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Registered Member #96
Joined: Thu Feb 09 2006, 05:37PM
Location: CI, Earth
Posts: 4062
Hi all.
After a long time in storage my OS1100 is jittering. It seems to be worse on channel 1, Ch2 is nowhere near as bad. Tried wiggling the controls but the problem comes back shortly.
Registered Member #543
Joined: Tue Feb 20 2007, 04:26PM
Location: UK
Posts: 4992
Conundrum wrote ...
Hi all.
After a long time in storage my OS1100 is jittering. It seems to be worse on channel 1, Ch2 is nowhere near as bad. Tried wiggling the controls but the problem comes back shortly.
Any ideas? -A
I do have ideas, yes, lad! Circuit values change over time, especially resistances. Capaictors begin to leak, and so on.
You will need a copy of the servicing manual, and the list of instruments cited in the manual needed to perform all the necessary diagnostics.
This isn't something you can fix if your only instrument is a multi-meter.
However, you are still in with a chance if you have a copy of the manual, and an LCR meter for making in situ measurements.
Having established that the jitter isn't mechanical (i.e. perform whatever vibration test you can devise) then you could do worse tha measure the value of each and every resistor in the defective channel and the time base, one by one, replacing those that have drifted away from their original specification. (dozens, I would expect in something 30 years old) Variable resistors such as trace rotate, variable sensitivity, variable sweep and variable trigger should all be treated with especial suspicion.
Woggle the time base switch ever so slightly on each setting, a very slight backwards and forwards, to see if the switch has gone U/S.
If you can, use the external trigger facility, and see if that clears it up.
Test all the capacitors in the same way. Don't fiddle with any pre-sets, unless you have a full set of instruments and know what you are doing.
This sort of approach can only help. You'll still have the fashionable Old Gould dim tube look , but will learn a great deal on the way!
I realize that these suggestions are rather a scatter gun approach, but unless you have all the servicing inventory in the manual, you don't have many other options.
Registered Member #1403
Joined: Tue Mar 18 2008, 06:05PM
Location: Denmark, Odense C
Posts: 1968
I repaired a similar problem on my own old scope simply by removing the cover and look for abnormalities, found a broken solderpoint and later some loose wires.
Inductive loads near the scope can also interfer quite bad with old scopes, I have to distance my weller soldering iron from the scope to have a steady picture.
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Gould OS1100 jitter
Circuit values change over time, especially resistances. Capaictors begin to leak, and so on. 