Drake TR-4 Transceiver going into oscillation

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AB5AA

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Mar 29, 2014
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My Drake TR-4 transceiver goes into loud oscillation now if I turn the volume control above minimum level. It will receive at minimum level and load antenna. Also, when I switch the bandswitch or transmit, a loud high-pitched oscillation begins.

Any troubleshooting advice would be greatly appreciated.

Best Regards,
Larry-AB5AA
 

n0nhp

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If it came across my bench, I would lift the lid and start hitting various areas, one at a time, with a can of freeze spray https://www.google.com/search?q=component+freeze+spray&oq=component+free&aqs=chrome.1.69i57j0l5.8246j0j8&sourceid=chrome&espv=210&es_sm=93&ie=UTF-8#q=component+freeze+spray&safe=off&tbm=shop

alternately using the end of a wooden cotton swab or similar, start pressing on various areas of the circuit board.
Paying special attention to the receive tank coils and crystals. It could be a bad solder joint, a bad shield on a coil, a bad cap in the audio section putting audio back on the VCC, etc, etc.
Probably won't be a "hit this solder joint, or replace this cap fix.

Good luck
Bruce
 
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