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Magnavox Astro-Sonic Combo Is Complete
Well this evening I put the finishing touches on my Astro-Sonic combo set and I gotta tell ya it works great! Before I start in with all of what I had done I want to thank all the members especially Randy Bassham who pointed me in the right direction with the exact chassis number of the TV receiver itself.
So far I have replaced the Pix tube twice, original was very weak to begin with and the second tube would loose the green gun over a few days time if left in the instant on position. I could shoot it with my B&K 467 but it would fall down again and the last dusting of the gun turned into a K+G1 short. Ended up dropping in another 25XP22 NOS tube. Ive also replaced all of the resistors on the horiz/vert/pin board, most of the resistors on the video board and several on the IF strip along with clipping out the OE supply caps and subbing in 450v low-loss photo caps. All the tubes are NOS american mades along with what I suspect are Telefunkin 6GH8's in the chroma circuits. Now I know this is gonna upset a few purists but I also added an older FRED MTS decoder and tapped off the sound IF to feed it, split the mixed audio line in the stereo receiver for TV and subbed the solid state amp with a Heathkit AA-100 chassis right under the turntable. The output transistors were shorted along with several drivers up the chain, my opinion is the set should have had a tube amp in the first place. Its a lowboy console not the upright so I have plenty of room and besides the tubes sound great driving alnico speakers anyway. The turntable works great but the auto changer is still a bit stiff, heck even the old ultrasonic remote works great for both the set and my dog. Ready for the clincher? I recently had a lightning strike on my property of 15 acres, a tree near the house was hit and the resulting spike took out the 1N34 chroma phase detect diodes along with the horiz AFC diodes along with many other solid state things in my home. Being Germanium devices and no access to these animals I instead subbed in 6AL5s and gained a little on the chroma stability and alot in the horiz AFC stability. I can now play a VHS tape from a crummy late model VCR and not have the flag waving at the top as I did before. This thing is rock stable and even the UHF has slightly better sensitivity, Im 36 miles away from our "transmitter central" in Shoreview/Arden Hills MN and knowing where our UHF stations transmit just getting a signal where Im at is a job in itself. For those in the MPLS area KTCI-17, CW-23 and 29 all broadcast from the channel-9 tower that is located east of the twin towers along with all the FM broadcasts. The UHFs are patterned south and west of the tower with a -9db null at 40 degrees from due north. If you want more details on the stations private message me as I do alot of work for the broadcasters and know the techs. Im going to work on getting some images of the set into the forum so you guys can see how nuts I really am. Dont know what resolution they will end up at but I will try to keep the details sharp, then I move on to my Works In A Drawer that needs the wires dressed. Thanks again to everyone! 109 |
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