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Phantom 12 Tube
- Thread starter dwilcox29
- Start date
Pretty neat, I don't know too much about amps, however I wanted to welcome you to the group,there's a lot of gentlemen here who will be more than happy to help you out if you need it, have a great day today!!!
73
Very LOW drive amp...made to use when radios did 5w max carrier...a "little" dirty signal wise...but produce 7-800+ watts when driven responsibly (3-5 watts max) 10 watts PEP...IF tubes are any good...That amp is close to 50 + yrs old...to retube it costs BIG $$$$
Looks like a Phantom 500 to me, but I could be wrong. Use a very low drive, tune it up and see what it does. Pop the top and see what tubes are in it. Everyone says those old 11m amps are boat anchors and tubes are insanely expensive. If you needed 8950's, that would be true. But I retubed a D&A 10 tube pdx 400 a few years ago with new old stock for less than $180. Sure it's an antique amp, but worth it to me to get it back on the air. Hell you can't buy a single 3-500z for that price. If it works run it and enjoy a piece of history.
Nope.
The 12-tuber has two plate-tune controls and a screw-slot trim cap to the right of them on the lower row of knobs. One plate tune is for high side, the other one for low side.
The 500 is a ten tuber, built with a ham-band selector switch at the center of the three lower kobs.
If you see that screw-slot trimmer cap on the front panel you know its the one with the suicidal high/low relay inside along with 12 tubes.
73
Thanks for the info I am no tech expert just trying to to get it back running the good news is it does work on High and Medium the the Driver Tune works but the Tune to the right does not or the screw -slot trimmer marked Load does not work and yes the Low Power setting is not working. My question to you Mr. Phantom expert is what could be the cause of no Low Power not working. Thank You for your comments and info you give.
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I'd definitely replace those electrolytic capacitors and bleeders.
Where to start?
Yeah, a bunch of 50 plus year-old stuff is in there, ready to create new problems.
Somebody identified one failed filter cap and replaced it with the orange "Sprague" brand part. How long before the next one fails is anybody's guess. Seconds, hours? Days? By rights none of them should still check good this many years down the road. They're not meant to last this long in the first place.
The left two of the three adjustments at the bottom of the front panel are divided by the left-most used only for High side. Does nothing in Low. The center and right capacitors are for low side only. They do nothing on High. The center knob is Low side-only Plate Tune, and the tiny screw slot is the Low side-only Load control.
The High/Low relay is the one just under the two outboard-most final tubes. The center contact lever looks crinkled. Can't remember what the center circuit on that relay does, but if Low side won't work, cleaning the contact points on that relay would be the first step. And if the contact points are pitted and rough, that's at least part of your problem. And if the black plastic that holds the contact points disintegrates when you touch it, I would not be surprised.
Something Ed DuLaney figured out about bleeder resistors is that you can get away with leaving out a separate individual bleeder for each cap if the caps all came from the same manufacturing batch. They tend to match and balance well. They need to divide the 900 Volts across three caps in series equally. If one of them hogs more than one-third of the voltage, the 350-Volt rating gets exceeded. This kind of cap doesn't tolerate over-voltage all that well. All electrolytic caps have some internal leagage resistance. And like any three resistors in series, all three have to match so that 900 Volts gets divided evenly three ways. And if one of those three gets replaced, it may or may not match the other two. It's kinda like russian roulette. Might be a winner, might not. Just because the factory, buying that cap by the thousand got away with this, doesn't mean you will.
This is why a separate resistor across each capacitor is the industry standard. The bleeders serve also to equalize the voltage when capacitors are stacked in a series string.
I could go on and on about quirky suicidal habits this model can have. Oh, wait! I alread did.
Just be sure the skinny keying tube is good. Might be a 12AQ5 or more likely a 6AQ5 type. A bad keying tube could activate the relays without keying the radio. I had a customer years ago who left a Phantom running on standby while he left the radio room for about 15 minutes. His kid came running to get him, said smoke was coming out of the linear. It had keyed itself. The driver tubes get really hot if you key them with no drive. No telling how long it took to overheat this way. No more than 15 minutes, to hear him tell it.
