Dark spaces on the traces of tektronix 2230 oscilloscope

[electronic_guy]

Hi,

I bought a used tektronix 2230. The first time I turned it ON, something blew inside and dark smoke came out of the air vents in the back where the cooling fan is. This is my first oscilloscope, Not a good experience. Probably it's a Cap.

Don't know if they are related. But after this the traces began to have dark spaces on it. Apparantly they move with the trace. Also the traces flicker more than usual. Please see the pictures. Does anyone knows how to repair this ?

[james_s]

Smoke came out and you didn't shut it off immediately? Stop using it right now, you risk doing further damage if you have not already. Find out what smoked, sounds like probably a capacitor in the power supply blew up.

[electronic_guy]

Yes, I did turn it off when this happened. But I turned it ON later several times to see if its working or not. 

I tried removing the cover and see where it blew, but this model of oscilloscope has lot of circuits crammed in, I didn't want to disassemble without knowing how to put it back together. Plus the power supply is in a metal box, so i have to remove the top circuit to reach it.

[james_s]

Do you have the service manual?

https://elektrotanya.com/tektronix_2230_sm.pdf/download.html#dl

[electronic_guy]

 Not yet. I have ordered one on ebay, but its still on its way. Pdf is good but in most pdfs have copied the shematics to small pages rendering it difficult to read.

[tggzzz]

Hi,

I bought a used tektronix 2230. The first time I turned it ON, something blew inside and dark smoke came out of the air vents in the back where the cooling fan is. This is my first oscilloscope, Not a good experience. Probably it's a Cap.

Don't know if they are related. But after this the traces began to have dark spaces on it. Apparantly they move with the trace. Also the traces flicker more than usual. Please see the pictures. Does anyone knows how to repair this ?

Probably RIFA capacitors. The exact value isn't critical, but the voltage and X/Y rating are.

Turn off the annotations and see if the dark spaces disappear. The scope "steals time" from the trace to dray the characters.

[wn1fju]

The 2230 is one of my least favorite Tektronix scopes to work on.  You have to remove the top row of front panel pushbuttons, then remove the screws holding the top board, swing the board away, remove some more brackets and hardware, remove the power supply cover, and gently maneuver it out.  Be careful with the screws on the back panel securing the power supply cover - they sometimes are frozen after years of use and are easily stripped (I had to drill some of mine out).

Might I suggest two things to aid in your effort.  First, use your phone/camera and take lots of pictures as you go.  Second, get a small tray with compartments and put the screws in them in a logical, labeled manner.  Several of the screws in the same disassembly step have different lengths.

As others have indicated, it's most likely the two Rifa Y-suppression capacitors.  A two minute job to replace after you've spent an hour getting to them.

[electronic_guy]

@tggzzz and @wn1fju Thank you for the diagnosis and guidance on how to disassemble it.
@tggzzz you are correct. I did what you said and dark spaces dissappeared.

[tggzzz]

Thank you for listening(!) and reporting back.

Enjoy the scope