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Old 10th September 2010, 04:34 AM   #1
AdumNLV is offline AdumNLV  United States
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Smile Tektronix 2235 Scope

Hello. I have a Tektronix 2235 Am/usm just purchased from eBay. On the auction the pic showed a single trace (ms) tracking on the screen. When it was delivered there seems to be no horizontal deflection. On the beam find, both beams are there and they focus but dont deflect in the horizontal field. I've tried all the horiz adjustments and still no beam. I'm thinking the horizontal output amp (two push pull transistors) has no output.

Wave form should be +25 to +70 volt saw tooth wave. I have another scope and the repair manual and another 2235 part scope. My question is; Is this a usual problem for this model scope, to loose horizontal deflection? And is there a usual suspect component? Any help will be appreciated!

ps. This is my first scope repair and I haven't opened it up yet, just looked at the schematics.
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Old 24th September 2010, 09:37 AM   #2
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Horizontal deflection?
Turn the big red knob on the right side clockwise till the trace begins to move {:-)
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Old 24th September 2010, 09:43 AM   #3
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Have you rotated the sample rate (trace speed) knob clockwise?
If not the beam will just sit there as a dot and then when you drive the input, the trace will only deflect vertically.
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Old 24th September 2010, 11:18 AM   #4
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I assume that, on buying a scope, you know how to use it. I must then assume there's a failure in the scope itself. On those assumptions... First thing you do on a used Tektronix (and many others) is open it and resolder EVERYTHING especially after shipping. Wouldn't be the first time.
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Old 24th September 2010, 11:46 AM   #5
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Just had to ask even though I know Adum must have done so {:-)

Once had an engineer tell me the monitors in the control room were not working and I needed to get them working immediately.

After disengaging the solo button on one of the effect returns the monitors worked fabulously well!

This was on an MCI JH-626 console

Really sorry for the double post, I can't edit yet so perhaps a mod could dispose of my first response.

I hope the problem is an easy fix so you can get your new scope working quickly.
I bought the same one 20 some odd years ago and it is a very nice scope.
BTW, the trace knob is gray, but we know that;-)
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Old 24th September 2010, 06:23 PM   #6
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Quote:
Originally Posted by lazzer408 View Post
I assume that, on buying a scope, you know how to use it. I must then assume there's a failure in the scope itself. On those assumptions... First thing you do on a used Tektronix (and many others) is open it and resolder EVERYTHING especially after shipping. Wouldn't be the first time.
This is just bad advice. It may well be that the problem has nothing to do with solder connections. Get a operators manual (proballly free online) and make sure that you are operating the scope correctly. If you have any suspiction that it could be "operator error" drag the scope to someone who can confirm that it's broken. Sorry to hear that your got burned, but don't take it apart without a service manual.
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Old 24th September 2010, 06:44 PM   #7
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Here is a link to a free operators manual - http://mil.ufl.edu/4712/docs/Oscope_Tek2235-op.pdf

I was a tech in a repair and calibration lab in another life and firechief is right about not getting into calibrated gear if you don't have the service manual around (or know it like the back of your hand - maybe). The HV section and ps can shorten your life!!!
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Old 24th September 2010, 09:55 PM   #8
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Quote:
Originally Posted by firechief View Post
This is just bad advice. It may well be that the problem has nothing to do with solder connections. Get a operators manual (proballly free online) and make sure that you are operating the scope correctly. If you have any suspiction that it could be "operator error" drag the scope to someone who can confirm that it's broken. Sorry to hear that your got burned, but don't take it apart without a service manual.
The advice was given assuming he IS operating it correctly. I made that clear.
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