 Posted: Fri Dec 24, 2010 10:44 am Post subject: |
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| The resistor value was changed but not constant,it sifted slowly or unsteady 3,4,6...KOhm | |
| Posted: Fri Dec 24, 2010 3:31 am Post subject: |
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Unlike the, for example, 1.8 ohm ones in some convergence circuits?  |
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| Posted: Thu Dec 23, 2010 10:35 pm Post subject: |
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| Disregard the previous moronic poster--- I deleted it
Good find..It is rather rare for low-value resistors to change so much in value.--probably more age related. More common for higher value resistors to change value. |
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| Posted: Thu Dec 23, 2010 10:12 am Post subject: |
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| It's not a joke,it's true.It happened for second time to me resistor to change the value and it was not power resistor.Really more often happened resistor to break off...
The voltage on the capacitor is 160V and its value was 2.2uF/350V.I putted 4.7uF/450V. The oscilloscope is still about 20 years old... |
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| Posted: Wed Dec 22, 2010 10:22 pm Post subject: |
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| I found the problem without schematic.Very hard to find - one resistor have been changed the value from 220 Ohm to 6 KOhm and a capacitor leakage...
Now everything works fine. |
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| Posted: Thu Dec 16, 2010 10:27 am Post subject: |
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| Any help for power supply diagrams? | |
| Posted: Sun Dec 12, 2010 4:27 pm Post subject: Oscilloscope Topwad 7021 repair |
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| The oscilloscope (Topwad 7021) does work but in the beginning of the beams there is bright dots and at the beam ends the image is shrinked.Intensity regulator is turned completely back but beams are bright and turning the regulator makes week influence.The same is with the focus regulator as well.
Here are the pictures: http://www.picvalley.net/v.php?p=u/1776/19069740909772369061292075432SY1XQaYjIjpS0GLMwAR0.JPG http://www.picvalley.net/v.php?p=u/2194/135517110811181386051292075449ViPhYAI285NwumZAQOdA.JPG http://www.picvalley.net/v.php?p=u/1888/5630784074204399381292075825pRl4QeGlpfl1Mkm35LMj.JPG I think the problem is in power supply of tube which is Toshiba 150BTB31A. I couldn't find a schematic diagram of power supply ,service manual,or tube pin outs... Any help will be appreciated. |
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