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1-2 of 2 messages
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Need Help with 901dm
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by K9SAT on October 1, 2008
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Greetings, Im new to ham radio and haveing issues. I bought a Yaseu 901-dm from flea bay and a slinky antenna. I live in an aparmtent building and dont have many optins as far as an antenna. I just want to get up and running for contesting.
I recived the radio and it powers up. I put in the tubes, and hooked up the anteanna. Once I turn on the unit and the heater and go to tune up the unit, the tubes inside glow orange after about 60 seconds of the unit being on the tubes inside start to spark and then it blows the 5 amp fuse.
1. How do I get rid of this spark and get the unit to transmit and to stop blowing the 5 amp fuse.
Also, how do I nutralize the unit and what is a good dummy load to get to test the unit out. I have followed the instructions in the manual to tune up properly but I can never get the unit to last long enough before the tubes to start to spark internally. Thanks for all of your help.
The tubes in the unit are the ones the manual recommends.
Best Reguards,
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RE: Need Help with 901dm
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by WD9T on November 5, 2008
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Sounds like the 6146B's may be shorted and is causing the unit to draw too much current on transmit. That may be why you are seeing the tubes glowing orange before the fuse blows. If you are only keeping the unit keyed for no longer than 10 seconds maximum while tuning into a 50-75 ohm dummy load, you shouldn't see the bright orange color with that short of keydown time. You may have some slight orange color during keydown but not bright unless it is drawing excessive current. You can see what the current draw is by placing your switch to the IC position. Normal cathode current is in the order of 275ma for the 6146B's at full output. I would try to replace the finals with another set which you can sometimes find on Epay as NOS (New Old Stock). Be careful as there can still be 800 volts on the B+ stored in the high voltage capacitors even with the unit unplugged. These caps will have to be shorted to drain off any voltage that may be stored. If you've never done this, you may want to refer to an experienced Ham in your area that may be more familiar with this. The Fox-Tango club website has loads of documents on these rigs. You can google to find this site. Note: If you don't have a dummy load handy, I remember back in the day that some people used to use a 100-watt light bulb as a dummy load. The only problem was that as the bulb got brighter and warmer, the actual impedance would change. It works as a temporary dummy load if you're really pressed for one.
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