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Old 29th Apr 2018, 10:53 pm   #1
wizzer2k
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Default Techtronix 2213

Just picked up one of these osciloscopes but it does not work
i can only get one base line trace and it will not move very much from the mid point on the screen also if i put my probe in the test slot there is very little in vertical diflection the output from the test port looks ok on my hand held scpope

i have a hand held scope a multimeter and a audio signal generator to use for trouble shooting any info or advice would be apreciated
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Old 30th Apr 2018, 1:27 am   #2
Argus25
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Default Re: Techtronix 2213

From the information you have provided, one could conclude that the CRT support circuits are working, probably the EHT is ok and the horizontal Timebase is working.

But there are obviously problems in the vertical amplifiers. The vertical beam position circuits are not normal and least for the one trace you can see are faulty, it might be that the other trace is actually there and the beam switching that controls the two traces is ok, but the beam deflected out of view and this could relate to a large DC offset in that channel.

Assuming that one fault accounts for this (not always the case) and the fault came about due to user error (not always the case) then this could have been caused by excessive voltage presented to one of the vertical amplifier inputs damaging the input FETs. Since the vertical amplifiers are DC coupled from the input to the CRT def plates, this causes big problems.

In any case it could also be a power supply failure (nothing to do with user error) of parts of the vertical amp circuits too, or any number of failed parts.

So, to fix this problem you need the service manual for the scope model. Then you need to go through the circuitry, starting at the inputs of the vertical amplifiers, checking voltage levels and the power supply voltages in the scope's circuits that should always be checked before anything else.

In older scopes the power supply electrolytics can dry out and fail. A cheap ESR meter is helpful here. So check the power supply test points before doing anything else.

Don't be tempted to start removing parts or modifying anything until you are 100% sure the components/s you are removing are defective or it can create a downhill spiral where more faults are created with time and the scope will never get fixed.

I looked up the 2213 and it is a fairly simple and straightforward model (compared to some Tek scopes) so it should be fairly easy to repair.

Last edited by Argus25; 30th Apr 2018 at 1:33 am.
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Old 30th Apr 2018, 10:20 pm   #3
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Default Re: Techtronix 2213

i have checked the power supply and the supply voltages seem to be about right i have downloaded the service manual so have the relevant diagrams to aid trouble shooting the only voltage i have not checked was the headroom voltage

i totaly agree its not wise changing parts as i work in the automotive industry and find the same issues there people replace parts not always fixing the fault but merely inducing new faults that then mask the actual fault lol

I have just ordered a signal generator so hopefully will help with tracing through the input circuits as per the service manual

i did find some corrosion and a few wires had come away from the board but have since cleaned this up and replaced the bad wiring which mad no change so i think its start at the beging and work my way through in a logical order i am satisified its not a horizontal or time base fault as this does look to be working
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Old 30th Apr 2018, 11:01 pm   #4
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Default Re: Techtronix 2213

Quote:
i did find some corrosion and a few wires had come away from the board but have since cleaned this up and replaced the bad wiring which mad no change so i think its start at the beging and work my way through in a logical order i am satisified its not a horizontal or time base fault as this does look to be working
This is a concern. Do you know what caused the corrosion ?

If it was caused by a leaking surface mount electrolytic capacitor (if there are any nearby) then the there can be damage to tracks, inter track leakage, component damage, especially surface mount parts, the electrolyte eats away the films in surface mount resistors etc. But it might not be this. I am unfamiliar with this tek scope model.

In any case you are doing the right thing so far. Start at the inputs of the vertical amplifier and work your way through checking the circuit voltages.
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Old 1st May 2018, 1:04 pm   #5
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Default Re: Techtronix 2213

Looking at it I suspect it was moisture from where it has been stored or something. No electrolytic capacitors are near to the affected area and I have cleaned it up now so hopefully not a issue now. Just waiting on the generator to arrive then hopefully I'll start trouble shooting.
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Old 2nd May 2018, 2:55 am   #6
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Default Re: Techtronix 2213

Quote:
Originally Posted by wizzer2k View Post
No electrolytic capacitors are near to the affected area
That is good.
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Old 5th May 2018, 11:33 pm   #7
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Default Re: Techtronix 2213

It looks like both transistors in the vertical deflection circuit are faulty.
Q376 and Q386 both fail on a transistor tester
Part number LT4403, i cant seem to source this part are there any alternatives i can use?
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Old 5th May 2018, 11:38 pm   #8
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Default Re: Techtronix 2213

According to the following book:

https://ia800504.us.archive.org/30/i...ferenceOCR.pdf

BFR96 is equivalent. Can get these off eBay for not much.

Make sure you isolate the fault first or it'll cost you two more BFR96's instantly. Very fragile!

Datasheet: http://www.qsl.net/df7tv/datasheets/bfr96_mot.pdf
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Old 5th May 2018, 11:42 pm   #9
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Default Re: Techtronix 2213

thanks for the quick reply the book will come in useful will take a look for the BFR96 and see what that does once fitted and as you suggested make sure there are no underlining issues first

Last edited by wizzer2k; 5th May 2018 at 11:56 pm.
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Old 10th May 2018, 12:42 pm   #10
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Default Re: Techtronix 2213

A little more progress fitted the replacement transistors i now can get a square wave and even a dual trace much better than before but now i can only move the base line between the top half of the screen and above it will not come down any lower also when pressing beam find the beam is about half way between the center and top of the screen where as before i did the repair the single base line was dead centre with no deflection at all
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Old 10th May 2018, 12:54 pm   #11
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Default Re: Techtronix 2213

There is a DC offset still and you need to find the cause of it. Good progress so far though
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Old 10th May 2018, 1:45 pm   #12
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Default Re: Techtronix 2213

Quote:
Originally Posted by wizzer2k View Post
A little more progress fitted the replacement transistors i now can get a square wave and even a dual trace much better than before but now i can only move the base line between the top half of the screen and above it will not come down any lower also when pressing beam find the beam is about half way between the center and top of the screen where as before i did the repair the single base line was dead centre with no deflection at all
Check the bottom CRT plate is still connected to the vertical amp properly. Tektronix ones always seem to fall off.
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Old 10th May 2018, 2:57 pm   #13
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Default Re: Techtronix 2213

That is a very good/clever suggestion. If one of the vertical def plates was disconnected, it would accumulate electrons/charge and repel the beam producing a beam offset, as well as the reduction in overall electric field deflecting the beam.
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Old 10th May 2018, 3:03 pm   #14
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Default Re: Techtronix 2213

I learned that one the hard way. I spent 5 hours tracing the horizontal amp on a 465 wondering what was going on - couldn't find anything wrong. Then SWMBO looked at it and said "is that wire supposed to be hanging off?" after two seconds of looking at it
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Old 10th May 2018, 9:36 pm   #15
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Default Re: Techtronix 2213

Funny you should say that i did find the bottom one loose before I replaced the transistors i will recheck that connection and retest
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Old 11th May 2018, 2:33 am   #16
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Default Re: Techtronix 2213

Check the calibration of the base line vr pot, whichever part number that would be??,, working properly this should allow you to lower the base line, doesn`t take much.
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Old 11th May 2018, 11:41 pm   #17
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Default Re: Techtronix 2213

Had 5 mins on the scope and check the connection to the vertical plates and the bottom connection had come of again so remade the connection and rechecked now getting full movement of the trace as you would expect thanks for the help everyone
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Old 12th May 2018, 4:21 pm   #18
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Default Re: Techtronix 2213

Excellent. Good news all round.
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