[Collins] 30L-1 Problem

[Robert & Linda McGraw K4TAX]

At present my 30L-1 is being operated from a 120 volt mains.  Actually 
measures about 126 VAC no load.  I'll switch it over to the 230 volt 
configuration when I replace the 6 filter caps and perform a diode check.

Plate voltage (no load) is 1950 volts
Plate voltage (full load) is 1600
Plate current is 0.650 A
DC input power is 1040 watts
Output is 700 watts
Efficiency is 700/1040 or 67.3%

I suspect the 811A's are getting a bit soft in your case.  Every thing else 
seems about normal even though the voltages are a wee bit high.  The book 
says 230 VAC +/- 10%.  Remember this is a voltage doubler type power supply 
so a 5% increase on the primary would net about 10% on the secondary which 
is about what you are seeing.

As to the voltages on my amp, I measured these using the front panel meter 
after confirming its accuracy at 1000 volts with the unit being powered via 
a Variac.  I was in the process of "bringing it up" after it being stored 
for 20+ years.  My DVM only measures to 1000 volts.  It still has the 
original filter caps and diodes.  However, new caps are on order.

73
Bob, K4TAX

----- Original Message ----- 
From: "Ken Plesser" <kenplesser at alltel.net>
To: <collins at mailman.qth.net>
Sent: Sunday, June 25, 2006 11:01 AM
Subject: [Collins] 30L-1 Problem




Perhaps someone can help me with two 30L-1 problems (they may be related)



Problem #1 facts:

Input voltage: 241 VAC (4.8% over 230 VAC nominal)

Plate voltage (no load): 1920 VDC (6.7% over 1800 VDC nominal)

Plate voltage (full load):1750 VDC (9.4% over 1600 VDC nominal)

No reports of hum on my signal.

Question: Why is the plate voltage so much higher than can be attributed to 
high input voltage?



Problem #2 facts:

RF drive from 32S-3: 82 watts CW on 14.2 mHz

Plate current of 30L-1: 430 ma (should be 600 ma)

Advancing mic gain beyond 3 o'clock causes no additional plate current.

DC input power to 30L-1: 1750 x 0.43 = 752 watts (should be 960 watts)

RF output power from 30L-1: 380 watts

Efficiency: 380/752 = 50%

RF drive and output power measurements (into a 1:1 SWR dummy load) the same 
on both 312B-4 and Palstar wattmeter.

Question: Why such low plate current (hence low input/output power) and low 
efficiency?



Could it be as simple as the 811s are going "soft," hence I can't draw 
enough plate current, hence the plate voltage rises?  Or is something more 
subtle taking place?



Any hints or suggestions will be appreciated.



Thanks and 73.



Ken, W3ESH

Gilbert, SC
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