Tektronix 2213A troubleshooting

[IonizedGears]

I have a tek 2213A oscilloscope that I'm trying to troubleshoot. I only have the the service manual for the 2213 version which is pretty different from the 2213A version.
I have been using the image in this thread: https://www.eevblog.com/forum/repair/tektronix-2213a-repair/

The first problem was that C970 was shorted, which caused the power supply to fail. I replaced it (the 100v, 30v, +/-8.6v, 5v rails now work) but now I'm getting these issues that you can see in the video. I'm kind of lost in trying to troubleshoot anything past the power supply even with the proper documentation (which I don't have for the A model). I also don't have access to an isolation transformer or another oscilloscope/signal generator to work with at the moment. I'm stuck with line voltage, a multimeter, and a soldering iron.

The issues are:

The beam doesn't show without the beam find button.
Odd buzzing sound in the back of the oscilloscope (might be totally normal).
Horizontal position isn't a linear movement for the beam.
Focus doesn't really focus the beam.
Intensity doesn't do much.
Anything else you might have seen in the video

Front panel operation:


Buzzing sound:

[tautech]

A 7 part Service manual for these is here:
http://www.eserviceinfo.com/download.php?fileid=30598

I've not downloaded it to check that it's complete, so let us know if it's the real deal please and I'll put a link into the Repair Docs thread.

It's in a rar package so you'll have to unpack it. There's instruction at the foot of the page.

[IonizedGears]

It is a complete scan, but it's a complete scan for the 2213 service manual which is different from the 2213A model. I have the physical copy of the 2213 service manual and it's pretty useless for my tektronix 2213A. Thanks, though.

[tautech]

It is a complete scan, but it's a complete scan for the 2213 service manual which is different from the 2213A model. I have the physical copy of the 2213 service manual and it's pretty useless for my tektronix 2213A. Thanks, though.

Well wouldn't that piss you off when it's listed as for the A.   

I'll have another look around for you.

[IonizedGears]

Yeah, i simply don't understand why it's so difficult to find the service manual for the A model.

I found this: http://www.qservice.tv/SAMPLES/2213A_SRV_SAMPLE.pdf

It's exactly what I need yet they are charging 10 bucks for the pdf: http://www.qservice.tv/vpasp/shopexd.asp?id=1481&bc=no

I also don't understand how the PDF hasn't been leaked after 16 years.

Thanks for the help!

[tautech]

Yep, I found that one too and it's not too bad a deal for $10.

I do wonder if the 2213A is very similar to 2215A and maybe that SM can be of help.
Have a look at these:
http://www.ko4bb.com/getsimple/index.php?id=manuals&dir=Tektronix/Tektronix_-_2215A
http://www.ebaman.com/index.php/remository/ELECTRONICS/Test-Equipment/Tektronix/Scopes/2XXX-Series/orderby,2/page,3/
http://www.schematicsunlimited.com/t/tektronix/tektronix-2215a-oscilloscope-service-manual

[alsetalokin4017]

Yes, the 2215A service manual covers those parts of the 2213A that are different from the 2213. I've already been down this route, and the 2215A SM is essential for 2213A owners.

[IonizedGears]

Huh, the 2015A service manual is actually pretty close to the 2213A regarding part numbers. Thanks for the help! Hopefully i can fix this problem.

[IonizedGears]

I have one question, is it possible for the timebase to just not work but everything else seems to work? When i test channel 1  (or channel 2) with the built in probe adjust, it shows two dots that are exactly .5v apart from each other.

[alsetalokin4017]

I have one question, is it possible for the timebase to just not work but everything else seems to work? When i test channel 1  (or channel 2) with the built in probe adjust, it shows two dots that are exactly .5v apart from each other.

Yes, it's definitely possible.

In the 2215a SM that I have, there is a troubleshooting section (6-5) with a lot of important information that you might like to review. There are also complete directions for disassembling the various parts, how to get the circuit boards out, etc. in the manual.
On my pdf manual's page 187, the last page in Section 9, there is a Troubleshooting Flowchart. Once you've reviewed 6-5 and the rest of section 6, this flowchart will show you how to proceed and will probably isolate the problem to a particular circuit, where you can then focus further efforts.

[David Hess]

The 2213A has a single delayed timebase and the 2215A has a dual delayed timebase; except for the timebase differences, they are identical so you should be able to use the 2215A manual without too many problems.

I cannot see the sweep and trigger settings in your video but if the sweep is not active, then the CRT will not be unblanked so the beam finder will be the only way to display something.

Go back and reset the sweep and trigger settings as recommended in the manual.

[David Hess]

The problem appears to be between the trigger circuits and the horizontal amplifier which includes the horizontal mode logic and A sweep.

