"Jim Shorney" <[EMAIL PROTECTED]> made an utterance to the drakelist gang ---------------------------------------------------------------------- On Sun, 22 Jan 2006 15:58:17 -0800, Jim Pruitt wrote:
>According to the article itself (mods done on a late R4C with 6EJ7 first and >third mixer). Thanks, Jim. Sounds like mostly old stuff, re-done a little. I'm always wary of AGC mods, sice the AGC is so good to begin with and is what makes the R4C so "listenable". I did do the third mixer mod as descibed in Drakemods to my late R4C, and it seems to work as advertised. Otherwise, no other mods as of yet. >I did wonder about the LM1875 audio amp (20 watt). My R4C needs work >(motorboats) and I wanted to do the Sherwood PS4 mod and the audio amp. I >have a Velleman audio amp kit that I was going to use but in reading Bob >Sherwood (NC0B) mods a few decades ago in Ham Radio Magazine made me wonder >how my Velleman audio amp would work since Bob said to be careful about lead >lengths (had to be exact lengths or would oscillate). So the LM1875 audio >amp was the one mod I was considering but did not want to butcher my R4C. 20 watts sounds like massive overkill. I would worry about power supply loading with that monster, unless the gain is limited somehow. I've got one of the Velleman amps. It looks good and works as advertised on the test bench. I think the warnings are scare tactics to make sure that people follow the manufacturer's recommendations as far as component dress and circuit layout - the devices are not tolerant of sloppy construction, but they are stable and robust with a little care. The one change I did make was the capacitance in the feedback circuit to roll off the high end around 3 KHz; this is a hi-fi amp module, and response to 20 KHz in a communications receiver is NOT a good thing. I wouldn't be afraid of trying the Velleman amp, as long as you follow Bob's hookup recommendations. I just haven't gotten the round tuit that I need to put mine in my R4C yet. Thanks again for the info, Jim. I may have to look at the article and see what it says in more detail. 73 Jim -- Jim Shorney -->.<--Put complaints in this box jshorney (at) inebraska.com Ham Radio NU0C Lincoln, NE, USA EN10ps http://incolor.inetnebr.com/jshorney/ ---------------------------------------------------------------------- Submissions: drakelist@www.zerobeat.net Unsubscribe: [EMAIL PROTECTED] - unsubscribe drakelist in body Hopelessly Lost: [EMAIL PROTECTED] - help in body of message Zerobeat Web Page: www.zerobeat.net - sponsored by www.tlchost.net ----------------------------------------------------------------------
