Tektronix TDS320 blank screen and doubt about AD converter - Page 1
Forum section: electronics / repair

author: SAUL BRITTO
author_rank: Frequent Contributor
timestamp: January 21, 2016, 04:36:07 am
content: Hi. I have a Tektronix TDS320 dead, blank screen.I want to know if it's possible be the AD converter because I did look at the datasheetand found some voltages not so right look:I have found on the main board the IC MC10319DW that is an AD converter with this voltagePin11 0,4vPin12 - 5 vPin13 0,3 vpin14 5 vpin15 - 0,3 vpin16 -0,3 vpin17 5 vpin18 5vBut I don't have schematic and using this datasheet:http://www.datasheetcatalog.com/datasheets_pdf/M/C/1/0/MC10319DW.shtmlI do not know if the manufacturer followed the datasheet , I do not know if these voltages are correct, On pin 18 is the clock but , on the oscilloscope do not see any clock

author: poot36
author_rank: Frequent Contributor
timestamp: January 21, 2016, 04:51:44 am
content: I would start by checking the power supply voltages first. It could be a problem with the ADC but highly unlikely to cause a no screen issue. See if you can find the service manual for this scope.

author: SAUL BRITTO
author_rank: Frequent Contributor
timestamp: January 21, 2016, 05:05:17 am
content: I saw all the voltages on the PS it's all right no problem. It starts normal just don't signals on screen,The screen lights up but does not show anything. Service manual for this kind of scope I never saw, just user manual, if any friend help me with one...

author: poot36
author_rank: Frequent Contributor
timestamp: January 21, 2016, 05:59:58 am
content: So as far as I understand the problem the scope runs but you just get flat traces shown for all the input channels regardless of the input signal? Or are there no traces shown at all? Make sure to test the inputs on all V/Div settings just incase there is a bad switching relay or other input selection problem. What does a self calibration do if this scope has this feature? Does it pass all built-in diagnosis tests?

author: SAUL BRITTO
author_rank: Frequent Contributor
timestamp: January 21, 2016, 06:11:01 am
content: No guy,the screen just lights up no more.No traces nothing more than a green screen

author: poot36
author_rank: Frequent Contributor
timestamp: January 21, 2016, 06:37:39 am
content: Ok, if your scope was made in the early to mid 1990s it will have the problem of the capacitors on the digital board going bad. They are the rectangular shaped tantalum ones that leak corrosive fluid onto the board and can damage the traces on the board around the cap. I would also check the power supply rails for ripple by setting your multimeter to AC volts and testing each voltage rail from the power supply. Any reading higher the 200mV is bad. If you get a reading of more then 3V or so your meter cannot be used for this test.

author: ArcticGeek
author_rank: Regular Contributor
timestamp: January 21, 2016, 05:19:24 pm
content: A good start is to download the service manual for the TDS320 from the Tektronix website. The Tek website does in fact have schematics available for the TDS320 and other scopes in the TDS3XX series. Once you have the schematic you can scope the power supply rails and other things. Things I would look for:1. Make sure all voltages are good coming from the PS2. Check the reset signal and clock to the CPUBe sure to check for the reset and clock, I fixed a TDS380 by replacing the oscillator - for some reason the oscillator was no longer producing any clock. Replacing the can oscillator fixed the problem and I am using the scope to this day. The lack of oscillator caused a green screen that you describe.Good luck!

author: SAUL BRITTO
author_rank: Frequent Contributor
timestamp: January 21, 2016, 11:31:00 pm
content: ArcticGeek thank you for your answer and your time.I was testing any others things and will look for, that you wrote sure. But look this:

author: SAUL BRITTO
author_rank: Frequent Contributor
timestamp: January 21, 2016, 11:34:07 pm
content: I made all those tests and they says me: replace monitor board! It has two metallic transistors tha are working cold very very cold.What do you think about? I just need to know how the video signal goes at those Tr.

author: SAUL BRITTO
author_rank: Frequent Contributor
timestamp: January 21, 2016, 11:35:48 pm
content: Quote from: poot36 on January 21, 2016, 06:37:39 amIt dont have this kind of caps poot36,just the smd.Just saw three electrolitycs inside de aquisition unit 220/35V

author: SAUL BRITTO
author_rank: Frequent Contributor
timestamp: January 22, 2016, 02:12:37 am
content: Quote from: ArcticGeek on January 21, 2016, 05:19:24 pmWell I did this but RESET I did see a negative pulse a bit slow,Clock just on the pin 66 (clkout) a sine signal of high frequency,all the others pins that has the name clock nothing. All VDD and VSS are ok.

