Hi gary,
Actually I am now running the amp with HV on new tubes but no drive.I plan on
doing this for 24 hours.The previous tubes were cooked in also and lasted 3
years under severs usage (many contests,etc).The previous tubes never came up
to full power during the 3 years where the previous Eimac tubes had no
problem.I have heard the ZG tubes require more drive than the Eimacs but my 850
is good for 80 watts only and I don't want to push it any harder.I am hoping I
can recover full power by tuning the input,getting the ig up or changing the
bias,if needed for the ZG's.I don't want to try any of this without some expert
advice,hi.
Interestingly since I posted this request I found the Kenwood benchmarks for
ig,lp and power out in the Kenwood service Manual.
At 80 watts in and 1KW out,the plate current should be 600ma,the grid current
should be 190ma and I have never seen this with the ZG's.My max ig is 100-125ma
and plate current is 400-450ma based on band of operation.This is with no ALC
control connected.
I'm betting that if I can get the ig up to 190-200ma this will fix my
problem.My question is how to do this with 80 watts in.
It's a real leaning experience for me and this group has been a big help.Thanks
for your comments.
----- Original Message -----
From: Gary Smith
To: Bob Jones ; Amps@contesting.com
Sent: Thursday, February 24, 2005 11:48 AM
Subject: Re: [Amps] TL-922 Help
Did you give the new tube a reasonable amount of time to "cook in ?"
Do recall that rf parts suggests at least 24 hours, did note when I installed
my new rf parts 3-500, after 24 hours of warming and then putting it to usage
my output was lower than what I expected. Then, not expecting, and three week
later output power had risen to rated amp rf output levels.
73,
Gary... wa6fgi
----- Original Message -----
From: Bob Jones
To: Amps@contesting.com
Sent: Thursday, February 24, 2005 6:54 AM
Subject: [Amps] TL-922 Help
A few quick questions:
1.In transmit mode with no drive,I have 50ma idle plate current on CW and
100 ma on SSB.Is this OK and if not how to adjust?Book says should have
twice this level.Zener checks OK,100 volt supply is OK,both relays check OK.
2.Using the RF Parts ZG tubes and 80 watts drive I cannot drive the amp to
full output.I notice SWR on TS-850 is higher than with the Eimac tubes and
even placed a tuner and different lengths of 50 ohm coax between the 850 and
amp,this helps but still only 400 ma plate current under full load.Plate
volts drop from 2000 to 1900 from no load to full load.Ig rarely gets above
100ma.Have tried tuning input coils using Kenwood method but tuning is very
broad and has little effect on power out.Any ideas and a safer way to tune
the input coils?I do have a MFJ Antenna Analyser and thought I could use it
to look at the coils??
Note:Amp is running on 220 vac primary power.
3.Am presently installing Rich measures supressor kit and hope this helps
the parasitic problem Just lost grid resisters and chokes when one tube went
cathode to grid short,saved the filament transformer though.
Any help on item 1 and 2 would be appreciated and I'll have the amp ready to
put back on the air.
Thanks and 73,
Bob
W0OXJ
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