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Message |
    
Legend
Junior Member
Username: Legend
Post Number: 24
Registered: 12-2002
| | Posted on Monday, March 29, 2004 - 7:21 pm: | 
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Hi...
I recently purchased a Palomar Skipper 300. It has been many years since I ran a tube type. I have seen conflicting information concerning the proper operation (tuning).
I saw a post of yours from a long time ago, describing the proper tuning procedure, but I can't find it again. Also, I remember that your post used the words "plate" and "grid", instead of "tune" and "load". Could you please explain the exact procedure again, using "tune" and "load", instead of plate/grid?
You said "dip the plate", and "peak the grid". Could you please walk me through this in as simple a description as possible? I just need to know how to properly manipulate three controls:
Input, on the back of the box.
Tune
Load
________________________________
Thank you. I chose to ask you, because you mentioned in your post that a lot of people do not run their amps correctly. I do not want to be one of those people. This amp has brand new 8950's in it, and I don't wan to shorten their life, by running it improperly. From what I understand, 8950's are very hard to come by nowadays.
Any input from any of the other techs is certaily welcome as well. Thanks again.
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Tech833
Moderator
Username: Tech833
Post Number: 607
Registered: 8-2002
| | Posted on Friday, April 02, 2004 - 2:54 pm: |
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Hi Legend.
Tuning is what brings the final amp plates into resonance. This is the most critical control on the whole thing. Tuning should always be done first and next to last.
Tune in this order-
1. Tune the 'TUNE" control for minimum plate current.
2. Tune the 'LOAD" control for maximum watts out of the amp.
3. Retune the 'TUNE' control for minimum plate current.
4. Tune the 'INPUT' control for minimum SWR to the radio driving the amp. Then, repeat as needed until no further changes occur.
The above procedure is exactly the same as dipping the plate (tuning for minimum plate current, thus resonance) and peaking the grid (tuning input for minimum SWR into the radio, thus resonating the power tube grids).
This is exactly how I tune the magawatt monsters too. It is the same for any non-cavity tube amp. |
Legend
Junior Member
Username: Legend
Post Number: 28
Registered: 12-2002
| | Posted on Saturday, April 03, 2004 - 4:57 am: |
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Thank you 833. I assume that my Skipper is a 'non-cavity tube amp".
Quote:
"Tune the 'TUNE" control for minimum plate current.
Tune the 'TUNE" control for minimum plate current."
OK... this is the only part left that I do not understand how to do.
How do I determine "plate current"? What am I supposed to be looking at while I adjust plate current? The meter on the amp? There is only one meter on the Skipper, and if you had to guess, what would you say it is for?
Thank you very much. I am getting this down, slowly but surely. lol... |
Tech833
Moderator
Username: Tech833
Post Number: 613
Registered: 8-2002
| | Posted on Tuesday, April 06, 2004 - 11:55 am: |
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Plate current is measured by placing an amp meter in series with the plate DC supply.
Can someone who is familiar with that amp help with this one? What is that meter reading?
You can experiment and see if that meter dips when output power increases. That might indicate a plate current sample. If not, you can substitute an amp meter on the AC supply line. Not quite as good, but better than nothing.
What you are trying to do is increase efficiency so that power is converted into RF and not heat. Heat will ruin your tubes and hurt your output power at the same time. |
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