The biggest risk of just patching "one" fault in something that old is that the next thing to break only takes a day or a week. After this happens repeatedly, we call that "electronic whack-a-mole".
At the very least those six electrolytic caps should get replaced. Or just keep a fire extinguisher handy.
73
Yeah, a bunch of 50 plus year-old stuff is in there, ready to create new problems.
Somebody identified one failed filter cap and replaced it with the orange "Sprague" brand part. How long before the next one fails is anybody's guess. Seconds, hours? Days? By rights none of them should still check good this many years down the road. They're not meant to last this long in the first place.
The left two of the three adjustments at the bottom of the front panel are divided by the left-most used only for High side. Does nothing in Low. The center and right capacitors are for low side only. They do nothing on High. The center knob is Low side-only Plate Tune, and the tiny screw slot is the Low side-only Load control.
The High/Low relay is the one just under the two outboard-most final tubes. The center contact lever looks crinkled. Can't remember what the center circuit on that relay does, but if Low side won't work, cleaning the contact points on that relay would be the first step. And if the contact points are pitted and rough, that's at least part of your problem. And if the black plastic that holds the contact points disintegrates when you touch it, I would not be surprised.
Something Ed DuLaney figured out about bleeder resistors is that you can get away with leaving out a separate individual bleeder for each cap if the caps all came from the same manufacturing batch. They tend to match and balance well. They need to divide the 900 Volts across three caps in series equally. If one of them hogs more than one-third of the voltage, the 350-Volt rating gets exceeded. This kind of cap doesn't tolerate over-voltage all that well. All electrolytic caps have some internal leagage resistance. And like any three resistors in series, all three have to match so that 900 Volts gets divided evenly three ways. And if one of those three gets replaced, it may or may not match the other two. It's kinda like russian roulette. Might be a winner, might not. Just because the factory, buying that cap by the thousand got away with this, doesn't mean you will.
This is why a separate resistor across each capacitor is the industry standard. The bleeders serve also to equalize the voltage when capacitors are stacked in a series string.
I could go on and on about quirky suicidal habits this model can have. Oh, wait! I alread did.
Just be sure the skinny keying tube is good. Might be a 12AQ5 or more likely a 6AQ5 type. A bad keying tube could activate the relays without keying the radio. I had a customer years ago who left a Phantom running on standby while he left the radio room for about 15 minutes. His kid came running to get him, said smoke was coming out of the linear. It had keyed itself. The driver tubes get really hot if you key them with no drive. No telling how long it took to overheat this way. No more than 15 minutes, to hear him tell it.
The biggest risk of just patching "one" fault in something that old is that the next thing to break only takes a day or a week. After this happens repeatedly, we call that "electronic whack-a-mole".
At the very least those six electrolytic caps should get replaced. Or just keep a fire extinguisher handy.
73
Well thank you for being honest yes I do know all all the filter caps electrolytic capacitors and bleeders need to be replaced there are three resistors that look all sweaty and just look bad that center relay is another problem I have a tube tester and have checked the keying tube and all the sweep tubes and replaced three two had shorts and one was completely dead I know it needs work and it will get repaired over time caps are first on the list I have uploaded more photos to the dxGallery and I count 8 Caps the fun begins lol.
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I sell a set of 450-Volt filter caps for the ten-tube version. Takes eight of them for that version. They come with a bleeder resistor already soldered across each capacitor.
https://www.ebay.com/itm/1162580681...pid=5336136228&customid=&toolid=10001&mkevt=1
Seems to me the 12-tube used only six of them. Don't have a separate sale listed for just eight caps, only for a set of eight.
73
https://www.ebay.com/itm/1162580681...pid=5336136228&customid=&toolid=10001&mkevt=1
Seems to me the 12-tube used only six of them. Don't have a separate sale listed for just eight caps, only for a set of eight.
73