help! i broke my oscilloscope

Thread Starter

lokeycmos

Joined Apr 3, 2009
431
i have an old school tektronix scope that i F'd up today. i cleaned the pots and rotary switches with radioshack tv-tuner cleaner/lubricant and now it turns on but nothing on the screen. the can said to wait 5 minutes, but i waited 10. anything i can do about it? thank you in advance!
 

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spinnaker

Joined Oct 29, 2009
7,835
I'd carefully check the connections in back of both of those feature bays. A scope that old is bound to have some brittle connections.
 

holnis

Joined Nov 25, 2011
49
Actually, I'm not really qualified to answer your question but you should check and clean the connectons to the modules and the brightness of the oscilloscope if it has been lowered, Also Because nothing is displayed on the screen when a vertical, horizontal positioning shifts greatly, it tends to be thought that this is broken, too.
 

Thread Starter

lokeycmos

Joined Apr 3, 2009
431
i cleaned the contacts best i could. all i get on the screen is a dot. i can move the dot up and down and left to right with the x/y adjustment knobs, but there is no continuous trace on the display.
 

MrChips

Joined Oct 2, 2009
21,165
Well that is a good sign to begin with. Do you have a signal source such as a function generator that you can feed into the input channels? Even touching the input probes when the sensitivity is set to .01 VOLTS/DIV would help. You should get a vertical line in the middle of the screen.

The next step would be to set the TIME BASE TIME/DIV to EXT HORIZ IN and feed a signal into this BNC input. You should get a horizontal line.

If the two tests above appear to be ok, the next step would be to trouble shoot the TIME BASE module.

Can you post the model numbers of all the modules and a photo of front of the scope?

(Edit: Ok, I can see them from your first post, 3A1 and 3B4)
 
Last edited:

DerStrom8

Joined Feb 20, 2011
2,390
Well that is a good sign to begin with. Do you have a signal source such as a function generator that you can feed into the input channels? Even touching the input probes when the sensitivity is set to .01 VOLTS/DIV would help. You should get a vertical line in the middle of the screen.

The next step would be to set the TIME BASE TIME/DIV to EXT HORIZ IN and feed a signal into this BNC input. You should get a horizontal line.

If the two tests above appear to be ok, the next step would be to trouble shoot the TIME BASE module.
I'm almost positive the problem is with the TIMEBASE. Lokey posted this on another forum too, and I think it should be resolved shortly. If anyone's interested in reading some other replies on the other forum, you can find it here.

Hope you figure it out Lokey!

regards,
Der Strom
 

Thread Starter

lokeycmos

Joined Apr 3, 2009
431
Do you have the manuals for the Model 3A1 AMPLIFIER and Model 3B4 TIME BASE?
yes i do have the manuals. ill check into those. i posted some pics of my adjustments. the wierd thing is that the only time i get the dot on the screen is when the time/div know is all the way counter clockwise in the gray area indicated next to the numbers. i dont get anything at all when its in any of the other positions.anyone have a 3b4 timebase or 3a1 amp for sale?
 

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MrChips

Joined Oct 2, 2009
21,165
There is a possibility that the scope is not broken at all.
Two things I would check are the intensity setting and the trigger settings.
Your settings seem ok except set the TIME/DIV to 10mSEC.
If this does not work, you need to look that the sweep circuitry with a scope.:(
 

Thread Starter

lokeycmos

Joined Apr 3, 2009
431
im pretty pissed about this. the scope worked fine(the knobs where scratchy though) till i used this damn radioshack cleaner to clean them up. i tried spraying some rubbing alcohol on the rotary switches to try and clean away any residue this lubricant may have left behind.
 

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BillB3857

Joined Feb 28, 2009
2,533
I used some DeOxit on a 4 channel counter (Nixie tubes to show how old) and after cleaning, the frist time I rotated the wafer switches, they literally fell apart. The DeOxit had reacted with the plastic and crystallized it. Sad part was that the switches were obsolete and had to make a major mod to repair the unit. Gotta be really careful with spray stuff.
 

spinnaker

Joined Oct 29, 2009
7,835
im pretty pissed about this. the scope worked fine(the knobs where scratchy though) till i used this damn radioshack cleaner to clean them up. i tried spraying some rubbing alcohol on the rotary switches to try and clean away any residue this lubricant may have left behind.
Have you checked the connectors in those bays?
 

Thread Starter

lokeycmos

Joined Apr 3, 2009
431
Have you checked the connectors in those bays?
yes. i thought there might be a problem with those. so i sprayed some electric parts cleaner on them and buffed them with(non metal) buffing wheel on my dremel. its hard to get inside the bays, but i put the electric parts cleaner on Qtips and reached in best i could. this electric parts cleaner is not the same as the radioshack stuff. its made for motor brushes, contacts, relays, and selenoids.
 

spinnaker

Joined Oct 29, 2009
7,835
I mean have you checked the connectors themselves? Can you see inside? At they soldered to a backplane or is there a wiring harness? (If there are individual wires it might be more likely there could be a broken wire, but check the backplane too.
 

spinnaker

Joined Oct 29, 2009
7,835
Drop a message in this Yahoo group

http://tech.groups.yahoo.com/group/TekScopes

These guys are every bit as helpful kind and patient as the folks here and they know their Tek scopes backward and forward.

They got me down to the exact circuit I needed to look at and where it was in the scope within 2 or 3 posts. There was a last disagreement of what exact part was faulty between me and them. I turned out to be right! :) But hey I had the scope right in front of me and they were handicapped by the information I provided.
 
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