Re: Help with 465 repair - no signal on 50mv/100mv/200mv ranges


Tom Gardner
 

On 06/03/19 17:12, bbortnick@2bcool.ca wrote:
The fingers are gold plated and looked very clean before I IPA'd them. Is there anything else in the circuit that could be causing the problem? Here is the relevant page from the service manual:
https://groups.io/g/TekScopes/album?id=86337
If the 5V/div range is also faulty, my guess would be the *10 attenuator.

Have you tried applying a signal to the faulty channel's input, and using the /other/ channel to follow the signal forward until it disappears? That could indicate whether the attenuator or the switch was faulty.

If you then suspect the attenuator, remove it and /cautiously/ replace it with a wire jumper. If the signal then "gets through" (albeit at the wrong amplitude and possibly distorted due to the wire and poor connections), then the attenuator is faulty.

Alternatively, you can use an ohmmeter to measure the contact resistance of the switch fingers.

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