My tek 2465 smokes


hardyhansendk
 

Thanks

Problem solved for now!

Opened up the scope-have never before serviced tek 2465-fuse ok,so did
exactly as you proposed-turned on/off the instrument several times.The smoke
disappeared---a capacitor in the mains cracked---and viola it works,with a
selftest fault.

Great

Happy christmas

Hardy



Fra: TekScopes@yahoogroups.com [mailto:TekScopes@yahoogroups.com]
Sendt: 15. december 2017 08:50
Til: TekScopes@yahoogroups.com
Emne: Re: [TekScopes] My tek 2465 smokes





On 15 Dec 2017 7:52 a.m., "'hardy hansen' hardyhansen@mail.tele.dk
[TekScopes]" <TekScopes@yahoogroups.com> wrote

After not having used my tek 2465 for a while-now it really smokes-do
vagely recall it have been seen before??

The smoke is probably from the mains input filter capacitors which, after a
few decades, crack and admit moisture, then fail with a cloud of smoke. The
proper fix is to replace the capacitors. The fix I use is just to wait for
the smoke to stop (it does, eventually) and carry on using the scope.

The operation of the instrument is not affected by these capacitors, but
there's a chance it won't meet its conducted radio interference spec if
they've failed. You are free to decide whether this is something you care
about.

Chris









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Tom Gardner
 

On 15/12/17 06:51, 'hardy hansen' hardyhansen@mail.tele.dk [TekScopes] wrote:

After not having used my tek 2465 for a while-now it really smokes-do vagely recall it have been seen before??

Any advise welcome as i am not in a position right now to dig very deep because of health issues.
A good starting point would be
http://www.condoraudio.com/wp-content/uploads/Projects/Tektronix-2465B-Oscilloscope-Restoration-Repair.pdf


cmjones01
 

On 15 Dec 2017 7:52 a.m., "'hardy hansen' hardyhansen@mail.tele.dk
[TekScopes]" <TekScopes@yahoogroups.com> wrote

After not having used my tek 2465 for a while-now it really smokes-do
vagely recall it have been seen before??

The smoke is probably from the mains input filter capacitors which, after a
few decades, crack and admit moisture, then fail with a cloud of smoke. The
proper fix is to replace the capacitors. The fix I use is just to wait for
the smoke to stop (it does, eventually) and carry on using the scope.

The operation of the instrument is not affected by these capacitors, but
there's a chance it won't meet its conducted radio interference spec if
they've failed. You are free to decide whether this is something you care
about.

Chris


Ed Breya
 

You said it smokes, but does it run? Open it up and look for the source. Could be one of the infamous bad X-caps, or something else burning up and ready to crap out entirely. It's best to look while there's still some smoke left.

Ed


hardyhansendk
 

Hello

After not having used my tek 2465 for a while-now it really smokes-do vagely recall it have been seen before??

Any advise welcome as i am not in a position right now to dig very deep because of health issues.

Thanks

Hardy.





Fra: TekScopes@yahoogroups.com [mailto:TekScopes@yahoogroups.com]
Sendt: 14. december 2017 17:58
Til: TekScopes@yahoogroups.com
Emne: Re: [TekScopes] My 2462A died suddenly





El 14/12/2017 a las 10:47 a.m., machine guy machineguy59@yahoo.com
[TekScopes] escribió:

Sorry, my reply will be slow and limited while on holiday. Your
symptoms seem like a bad capacitor. There is a fault in the service
manual that interchanges C1115 and C1132. This causes you to fit a 35
volt capacitor (c115) in a 87 volt circuit (where C1132 should be).
So trust the schematic and your ohm meter, buzz out the circuit and
make certain that your caps are fitted to the schematic. Ignore the
board outline drawings.

