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XLAXX
| | Posted on Tuesday, September 17, 2002 - 12:05 pm: | 
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Does anyone know where I can track one of these rascals down??? Anybody on the forum got one of these rolling around on the ole bench or in a box of old parts... would sure love to talk with you.
Mine is losing juice when I key on it. 1 driving 4 35LR6's. Thanks!
XLAXX |
bruce
| | Posted on Tuesday, September 17, 2002 - 1:03 pm: |
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for a start
tubesandmore
fairradio
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2600
| | Posted on Tuesday, September 17, 2002 - 2:59 pm: |
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If the power falls off while you are keyed, this is about the LAST part on the list of suspects to blame. Start with the tubes. Just because they check good on a tester (you DID check them on a tester, didn't you?) doesn't mean they will deliver full power. A tube tester puts only a small fraction of a watt to these tubes. It CAN'T fully predict what they will do at full load. On the other hand, if the meter on the tester falls back when you push (or turn) the emmissions test switch, that's a clue, too. A tube that falls back on the tester reading will do the same thing in an amplifier, usually. I do not have specs on that transformer. I have never been able to locate a schematic or parts specs on the Galaxy tube amps that were built with the 12-pin tubes. I can tell you that the odds are less than 1 in a thousand that the transformer is to blame for this problem.
73 |
XLAXX
| | Posted on Wednesday, September 25, 2002 - 12:28 pm: |
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Checked out everything on this amp. Tubes good!
Do I need to get a 35V 1amp transformer for this Galaxy 1000?? Is this sufficient?
Thanks! |
2600
| | Posted on Wednesday, September 25, 2002 - 4:15 pm: |
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I'm not real sure just where to start here. It's as if you asked about using a spark plug from your lawn mower in a diesel engine. There's just no place to put a spark plug in a diesel. And there's no place to put a 35 Volt 1 Amp transformer in this tube linear. You seem to have concluded that everything else in the amplifier is good. I say you're missing something. Unless you put this set of tubes in another amplifier AND THEY HOLD STEADY POWER, you CAN'T just assume they are NOT the problem. A tube tester will NOT establish that a power tube is good. It will ONLY weed out the ones that are REALLY bad. My experience with other amplifiers that use the 12-pin tubes is that EVEN IF BY ACCCIDENT, they are overheated and "cherry" once or twice because of mistuning, overdriving, too much radio carrier, or keying for too long, THEY WILL BE PERMANENTLY CRIPPLED. Once this happens, the swing will be a lot less than it used to be, and the power will fall off steadily while it is keyed. THIS IS A PROBLEM THAT TRANSFORMERS *DO NOT*,repeat *DO NOT* usually cause. Did this amplifier EVER perform correctly with these tubes, or has it always acted this way? Did it start after somebody keyed it a little too long, EVEN JUST ONCE? Or maybe it started after trying MORE DRIVE THAN YOU USED BEFORE, even JUST once? Did it start AFTER changing tubes?
Never mind the fact that the folks who made this box JUST DO NOT PUBLISH DIAGRAMS, or that the transformer that is already in there has AT LEAST six wires coming out of it, probably more. That makes it a custom part that WON'T be found in a transformer catalog where the "35 Volt 1 Amp" part you mentioned is sold. RF Parts used to sell power transformers for other amplifiers that use these tubes, but THE VOLTAGES HAVE TO MATCH. If you want to get one made custom,or use a substitute, you need the voltage/current rating for the high-voltage winding, for the filament winding, and whatever else yours has on it.
Unless you can find someone who HAS worked on these, those specs are not available anywhere I know.
I have turned down every request but one in the last 10 or 12 years to work on a Galaxy tube amp. The one I didn't turn down, I offered to draw a schematic of the thing before going to work on it. The price I quoted him made replacing the amp sound like a better idea, so he turned me down. Smart fella.
Heck, we haven't even gotten to the question about tuning it right. Running the thing mis-tuned, EVEN BY ACCIDENT is hard on the tubes, and will weaken them after running that way for a while. Once that happens, that set of tubes is just no good any more.
The way this amp runs these small tubes is hard on them, even if you run it right.
I would like to get ONE little question answered. This thing has a driver tune knob and a final tune knob. These will be variable capacitors with the plates spaced FARTHER apart, and fewer plates than the LOAD control. Key the thing and tune it for max swing. Now, unkey it and look at the plates on both the TUNE control variable capacitors. I predict that either one or both of them has the plates EITHER ALL THE WAY APART AS FAR AS THEY GO, OR ALL THE WAY TOGETHER AS CLOSE AS THEY'LL MESH. Please, LET US KNOW if this is what you find. If I'm right, the coil attached to each of these controls is out of adjustment, and preventing a TRUE PEAK on either or both of these knobs. This kind of variable capacitor does not have and END STOP like most Load controls will have. If you try to turn the load control too far, "CLUNK", you run into the end stop. The Tune controls on this one typically spin 360 degrees with no stop point. If this control goes ALL THE WAY TO THE END OF ITS TRAVEL, you can't tell from the outside of the cabinet. It can fool the operator into thinking that he got a "PEAK" on the wattmeter, but what he really got was a control THAT DOESN'T TURN FAR ENOUGH TO REACH A TRUE PEAK. When this happens, the coil must be adjusted to bring the TRUE PEAK on this knob back into the end-to-end range that it covers. An amplifier doesn't care WHY the tune controls aren't peaked, whether because of a coil that isn't adjusted right, or someone who just runs it wrong. The result will be the SAME either way. The tubes will overheat and be permanently damaged, if it goes on long enough. Once that happens, you need TWO things: 1) a set of tubes, and 2) a way to set the coils right so the next set of tubes doesn't get hammered the very same way.
Please, let us know if I'm right about the two Tune controls.
I know you WANT the tubes to be good, you HOPE the tubes are okay, you BELIEVE the tubes are alright. You just can't PROVE that they are good. Proof and belief just aren't the same thing.
73 |
2600
| | Posted on Thursday, September 26, 2002 - 3:01 pm: |
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Hey, XLAXX! I tried to reply to your e-mail. It bounced back "User Unknown". I used the 'reply' button, so I didn't mis-spell anything in your Hotmail address.
Oh, and I got one thing completely wrong. A 35-Volt 1-Amp transformer would do fine to LIGHT THE HEATERS (filaments) of exactly TWO of your four tubes. They draw just under a half Amp apiece to light that thing in the middle of the tube. The REAL power in the transformer comes from the High Voltage winding, not the section that lights the heaters. The numbers for that winding can only be determined easily by a look at the schematic, or better, the amplifier itself. Starting with the numbers (Voltage and current) for EACH winding, Peter w. Dahl Co. could custom-make one for this box. Doing it that way should cost between $180 and $250, depending on how you ship it.
On the other hand, by the time you do all that work to prepare specs, order the thing, pay for it and put it in, YOU'LL STILL HAVE THE SAME PROBLEM YOU HAVE NOW. Anyway, when I re-read that post and saw those errors, It seemed appropriate to post a correction. Don't wanna get flamed by some engineer type who spots the error.
73 |
Funtimebob
| | Posted on Sunday, October 06, 2002 - 12:49 am: |
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Peter H Dahl company supplies replacement transformers for a lot of older rigs. tell them what ya got and they probably have the specs on file. |
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