It's now official...... The Drake PTOs seem to be 'all over the map' as far as what you might find inside the can.
I have worked on perhaps a half-dozen in 'recent' times, and ALL were different. Some were 'close' to the schematic for what they were found in, but more were not.
Now we know that some were replaced by Drake over the years, and apparently they put in whatever they had on hand. I just opened a PTO out of and marked R-4B, and in scoping out the circuit, the board is closest to a late TR-4C PTO schematic! It has the output clipping diode, and most values are comparable to the much later PTO, including the semi-conductors. It covers 500 kHz, not 600 kHz.
I understand it's possible that this is a cobble job, but the linearity and tempco are good, which 'may' be significant.
I would be very interested in any photos of any PTO PC boards that you have occasion to open, indicating what they were take out of, model and s/n.
-- 73, Garey - K4OAH Glen Allen, VA Drake 2-B, 2-C/2-NT, 4-A, 4-B, C-Line and TR-4/C Service Supplement CDs <www.k4oah.com> _______________________________________________ Drakelist mailing list [email protected] http://mailman.zerobeat.net/mailman/listinfo/drakelist
