Problème Tek 2445B

[skopg]

Good evening, I'm coming back to you because ...
who has already had this screen on their Tek 2445B.
If so what should I do, thank you for your help.

Electronically yours, Skopg

[jonpaul]

Hello: Test is  is for the DAC REF range, and must be approx _1.25V>>0>>+1.25V.

Bonjour cher Monsieur, Your result is typical of  bad CRT/HV section or scratchy INTEN/ASTIG/FOCUS controls.


Have not fixed 2445B, but seems similar to 2465/7B:

See long threasd on "2465B teardown" 79 pages.

Check service manual for trubleshoot of HV/CRT, and also LV PSU.

Also see groups.io>>tekscopes and tekscopes2 groups.

Bon chance,

Amicalment
 Jon

[skopg]

Thank you, But I'm on vacation for 2 week-end. I'Il getter Black to you as son as I getter Black...If i can

[skopg]

Good morning,
I am extending my vacation for the moment by 2 weeks.
To get a little head start for my return.
I'm asking you if it's possible for you to explain a little (because I'm new to electronics).
What do you mean by: The test concerns the DAC REF range and should be approximately_1.25V » »0 » »+1.25V How to do this adjustment...and do you have a link for 'Disassembly of 2465/7B, 79 pages.
But above all a link to the maintenance manual for troubleshooting the HV/CRT, as well as the BT power supply. This will allow me to take notes during my vacation and when I get home to get started.
Many, many thanks in advance.

[jonpaul]

Rebonjour cher Monsieur: BRAVO pour le initiative!

Les étapes meilleur:

1/ Get PDF of service manual for the exact model and serial number.

TekWiki 

https://w140.com/tekwiki/wiki/

BAMA https://bama.edebris.com/manuals/tek/2445

2/Has full disassembly, service, calibration procedures. Some special tools like TORX 15 drivers and TEK CAL modules may be required.

3/ See VERY long thred on EEVblog  Tektronix 2465B teardown

4/ See groups.io tekscopes and tekscopes2 and ask there, amy Tek veterans and ex engineers.

5/ Repair may invoice rework of SMD leaky caps on A5 control, and full CAL. Even for veteran TEK folks, not trivial.

6/ A beginner can easily cause damage or get an HV or mains shock, or damage test equipment.

Just a few tips


Bon Chance,

Jon



 

[skopg]

Good morning,
On the front of my screen I know it says Serial G153097, so to avoid confusion, which manual should I download?
Because on your links that you gave me...for me it's the jungle LOL.
Sorry
Have a nice day

[jonpaul]

Yes it is work to find the correct documentation. First letter of SN designates factory.

B050 = Beaverton USA


Your scope was made in UK (Gurnsey?) or EU not USA.


ask about your SN and manual on Tekscopes  and Tekscopes 2 on Groups .io 

I cannot do this for you.

Jon

[calibrationfixture]

Hi skopg,

I think this is an Early 2445B, because its Bandwidth is 150 MHz. Late 2445B's have a 200 MHz Bandwidth. I repaired in the past a Guernsey 2445B (G114649). Also a 150 MHz Model. No SMD Parts on its Controller Board (A5) and a separate Readout Board (A4).

Its Manual:

https://xdevs.com/doc/Tektronix/24X5B/Tek_2445B_Service.pdf

Succes,

Calibrationfixture

[jonpaul]

Skopg:

Agree with comment by "calibratiionfixture"

manual he mentions is different than your model (B vs A) but may be close enough to start.

Jon

[skopg]

Good evening,
The link does not work.
What do you mean not any SMD part...
I am new to these electronic terms.
I know I have to control the points in J119 in the 5-1 table. If no point gives its value...( hope not).
But if otherwise where to go, what components would be to replace resistance, capacitor ... to get an idea before I get home.
Thank you for your help.
Electronically yours skopg

[calibrationfixture]

Hi skopg,

Just downloaded the Manual. Just try again. Google and eevblog are your "friends". On eevblog and the www are Pictures of both Boards.

Calibrationfixture

[skopg]

Hello,
ok managed to download it.
Good day

[skopg]

Hello,
I know that I must check the points in table 5-1 on D119.
If no point gives its value...(hopefully not).
But if otherwise, where should I go, which components should be replaced... resistor, capacitor... to have an idea before I return home.
Thank you for your help

[jonpaul]

Hello: You cannot fix this compex and "fly by wire" computer comtrolled scope by "asking which components should be replaced... resistor, capacitor..."

You need to learn how to troubleshoot and logically narrow down the problems, there may be several. .

IF U119 has all V close to the manual values, the LVPS is OK.
If not go to LVPS flowchart in manual.

Most likey

Dirty/scratchy controls, switches,
Bad electro caps in PSU
Shorted tant caps
Out of CAL, needs full CAL

Bon Chance,

Jon

[factory]

I agree this is not a easy scope to diagnose & repair.

First thing that is recommended is to service the PSU, a set of new capacitors is a must to avoid damage from electrolyte leakage & possible damage to other parts (some of which are expensive to replace) from overvoltage.

Once the PSU is serviced & output voltages/ripple is correct, then move on to the display & readout fault.

The readout circuitry on older scopes is spread across several boards, the readout sub board and the display sequencer part on the mainboard, there have been occasional failures of CA3046 transistor array.

Most controls are done by computer control, the switch matrix is scanned to detect the switch positions, the analog controls are compared with the DAC value, the DAC value is adjusted by the processor until they match and the digitized value stored in the EAROM, along with the switch settings.
Some controls use sample & hold circuits and some are directly connected to the function they control.
The DAC needs the +10Vref to be working, the sample & hold needs the +/-1.25V to be working.

If you end up with a line of dots or question marks in the readout, the cal data has been lost/corrupted.

If working on the scope with the casing removed, it's recommended to direct a fan at the hybrid ICs & U800 on the mainboard to prevent overheating. In normal use with case fitted, make sure the case fan works, for the same reason.

David

[skopg]

Hello,
thank you for your answer, I do it as soon as I return.
You can see the screen during my post.
When I ask what I need to do (to be a little ahead, go home).
I do not ask to be told it is this or that Resistance or Cap or Diode ... complex problem... but to control a card (if J119 wrong value) and not to control the elements one by one (put the DMM) to eliminate certain parts of the card (I do not know if you understand what I mean).
Heve a nice day