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dutchbird 17th February 2013 02:53 PM

TEK2225 not focusing
Hello everybody,

I have a tek2225 scope and today I can not get the trace on the screen focused anymore :confused:. It appears that the pot has not enough range. Fully CCW is the best position, but still not focused.

I saw some post about adding (and changing) resistors around the pots HV part. Can anyone help me to get this problem tackled. For instance with the schematic of this part.

Thanks in advance,

Gyuri 17th February 2013 03:56 PM

There are two good videos:
Tektronix 2225 Oscilloscope Teardown and Calibration - EEVblog #208 - YouTube
Tektronix 2225 Analog Oscilloscope - EEVblog #196 - YouTube

Gyuri 17th February 2013 04:21 PM

Here is a Tektronix 2225 service manual:

dutchbird 18th February 2013 07:22 AM


Originally Posted by Gyuri (
Here is a Tektronix 2225 service manual:

Gyuri, this helps a lot! Thank you!

dutchbird 19th February 2013 06:21 PM

Gyuri, I have fixed the problem the scope is now well focused.
Resistor R984 was increased to ~2M, instead of 1M, as mentioned in the schematic ... I have replaced the part.

Thanks again for your help!

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