The trigger appears to be working based on when the calibration signal was removed from channel 1 and the trigger indicator went out.  However when you momentarily changed the mode to Single Sweep, the trigger lamp should have gone out but did not.

My guess is that the trigger is starting the sweep unblanking the CRT but the sweep never actually ramps so it never resets.  The sweep is practically the only place were the 2213A and 2215A differ so I think you will need a actual 2213A service manual which I do not have either.

The problem is very likely repairable because there are no custom circuits in the horizontal mode logic or sweep.

[IonizedGears]

Yup, it looks like the sweep is not working. In the video you might see the trace jumping horizontally as i turn the sec/div knob. I confirmed this in the circuitry by seeing that the sweep voltage follows these jumps and doesn't output a ramp for the sweep. I also confirmed that there is a squarewave coming from the trigger when the triggered light is on, so it seems that yes, the triggering circuit is okay.

Now I just need to troubleshoot the sweep generator circuitry as to why it's only outputting a stable dc voltage. Do you know anything that usually fails and causes the sweep to not function?

After reading the theory of operation from the 2215A service manual, it seems that even when I short out the base of Q701 to simulate A GATE going low so that the caps can charge, they don't charge. The other thing is it seems that I'm not seeing any of the other waves propagating through the circuit (with my multimeter).

[David Hess]

You posted two of the same images which I will assume are part of the 2213A A-sweep circuit diagram.  They look identical to the 2215A A-sweep diagram so I will work from that.

Now I just need to troubleshoot the sweep generator circuitry as to why it's only outputting a stable dc voltage. Do you know anything that usually fails and causes the sweep to not function?

The most common failure is probably the JFET buffer transistor which in this case is Q701.  I do not know *why* it would fail though since it is protected from ESD while in the circuit.

After reading the theory of operation from the 2215A service manual, it seems that even when I short out the base of Q701 to simulate A GATE going low so that the caps can charge, they don't charge. The other thing is it seems that I'm not seeing any of the other waves propagating through the circuit (with my multimeter).

There are a couple of things to check before Q701 and the other three transistors.

1. R707 could be open and it provides all of the collector current for Q701.
2. The voltage at the wiper of R721 should be -8 volts when R721 is fully clockwise.

[IonizedGears]

I only meant to post it once, but it somehow posted twice. The schematic is still the 2015A version, but it appears from my testing that they were pretty similar. I'm trying to hold off on buying the proper service manual for my device if I can get by with the 2015A version for now.

1) I don't want to take it out just yet as it involves taking it apart to desolder it. One thing I noticed, however, is that R707 gets really toasty but I think that's by design as the sweep output is 0.86v. It's just that more current is flowing through the resistor over time because the ramp signal isn't working.


2) Yup, i just confirmed that the wiper of R271 ranges from -2v to -7.99v clockwise.

[David Hess]

I only meant to post it once, but it somehow posted twice. The schematic is still the 2015A version, but it appears from my testing that they were pretty similar. I'm trying to hold off on buying the proper service manual for my device if I can get by with the 2015A version for now.

The 2213A and 2215A A-sweep circuits may be almost identical but I do not know.

1) I don't want to take it out just yet as it involves taking it apart to desolder it. One thing I noticed, however, is that R707 gets really toasty but I think that's by design as the sweep output is 0.86v. It's just that more current is flowing through the resistor over time because the ramp signal isn't working.

30 volts across 2 kilohms is almost 1/2 watt so it should be hot.

2) Yup, i just confirmed that the wiper of R271 ranges from -2v to -7.99v clockwise.

So that is not the problem but it was easy to check.

You said you shorted the base of Q701 so the cause is not the -A-gate signal.

Q704B and R705 must be working because otherwise the collector of Q706 would be lower than the 0.86 volts you measured.

Vgs of Q704A is set by the Vgs of Q704B to 0.0 volts so the output voltage does not reveal if Q704A is shorted or not.

I think the 0.86 volts at the collector of Q706 is the Vbe of Q706 (so Q706 is good), plus the short or Vgs of 0.0 volts of Q704A, plus the Vce(sat) of Q701 so Q701 is good.

That leaves just Q704A being shorted from gate to source with the drain open.

But to check, I would pull Q701 and test Q701 out of the circuit and then measure the collector voltage of Q706 without Q701 installed.

[IonizedGears]

The collector voltage on Q706 is about 22volts with it transistor Q701 disconnected. I tested Q701 with a transistor tester and it failed the test so I replaced it with what I had on hand. I replaced it with a 2n222 as I have no idea what I should replace it with (googling the part number in from the manual and from the transistor itself yielded nothing so I couldn't compare data sheets) and the sweep now seems to work well.

