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Author Topic: Collins 30L-1 TUNING?  (Read 6444 times)
N6QWP
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« on: February 25, 2017, 06:03:11 PM »

Finally did get my 30L-1 up and running...and attempted to lower the output of TS-430 to 65 watts (too much??) to keep from overdriving the amp-but later noticed that the ouput had climbed to 75 watts.  Was getting 1625 vdc on transmit and could load to 600 mils max.  At those settings, output read 600-650 watts when peaked for maximum output--but that did not happen at 0 on the Tune meter.

Found that when I tuned to 0 on the Tune meter, output dropped to 300 to 400 watts--200 watts or more less than when peaked for max output.  The loading dial was about 3.5 when amp tuned to 0 on dial and when loaded to max output read 5.5

While I tried to limit my tune ups to 5-10 seconds with 65 watts of carrier, I did do so repeatedly several times without letting tubes cool down enough.  When I checked tubes (that were fine) after 3 days of this, I found that I had burned plates on all four tubes-no holes, but can see the damage that I have done...small spots on plates that look like coating is blistering and lifting....also silver spots?

Since I retuned output of TS-430 to 65 watts, output of amp now maxes at about 500 watts when peaked and about 250 to 300 watts when "tuned" to 0.  When tuned to max output, the Tune meter drops by one to one and a half marks.  Would appreciate any pointers of where to tune--between 0 and peaked for max.  Looking for another set of tubes but do not want a repeat.  

Also, peak reading meter SSB is nowhere near the output reading of CW carrier output...my meter or normal?  Thought I should get more out PEP than CW???  This is my first amp.  Tnx es 73
« Last Edit: February 25, 2017, 06:24:27 PM by N6QWP » Logged
KM1H
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« Reply #1 on: February 25, 2017, 06:52:53 PM »

Leave it alone and settle for 500W as nobody can hear the difference and the tubes just may survive a while longer.
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N6QWP
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« Reply #2 on: February 25, 2017, 07:21:53 PM »

Trying to figure out the proper tuning procedure for the 30L-1.....using the Tune position of the meter or tuning for Maximum output--and if so, limiting it to what power out???  Hoping for replies from owners and users of this amp.  Given it's peculiarities, a few replies from veteran users with experience with this particular amp will be the most helpful.  Hoping for pointers from owners who have already gone through all of these issues and have advice on how to deal with them in detail.  Generic answers are not really helpful at this point.  
« Last Edit: February 25, 2017, 07:24:41 PM by N6QWP » Logged
G3RZP
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« Reply #3 on: February 26, 2017, 03:26:37 AM »

Should R19 or R20 have drifted or one of CR17 or 18 gone partially bad, or one of  C13, 14 or 19 drifted or trimmer C18 been mal-adjusted, the meter won't read zero when correctly tuned. Section 4.7 of the manual tells you how to adjust C18. I would suggest checking R19 and R20 first, since they are composition resistors (39k, 10%, 1/2 watt)which are known to drift with time.

Or just tune for max output.

Switch off and pull the power plug and allow some time for the power supply to discharge before removing covers, as other wise when the interlock short circuits the HV, you might damage something.
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W1QJ
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« Reply #4 on: February 26, 2017, 03:47:24 AM »

Should R19 or R20 have drifted or one of CR17 or 18 gone partially bad, or one of  C13, 14 or 19 drifted or trimmer C18 been mal-adjusted, the meter won't read zero when correctly tuned. Section 4.7 of the manual tells you how to adjust C18. I would suggest checking R19 and R20 first, since they are composition resistors (39k, 10%, 1/2 watt)which are known to drift with time.

Or just tune for max output.

Switch off and pull the power plug and allow some time for the power supply to discharge before removing covers, as other wise when the interlock short circuits the HV, you might damage something.

