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info on gould oscilloscope dso400

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grayt

New Member
anybody know what the problem is with a gould 400 scope that i have.
on the screen is a message saying calibration in progress...
if i press the all button a series of horizontal lines appear for a couple of seconds, thats all, nothing else.
any help appreciated.
grayt
 

Stane

New Member
Hello,

I have the same scope and the same problem with it. Have you found a solution for it?

Regards,
Stane
 

Mr RB

Well-Known Member
This is an absolute GUESS, but most scopes get faults as they age because the capacitors fail. This causes big AC ripple on the internal power supplies, messes up the calibration etc.

Often you can see the capacitors are dead because they have bulged or squirted. Check any caps anwhere hot, PSU's, near heatsinks etc.
 

Stane

New Member
Thanks for your reply Mr. RB. Seems like good idea. I'm going to check caps on the board.

Greetings,
Stane
 

grayt

New Member
gould repair

hi. i replaced 9v regulator, this is under the crt where its flared out, near to R35, this NEARLY fixed it, lines and cal message gone, screen back to its more recognisable disply, however did not display applied known good waveform.
the regulator before replacement was getting hot very quickly, it still got hot after replacement, it lasted about 15 mins then failed, must be something downstream from this regulator,prob. a duff capacitor. see if your regulator gets very hot when on. i have put it to one side , got a bit fed up with it, however i will have another shot at trying to trace the faults, any success and i will post results.
thanks.
 

Mr RB

Well-Known Member
Try checking the capacitors UPstream, they are likely to be in a PSU section that might be a switchmode PSU in a metal cage etc. It's probably high freq ripple that is being fed to the input of your 9v regulator.

Now if you had a scope you could look at the waveform of the PSU rails... ;)
 
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