The caps look brand new ,not the 3 amp power transistors they look original.i can change them all and try again. Is there a number for the teflon coax? I have the other stuff that comes in the recap kit on ebay. Except the 120uh 450v volt cap the wise guy on ebay tried to RIP me it said ten quantity he sent one now he said oh sorry on the way now.I'm stuck no parts to play now.
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Palomar 300a amplifier
- Thread starter Tweetybird
- Start date
I used the crappy avanti foam wire .I found some tandy wire with the hard plastic. That avanti wire can be stripped with your fingernails.
I would use rg316 because it has a larger gauge center conductor and is what I've always used for this kind of work.
RG178 is plenty heavy enough. The coax that runs from the High/Low switch to feed RF to the four final tubes never handles more than 30 or 40 Watts average RF power, tops.
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Thank you nomad. I thought it would be ok on inlet side. Like a fuse able link overdrive the amp maybe fry the wire before the amp .wire was rated at 55 watts 10 times what circuit requires.of course this is a a guess because I have no training or formal education past high school. I do want to learn! I built rifles from parts kits. Ak 47 first reciever was made from a two inch fence post it was ugly,but it functioned the cost of parts kits exceeds the cost of a new rifle. Time to find a new hobby. Built some nice rifles compared to the first one.
Not on hand ,but I jumped the gun and ordered it. I have the plastic core 20awg for the high side, or should I get the 316 stuff not in a hurry just right.
Wrapping a heat shield from aluminum foil around the stretch of black plastic coax where it's close to the tubes would probably protect it okay. Zip ties would hold it in place.
Until they melt.
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Until they melt.
73
Not sure what you mean by the high side because I'm not that familiar with your amp. Just be sure the stuff you use is rated for more than the power you're going to put through it. If in doubt use something bigger.
"High side" on a 300A refers to the "High/Low" switch on the front.
When Low is selected, the radio's drive power bypasses the two driver tubes altogether. The radio drives the four final tubes directly. You can remove the two driver tubes entirely and it will still work on Low side.
High side feeds the radio into the two driver tubes, and they feed into the four final tubes. Takes all six for High side.
The coax we're discussing runs from the High/Low switch to the input of the four final tubes. It's routed near the sockets of the final tubes, and radiated heat from them softens the polyethylene insulation inside the coax. Eventually the center wire migrates through the softened plastic and shorts to the ground braid of the coax. Making the replacement coax heat resistant is just cheap insurance against repeating the problem later.
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When Low is selected, the radio's drive power bypasses the two driver tubes altogether. The radio drives the four final tubes directly. You can remove the two driver tubes entirely and it will still work on Low side.
High side feeds the radio into the two driver tubes, and they feed into the four final tubes. Takes all six for High side.
The coax we're discussing runs from the High/Low switch to the input of the four final tubes. It's routed near the sockets of the final tubes, and radiated heat from them softens the polyethylene insulation inside the coax. Eventually the center wire migrates through the softened plastic and shorts to the ground braid of the coax. Making the replacement coax heat resistant is just cheap insurance against repeating the problem later.
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Thanks for the clarification. I wasn't sure and didn't want to mislead him. I though he might have been replacing coax from the output of the final tubes...if there is any. I've never had the lid off of a 300a.
This is one of those "personality quirks" unique to that model.
Not found in any book that I know to recommend.
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Not found in any book that I know to recommend.
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