Hi folks,
Does anyone have a calibration/maint manual for a JDR Instruments model 3500 o'scope? I bought it cheap for my son ($100), he is building his own analog synth, and it works great, but the focus control no longer brings the trace into focus when I turn it all the way to the right. I need to adjust this but I don't have a manual.
Detailed instructions will do as well.
bd5 at bd5 dot com
Thanks!
If it's not a problem with the tube itself, then likely one of the high value resistors in the chain which divides down the PDA voltage to the right level for the focus grid ( via the focus control ) will have gone high in value. In the absence of a set of schematics for it, I would follow the connections from either end of the focus control ( especially the clockwise end which is probably the higher voltage end ) back to wherever they go, and look for some big-ish high value resistors right there, and carefully check their values. If you find one that has changed substantially in value, make sure that you use a resistor with a high voltage specification to replace it with ( many readily available resistors are only rated for operation up to a couple of hundred volts )
Arfa
Sounds reasonable. Thanks!
juan
Does it have an astigmatism control? Is that working correctly?
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