Author Topic: Tektronix 2225 Repair no vertical  (Read 1411 times)

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Offline DeanKindleysides

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Tektronix 2225 Repair no vertical
« on: December 18, 2017, 10:45:57 am »
Iam a newbie and trying to repair Tektronix scope
The problem is both traces are visible for a very sort time
Then jump about and disappear of the top of the screen
The vertical knobs have no affect wile the traces are visable or after
they disappear
Pressing beam find brings a short trace back to view
All power supply voltages are there
Please help
 

Offline tggzzz

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Re: Tektronix 2225 Repair no vertical
« Reply #1 on: December 18, 2017, 04:47:41 pm »
There are many "scope repair" threads on this forum.

They all start by saying check all the low voltage power supplies for DC voltage and AC ripple.

Then look at your particular scope's service manual; Tek have useful fault-finding guides.

Safety: know where the high voltages are, and how long they stay high after turning the scope off.
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 DeanKindleysides

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Re: Tektronix 2225 Repair no vertical
« Reply #2 on: December 18, 2017, 08:44:24 pm »
Power supply caps replaced dc voltages all in spec and checked for ripple.

 

Offline tggzzz

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Re: Tektronix 2225 Repair no vertical
« Reply #3 on: December 18, 2017, 08:58:10 pm »
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".
Having fun doing more, with less
 

Offline wasyoungonce

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« Last Edit: December 18, 2017, 09:26:02 pm by wasyoungonce »
I'd forget my Head if it wasn't screwed on!
 

Offline DeanKindleysides

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Re: Tektronix 2225 Repair no vertical
« Reply #5 on: December 19, 2017, 09:40:36 am »
Ok thanks
Will dig deeper
Going to check with circuit diagram
Thought it might have a common fault (quick fix)
« Last Edit: December 19, 2017, 03:24:20 pm by DeanKindleysides »
 

Offline bd139

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Re: Tektronix 2225 Repair no vertical
« Reply #6 on: December 19, 2017, 12:18:28 pm »
Definitely check power supply voltages. I just refurbed one of these and ALL of the Philips axial capacitors in it were dead or dying so I just shotgunned the entire thing and it's working perfectly now.

You don't need to worry about EHT voltage checks on these - entirely not needed unless the intensity pot is shot.

The 2225 service manual is freely available (google) and the voltage rails are brought out nicely onto the main board as jumper wires. There is a power supply fault isolation procedure in the manual as well if you find that rails are down.

Also the best place to post is here: http://groups.io/g/TekScopes2

Edit: you can see the jumper wires at the top left (and all the replaced capacitors):



As you're in the UK, CPC are the best place to buy cheap replacement caps. Vishay 030 are suitable replacements for the axial ones (the blue ones). I did the rest with Rubycon and EPCOS. EPCOS one is the main filter cap and had to be purchased from RS.
« Last Edit: December 19, 2017, 12:22:37 pm by bd139 »
 

Offline DeanKindleysides

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Re: Tektronix 2225 Repair no vertical
« Reply #7 on: December 19, 2017, 03:28:03 pm »
Thanks I will replace the axial caps next
 


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