[Collins] 30L-1 Question

[Dr.Gerald N. Johnson]

I agree with the school of adjusting the linear for the maximum output. I think the 30L-1 tuning meter compares RF plate voltage to DC plate current or something like that to set a load impedance so it can be tuned at any power level and still be set for optimum. 

After 30 or more years, if the ratios in the meter circuit were set by carbon composition resistors, its very likely that they have drifted due to heat, time, and humidity, and it might be necessary to replace the resistors in that circuit which ought to make the meter zero when the output is set for maximum.

Another thing that would change the optimum load R for the tubes is the DC plate voltage. Larger capacitors could have raised the DC under load, and higher line voltage than what the PA was deisgned for could have also raised the DC plate voltage making the optimum load R a little higher than the design value.

I can't check my 30L-1 downloaded manual, since I'm 400 miles from my own computer this week.

73, Jerry, K0CQ
Dr. Gerald N. Johnson, Electrical Engineer
----- Original Message -----
From: Gary H. Harmon, Jr. [mailto:gharmon at idworld.net]
Sent: 12/4/2004 7:12:59 AM
To: collins at mailman.qth.net
Subject: [Collins] 30L-1 Question

> I replaced the 4 HV caps with new ones.  All diodes checked good.  HV is
> stable at expected ratings.  Linear puts out appropriate wattage BUT when
> the power is maxed the meter reads below zero.  The manual says to minimize
> the reading to zero and that will indicate maximum output.  Thoughts please?
> 
> 73, gary
> 
> ==========////==========
> Gary H. Harmon, Jr. - K5JWK
> 6302 Robin Forest
> San Antonio, TX  78239-3218 
> 210.657.1549-home
> 210.884.6926-cell
> 210.203.7000-pager
> gharmon at idworld.net
> 
> 
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