Tektronix 2201 New Problem + Repair Video

[ManCave]

Hey guys,

I have just posted a video where I fixed the power supply for this scope, but unfortunately something else has gone wrong.

After the first partially successful repair I ended up with too high voltages on the rail and that must have blown something up. Since this is my first repair, I'm now studying the service manual, but if anyone has any ideas where to go from here, please let me know.

Thanks!
Filip @ ManCave

Video is Here:
http://youtu.be/4dmfBVValns

[ManCave]

For those who don't have time or aren't interested in watching the vid, the fault seems to be pointing to the horizontal amp or some other horizontal part. Basically, I get the waveform displayed only as a vertical line. This happened after very slight over voltage on the rails.

My first suspect were ICs on the 5V rail. I checked all the digital ICs in the circuit and went through the datasheets to see maximum voltage ratings. Picked the ones which could have been affected by the slightly higher voltage, checked and they seem to be OK. I haven't had much time to spend on it yet, I'll need to go through this in more detail and also consult the service manual.

Does anyone have any ideas?

Thanks!

[bance]

Have you read this document? Maybe it will be of some help....
https://copy.com/vhszaRuZR4O76pQa

[ManCave]

Have you read this document? Maybe it will be of some help....
https://copy.com/vhszaRuZR4O76pQa

Thanks Bance, I have this and have read parts of it, but not the whole thing. But good to remember that I've got it! Thanks for reminder!

[bance]

I bought a faulty 2213a that had a similar fault as that described by you, all I needed to do was clean the switches and pots..... easy repair
I would be looking at the sweep circuits if I were you.

Good luck, Steve.

[ManCave]

I bought a faulty 2213a that had a similar fault as that described by you, all I needed to do was clean the switches and pots..... easy repair
I would be looking at the sweep circuits if I were you.

That looks too easy   ...but sometimes the obvious is overlooked. I did actually clean the front panel and all the buttons and knobs between the "working" and "not working" states (and they were filthy!!), but I never thought a possible contamination of a switch would have caused a fault like this. I'll look into it!

Thanks Steve!

[kjn4685]

I had the same problem with my oscilloscope and found a transistor had blown. I hope this will help you.

[ManCave]

Thanks KJN! Do you remember in which block was the transistor blown?

So far I have managed to narrow it down to the unblanking circuit. I'll look into it later in the week.

[kjn4685]

It was in the horizontal board. I also want to say that my oscilloscope was not a Tektronix. But I hope this will help you.

[ManCave]

It was in the horizontal board. I also want to say that my oscilloscope was not a Tektronix. But I hope this will help you.

Thanks!

[Shock]

Nice video. Is that your first time using a hand solder sucker? If so you learn fast, charge it away from the PCB as it spits solder back on the board. You could also share where you got it from and do a mini review if you have some old PCB to show it in action. It's handy to also apply extra flux and solder for stubborn holes. I use a plain solder sucker without an iron, old school skills.

You should share a link to the service manual now you have it, on here at least.
Tektronix don't mind, they want us using their scopes.

One thing I suggest, is it's handy to write the expected and actual voltages on a notepad.
It's a breeze to fly through them again for tolerances and see if anything has changed or write down new voltages. I also copy parts of the schematic in a graphical editor rather than print the schematic out and will highlight a whole circuit if I cannot see it clearly.

I suspect a semiconductor or I/C has given up.

[ManCave]

Nice video. 

Hi Shock! Thanks very much!

Is that your first time using a hand solder sucker? If so you learn fast, charge it away from the PCB as it spits solder back on the board. You could also share where you got it from and do a mini review if you have some old PCB to show it in action. It's handy to also apply extra flux and solder for stubborn holes. I use a plain solder sucker without an iron, old school skills.

It certainly isn't the first time I used a solder sucker ...but it is only my third video and concentrating on quite a few things at a time takes a bit of a practice! You can see that once I get comfortable I do actually charge it off circuit.

I have never used a heated solder sucker before and only used plain one with iron, as you say. However, this is definitely worth it. I mentioned in the video that I got it from Farnell (UK) for about £7 and I call that an absolute bargain It will be probably a disposable item, but with same price point as spare tips or filters for some expensive vacuum guns, it's quite justifiable.

I am planning to do a review of this and I definitely will, might release it in a few days.

You should share a link to the service manual now you have it, on here at least.
Tektronix don't mind, they want us using their scopes.

I shared the service manual in the youtube video description including link to service manual for Tek 2225 (which has same PSU design but better schematic) and all relevant datasheets from the video.

One thing I suggest, is it's handy to write the expected and actual voltages on a notepad.
It's a breeze to fly through them again for tolerances and see if anything has changed or write down new voltages. I also copy parts of the schematic in a graphical editor rather than print the schematic out and will highlight a whole circuit if I cannot see it clearly.

Good ideas! Thanks. Might do that next time

I suspect a semiconductor or I/C has given up.

Yep, would be my first guess too. And having it narrowed down, hopefully correctly, there will not be many to go through to find out which one has failed.