Author Topic: Tektronix Oscilloscope 2225a  (Read 692 times)

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Offline ramptonp

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Tektronix Oscilloscope 2225a
« on: January 11, 2018, 12:08:00 pm »
I have a Old Analogue 2225 Tektronix Oscilloscope. When I switched it on yesterday after a few months of inactivity, the screen didn't light up and after 5 seconds or so I heard a pop and a burning smell from the rear. I had a look inside and found that a capacitor on the main power supply board had blown up (see attached photo). This capacitor is labelled on the circuit board as C903. I have found a service manual with circuit diagrams and this capacitor is placed between neutral and earth, it says 0.0022 next to it. There is an identical capacitor between the live and earth too (C904) but this one appears to be ok.
After contacting Tektronix directly they do not have parts for these anymore so I am trying to find an alternative.
If any one can help it would be much appreciated.
 

Offline tggzzz

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Re: Tektronix Oscilloscope 2225a
« Reply #1 on: January 11, 2018, 04:18:54 pm »
It is one of the infamous Rifa smoke generators.

Have a look on this forum for Tek 2445/2465, and apply the techniques shown in http://www.condoraudio.com/wp-content/uploads/Projects/Tektronix-2465B-Oscilloscope-Restoration-Repair.pdf
There are lies, damned lies, statistics - and ADC/DAC specs.
Glider pilot's aphorism: "there is no substitute for span". Retort: "There is a substitute: skill+imagination. But you can buy span".
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Offline bd139

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Re: Tektronix Oscilloscope 2225a
« Reply #2 on: January 11, 2018, 04:59:21 pm »
Indeed. Congratulations on your first and probably not last RIFA explosion. Those RIFA X2's just love to explode. I've had at least 5 go off on me at some point or another. My Tek 2225 will no doubt explode soon as well. It has eaten about £20 of electrolytic caps already.

Remove all of them. Replace them with roughly the same value X2 / Y2 class capacitors. Cheap Chinese ones will do the job. You can get them here individually for a reasonable price in the UK: https://www.bitsbox.co.uk/index.php?main_page=index&cPath=65_81

Note: X2 capacitors go across the mains. Y2 capacitors go from the mains to earth. I think there's a combination of them in there. Make sure you use the correct ones for the job.

comedy timing of one exploding here:

 

Offline ramptonp

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Re: Tektronix Oscilloscope 2225a
« Reply #3 on: January 11, 2018, 08:21:23 pm »
Ok thanks for that I will take a look.
 


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