Trio/Kenwood CS-1022 Scope Repair

[frampy]

Hey guys,

I acquired this scope at my old job for a bargain. Channel 1 works nicely, but channel 2 only works intermittently. CH2 is being used as the trigger, so there's definitely a solid signal there. I found that playing around with the CH2 invert button sometimes fixes the issue, as you can see in the second image.

Does anyone have any ideas about what might be causing this issue? I haven't taken it apart yet. Also, does anyone know where I can find a service manual?

Scope faulty

Scope working - kinda

Cheers.

[w2aew]

If wiggling the coupling switch (or vertical sensitivity knob, etc.) makes a difference, then the likely causes are either dirty switch contacts or a intermittent/cold solder joints.  Neither of these would really require the service manual to address/fix.  Careful dis-assembly of the case, and judicious use of a contact cleaner like Caig DeOxit might be all you need.  If the switch contacts are open/visible, sliding a piece of isopropyl soaked paper between the contacts will do a nice job of removing oxidation and gently burnishing the contacts.  Take a careful look under magnification at any solder joints associated with switches and assemblies that are subject to vibration/movement when used - i.e. where switches mount to PC boards, etc.  Look for cracked joints, etc.  It's generally not a bad idea to re-solder these connections.

[frampy]

Cheers for the info, i'll take a look at the offending switch tonight.

I can see how a fualty channel invert switch would cause this if it's a two-pole switch, getting stuck somewhere in the middle.

[w2aew]

It's not so much getting stuck in the middle, more likely dirty contacts that make them appear open when closed.

[frampy]

I de-soldered the switch and found that the contact was damaged. I tried to reshape it but It kept bending out of shape after a few presses. So I bypassed the switch so that channel 2 is always non-inverting. Not ideal, but at least I have both channels working now.

Thanks for the info. Keep up the good work on your youtube channel too!