dya@unccvax.UUCP (York David Anthony @ WKTD, Wilmington, NC) (03/28/89)
Ladies and Gentlemen of the net: I have a terrible problem...my RCA BTA 50-J AM transmitter just ate one of its MC899 logic chips. Fortunately for me, I could adapt this circuit to use TTL (works, too at 3.6 volts) but there are plenty more of these beasties which depend on the characteristics of this family for waveshaping, etc. The logic chips are part of the "Ampliphase" exciter modulator card (as opposed to the drive regulator, oscillator, and reflectometer which are not nearly as packed with DTL). A triangle wave is generated inside which is summed with the incoming audio, and then "clipped" to form pulses of variable width and hence phase (and hence Ampliphase at the antenna output...). Are there sources (even MIL/JAN parts are fine) for MC-8xx family spares? RCA-GE doesn't have them. If this exciter were to lose another one, I'd have to convert it back to its vacuum tube counterpart (blecch, hock-ptewey). Of course, if you have a "spare" BTE-20 exciter gathering dust in your junk box, I'd be interested in that, too. My transmitter came from WHN New York (now WFAN) but the "broker" swiped the second exciter and the spares. Yours for $5000/mo power bills, York David Anthony KGOL Humble-South Houston, Texas