BK Precision Portable Oscilloscope Model 1420

2/12/2003 1:16:53 PMPeter

Good day,
If anyone can help me I would greatly appreciate it. When the scope is turned on the red led lights, but there is no deflection on the screen. The only time you can see any life or deflection is when the scope is turned off. When turned off you can see a vertical line closing to the center as a dot, that is it nothing else. I don't have the schematic or service manual. If someone does or knows about this type of problem I would appreciate help and/or a copy.
Thank you, Peter

2/12/2003 5:47:52 PMEdd

:Good day,
:If anyone can help me I would greatly appreciate it. When the scope is turned on the red led lights, but there is no deflection on the screen. The only time you can see any life or deflection is when the scope is turned off. When turned off you can see a vertical line closing to the center as a dot, that is it nothing else. I don't have the schematic or service manual. If someone does or knows about this type of problem I would appreciate help and/or a copy.
:Thank you, Peter
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Well Peter:
Looks like your HV supply to the CRT and its filament is good, from what you have told us. Only one thousand and lebenteen possibilities left.The first would be is if this is is a new acquisition and you are not familiar with triggered oscilloscopes. Or is(was) this your working oscilloscope that stopped working for you, and even at that, if you are not familiar with that unit it could be as simple as a triggering adjustment not be setting correctly.RSVP

2/12/2003 10:18:31 PMPeter

:: Thank you Edd for your quick response. This is not my own personal scope. I have my own older tube scope. My job is purchasing a new one and was going to toss this one, so I grabed it. It is smaller and will give me more room on my work area. I even tried to lock in on the test point on the scope but nothing appears on the screen. It only shows life when you turn the unit off.
:: Thank you, Peter

::Good day,
::If anyone can help me I would greatly appreciate it. When the scope is turned on the red led lights, but there is no deflection on the screen. The only time you can see any life or deflection is when the scope is turned off. When turned off you can see a vertical line closing to the center as a dot, that is it nothing else. I don't have the schematic or service manual. If someone does or knows about this type of problem I would appreciate help and/or a copy.
::Thank you, Peter
:~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
:Well Peter:
:Looks like your HV supply to the CRT and its filament is good, from what you have told us. Only one thousand and lebenteen possibilities left.The first would be is if this is is a new acquisition and you are not familiar with triggered oscilloscopes. Or is(was) this your working oscilloscope that stopped working for you, and even at that, if you are not familiar with that unit it could be as simple as a triggering adjustment not be setting correctly.RSVP

2/13/2003 8:48:48 AMJohn McPherson

Hi,
Assuming the problem is not from a lack of familiarity:

I had a similar situation with a Heathkit solid state unit. If you can turn the unit on in a darkened room, set up the scope as you would for normal calibration, with swep set to auto, and internal. If you turn the position controls systematically, you will see when the beam is close to the screen. If you are at maximum position on the position controls, you may need to select a different value resistor in series with that control to get the beam back onto the screen.

I had to reduce a resistor value from 1 Meg to 470K in order to get the beam centered with control near center.

::: Thank you Edd for your quick response. This is not my own personal scope. I have my own older tube scope. My job is purchasing a new one and was going to toss this one, so I grabed it. It is smaller and will give me more room on my work area. I even tried to lock in on the test point on the scope but nothing appears on the screen. It only shows life when you turn the unit off.
::: Thank you, Peter
:
:
:
:::Good day,
:::If anyone can help me I would greatly appreciate it. When the scope is turned on the red led lights, but there is no deflection on the screen. The only time you can see any life or deflection is when the scope is turned off. When turned off you can see a vertical line closing to the center as a dot, that is it nothing else. I don't have the schematic or service manual. If someone does or knows about this type of problem I would appreciate help and/or a copy.
:::Thank you, Peter
::~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
::Well Peter:
::Looks like your HV supply to the CRT and its filament is good, from what you have told us. Only one thousand and lebenteen possibilities left.The first would be is if this is is a new acquisition and you are not familiar with triggered oscilloscopes. Or is(was) this your working oscilloscope that stopped working for you, and even at that, if you are not familiar with that unit it could be as simple as a triggering adjustment not be setting correctly.RSVP

2/13/2003 8:20:01 PMEdd Whatley

Well Peter:
Looks like its not even possible to find a picture of that unit, but I’d just take a guesstimate at it being ~4in (with blue filter in front !) CRT and possibly a dual trace 25 Mhz unit ???? Even Tannenbaums doesn’t list tech data being available for it. However there’s always the BK svc depot in Yorba Linda Cal
If I was up against the unit in the dark with only my 50 yrs of T/S exp I would first pull the dust covers and locate the power supply and figure how many supplies there are and check for their presence. Then fire up the unit and subject the chassis PCB’s to the old tap- tap-test or a lateral brushing of the foil side with a very stiff bristled tooth brush to see if anything shows on the screen. Inspect the chassis’ heat sinked devices, leads of power resistors, and connector plug/jacks for floating cold solder ring joints.Your trouble could be just that simple. Next move to your Vert and Hoz circuits and see if every transistor has its B+. Same for the Triggering cktry and Hoz time base cktry.Then too since U said that U had an older tube scope…..be it the free running Eico 460 kluge…not good at all…. or maybe the behemoth Tek 5XX series, but still a fine unit.Then I guess U could use the new scope at work ! You could always inject a signal and trace down the line in your vert and hoz ckts. Your injected signal could be the Cal ref Sq Wave out put thru a .01-.1 /600v paper cap and then scope it on down the stages. However,first scope the Cal sig to see if even it is there!.
Fill me in as U progress

73’s de Edd
eddw35@attbi (Interstellar ~~~~Warp~~~~Speed)
FMW4409@DCCCD.EDU (Firewalled-Spam*Cookies*Crumbs)

