Garey - I'll take some decent photos of my R-4A PTO when I take it apart again next week, as well as some close-ups of the bad kidney-bean SM cap (3000 pf). I'll email them to you once I'm done.
Right now, I still have the .003 disc ceramic in the PTO and ran it for several hours last night and still had decent-sounding signals and no jumping. The audio did begin to sound harsher as everything warmed up - which could be something else (won't know until I have the twins working together again and can switch PTO's). I also noticed that the phenolic PTO board in mine (an early 13-tuber) has several insulated jumper wires on the component side and that the 3000 pf SM was mounted through the holes but mounted on the solder side of the board. Again, I'll get some pics together next week. I'm trying to get all this together and working again ASAP, as I am expecting my "new" B-Line any day now. 73, Steve, W1ES/4 Date: Thu, 11 Aug 2011 16:46:51 -0400 From: Garey Barrell <[email protected]> To: drakelist <[email protected]> Subject: [Drakelist] Drake 4 Series PTOs Message-ID: <[email protected]> Content-Type: text/plain; charset=ISO-8859-1; format=flowed 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 _______________________________________________ Drakelist mailing list [email protected] http://mailman.zerobeat.net/mailman/listinfo/drakelist
