Author Topic: TEKTRONIX TDS220  (Read 3312 times)

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Offline lionelkjh

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TEKTRONIX TDS220
« on: July 05, 2017, 08:56:03 PM »
Hello; I have a faulty TEKTRONIX TDS220 oscilloscope. The latter lights up, with the backlight present, but nothing is displayed on the screen. After disassembly, I checked the power supply; But it is functional, the tensions are good. Do you think the screen is defective ?? What do you think?? |O
 

Offline Armadillo

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Re: TEKTRONIX TDS220
« Reply #1 on: July 05, 2017, 09:17:25 PM »
The 12 pin J202, 10x probe with oscilloscope pin 10, 11, 12 any sign of pulse life there?
or use a TTL logic probe.
 

Offline lionelkjh

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Re: TEKTRONIX TDS220
« Reply #2 on: July 05, 2017, 10:19:48 PM »
OK, thanks; Here is what I noted: on j202: pin 10: square wave permanently, pin 11: pulse train, pin12: nothing. Is this normal ??
 

Offline Armadillo

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Re: TEKTRONIX TDS220
« Reply #3 on: July 05, 2017, 10:37:20 PM »
OK, thanks; Here is what I noted: on j202: pin 10: square wave permanently, pin 11: pulse train, pin12: nothing. Is this normal ??

Pin 12 is a 75.5 Hz "Clock".
Download the service manual, go to page 6-42, complete the signal measurement there, particularly carefully "carefully" disconnect the J202 from socket and measure again. Because no signal means the main board is faulty, better hope is the display module than the main board.

 

Offline capt bullshot

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Re: TEKTRONIX TDS220
« Reply #4 on: July 05, 2017, 11:15:14 PM »
There's this flat cable from the front panel to the main board (I guess it's the one you were told to check the signals). This goes loose quite easily, resulting in the symptoms you describe afair. Just check if it's sitting proper in its connector.
Next, check the electrolytic capacitors on the power supply board for their capacitance and signs of ooze or bulging.
Safety devices hinder evolution
 

Offline lionelkjh

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Re: TEKTRONIX TDS220
« Reply #5 on: July 06, 2017, 06:33:22 PM »
Hello: here are the measurements I made on the j202 (lcd connector depressed): pin 1: 0.78v, pin 2: -23v, and connector removed: pin1: -21v, pin2: -23v. Do you think the lcd slab is short-circuited ??
 

Offline Armadillo

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Re: TEKTRONIX TDS220
« Reply #6 on: July 06, 2017, 09:36:28 PM »
With the cable removed from J202, do you have all the power and signal from Pin 1 to 12 accordingly to page 6-42?
 

Offline lionelkjh

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Re: TEKTRONIX TDS220
« Reply #7 on: July 06, 2017, 10:38:50 PM »
Voltages and frequencies detected lcd connector removed: pin1 = -23 v, pin2 = -21v, pin3-6 = digital data, pin7-8 = gnd, pin9 = 5v, pin10 = 1.36MHZ, pin11 = 17KHZ, pin12 = nothing; Voltages and frequencies measured with the lcd connector: pin1 = 0.78v, pin2 = -23v, pin3-6 = digital data, pin7 = 8, gnd, pin9 = 5v, pin10 = 1.36MHZ, pin11 = 17KHZ, pin12 = nothing. ... Thank you for your help!
 

Offline Armadillo

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Re: TEKTRONIX TDS220
« Reply #8 on: July 07, 2017, 12:15:19 AM »
Pin 12 is the scan start up signal, or Vsync. Your main board is defective.
What you can do;
Check for poor connection, broken trace to Pin 12.
Unless someone has the schematic.
 

Offline lionelkjh

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Re: TEKTRONIX TDS220
« Reply #9 on: July 07, 2017, 03:45:21 AM »
Good evening; Thank you for your help. But if the mainboard is defective, why in this case, the voltage on pin 1 is it of 0.78v (connector lcd set up), then it should be -21v ??
 

Offline Armadillo

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Re: TEKTRONIX TDS220
« Reply #10 on: July 07, 2017, 06:21:31 AM »
I know how you feel. I hope for you that it was the LCD board as well.

Pin 1 is the contrast adjust voltage [unloaded] it float up.

Maybe you should wait a while, someone with the better expertise could have the solution for you.

If not, then you decide again.

In ebay, even the power supply is selling at $250. Each knob is $8.

Good Luck.

« Last Edit: July 07, 2017, 06:40:59 AM by Armadillo »
 

Offline JFJ

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Re: TEKTRONIX TDS220
« Reply #11 on: July 07, 2017, 07:25:41 AM »
... I checked the power supply...