But other than that possible replacement, everything seems to be running really well.

https://goo.gl/photos/gcyyVBJdSPtpP3vt8

Thanks for the help!

[David Hess]

I replaced it with a 2n222 as I have no idea what I should replace it with (googling the part number in from the manual and from the transistor itself yielded nothing so I couldn't compare data sheets) and the sweep now seems to work well.

Q701 is a fast saturated switch meaning that it has little storage time and recovers quickly from saturation. 

Q701   151-0424-00   2N5769   6-2 6-12
500MHz 40hfe 15Vceo 40Vcbo 200mA

The 2N2369, 2N2369A, PN2369, or PN2369 would be the common replacement however a 2N2222 or 2N3904 may work acceptably.  Test how the sweep performs at the fastest sweep speed; the problem which may show up is nonlinearity at the start of the sweep.  A small signal schottky diode placed in anti-parallel across the base-collector junction could be used as a Baker clamp to improve performance.

Mouser has the PN2369A in stock for a reasonable price.

[IonizedGears]

Awesome, I've already ordered the PN2369A from mouser.

Thanks for helping me out with this stuff. I'm sure without it troubleshooting this would have taken quite a bit longer.

[tautech]

Sphere's Tek X reference page:
http://www.sphere.bc.ca/test/tekequiv.html

[David Hess]

Thanks for helping me out with this stuff. I'm sure without it troubleshooting this would have taken quite a bit longer.

You helped yourself by providing a detailed example of the problem and then making the suggested tests and measurements.  Without those it would have been much more difficult.

Sphere's Tek X reference page:
http://www.sphere.bc.ca/test/tekequiv.html

Which annoyingly enough does not list the 151-0424-00 but Sphere does have the original 2N5769 available used for $2.

I know some people go out of their way to maintain the exact stock condition of these instruments (I am not accusing you of this) but for something trivial like this I think it is a wasted effort and doubly so when a replacement part is such a close match.  I would have baker clamped a 2N3904 and tested the results just to see how it would work.

I may even have a note somewhere saying that the 2N5769 and 2N2369/2N2369A are ultimately the same part.

[IonizedGears]

Sphere's Tek X reference page:
http://www.sphere.bc.ca/test/tekequiv.html

Oh cool, didn't know there was a dedicated site for tek components.

You helped yourself by providing a detailed example of the problem and then making the suggested tests and measurements.  Without those it would have been much more difficult.

I understand the frustration of trying to help someone who doesn't present the problem completely (I've seen it a few times in this forum) so I try to explain things as thoroughly as possible. Even a tiny clue can make a problem easy to troubleshoot. But still, it was great to come here and be able to get your and everybody else's help through finding a service manual and some directions on where to look.

I would have baker clamped a 2N3904 and tested the results just to see how it would work.

I thought about this but but I didn't have a schottky diode on hand and if I was going to order parts it would be better to just get the transistors. Also, as it stands, I don't have access to most of my diagnostic gear to even test for nonlinearity at the faster timebases (Only a multimeter, soldering iron, and the built in 1khz square wave generator of the scope).

[David Hess]

I would have baker clamped a 2N3904 and tested the results just to see how it would work.

I thought about this but but I didn't have a schottky diode on hand and if I was going to order parts it would be better to just get the transistors. Also, as it stands, I don't have access to most of my diagnostic gear to even test for nonlinearity at the faster timebases (Only a multimeter, soldering iron, and the built in 1khz square wave generator of the scope).

That makes sense to me; I was just suggesting an alternative.  I am sure the PN2369A will work great.

For testing the nonlinearity which is part of the horizontal calibration anyway, it does take like a 50 MHz signal source although for just the sweep, I think it can be done with a 10 MHz source.

[IonizedGears]

So how exactly would I check for a nonlinearity? Would I just get another scope and look at the ramp waveform? Wouldn't the capacitance of the leads affect the switching time of the transistor? The other thing I thought of is putting a known waveform on the input of the fixed scope and seeing if the timebase looks irregular (if the waveform looks stretched or compressed at specific points on the screen).

[David Hess]

So how exactly would I check for a nonlinearity? Would I just get another scope and look at the ramp waveform? Wouldn't the capacitance of the leads affect the switching time of the transistor? The other thing I thought of is putting a known waveform on the input of the fixed scope and seeing if the timebase looks irregular (if the waveform looks stretched or compressed at specific points on the screen).

The later is how it is done.  At 50ns/div, a 10 MHz sine wave will have a zero crossing at every division.  With x10 magnification, this becomes 5ns/div so a 100 MHz sine wave is needed which gets tricky because the 60 MHz 2213A may not reliably trigger which is why time-mark generators have low frequency trigger outputs.

If there is a problem, then it will show up at the beginning of the 50ns/div sweep.