Need ham radio help

[goaliebob99]

Calling all hams out there....

I need some help.

I have a yaesu 901dm and I keep blowing fuses. I have the radio all hooked up to my diapole antenna. I turn on the heater tubes and 30 seconds later there glowing red... 30 seconds after that, the tubes get white electrical shocks inside the tube and then the power's 5 amp fuse blows turning everything off. Is there something that im not doing right or is there something wrong with this rig?

Thanks.

 

[jayn_j]

Calling all hams out there....

I need some help.

I have a yaesu 901dm and I keep blowing fuses. I have the radio all hooked up to my diapole antenna. I turn on the heater tubes and 30 seconds later there glowing red... 30 seconds after that, the tubes get white electrical shocks inside the tube and then the power's 5 amp fuse blows turning everything off. Is there something that im not doing right or is there something wrong with this rig?

Thanks.

The fuse is blowing because you are getting plate to grid arcing. Not good for the tubes. This shouldn't be happening, especially if you are not attempting to transmit. Are you sure the transmitter is off? I've seen this sort of thing with a shorted antenna when transmitting.

When you say red, do you mean a dull orange? Red would set off some alarms. Is the power switches set to 115 volts?

I would say the set is defective. Possibly a bad capacitor, or coils shorted within the primary of the HV transformer. Others?

 

[goaliebob99]

Yep I mean dull orange

 

[goaliebob99]

The fuse is blowing because you are getting plate to grid arcing. Not good for the tubes. This shouldn't be happening, especially if you are not attempting to transmit. Are you sure the transmitter is off? I've seen this sort of thing with a shorted antenna when transmitting.

When you say red, do you mean a dull orange? Red would set off some alarms. Is the power switches set to 115 volts?

I would say the set is defective. Possibly a bad capacitor, or coils shorted within the primary of the HV transformer. Others?

Transmitter is on.. When its off I can recive fine...

 

[jayn_j]

Transmitter is on.. When its off I can recive fine...

Ah, you didn't say that.

Transmitting puts out a lot of energy. If you have a bad SWR, all that energy gets reflected back into the transmitter and bad things happen. I have seen plates melt in vacuum tubes, arcing like you are getting, and even connector fusing.

disconnect the antenna from the transmitter. If you can get ahold of a 50 ohm load, do so. A dummy load is always nice to have around. Try connecting the dummy load and see if it will load ok.

Second step. Take an ohmmeter and check across the center connector to ground. It should show an open. If shorted, you have found your problem. Check both the antenna and the coax. I have found more problems with bad coax joints.

If the open test is OK, repeat, but short across the coax at the antenna end. Does it show shorted? If not, you have a cold solder joint somewhere in the co-ax.

If this all checks out OK, look at the section of the manual that talks about peaking the final amplifier stage. There is generally one, or a pair of adjustments you make by alternatingly dipping and peaking the final tank circuit. Failing to do this will cause exactly what you are seeing.

Finally, double check the antenna length. Use an SWR bridge if possible.

Try all of that and get back to us.

 

[truckracer]

I was thinking (common problems) is a shorted coax.