Sent from Yahoo Mail for iPhone

On Tuesday, December 12, 2017, 4:35 AM, Joachim Lange ti8jlh@gmail.com
[TekScopes] <TekScopes@yahoogroups.com> wrote:


El 10/12/2017 a las 11:54 p.m., machine guy machineguy59@yahoo.com
[TekScopes] escribió:

Glad to hear it is fixed. Thanks for reporting back. I was worried
because I am leaving for a winter holiday and was not going to be much
help until 2018. Best wishes for the Holidays.
Mac

On ‎Saturday‎, ‎December‎ ‎9‎, ‎2017‎ ‎09‎:‎09‎:‎38‎ ‎PM‎ ‎CST,
Joachim Lange ti8jlh@gmail.com [TekScopes] <TekScopes@yahoogroups.com>
wrote:


El 08/12/2017 a las 01:30 a.m., machine guy machineguy59@yahoo.com
[TekScopes] escribió:

Change C1066. Then verify that you have the dummy load connected
properly and check the voltage on the collector of Q1062. If the
voltage on the collector of Q1062 is wrong after that, double check
the voltages on Q1050. Here is how everything is supposed to work:
Q1050 creates pulses that energize T1050. One of the windings of
T1050 drive a full wave rectifier CR1062 through CR1065. The
rectified pulses are filtered by C1066 to provide the 12.5 volts on
the collector of Q1062. Its pretty hard for other parts, like Q1066,
to drag down that voltage. I think Q1062 would get really hot if that
were happening. My opinion, is that either T1050 is not being properly
energized or there is a fault in the rectifiers CR1062 through CR1065,
or the filter capacitor C1066 is not storing enough energy. C1066 is
the most likely fault and its easy to change.

On ‎Thursday‎, ‎December‎ ‎7‎, ‎2017‎ ‎08‎:‎49‎:‎57‎ ‎PM‎ ‎CST,
Joachim Lange ti8jlh@gmail.com [TekScopes] <TekScopes@yahoogroups.com>
wrote:


El 04/12/2017 a las 12:18 a.m., machine guy machineguy59@yahoo.com
[TekScopes] escribió:

Its a problem that the voltage on the emitter of Q1062 is less
than 11
Volts. Check the voltage on the collector of Q1062, it should be at
least 12.5 Volts. If it is not, check C1066 (or replace it). Until
you get the voltage at the collector of Q1062 and emitter of Q1062
right the gate drives of Q1060 and Q1070 will have errors that can
keep the rest from working.

On ‎Sunday‎, ‎December‎ ‎3‎, ‎2017‎ ‎08‎:‎30‎:‎33‎ ‎PM‎ ‎CST,
Joachim
Lange ti8jlh@gmail.com [TekScopes] <TekScopes@yahoogroups..com>
wrote:


El 17/11/2017 a las 01:18 a.m., machine guy machineguy59@yahoo.com
[TekScopes] escribió:

Much of the 2465B is the same as the 2465A. The power supplies are
identical. But a service manual for the 2565A will eventually be
necessary (calibration, etc.). I got the manual for my 2465A from
Artek manuals. They are excellent scans of original manuals. The
owner is a member of this group.
On Thursday, November 16, 2017, 8:27:10 PM CST, Joachim Lange
ti8jlh@gmail.com [TekScopes] <TekScopes@yahoogroups.com> wrote:


El 16/11/2017 a las 06:28 p.m., machine guy machineguy59@yahoo.com
[TekScopes] escribió:

First, I assume you are aware that the power supply will not
operate
properly without a load and may in fact be damaged if operated
without
a load. After that, I am very doubtful that the problem is
caused by
U1030 (a TL494). The operation of U1030 depends on voltage
from the
collector of Q1021 and you measured that to be zero. I am not
concerned that you have a TL594 instead of a TL494, I think
TL594 is a
suitable substitute for a TL494. So I suggest you not change
TL494
without more information.
Second, I assume you are aware that measurements in this
area are
directly connected to mains power and can be dangerous. It is
advisable that you use an isolation transformer to remove the
scope
from direct mains connections when working in this area. After
that,
the zero voltage on Q1021 collector is a key indicator that the
PSU is
not starting at all. You may want to refer to the service manual
theory of operation for the PSU and the key role that Q1021
plays in
start up and static operation. Specifically, the conduction of
Q1021
depends on base current drive from Q1022 and Q1022 can be shut
down by
over-current sensed by Q1040. More measurement in this area
may give
a clue to why there is no voltage on the collector of Q1021. I
suspect the collector voltage on Q1040 will be low (say less
than 6
volts).
Did you check the resistance of R1020 and the leakage of C1025?