Some of the IC's on the main board work at lower voltages to those provided by the power supply. The lower voltages are supplied from the emitters of transistors Q110, Q141 and Q151 (surface mounted on the main board). Typical output voltages are shown on the attached picture.

Obviously, if any of the emitter voltages are absent, or significantly wrong, then something on the main board isn't going to function correctly. So, it's always best to check those voltages, before looking for other faults on the main board.

 

Offline bg8up

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Re: TEKTRONIX TDS220
« Reply #12 on: July 07, 2017, 01:53:27 PM »
Check the frequency of Probe compensate hook,7.5KHz,5K,3.5K3K,2K,1K?
 

Offline Armadillo

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Re: TEKTRONIX TDS220
« Reply #13 on: July 08, 2017, 07:20:01 AM »
There is a contest going on and you could win the scope much better than this old 22 years scope. Just tell Dave that your scope is broken in 2 mins.

http://www.eevblog.com/forum/contests/giveaway-rohde-schwarz-rtb2004-oscilloscope/

 

Online alm

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Re: TEKTRONIX TDS220
« Reply #14 on: July 08, 2017, 07:29:47 AM »
Assuming you can afford the import charges (see the giveaway discussion topic).
 

Offline lionelkjh

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Re: TEKTRONIX TDS220
« Reply #15 on: July 08, 2017, 10:38:58 PM »
Hello; Thank you for this info. The motherboard that I have is somewhat different from the one in picture. Here are the voltages I have detected on the emitters of each transistor: Q140 = 2.6V; Q131 = -2.6V; Q141 = -2.6V; Q143 = 2.6V. Thank you for your help
 

Offline lionelkjh

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Re: TEKTRONIX TDS220
« Reply #16 on: July 08, 2017, 10:44:46 PM »
As a reminder; Here the symptom on the screen ...
 

Offline lionelkjh

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Re: TEKTRONIX TDS220
« Reply #17 on: July 10, 2017, 02:15:41 AM »
Hello; I do not have on this oscilloscope the data acquisition module, located at the back of the device. Is it important ?? Is there a correspondence with the failure ??? I ask myself all the questions, even the craziest! |O
 

Offline bg8up

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Re: TEKTRONIX TDS220
« Reply #18 on: July 11, 2017, 10:48:07 PM »
Check the frequency of Probe compensate hook,7.5KHz,5K,3.5K3K,2K,1K?
 

Offline lionelkjh

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Re: TEKTRONIX TDS220
« Reply #19 on: July 25, 2017, 04:46:48 AM »
Good evening; I took some pictures of the motherboard of my oscilloscope in failure. Can anyone help me because I'm lost ????? Thank you for your help!
 

Online tautech

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Re: TEKTRONIX TDS220
« Reply #20 on: July 25, 2017, 06:37:09 AM »
Good evening; I took some pictures of the motherboard of my oscilloscope in failure. Can anyone help me because I'm lost ????? Thank you for your help!
Twice you have been asked by member bg8up to measure the frequency of the probe calibration output.

Yes is should be 1 KHz but if is not the frequency it is can indicate where the failure is.


Edit to add.
The mainboard looks to be covered in dried salts like it has been wet.
Clean it with IPA and a soft brush.
« Last Edit: July 25, 2017, 07:16:12 AM by tautech »
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Offline lionelkjh

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Re: TEKTRONIX TDS220
« Reply #21 on: July 31, 2017, 12:28:09 AM »
Hello; I do not understand what you mean. I attach the pictures of the motherboard ....
 

Offline lionelkjh

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Re: TEKTRONIX TDS220
« Reply #22 on: July 31, 2017, 12:31:39 AM »
the following
 

Offline tooki

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Re: TEKTRONIX TDS220
« Reply #23 on: July 31, 2017, 01:55:25 AM »
Good evening; I took some pictures of the motherboard of my oscilloscope in failure. Can anyone help me because I'm lost ????? Thank you for your help!
Twice you have been asked by member bg8up to measure the frequency of the probe calibration output.

Yes is should be 1 KHz but if is not the frequency it is can indicate where the failure is.

Hello; I do not understand what you mean. I attach the pictures of the motherboard ....

In every oscilloscope, there's an output terminal on the front for performing probe compensation. It outputs a 1KHz square wave. You are being asked to measure the frequency of that output and report back whether it is 1KHz or not.

Page 5 (PDF page 17) of the user manual for this scope shows you where this output is.
« Last Edit: July 31, 2017, 01:59:12 AM by tooki »
 

Offline lionelkjh

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Re: TEKTRONIX TDS220
« Reply #24 on: July 31, 2017, 02:48:56 AM »
What is the ratio between the calibration signal of the probe and the failure ???
 


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