What Peter is basically saying is this: Loading up according to the manual using the "0" method won't work on an a 30L1 at this point in time.  That sensing circuit is so far from being "right" you will chase your tail from now till doomsday.  Bottom line, Tune the amp up for maximum power output to a max of 600 watts and leave it like that.  Unless you are good a repair work then, and only then attempt to rebuild that circuit as Peter suggested.
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VK3BL
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« Reply #5 on: February 26, 2017, 04:02:10 AM »

I concur, tune for max output on your power meter.

65 Watts is probably a fair bit of drive for that amplifier.  As Carl suggested, aim to tune for around 500 watts, and all things being equal you should enjoy longer tube life.

As a sanity check, you should do the following after a proper peak output tuneup:

1) Observe the plates of the tubes while transmitting into a dummy load using SSB or CW.  If they end up glowing any more than a dull to medium red, you may have not tuned properly.  If you see orange, let go of the key as soon as possible.  Orange is the threshold of damage with 811As.

2) Calculate the input power, and then subtract the output power; this will give you the dissipation occurring in the tubes.  Divide this by 4.  If the number is greater than 65 watts per tube, you may have not tuned properly.  The lower you get this number, the longer tubes will last.  Most amplifiers have a sweet spot/range, find it and enjoy maximum tube life.

If you go through these post tuning steps a few times, and write down the settings that give results for each band, you will find you get good life, perhaps ~750-1000 hours, out of a set of 811A tubes.

Always turn the linear off when you are not going to be using it in the next few hours.  The tube lifetime clock ticks whether you are transmitting or not.  I have never snapped a filament, but have plenty of 'NOS Appearance' 811As in my shack with no filament emission left.  There is no need to worry about cycling the filaments with normal usage patterns.
« Last Edit: February 26, 2017, 04:04:14 AM by VK3BL » Logged

J.D. Mitchell - VK3BL / XU7AGA - http://vk3bl.wordpress.com
N6QWP
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« Reply #6 on: February 26, 2017, 08:22:35 AM »

 Any consensus on what the "proper" drive power for the 30L-1 should be?  Have been told several from 35 to 65 watts.  Hi voltage drops to 1625 vdc on key down.  Plate current varies from 500 to 600 ma on key down.  

Is it damaging to tune to 600 or 650 watts output for short periods and then increase loading (past max out) to lower output to 500?

or....would it be better to decrease the drive to get a maximum output when peaked to 500 watts on cw and not push the envelope?

And finally......when my power output meter is switched to "peak" it only measures (on voice peaks)  less than half of the key down with carrier output in normal position.  Is my meter faulty or is this normal?  

Many thanx to all that have taken the time to help a newbie to QRO.....new set of tubes in future-want to do right by them.
« Last Edit: February 26, 2017, 08:41:12 AM by N6QWP » Logged
G3RZP
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« Reply #7 on: February 26, 2017, 09:02:37 AM »

Quote
....would it be better to decrease the drive to get a maximum output when peaked to 500 watts on cw and not push the envelope?


I say 'YES!' 

According to the manual, the plate current should be about 300 to 350mA on voice peaks.
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N6QWP
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« Reply #8 on: February 26, 2017, 09:23:52 AM »

Just reduced drive to 50 watts and into a dummy load the key down voltage is 1700vdc and current is 400 ma (input 680?) with an output of 500 watts.  

Into the 40 meter dipole with swr of 1.4,  1800 vdc at 425 ma (input 765?)=500 watts output.

Line voltage appears to be fluctuating some here on this Sunday morning, changing the plate voltage some.  This seems like a good point to leave things alone.  Anyone agree or disagree?
« Last Edit: February 26, 2017, 09:33:18 AM by N6QWP » Logged
W1QJ
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« Reply #9 on: February 26, 2017, 10:13:35 AM »

A number of factors will determine what the "ideal" drive level is.  It will change depending on band and load (antenna) SO... ideal is subjective.  That said lets not put a specific value on "ideal" rather lets say this,  DRIVE THE AMPLIFIER WITH SUFFICIENT DRIVE TO OBTAIN APPROXIMATELY 600 WATTS OUTPUT WHEN AMP IS FULLY LOADED.  That means when the load and tune controls are adjusted for a maximum power at 600 watts.  It does NOT mean load the amplifier to some amount of power HIGHER or LOWER than 600 watts and then adjust the drive level for 600 watts.  You don't want to reduce the drive level or raise the drive level after you have made the loading adjustments at the drive level that produced the 600 watts peak output.  Doing so does one of two things. 

