Author Topic: tektronic 475  (Read 177 times)

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Offline JDL Taiwan

  • Newbie
  • Posts: 3
  • Country: tw
tektronic 475
« on: July 22, 2018, 10:50:18 pm »
Hello Evert Body,
So I bought a Tektronix 475, actually it should be a gift for my friend.
So it's a 475 with a DM43. Has also arrived but when switching on the first surprise came the beam, stuck at the top. With the circuit schematic I could find the vertical output IC U470 as defective.
I found one IC in UK and its arrived too. Now the function is there, but all switches and pots are dirty and scratching. When measuring I noticed that my rectangle looks stringed after the input attenuator.
Picture 001 shows attenuator at 5mV at 1KHz at output from attenuator and
Picture 002 shows attenuator at 20mV at 1KHz at output from attenuator.

But it is the same on both channels. But if I may say so, it crashes in the switches and Potis.
Now to my question, I have read that one cleans the switches with IPA and a piece of paper. It makes sense to me, but how is it with the potis? I have not found anything yet.
And then another things in the old radios I do, I change the Elkos is this also necessary?

Thanks for your help
John D.Lehmann
Taiwan (Zhubei)



 


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