the merry go-around for a while :).

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

Hi Siggi,
I pulled out one side R2013 and R2012 and to my surprise R2013 is 13,98k
instead of 10k.
R2012 is 10,00k.
I will try to find a 10,00k resisor to replace R2013 and tell you later.
Joachim


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


Re: Hi I'm Lennart

Siggi
 

On Tue, 29 Aug 2017 at 12:05 lennart.j.hbg@gmail.com [TekScopes] <
TekScopes@yahoogroups.com> wrote:



Hello everyone!
Thanks for accepting me, glad to take part of the group.
My name is Lennart and I'm from souther part of Sweden.
My hobbies are building guitar amps, also woodworking cabinet etc.
Just bought 2 scope a 465 and a 2215. The 465 works like a charm
the 2215 won't trigger, well will look into that ASAP.

Thanks alot, and glad to be here.
Take care.
Hey Lennart,

welcome to the group. You already possess the minimum viable number of
scopes - 2 - as you need one to fix one. Now you can work your way up to
the correct number of scopes to own, which is "one more" :).

Siggi


Re: Restoring a type 547 and 422 scopes (also my introduction to the group=

Chuck Harris <cfharris@...>
 

What that symptom indicates is that the regulator
tube is demanding that the transformer's oscillator
create more and more power to keep the HV at the
desired voltage, and eventually it can't.

The only thing I have seen that gives that behavior
is a bad transformer.

-Chuck Harris

nicolas.sog@yahoo.com [TekScopes] wrote:

Okey dokey... measured the screen voltage. And you were right Chuck, it started at
96VDC and went slowly up until it reached 122VDC. At that point the trace went
completely away.

I guess I have one of the late 547 then right? And I also guess it's the HV
transformer the faulty guy...




Cheers.


Re: Restoring a type 547 and 422 scopes (also my introduction to the group=

The Guy
 

Okey dokey... measured the screen voltage. And you were right Chuck, it started at 96VDC and went slowly up until it reached 122VDC. At that point the trace went completely away.

I guess I have one of the late 547 then right? And I also guess it's the HV transformer the faulty guy...




Cheers.


Re: 7704 issues

regman10
 

Thanks Dennis! That little bugger hides pretty good in all of those schematics. They marked all off the other connectors and jacks pretty well - no so much on this one.


New, Expanded, VintageTEK Museum On-Line Content

 

If you haven't been to the vintagetek.org website lately I would suggest you
take a look. They have added a number of scanned articles, scanned
publications, on-line exhibits, locations, STEM, employee stories,
schematic cartoons, patents, hams, some repair information, and a couple of
audio files. The locations pages include history/photos/videos for Grass
Valley, Heerenveen, Guernsey, Hoddesdon, Wilsonville, Sunset, and Beaverton.




The link is http://vintagetek.org/



Dennis Tillman W7PF


Re: Tektronix 24xx Blue filter and Implosion Shield replacements

n4buq
 

Is this a request for a commitment to buy or will that opportunity be after costs and availability are posted?

Thanks,
Barry - N4BUQ

----- Original Message -----
From: "mosaicmerc@yahoo.com [TekScopes]" <TekScopes@yahoogroups.com>
To: TekScopes@yahoogroups.com
Sent: Tuesday, August 29, 2017 1:47:31 PM
Subject: [TekScopes] Re: Tektronix 24xx Blue filter and Implosion Shield replacements

Hi All:
An update:
I should have costs, shipping and availability by the weekend.

So this is the last call for anyone interested in the group buy for these
items . This includes several of the 7000 Scope models.

I'll try to stock a few extra of the popular sizes.
Items will come in a waterproof bubble envelope. The polycarb. implosion
shield will have a peel off plastic sheath and the composite filter will be
polythene bagged to prevent scuffing during shipping. Both items can flex
and will not crack or break.

Items are laser machined to size.




Re: 7704 issues

regman10
 

Thanks I will!

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