Tektronix T912 with no display help - UK Vintage Radio Repair and Restoration Discussion Forum

Consolehobbiest · 17th Jan 2022, 12:15 am

Hey everybody, I hope I'm doing this right. I'm not very versed in forum websites but I will just get down to it. I recently purchased a T912 Oscilloscope that originally powered on and I had picture. I was going through my normal test to make sure everything was in working order and shortly after turning on the back- light I got the magic smoke. It turns out a capacitor blew causing a resistor an a diode to go with it. I dismantled it and tested all the parts in the area and replaced anything blown or out of spec. Now that I've put it back together I an not getting anything to display at all.

I was curious if anybody would have more info on this machine and maybe have a guide on putting the CRT back on correctly. I suspect I might have crossed a few wires or something because when I went back to put everything together I found my camera angles from the photos I took didn't do as well of a job showing where everything went as I first thought.

The machine gets power, the PSU fan turns on and the power LED is on but nothing on the display. Sorry if I wrote a book but I wanted to be as detailed with what I did as possible. Thanks for any possible help.

Chris55000 · 17th Jan 2022, 12:45 pm

Hi!

Don't attempt to fault–find any Tektronix Oscilloscope until you've got a good, readable copy of the manual to hand – many of them are very awkward to dismantle!

You can get a copy of the book free from here:

http://w140.com/tek_912.pdf

Unfortunately you didn't specify which items had failed/burnt out, if there is no component legend/silkscreen on your PCBs, there will be a drawing in your book to help identify them, the circuit will show where they are electrically and the parts list will give the value, rating(s) and type!

There will be instructions under "Maintainance" that give the procedures for removal and replacement of the CRT in most of the older Tektronix CRT based Oscilloscopes !

Remember that Oscilloscopes use both positive h.t. of up to +200 V and negative e.h.t. of up to –2500 V below earth, both of these are potentially very dangerous if accidentally contacted whilst the instrument is on – always switch it off, disconnect it from the mains and wait a minimum of 30 minutes before attempting any repair work on any Oscilloscope !

Chris Williams

17th Jan 2022, 12:15 am	#1
Consolehobbiest Diode Join Date: Jan 2022 Location: Austin, Texas, USA. Posts: 1	Tektronix T912 with no display help Hey everybody, I hope I'm doing this right. I'm not very versed in forum websites but I will just get down to it. I recently purchased a T912 Oscilloscope that originally powered on and I had picture. I was going through my normal test to make sure everything was in working order and shortly after turning on the back- light I got the magic smoke. It turns out a capacitor blew causing a resistor an a diode to go with it. I dismantled it and tested all the parts in the area and replaced anything blown or out of spec. Now that I've put it back together I an not getting anything to display at all. I was curious if anybody would have more info on this machine and maybe have a guide on putting the CRT back on correctly. I suspect I might have crossed a few wires or something because when I went back to put everything together I found my camera angles from the photos I took didn't do as well of a job showing where everything went as I first thought. The machine gets power, the PSU fan turns on and the power LED is on but nothing on the display. Sorry if I wrote a book but I wanted to be as detailed with what I did as possible. Thanks for any possible help.

17th Jan 2022, 12:45 pm	#2
Chris55000 Nonode Join Date: Aug 2007 Location: Walsall Wood, Aldridge, Walsall, UK. Posts: 2,868	Re: Tektronix T912 with no display help Hi! Don't attempt to fault–find any Tektronix Oscilloscope until you've got a good, readable copy of the manual to hand – many of them are very awkward to dismantle! You can get a copy of the book free from here: http://w140.com/tek_912.pdf Unfortunately you didn't specify which items had failed/burnt out, if there is no component legend/silkscreen on your PCBs, there will be a drawing in your book to help identify them, the circuit will show where they are electrically and the parts list will give the value, rating(s) and type! There will be instructions under "Maintainance" that give the procedures for removal and replacement of the CRT in most of the older Tektronix CRT based Oscilloscopes ! Remember that Oscilloscopes use both positive h.t. of up to +200 V and negative e.h.t. of up to –2500 V below earth, both of these are potentially very dangerous if accidentally contacted whilst the instrument is on – always switch it off, disconnect it from the mains and wait a minimum of 30 minutes before attempting any repair work on any Oscilloscope ! Chris Williams __________________ It's an enigma, that's what it is! This thing's not fixed because it doesn't want to be fixed!