:Hi,
:Assuming the problem is not from a lack of familiarity:
:
:I had a similar situation with a Heathkit solid state unit. If you can turn the unit on in a darkened room, set up the scope as you would for normal calibration, with swep set to auto, and internal. If you turn the position controls systematically, you will see when the beam is close to the screen. If you are at maximum position on the position controls, you may need to select a different value resistor in series with that control to get the beam back onto the screen.
:
:I had to reduce a resistor value from 1 Meg to 470K in order to get the beam centered with control near center.
:
:
:::: Thank you Edd for your quick response. This is not my own personal scope. I have my own older tube scope. My job is purchasing a new one and was going to toss this one, so I grabed it. It is smaller and will give me more room on my work area. I even tried to lock in on the test point on the scope but nothing appears on the screen. It only shows life when you turn the unit off.
:::: Thank you, Peter
::
::
::
::::Good day,
::::If anyone can help me I would greatly appreciate it. When the scope is turned on the red led lights, but there is no deflection on the screen. The only time you can see any life or deflection is when the scope is turned off. When turned off you can see a vertical line closing to the center as a dot, that is it nothing else. I don't have the schematic or service manual. If someone does or knows about this type of problem I would appreciate help and/or a copy.
::::Thank you, Peter
:::~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
:::Well Peter:
:::Looks like your HV supply to the CRT and its filament is good, from what you have told us. Only one thousand and lebenteen possibilities left.The first would be is if this is is a new acquisition and you are not familiar with triggered oscilloscopes. Or is(was) this your working oscilloscope that stopped working for you, and even at that, if you are not familiar with that unit it could be as simple as a triggering adjustment not be setting correctly.RSVP

2/14/2003 1:16:25 PMpeter

:Good day Edd,
:Yes it's a 2x2" blue filter screen dual trace 15Mhz unit. I found that the switches needed a good cleaning especially the norm/video, source int/ext and the slope +/-. Yes, the trigger switch needed a real good cleaning too. Also the board with these controls and the sweeptime/div needs to be resoldered (some cold solder joints). I have the scope working now, but further cleaning and soldering will be required. Out of curiosity I priced the repair on such a unit, they are getting $75.00/hr. Not bad and if you don't like the est. they give you they charge you $75.00 just for looking at it. Well thank you again, I can now have more work space with this smaller scope on the desk at home to repair those great old radios.
:I also would like to thank John for his quick reponse. Thank you John.
:OK I have to get back to work now. Have a good day everyone.
:Peter
:
:Well Peter:
:Looks like its not even possible to find a picture of that unit, but I’d just take a guesstimate at it being ~4in (with blue filter in front !) CRT and possibly a dual trace 25 Mhz unit ???? Even Tannenbaums doesn’t list tech data being available for it. However there’s always the BK svc depot in Yorba Linda Cal
:If I was up against the unit in the dark with only my 50 yrs of T/S exp I would first pull the dust covers and locate the power supply and figure how many supplies there are and check for their presence. Then fire up the unit and subject the chassis PCB’s to the old tap- tap-test or a lateral brushing of the foil side with a very stiff bristled tooth brush to see if anything shows on the screen. Inspect the chassis’ heat sinked devices, leads of power resistors, and connector plug/jacks for floating cold solder ring joints.Your trouble could be just that simple. Next move to your Vert and Hoz circuits and see if every transistor has its B+. Same for the Triggering cktry and Hoz time base cktry.Then too since U said that U had an older tube scope…..be it the free running Eico 460 kluge…not good at all…. or maybe the behemoth Tek 5XX series, but still a fine unit.Then I guess U could use the new scope at work ! You could always inject a signal and trace down the line in your vert and hoz ckts. Your injected signal could be the Cal ref Sq Wave out put thru a .01-.1 /600v paper cap and then scope it on down the stages. However,first scope the Cal sig to see if even it is there!.
:Fill me in as U progress
:
:73’s de Edd
:eddw35@attbi (Interstellar ~~~~Warp~~~~Speed)
:FMW4409@DCCCD.EDU (Firewalled-Spam*Cookies*Crumbs)
:
:
::Hi,
::Assuming the problem is not from a lack of familiarity:
::
::I had a similar situation with a Heathkit solid state unit. If you can turn the unit on in a darkened room, set up the scope as you would for normal calibration, with swep set to auto, and internal. If you turn the position controls systematically, you will see when the beam is close to the screen. If you are at maximum position on the position controls, you may need to select a different value resistor in series with that control to get the beam back onto the screen.
::
::I had to reduce a resistor value from 1 Meg to 470K in order to get the beam centered with control near center.
::
::
::::: Thank you Edd for your quick response. This is not my own personal scope. I have my own older tube scope. My job is purchasing a new one and was going to toss this one, so I grabed it. It is smaller and will give me more room on my work area. I even tried to lock in on the test point on the scope but nothing appears on the screen. It only shows life when you turn the unit off.
::::: Thank you, Peter
:::
:::
:::
:::::Good day,
:::::If anyone can help me I would greatly appreciate it. When the scope is turned on the red led lights, but there is no deflection on the screen. The only time you can see any life or deflection is when the scope is turned off. When turned off you can see a vertical line closing to the center as a dot, that is it nothing else. I don't have the schematic or service manual. If someone does or knows about this type of problem I would appreciate help and/or a copy.
:::::Thank you, Peter
::::~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
::::Well Peter:
::::Looks like your HV supply to the CRT and its filament is good, from what you have told us. Only one thousand and lebenteen possibilities left.The first would be is if this is is a new acquisition and you are not familiar with triggered oscilloscopes. Or is(was) this your working oscilloscope that stopped working for you, and even at that, if you are not familiar with that unit it could be as simple as a triggering adjustment not be setting correctly.RSVP