dead channel on CRO

[SkyDemon]

Hi, i have a Kikusui COS5020 oscilloscope and channel 1 on it doesnt work
(not getting any trace at all). Does anyone know where to get the
schematic/service manual for it? (I have found a paid site but ill try and
see if i can get it free first).

Also can anyone point me in the right direction where to look for the fault?
When no channel is selected there is a faint unfocused mark on the screen
which stays there when ch 1 is selected so this leads me to believe that
maybe there is something wrong with the input selection section.

Hope that made sense

Cheers

 

[Jerry G.]

It is very common that in most scopes people blow the front end by injecting
too high a voltage, as like in TV sets or power supplies. The MosFets are
most likely blown.

--

Greetings,

Jerry Greenberg GLG Technologies GLG
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WebPage http://www.zoom-one.com
Electronics http://www.zoom-one.com/electron.htm
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"SkyDemon" <c_mick@REMOVETHIShotmail.com> wrote in message
news:bo5kpb$kta$1@otis.netspace.net.au...
Hi, i have a Kikusui COS5020 oscilloscope and channel 1 on it doesnt work
(not getting any trace at all). Does anyone know where to get the
schematic/service manual for it? (I have found a paid site but ill try and
see if i can get it free first).

Also can anyone point me in the right direction where to look for the fault?
When no channel is selected there is a faint unfocused mark on the screen
which stays there when ch 1 is selected so this leads me to believe that
maybe there is something wrong with the input selection section.

Hope that made sense

Cheers

 

[Nigel Cook]

"SkyDemon" <c_mick@REMOVETHIShotmail.com> wrote in message
news:bo5kpb$kta$1@otis.netspace.net.au...

Hi, i have a Kikusui COS5020 oscilloscope and channel 1 on it doesnt work
(not getting any trace at all). Does anyone know where to get the
schematic/service manual for it? (I have found a paid site but ill try and
see if i can get it free first).

Also can anyone point me in the right direction where to look for the
fault?
When no channel is selected there is a faint unfocused mark on the screen
which stays there when ch 1 is selected so this leads me to believe that
maybe there is something wrong with the input selection section.

Hope that made sense

Cheers

Generally speaking the diagnostic problem with
scopes as far as X and Y amps is they have
to be DC coupled throughout. So anywhere in
the chain something failing and sending the
signal high or low will shift the o/p well off beam.
Other than i/p FET overdriven the other common
problem is one of the pair of push-pull output
drivers to the CRT plates having failed.

e-mail (removing .....) diverse2@tcp.co.u.....k
electronic hints and repair briefs , schematics/manuals list on
http://homepages.tcp.co.uk/~diverse

Nigel,Diverse Devices,Southampton,England