How to power up again a stored SSPA?

Hello,

I'm not sure why is it recommended to apply power on the unit if it is not used. I never heard such a recomendation and I can not understand the logic behind it. Did you provided with an explanation as well?

Anyway, if you do power the SSPA, make sure you terminate it in a safe manner, meaning connecting it to a dummy load. The transmission, especially at high-power SSPA and BUC could be harmful and even cause blindness!

If its what I think you and your friend are talking about, its called degassing.  Basically when you store an HPA or SSPA for a long period of time you have to degas it to burn all the unwanted stray air that may have built up in the tube during storage to prevent damage to the tube upon putting it into operation.  we usually do this by putting the hpa on a dummy load, turning on rf, and setting the u/c power to -30dbm for an hour and then increase it by 3dbm every 30 minutes after.


And be sure to check this site out. 

http://photos.imageevent.com/qdf_files/technicalgoodies/training/DeGassing%20of%...

"Avoiding Gassy Tubes : This is the easy part. All a customer has to do to avoid a gassy TWT tube is to
operate the amplifier, in High Voltage On, for a period of 24 hours every three months. At the end of this
operational cycle, verify that the quiescent Helix Current has returned to a very low value (typically
13mA)
and deactivate the amplifier. If this is done at a minimum of every three months, the customer
should not have any problems with Gassy TWT tubes."

Thank you sir for the information, it still useful for me since we are also maintaining TWT HPA.

thanks..

Keep a record of the helix current in a log book.  The pdf document above actually says 1-3 mA, not 13 mA.

Some TWTA have typical helix current of 0.5mA and helix current trip alarm at 4 mA.

Some very high power TWTA have maximum helix current of 15 mA.

Regarding cathode current, this is normally maintained at a steady value over tube lifetime by gradually altering the first anode voltage as the cathode gradually degrades.  Once the cathode gets really bad the cathode current starts to drop. Worth recording these values also in a log book.

I note the procedure described for de-gassing using short (1 day) ON periods every few months.

My opinion is that it is not a good idea to turn off tubes that have been on for a long time, 6 months or more. The surface of the cathode becomes ultra clean and dirt is concentrated down the collector end of the tube.  When switched off the dirt comes back up the tube and poisons the cathode.

Regarding SSPAs, the secret to long life is keeping them cool and not overdriving them. High temperatures and slight over-voltage spikes cause gradual deterioration of semi-conductors.

Best regards, Eric.

The advice in the pdf document is based on the theory that the tube is gradually leaking and, when left switched off,  needs de-gassing for 1 day every few months. Ask the manufactuer of your tube if they agree.

Powering on and off causes thermal cycling and this action in itself will stress joints etc.

According to my idea, if a tube has been on for six months, then it is best left on all the time.

Best regards, Eric.

Yes sir jets our SSPA is working without any problem including a mirror back-up, the one that I want to know on how to store is our spare SSPA which we are not using for more than a year. I just want to prevent a scenario where we needed it and we can't use it because we improperly stored it.

thanks,

ken