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Old 10th January 2007, 01:42 PM   #1
Dhul is offline Dhul  Spain
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Default tektronix 2235 problem

Hi,

First of all, sorry for my english.

I have a tektronix 2235 scope, but it has a problem.

It has peaks at channel1 traces.

Anyone can help me?

Anyone can send me service manual?

Thanks.

.HERRAN.
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Old 10th January 2007, 01:55 PM   #2
EC8010 is offline EC8010  United Kingdom
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Does a waveform on Ch2 stay perfect even when you use the vertical shift control to move Ch2 all the way from top to bottom of the screen? If it is, then it's worth getting a manual to fix the Ch1 input amplifier fault. If it isn't, then you probably have a vertical amplifier problem for which parts are no longer available.
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Old 10th January 2007, 06:37 PM   #3
Dhul is offline Dhul  Spain
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Default channel2 keeps its waveform

Hi, again

Channel2 waveform keeps its waveform if I move it from top to bottom.

So, I think I need the service manual.

Anyone has it?

Thanks
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Old 10th January 2007, 09:44 PM   #4
EC8010 is offline EC8010  United Kingdom
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Try a search. There's a site devoted to Tek...
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Old 12th January 2007, 04:58 PM   #5
gootee is offline gootee  United States
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Default Re: tektronix 2235 problem

Quote:
Originally posted by Dhul
Hi,

First of all, sorry for my english.

I have a tektronix 2235 scope, but it has a problem.

It has peaks at channel1 traces.

Anyone can help me?

Anyone can send me service manual?

Thanks.

.HERRAN.

You can look for the service manual at

http://bama.edebris.com/manuals/tek/

You can post requests for help in two good places:

1) The TekScopes group, at http://www.yahoogroups.com

2) The sci.electronics.repair group, at http://groups.google.com

Both of those groups have a few ex-Tektronix techs who are regulars.

Before posting your question, do some searches. At google groups (mentioned above, which now has the searchable archive of all Usenet newsgroup message-traffic from about 1981 to the present! A goldmine!), do a search like "Tek OR Tektronix 2235 problem OR repair OR fix -FS -FA -sale -auction", without the quotes. Note that the "OR"s must be in caps.

Make sure that you give a description of the symptoms that is as thorough and as complete as possible.

The 2235 is a nice scope and well-worth repairing. They are relatively easy to work on. I don't remember if they have any Tek-custom (i.e. no longer available as new parts) ICs, or not. But even if that were the problem, you can almost always still obtain them, either from a "parts unit" or from places like Sphere Research (http://www.sphere.bc.ca/test/tek1.html), or possibly from someone on the TekScopes group.

Good luck!

- Tom Gootee

http://www.fullnet.com/~tomg/index.html

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Old 12th January 2007, 05:14 PM   #6
gootee is offline gootee  United States
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Default Re: tektronix 2235 problem

Quote:
Originally posted by Dhul
Hi,

First of all, sorry for my english.

I have a tektronix 2235 scope, but it has a problem.

It has peaks at channel1 traces.

Anyone can help me?

Anyone can send me service manual?

Thanks.

.HERRAN.

The vertical amp chain is relatively easy to trace, in the 2235. And you should be able to use the scope to look at its own internal waveforms, if you don't have another scope to use.

Just start looking in the back, where the two vertical pins come out of the CRT and work your way "backward", to see if you can find out where the peaking starts. But do make sure that you don't probe any high-voltage nodes.

You can usually tell what parts of the circuit are vertical-related by using a scope or multimeter while you turn the vertical position pot. You'll see the DC level change as the pot position changes. (It's been a long time, but I think there are probably two parallel sets of circuitry and the DC level probably would change in opposite directions, in them, as you turn the pot.)

Be careful. You don't want to short anything with your probe and create another problem (or damage your meter, or get killed).

If you need to remove the CRT, DON'T touch the socket pins while the scope is on! (Don't ask me how I know that.)

Always keep one hand in your pocket, while working on powered-up equipment.

- Tom Gootee

http://www.fullnet.com/~tomg/index.html

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Old 13th January 2007, 12:33 PM   #7
Dhul is offline Dhul  Spain
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Hi again,

Here I show two photos of my problem.

As you can see, there is a peak wich I canīt eliminate with trimmer probes.

It only happens in channel 1, I have tried to use more trimmer caps, but the trace attenues.

The signal in photo is 0,5v amplitude and the peaks are 50mv.

Can anyone help me in solve this problem?
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Old 13th January 2007, 04:28 PM   #8
gootee is offline gootee  United States
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Quote:
Originally posted by Dhul
Hi again,

Here I show two photos of my problem.

As you can see, there is a peak wich I canīt eliminate with trimmer probes.

It only happens in channel 1, I have tried to use more trimmer caps, but the trace attenues.

The signal in photo is 0,5v amplitude and the peaks are 50mv.

Can anyone help me in solve this problem?

You might want to check the input cap(s), in the scope.

- Tom Gootee

http://www.fullnet.com/~tomg/index.html

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Old 15th January 2007, 12:28 AM   #9
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Place the probe on your scope's cal test point and then adjust the small trimmer in your probe for a flat top on the square wave.

Mark
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