1. Lowering drive level....This causes the efficiency of the tank circuit to drop and plate dissipation increases percentage wise.
2. Raising the drive level....This causes an over drive condition where the tank circuit will be too lightly loaded, this raises the tank circuit voltage at various points and could cause a rise in IMD

Do a trial of loading procedures on each band and frequency in that band into the antenna(s) you will be using.  Load to the stated 600 watts as described, record the load and tune positions and the drive level required.  Make a note of these 3 things.  When returning to those bands(frequencies) simply make the settings on the radio and amplifier.  All you have to do is go into transmit and "tweak" the load and tune.  It takes seconds to do.
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N6QWP
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« Reply #10 on: February 26, 2017, 10:49:51 AM »

Thanx for that.....it raises the question of: if I wanted to load to 500 watts output (not 600) for the purpose of prolonging the life of the tubes, would there be the problem you mention?  500 watts will be plenty for me and several others have suggested not running the amp "full bore".   Is there a happy medium that will prolong the tube life and not cause other problems?  

Right now I reduced the output of the driving rig (TS-430) to 50 watts and when peaked for maximum output, the amp puts out 500 watts.  Seems the difference between input and output (dissipation) is right on the 66 watts per tube=265).

I burned the plates on the present set of tubes by tuning for max output at 600-650 watts....due to keying too long, I am sure (it doesn't take more than a few seconds and need to cool down for longer).  Hoping that running at 500 watts, the tubes will be more forgiving?

I have a new set of tubes arriving momentarily and don't want to hurt them by pumping them too hard.....or too little.
« Last Edit: February 26, 2017, 10:54:19 AM by N6QWP » Logged
W1QJ
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« Reply #11 on: February 26, 2017, 10:55:14 AM »

Just substitute 500 watts for 600 watts in my outline, same thing applies.  Your original post suggested you did a lot of fiddling with that ")" meter reading.  I suspect it was that routine that made those tubes like that. 4 tubes can easily handle 600w pep output on SSB with no problem, however 500 is OK.  Same principles apply.
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N6QWP
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« Reply #12 on: February 26, 2017, 11:01:47 AM »

The problem occurred due to tuning up on cw......isn't that more stressful and risky for burning up plates than running SSB after amp is tuned?  Seems like the plates start to glow pretty quick during key down (cw).  Thought that SSB is more intermittent and not as likely to do the same damage??
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W1QJ
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« Reply #13 on: February 26, 2017, 12:29:03 PM »

Sure, a CW carrier will surely be more stressful bu  the idea is to make quick concise adjustments to the load and tune only taking seconds to do, letting the amp cool, and then making more adjustments.  It can be done with minimal stress.  With practice and a logging of load and tune positions and drive level tune up should take a total of 5 seconds of key down time.  You will get the hang of it as you do it more and more and in no time it will be second nature.  It's all practice and experience.
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N6QWP
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« Reply #14 on: February 26, 2017, 02:39:08 PM »

  It took a while.....several really helpful hams willing to Elmer the uninformed.....and injury to a nice set of old tubes to overcome the newbie tendency to get every last bit of power from one's first amp--and tuning up too long without cooling down between attempts.  Over driving them didn't help either.
 
Four NOS RCA 811A's just arrived.  Tried them out at 500 watts and all was well.  Went back to the old ones....as they too are still putting out 500 with the 50 watts of drive.


Sincere thanx to all for the great advice.  Should be able to keep this old 30L-1 on the air for a while now.  Hope this thread will be as helpful to others as it was to me.  73's
« Last Edit: February 26, 2017, 03:00:21 PM by N6QWP » Logged
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