Sb-220 power output at about half..

[John]

No I did mean 3-400z. This is what was available to me for the project.
Output was about 800 with 100 in with the pair until the condition in which
I described took place. I realize they will need to be replaced if I expect
A higher output from the amp. Never the less the 800 will work fine for now
if I can determine where the 400 I lost went. Tubes in different amp are
testing full output. 

John Godfrey
 



-----Original Message-----
From: Heytubeguy [mailto:heytubeguy at yahoo.com] 
Sent: Wednesday, May 23, 2007 8:56 PM
To: john at hughes.net
Subject: Re: Sb-220 power output at about half..


John, I hope you meant 3-500z!, Joe

----- Original Message ----- 
From: "John Godfrey" <john at HUGHES.NET>
To: <HEATH at LISTSERV.TEMPE.GOV>
Sent: Thursday, May 24, 2007 5:33 PM
Subject: Sb-220 power output at about half..


I do hope you guys can help me. I have been in the process of restoring 
a
heath kit SB-220. I replaced all the filter caps - diodes in the doubler
etc. all with new parts including a new air variable for the plate 
tuning.
All was well and output was plenty acceptable on all bands. Then output 
just
went to zero after a power-on condition. Meaning it was fine when turned
off. Then after much investigation I found that the little bolt/nut that
holds the output tuning 10/15 meter coil to the plate tuning capacitor 
was
loose. After tightening and re-power up and tune. I just get half the 
output
as before. Both tube filaments light bright and voltage to the pins on 
the
filaments is 4.9 volts ac on my meter. Cleaned the sockets and pins in 
case
of any resistance but like I said voltage seems to be correct. Zener 
diode
seems to deliver exactly 5 volts DC through the center tap of the 
filament
transformer to the tubes at transmit and the 117 volts dc at receive 
mode.
Tubes do produce gain. With 40 watts in you get about 150 out. 100 watts 
in
gives 400 watts out. Again about half what I was getting. Both tubes 
EIMAC
3-400z l believe them to be full output because I tested them in another
amp. Tested the high voltage on SSB mode and I have about 3010 volts DC.
Input SWR is acceptable and I am driving it with tubes as well instead 
of
transistors.



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