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Old 31st Jul 2020, 11:23 am   #1
cinema1
Triode
 
Join Date: Jun 2008
Location: Preston, Lancashire, UK.
Posts: 42
Default D61 oscilloscope

Hi,
D61 oscilloscope turning the focus control i can not obtain a thin line its about 1/4 of inch.
The resisters for the focus control i can not see them on the circuit diagram, would i have to remove front cover of the scope.
could any one help
kind regards
cinema1.
Eric.
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Old 31st Jul 2020, 4:50 pm   #2
See_Mos
Hexode
 
Join Date: Nov 2003
Location: Ossett, West Yorkshire, UK.
Posts: 332
Default Re: D61 oscilloscope

None of the photographs I found show what is behind the focus and brightness controls so I cannot say if you need to remove the front panel or not, and the information is not in the manual.

Connected to one terminal of the focus control is a1M5 resistor and the other side is a 390K. The chances are that one of them has changed value.

Proceed with caution and make sure the 'scope is disconnected from the mains for a few minutes to allow the capacitors to discharge. A 1,000 volts hurts!
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Old 1st Aug 2020, 7:33 pm   #3
micheal
Tetrode
 
Join Date: Mar 2007
Location: Croydon, London, UK.
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Default Re: D61 oscilloscope

If it is like the D61a then the focus and brightness pots are on the back chassis top left and right corners, just remove back cover.

Mike
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Old 2nd Aug 2020, 7:06 am   #4
Chris55000
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Join Date: Aug 2007
Location: Walsall Wood, Aldridge, Walsall, UK.
Posts: 1,352
Default Re: D61 oscilloscope

Hi!

You didn't get a D61A manual by mistake by any chance?

These two resistors are marked on the D61 Manual obtainable from "Jon's Valve Page", asterisked as *not mounted on the PCB" – the 390k is shown between chassis–earth and the clockwise end of the "focus" the control, whilst the 1M5 is marked between the anti–clockwise end of the control and the intensity control circuit!

Chris Williams
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It's an enigma, that's what it is! This thing's not fixed because it doesn't want to be fixed!
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Old 3rd Aug 2020, 10:07 am   #5
See_Mos
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Join Date: Nov 2003
Location: Ossett, West Yorkshire, UK.
Posts: 332
Default Re: D61 oscilloscope

The manual downloaded from thevalvepage.com for the D61 shows the focus and intensity on the front above the CRT. Page 32 shows the CRT components separate form the main PCB but does not show a CRT base PCB so I assume they are behind the controls.
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Old 3rd Aug 2020, 11:50 am   #6
cinema1
Triode
 
Join Date: Jun 2008
Location: Preston, Lancashire, UK.
Posts: 42
Default Re: D61 oscilloscope

Thank you all for your help with the focus fault on the D61 OSCILLOSCOPE, i made a mistake with the model number----its a D61A Model.
thanks for all the info.
kind regards
cinema1.
Eric.
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