Textronix 2205-40 scope rebuild question

[Planobilly]

Hi Guys,

I have a Textronix 2205-40 that was given to me. It turns on and there is a wide horizontal line so the CRT it self is working and no amplification.
I have never tried to rebuild a scope. I looked at the service manual and it looks pretty complex. I have a new 100mhz digital scope and a Hameg 20mhz analog scope so I am not hurting for a scope.
Have any idea how hard these type scopes are to rebuild in general? Is this model scope worth rebuilding??

Thanks,

Billy

 

[davenn]

hey Billy

like all old electronic things, electro replacement is top of the list

dunno if you are aware of the old restoration trick that many of us use...
in line with keeping the piece of gear looking original, and for large PSU caps, it is common to hollow out the guts of
the old caps and install the new ( and always physically smaller) replacement caps inside the old cansDave

 

[davenn]

ohhh I forgot to mention
there's a very active Tektronix scope yahoo group I have been part of for many years

http://groups.yahoo.com/group/TekScopes/ohhh and note it should be a k not a x ... Tektronix, not Textronix D

 

[Planobilly]

Hi Dave,

I have not poked around yet but the cap issue was first on the list.

Thanks,

Billy

 

[Planobilly]

LOL...I can not spell Billie...lol

 

[davenn]

LOL...I can not spell Billie...lol

well spelt either way, depending on gender, I think

 

[Planobilly]

Plus I am from Texas...lol

 

[davenn]

Plus I am from Texas...lol

ohh well that explains everything haha ... sorry just having fun

haven't been to TX since 2006, on one of my storm chasing trips to the USA
Sorry for sidetracking your thread

Dave

 

[Planobilly]

I live in Miami, Homestead actually. When everyone finds out I am from Texas I will most likely get banned from the site..lol

I will ask the question on the link you gave me also...plus spell it right!

 

[Averagesupernova]

A wide horizontal line as in out of focus? Does it sweep? If so that sounds like any easy fix unless there is an oscillation in the vertical circuit. An oscillation could cause something like this depending on where it is occurring. The scope may not be able to trigger on an internal oscillation.

 

[dlgoff]

dunno if you are aware of the old restoration trick that many of us use...
in line with keeping the piece of gear looking original, and for large PSU caps, it is common to hollow out the guts of
the old caps and install the new ( and always physically smaller) replacement caps inside the old cans

I wasn't aware or even thought of that. Thanks Dave.

 

[Planobilly]

A wide horizontal line as in out of focus? Does it sweep? If so that sounds like any easy fix unless there is an oscillation in the vertical circuit. An oscillation could cause something like this depending on where it is occurring. The scope may not be able to trigger on an internal oscillation.

Hi,

After messing with the scope a bit, most everything seems to be working except the focus control. I have a function generator hooked up and the scope changes both with frequency and amplitude as I change the frequency generator. I can see the wave form...several types. I had the case off a few days ago and there is a long shaft that goes to the focus pot and I think it is turning the pot but I need to check. I will see tomorrow if I can dig up the value of the pot and what it controls...getting late here.

Cheers, and thanks for the help.

Billy

 

[Svein]

I seem to remember that one generation of Tektronix oscilloscopes used Nuvistors in the amplification path. Are those still available?

P.S: I checked - the answer is here: http://w140.com/tekwiki/wiki/Nuvistor.

 

[Tom.G]

Tektronix also made conversion kits to replace Nuvistors with Transistors.
The Nuvistors couldn't stand the vibration and shocks of a portable instrument and had a very short life. Customers didn't like that.

 

[jim hardy]

Thanks for the yahoo Tektronix group link

i have a 2211 in the "fix me" pile...

looking forward to your adventures...

 

[Planobilly]

I dislike seeing any piece of electronics gear that has a usefulness be placed in the junk pile. There are plenty of young people just starting out in electronics who would love to have a working scope like this. I will most likely repair this scope and give it to someone in need. I am also sure I will most likely need some guidance in making that happen. I also think it is the responsibility of those who have skills in certain fields to share what they know and promote learning and education. I assumed from the start that this forum does just that and my assumptions have been proven to be correct. So...thanks to all of you who have helped me to learn new things.

As time goes by, I hope that I can be helpful to others who log on here looking to learn new things. I don't know much but I am always willing to help.

Cheers,

Billy

 

[jim hardy]

I also think it is the responsibility of those who have skills in certain fields to share what they know and promote learning and education.

Hear Hear !

We're all ignorant, just on different subjects.

 

[Planobilly]

Well Jim, my ignorance spans quite a large number of subjects...lol

Here is a short video of the scope in question.



My understand of oscilloscopes and how to use them is pretty limited to begin with so repairing one will require learning a bunch of new stuff I am sure.

Billy

 

[Averagesupernova]

Doesn't look like the trigger is working or maybe no set correctly?

 

[Planobilly]

Doesn't look like the trigger is working or maybe no set correctly?

Well...the fact that the display is showing the same line that is very wide with or without a signal and no change happens when I move the focus controls assuming that the focus control can even address this condition would indicate that the focus control is not working.

The trigger has to be working because I see the wave form and it changes in a normal way when I change the controls on the function generator. The scope is displaying the wave...just not as a fine line as one would expect. I assume several other repair issues will be required to have the information displayed in a correct and calibrated manner. Lots I don't know about how scopes work in general so I guess anythings is possible.

Billy

EDIT: As I have looked at another analog scope I have I am starting to think the focus control is not the cause of the issue

 

[jim hardy]

I always start with power supply voltages - check for <10% ripple unregulated, <1% regulated , if not figure out why.

Look at a signal that's sync'd to line voltage - if you have power supply troubles something should appear still.
Got an AC output wall wart laying around?

 

[Planobilly]

Hi Jim,
I still need to find a real schematic to work from if it exist. The service manual I saw was more about "follow these instructions". Truth is, I have not looked at it much yet. There are some really high voltages (around 1900V i think) around the CRT I want to know where they are before I start to poke around too much.
I have AC regulated power supply 0V to 140V and a DC regulated power 0V to 60V to work with.

I also have another small "learning" project going on at the moment. I am trying to understand just how to set up my digital scope to measure the value of a unknown capacitor or inductor using my function generator. Plus I think a nap is on the list...lol

Cheers,

Billy

 

[Averagesupernova]

If the trigger were working you would not see the waveform move through on the scope the way it does in your video. If this were my scope I would suspect that the trigger is set to auto and the trigger level is set all the way one way. Or, the trigger is just plain not working.