author: poot36
author_rank: Frequent Contributor
timestamp: January 22, 2016, 02:46:21 am
content: I found a service manual for the TDS340A model that has the video connector pinout in it on page 248. Link:http://jumi.lut.fi/elko/TDS340A/tds340a_service.pdf.I hope this will help you in fixing your scope. It looks like a standard VGA monocrome output but I am unsure of the horizontal and vertical frequency's.

author: SAUL BRITTO
author_rank: Frequent Contributor
timestamp: January 22, 2016, 05:00:08 am
content: Thank you! My tds320 has the option to vga video but,that connector is very antique and I don't have a monitor for it.

author: SAUL BRITTO
author_rank: Frequent Contributor
timestamp: January 22, 2016, 05:03:41 am
content: Quote from: SAUL BRITTO on January 22, 2016, 05:00:08 amThis link don't works to me, it seems broken.

author: SAUL BRITTO
author_rank: Frequent Contributor
timestamp: January 22, 2016, 05:33:17 am
content: Looking with another scope HP 1740A to that vga video output I get some signals thas seems that of a pattern tv generator.Seems the monitor of this Tektronix is bad guy.

author: poot36
author_rank: Frequent Contributor
timestamp: January 22, 2016, 05:56:07 am
content: If you search for "tds340a_service.pdf" you should find the link that I posted. I think that site does not allow direct linking. That service manual also has a partial schematic of the monitor in the scope. Most HD TVs have a VGA port on the back, if you have the cable try it.

author: SAUL BRITTO
author_rank: Frequent Contributor
timestamp: January 22, 2016, 06:06:26 am
content: I have a tv right there but the pins are different, thera are more pins. Unless I make an adjustment.

author: poot36
author_rank: Frequent Contributor
timestamp: January 22, 2016, 06:44:05 am
content: The standard VGA pinout has 15 pins and not all of them are used. I think your scope has a 9 pin connector for the external monitor so yes you will have to make a converter cable. Luckily you only need 4 wires to do it (video, h-sync, v-sync, and ground). You will have to lookup the pinout of the standard 15 pin VGA connector and use the service manual to figure out the scopes video pinout. It may be faster to try and fix the scopes monitor or just replace it with one of the cheap VGA lcds from China that would fit into the original CRT frame.

author: SAUL BRITTO
author_rank: Frequent Contributor
timestamp: January 22, 2016, 05:35:58 pm
content: Quote from: SAUL BRITTO on January 22, 2016, 06:06:26 amI found an ideia to convert vga 9 pins to the new vga

author: SAUL BRITTO
author_rank: Frequent Contributor
timestamp: January 22, 2016, 07:01:31 pm
content: Quote from: SAUL BRITTO on January 22, 2016, 05:35:58 pmTha's what my friend Drussel send me in another forum: drussell wrote:If you're saying you DO have option 14 with the VGA connector on it, I believe you should be able to make yourself a simple cable from the 9-pin "VGA" connector on the TDS 320 to a standard 15-pin VGA monitor connector as follows:- Pin 2 on the 9-pin D-Sub to pin 2 on the 15-pin D-Sub (Monochrome video signal -> Green)- Pin 4 on the 9-pin D-Sub to pin 13 on the 15-pin D-Sub (Horizontal sync)- Pin 5 on the 9-pin D-Sub to pin 14 on the 15-pin D-Sub (Vertical Sync)- Pins 6-8 on the 9-pin D-Sub to pins 5-10 on the 15-pin D-Sub (Ground)For an external color monitor, if you want a cyan display, connect the pin 2 video on the 9 pin input to pins 2 and 3 on the 15-pin output to the monitor. If you want white, connect pin 2 to pins 1,2 and 3 on the output to the external monitor.I hope this can help others.

author: SAUL BRITTO
author_rank: Frequent Contributor
timestamp: January 25, 2016, 02:24:12 am
content: Quote from: SAUL BRITTO on January 22, 2016, 05:00:08 amI found the site and really it was very good it has video schema and I think will be Very very usefull! Thank you guy.