How to Restore an URM 25D Signal Generator

Step-by-Step Guide

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   Step 1: Check the fuses are all okay.

   Replace any blown ones. , The "X-MULT" switch should be set to the band being used.
   
   The "SET CARRIER" or "RF OUTPUT" control should be set to indicate full scale on the meter with the "Microvolts" control set to max (fully clockwise).
   
   Then slowly adjust the "Microvolts" control down to the optimal setting. , This will help you determine if the the audio oscillator and modulation circuits work properly., This will help you determine if the RF section works properly., If not, the intermittent contact on the wheel may require cleaning or lubrication, or the spring fingers may require adjustment to ensure they are making good contact.,,, There are 9 tubes in the 25D model., Some spots may require re-soldering., These units are located on the underside of the unit., They may look like Mica.
   
   Replace any that are.
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   Step 2: Check all switches are set correctly.

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   Step 3: Check if the meter works in the 400/1000 Hz range.

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   Step 4: Check if the meter reads RF in the CW position.

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   Step 5: Check if the meter reads RF output on all bands.

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   Step 6: Test if all switches move smoothly

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   Step 7: or if they require cleaning.

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   Step 8: Check that the power plugs inside the front panel are connected.

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   Step 9: Test the tubes on a Dynamic Mutual Trans-conductance tester.

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    Step 10: Inspect the wiring connections.

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    Step 11: Check for broken or failed line feed-throughs.

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    Step 12: Check that none of the moulded paper capacitors are leaking.

Detailed Guide

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