On 2/19/07, ronnie.hull <[EMAIL PROTECTED]> wrote:
probably just a loose nut between the chair and microphone LOL
Hey! I RESEMBLE That remark! ;-)
just joking.. Geoff is a good friend, I gotta jab at him every once in a while!!
Trust me, he gets it right back, too! Alas, Ronnie had me sign a non-disclosure agreement so I can't share with y'all what he's shared with me (which would embarass the hell outta him, but, oh, well... just use your 'imagination' ;-) (LOL)
I think the problem is still with him though and in a IM QSO with him yesterday we discussed the possibility of bad mica's in the output stage. This is a common failure in the Valiant, but, they usually short and blow the rf choke on the bottom of the plate choke in the valiant. I'm not completely sure that would be the case in the Viking. But an interesting thought no doubt
I'm not convinced. Y'see, Larry (and all) if it were *one* of the coarse loading capacitors, then somewhere in positions 1 thru 7 on the coarse loading on the E.F. Johnson Viking II, then *one* of them wouldn't work. This problem is common to *all* positions on the coarse loading positions, *and* it's common on -all- bands. What's got me most intrigued now, is that now I know of about 5 of these old Viking II's that are exhibiting the exact same problem, the latest being reported by John/K5SEE in Houston, TX. Unfortunatly for me, I'm not in any shape to do any testing on the Viking II, at this time. Currently, I'm writing this message from the Mardi Gras capitol of the world, New Orleans, LA! Laissez les bons temps rouler! (I'll let Don Chester, who's fluent in French, translate). I'm here for work. In my absence, Jon/AD5HR has the aforementioned Johnson Viking II and when he's got some time off from working on roofs, he's going to be doing some tests and checks on it. Great guy, Jon. He took a Globe Chief 90, that was donated by KC5MIP, and put it back on it's feet, working to -it's- specs, built up a push-pull 807 modulator and power supply for that pair, and the pair in the Globe Cheif, running around 400vDC @ 100mA for around 30w of carrier output, and plate-modulating them. That rig sounds great! However, I got to say, when I went to his place out near New Braunfels, TX the first thing I did was grab a screwdriver and turn the pre-amplified D-104 upside down, and cranked DOWN the gain on -that- amplifier, and then grabbed the gain control on his speech-amp and turned -it- down some, and -then- looked at the scope and the envelope pattern no longer looked like a picket fence. The rig still sounds great, and (obviously) has -plently- of Audio drive. When I went there, I also brought Jon an old Hallicrafter R-274 receiver. He's now got a complete AM station, that very nearly qualifies for the Heavy Metal Ralley... cranking out a mighty 30w (*grin*) But it certainly sounds great. Now, if he could put the mic down a while, and check out that Viking II while I'm out here on the road (probably won't be home till late April) he'd be up to 100w, and still be modulated by a pair of 807's. I think a better modulator for the Viking II would be to use a modulation transformer that's about 2x the size of a Ranger modulation transformer, with a tiertiary(sp?) winding so that the screens of the 6146's are modulated at the same time, and use (4) 807's in push-pull parallel, and shunt the DC off of the secondary of the modulation transformer. Build all that up on a sub-chassis, and use an umbilical cord to plug into the back of the xmtr. MUCH better quality audio, greatly reduced distortion and a much cleaner signal. After all, we -are- about good engineering practices, aren't we? Happy Mardi Gras, y'all! Let The Good Times Roll! -- Hey, AD5HR! Did you know that "Operating your AM rig without a scope is like driving our car at night without headlights.(~K4KYV)" 73 = Best Regards -Geoff/W5OMR ______________________________________________________________ AMRadio mailing list List Home: http://mailman.qth.net/mailman/listinfo/amradio Partner Website: http://www.amfone.net Help: http://mailman.qth.net/mmfaq.html Post: mailto:[email protected] To unsubscribe, send an email to [EMAIL PROTECTED] with the word unsubscribe in the message body.
