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Products => Test Equipment => Topic started by: bolvan on April 19, 2014, 02:44:25 pm

Title: Tektronix 2445B 200MHz Problem
Post by: bolvan on April 19, 2014, 02:44:25 pm

Hello, I have Tektronix 2445B with 200MHz
Problem A5 PCB
I have made new 10µF and 33µF capasitor.

power suply the J119 with J251 A5 PCB

1. -2,6V ________________14. 0V ___GND
2. +4,46V ______________13 .0V
3. -17,4V _______________12. +2,3V
4. +1,7V ________________11. -1,4V
5. -0,9V ________________10. 0V
6. +2,6V________________ 9. +15,6V
7. 0V ___________________8. +15,1V

DS1225Y I have read
Whether the data are good, I do not know .....

Does anyone dump for 2445B 200MHz?

Title: Re: Tektronix 2445B 200MHz Problem
Post by: BravoV on April 19, 2014, 03:06:35 pm

Assuming you've measured the voltages at J119 properly, looks like many of the voltages are wrong.

These are the standard voltages that must be follow for your scope to work properly. Time for some serious work at the psu.  ???

(https://www.eevblog.com/forum/testgear/2467-no-power/?action=dlattach;attach=58502;image)

Title: Re: Tektronix 2445B 200MHz Problem
Post by: bolvan on April 19, 2014, 03:10:17 pm

Thanks,

power supply at the J119 with plug is removed  J251  (A5 PCB)

1. -15V ...........14. 0V ...GND
2. +4,98V ........13. 0V
3. -18,58V ........12. +4,96V
4. +9,99V ........11. -8,04V
5. -4,97V ------..10. 0V
6. +14,96V ......9. +42,3V
7. 0V .............8. +86,8V

Is board A5 PCB defective?

Title: Re: Tektronix 2445B 200MHz Problem
Post by: casinada on April 19, 2014, 04:03:15 pm

Look on the treads for Tektronix 2465-2467 Oscilloscopes in the forum and also at the Yahoo Tekscopes group. They are very much the same except the A1 board that is a little bit different. If you have a way to backup your DS1225Y you can download the one for a 2465B from the www.KO4BB.com (http://www.KO4BB.com) file repository. The A5 might be bringing down the power supply or the power supply is not able to provide enough current. Have a visual inspection of the LV power supply, look for suspicious capacitors or resistors. Measure the ripple of the power supply voltages using another oscilloscope. Good luck. :)

Title: Re: Tektronix 2445B 200MHz Problem
Post by: guido on April 19, 2014, 04:51:04 pm

If it's anything like my 2465 than all supplies depend on the +10V reference voltage to be good. If that one is out, the others will also be. So check that first.

In my case a 12V (iirc) zener diode on the output of the 10V reference voltage was broken, so the reference voltage was about 6V. It's just after the reference circuit on the supply pcb.

Title: Re: Tektronix 2445B 200MHz Problem
Post by: casinada on April 19, 2014, 10:04:58 pm

His reference voltage is fine at 9.99V but it seems that the A5 board is bringing all the voltages down.

Title: Re: Tektronix 2445B 200MHz Problem
Post by: guido on April 19, 2014, 11:10:05 pm

Maybe then the a5 board brings down only the reference.

Title: Re: Tektronix 2445B 200MHz Problem
Post by: bolvan on April 20, 2014, 09:11:38 am

Thanks:)
J251  - Pin 15, Pin 19 and Pin 20 not busy?

Title: Re: Tektronix 2445B 200MHz Problem
Post by: bolvan on April 21, 2014, 03:01:46 pm

A6 Front Panel S3004, S3013 and S3019 break down?

Tektronix 260-2283-00 Voltage per Division Switch