D61A oscilloscope - UK Vintage Radio Repair and Restoration Discussion Forum

cinema1 · 31st Jul 2020, 11:23 am

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.

See_Mos · 31st Jul 2020, 4:50 pm

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!

micheal · 1st Aug 2020, 7:33 pm

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

Chris55000 · 2nd Aug 2020, 7:06 am

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

See_Mos · 3rd Aug 2020, 10:07 am

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.

cinema1 · 3rd Aug 2020, 11:50 am

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.

cinema1 · 25th Aug 2020, 2:59 pm

Hi ,
Can any one help with the following, I've been on the forum about focus fault two weeks ago with good info.But removing the panels on the sides and half the front panel i can not fined the , back of the focus control resisters----
R302 1M5------R304 390K . They could be reason why i am not seeing a fine
line after turning the focus down.
appreciate it.
kind regards.
cinema1.
Eric.

31st Jul 2020, 11:23 am	#1
cinema1 Tetrode Join Date: Jun 2008 Location: Preston, Lancashire, UK. Posts: 50	D61A 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.

31st Jul 2020, 4:50 pm	#2
See_Mos Hexode Join Date: Nov 2003 Location: Ossett, West Yorkshire, UK. Posts: 483	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!

1st Aug 2020, 7:33 pm	#3
micheal Pentode Join Date: Mar 2007 Location: Croydon, London, UK. Posts: 111	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

2nd Aug 2020, 7:06 am	#4
Chris55000 Nonode Join Date: Aug 2007 Location: Walsall Wood, Aldridge, Walsall, UK. Posts: 2,873	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 __________________ It's an enigma, that's what it is! This thing's not fixed because it doesn't want to be fixed!

3rd Aug 2020, 10:07 am	#5
See_Mos Hexode Join Date: Nov 2003 Location: Ossett, West Yorkshire, UK. Posts: 483	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.

3rd Aug 2020, 11:50 am	#6
cinema1 Tetrode Join Date: Jun 2008 Location: Preston, Lancashire, UK. Posts: 50	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.

25th Aug 2020, 2:59 pm	#7
cinema1 Tetrode Join Date: Jun 2008 Location: Preston, Lancashire, UK. Posts: 50	D61A oscilloscpe telequipment. Hi , Can any one help with the following, I've been on the forum about focus fault two weeks ago with good info.But removing the panels on the sides and half the front panel i can not fined the , back of the focus control resisters---- R302 1M5------R304 390K . They could be reason why i am not seeing a fine line after turning the focus down. appreciate it. kind regards. cinema1. Eric.