On Thursday, November 16, 2017, 4:58:03 PM CST, Joachim Lange
ti8jlh@gmail.com [TekScopes] <TekScopes@yahoogroups.com> wrote:


Hello everybody,
I hope you can help me repairing the PSU of my 2465A.
I took out the power supply and connected it to power. The fuses
all are
ok. I coud see that there is a voltage at the emitter of
Q1021. Not
exactly 13.2V but one more Volt. At the colector of the same
Q1021
there
is 0V.
I revised all the resistors and also Q1021, Q1022, Q1030,
Q1040 and
Q1050. Also all the CR's (diodes).All these components are good.
I did not pull out U1030 because I am a little unsecure
doing that
and I
don't have a TL494. The scope has a TL594 instead. Are they the
same?
I will look at the computer PS I have laying around because I
think
these ICs are installed in some of those.
But please could anybody tell me if this could be the failure?
I have some other questions about the caps in this PSU but I
will make
them later.
Thank you very much for your advises.

Joachim TI8JLH

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

Thank you for your fast answer.
Yes the resistance R1020 is ok and C1025 looks healty.
Tomorrow I will assemble the two parts and look for the voltage
on the
collector of Q1021.
I was searching for the theory of operation on the web because my
manual
don¨t have it. I found one for 2465B.
The low power supplies are the same for both models.
I will write tomorrow with more.
Thank you

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

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

Hello,
Thank you for your help.
I am still trying to repair the PSU.
I replaced 11 resistors. Most of them were open and the others
doubled
their value. Also three caps looked as they were leaking. I replaced
them too. (the ESR was ok)
I reasembled the PSU and at first I was very happy, but after one
minute
the screen began to flicker and than it turned off.
I took it off again and build the Primary Test Load and also I
used my
power supply. Not together.
With the Test Load connected there is 120V across load but the gate
drives of Q1060 and Q1070 is only 4.6V instead of 11V.
The volts supplied from emitter of Q1062 is about 9V.
The U1030 is working. The gate drive of Q1050 is ok.
Do you think that the regulator board is the problem or could it be
U1066?
Thank's
Joachim





Hello
Now I got again 120V at the test load. I removed U1066 and used a
socket
to install it.
With the U1066 in place I have the same voltages as before.
With the removed U1066 there as about 10V at the gates and 10V on the
emitter of Q1062.
I wanted to know what is bringing down the voltages on the emitter and
collector of Q1062.
Without U1066 the voltages still dont match.
May be it is the Q1062.
Do you have an idea how to check for the missig voltages?
Thank you.

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

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

Hello ,
I am very sorry to tell you about the mistake I made and that made me
waste my time and a lot of energy.
I forgot to bridge J207 and J206.
After I did that, voltages are ok now.
Thanks for your time and for your explanation of the circuit.
I'm very sorry for wasting your time and of the others who helped.
Regards
Joachim

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



Hello Mac,
When I turned the scope on it worked for half hour and than it started
blinking. All leds where blinking and on the screen there was a big dot
tha disappeared and came back and so on.
I took the PSU apart again and connected the load I built.
The voltages on emitter of Q1062 is over 11V and the collector has about
19V.
BUT the gate drives of Q1060 and Q1070 are only 5.6V and not 11V.
Must I replace U1062, U1064 and U1066?
What do you think?
Sorry for bother you again on your holydays.
Joachim



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Hi,
I replaced U1062 and U1064 because there were laying around. but I don't
have U1066.
Now what I can see is that there is 11V on one gate of the Q1060 or
Q1070 and on the other there are only 5V.
Looks that U1066 is bad?
Capacitors are ok.
Thank you for responding on your holydays.
Joachim








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