You can force the filters with the attached file, the A2 is +2 to -4 DB of gain, the A3 is +55 DB of Gain and the A4 is about +60?DB of gain, the 10.00 Volt adjustment on the A4 card is critical for the BITE to run the filters.
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Gary
---------- Original Message ----------
From: "thoyer via groups.io" <thoyer1@...>
To: <
[email protected]>
Subject: [RacalRadio] RA6790 Bad Filters?
Date: Sat, 28 Dec 2024 19:56:17 -0500
After changing out several IC¡¯s on A4, A6 and A9 and replacing the EPROM sockets, that were corroded by a bad battery, I now have my 6790 up and running. Signal levels seem low though and running the BITE I get errors 33 thru 37 ¨C bad filters in slots 3 thru 7. I bench tested the filters using my sig gen and spectrum analyzer - I know the impedances don¡¯t match but this was just to see if they passed any signal. They each seem to have ¡°reasonable¡± response curves and all seem to have the similar peak amplitudes. The LSB and USB filters pass BITE and also tested ok with similar levels through them in my crude setup.
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My question is, I¡¯m wondering if the test level is possibly low (similar to the received signal level being low) and causing these indicated failures. I¡¯m going through the schematics looking for how the test signal is generated but could maybe use some guidance by those that know these receivers better then I.
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Thoughts?
?
Tom
W3TA
