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Title: Lost Ranger grid drive - found Post by: W8car on January 11, 2008, 05:09:45 PM :)
In another Post I commented on a total loss of grid drive in my Ranger. I found the problem. I pass this on in the hopes it helps some other poor soul down the road. I measured the voltage B4 the R3 18K 'Chernobyl' Resistor as over 300 volts (nominal) and after as 50 volts. This voltage is not enough to fire the OA2 so it basically was dead. After removal the R3 measured a whopping 9 Megs. I did the usual mod and located two 5 watt resistors in parallel to get the 18 K under the chassis (I found a terminal strip with two open lugs). The grid drive is back and soon I will completely check the radio before buttoning it up. 73 Dan W8CAR Title: Re: Lost Ranger grid drive - found Post by: Rick K5IAR on January 11, 2008, 05:12:30 PM Great info, Dan. Thanks! Nothing like a sweet talking Ranger!
Rick/K5IAR Title: Re: Lost Ranger grid drive - found Post by: N3DRB The Derb on January 11, 2008, 06:18:50 PM It pays off in the end to go over the stuff after a quick operational check. Usually I'll check the underside to make sure there's nothing dangerous, tack solder a new filter cap or 2, and give it a whirl. I want to check the transformers and see if the radio plays at all right off the bat. If it's a TX, it's a lot more involved. One again the objective is to see how bad off it is without killing anything else in the process.
Title: Re: Lost Ranger grid drive - found Post by: W3SLK on January 12, 2008, 07:47:25 AM Excellent! Glad you found what was ailing the Ranger. The only fly in the ointment is that its pretty much a day's effort to totally dismantle that VFO and re-assemble it. I hope you make sure that you took a close look at all the solder joints in there. Eric, WB4VVI(SK) one time had a Ranger that lost drive like yours. Duane, KK4AM and myself went down and tore it apart for him. Found an un-soldered joint on a tab that had been like that for about +40 years. Fixed it and the Chernolbyl resistor and re-assembled. But what a bitch tearing it apart >:(
Title: Re: Lost Ranger grid drive - found Post by: flintstone mop on January 12, 2008, 10:12:08 PM There is a victory after all!! That's a common problem in the Ranger. I'm surprised the OA2 was still good. The official fix is to mount the resistor outside of the VFO box, so it won't get so hot. And you have done good stuff. AMfone - Dedicated to Amplitude Modulation on the Amateur Radio Bands
The Ranger circuit design reminds me of working on the so-called "portable" 19 inch color TV's from the 80's. Everything jammed.............Well at least we could see the components. fred |