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Tektronix 2205 oscilloscope - Dot Only, no line

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Brian.Stover:
I purchased my first oscilloscope on eBay the other day... A bit of a gamble.  A Tektronix 2205 for $90 without confirmation of functionality.  Other than power light indicators coming on.

The scope powers up but only displays a single dot in the middle of the screen.  Both channel exhibit this.  It displays this way with AC, DC and GND.  If I use the calibration signal, it appears as two dots connected by a faint line.  The deflection of the two dots appears accurate to the calibration signal.  It can be positioned vertically with the positioning knob.  The vertical deflection seems to respond appropriately to a DC input as well (used a AA battery for this).

I've viewed hours of YouTube videos on this model and I believe I'm using it correctly (it is my first scope though).

I assume I'll need to open it up to troubleshoot further.  Just looking for some advice on where to look for the issue.  Note that I don't have another scope available for troubleshooting efforts... Just a pair of DMMs.

Thanks in advance.

andy3055:
You can download the opertor's manual and the service manual from th links n the right hand side of this page by TEK:

http://w140.com/tekwiki/wiki/2205

You should check the voltages at various places as per the service manual to begin with.

Bud:
Adjust brightness of the dot to  minimum while you working on repairing the scope, to minimize risk of damage for the display tube.

Brian.Stover:

--- Quote from: andy3055 on January 11, 2020, 05:03:56 am ---You can download the opertor's manual and the service manual from th links n the right hand side of this page by TEK:

http://w140.com/tekwiki/wiki/2205

You should check the voltages at various places as per the service manual to begin with.

--- End quote ---

Sorry - should have mentioned that I have copies of the operators and service manuals.  Checking the supply voltages per the service manual was going to be my first task.   In hindsight, I guess I should have held off on posting until that is done.  Maybe this weekend if I have time.


--- Quote from: Bud on January 11, 2020, 05:53:39 am ---Adjust brightness of the dot to  minimum while you working on repairing the scope, to minimize risk of damage for the display tube.

--- End quote ---

Thanks for the tip on the brightness.  Makes sense.

george.b:
Does X-Y mode work?

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