Hello...
Someone is lending me a TS-520S to use and I have been listening to HF
on it for a few months now. Thursday evening I got my CW and general
credits. I had only planned on leaving with CW but I got my general.
I have an inverted V, about 130' long, in my backyard. The feedline
is 450 ohm ladderline and it is converted to 50 ohm coax at a balun at
the window, where all my cables enter the shack. Last night (Friday)
I went through the manual and tuned up the radio for 14.075 CW
operation. I then tuned the antenna with the tuner, but could only
get 30 watts out, or the SWR would be over 2 : 1. That was fine since
I was on HF and running CW, so I proceeded to switch to SEND and
started calling CQ. I got as far as: CQ CQ CQ DE KB1JEC/AG KB1JE and
then the meter (set to IP position) pegged and the lights on the radio
dimmed and seemed to go on and off very fast. The overhead lights in
the room went dim. I could hear something, like an arcing noise,
apparently from the finals section (i think?) I immeadiatly shut the
main power on the radio off and turned off the heater and send
switches before turning it back on. I had done everything the manual
said to do, all in the proper order. I then re-tuned up for 14.075
CW, thinking maybe I had made a mistake somewhere and done something
wrong. Same thing happened again while calling CQ. I then turned to
a large group of hams i've known on IRC since before I had my ham
license. They walked me through everything for about 4 hours. They
had me look to see if the tubes were properly neutralized and
everything seemed to check out fine. After 4 hours and no success I
thanked them and then talked to the owner of the rig. He said that
the same thing had happened to him before, but he replaced the 6146
final tubes with a new 'match set' before giving me the rig to use.
He will be coming here to have a look at the radio Sunday, but hes not
sure of what could be wrong and neither am I. I tried a different
band, 80 meters, this morning to see if that would make a difference.
I tuned up for 3.530 CW and then tuned the antenna, still getting only
30W out to keep SWR below 2 : 1. I proceeded to call CQ, carefully
watching the plate current meter. The meter would rise a little from
60mA every time I keyed my straight key. But then, whether I was
keying or not, the needle slowly started to rise, slow at first, then
faster and faster until it pegged and then the lights on the radio
flickered quickly and the room lights dimmed, the rig making the
arcing noise again. I can prevent it from pegging by switching from
SEND to REC before the needle pegs, but how am I supposed to hold a CW
QSO like that? And what about SSB phone? I couldnt talk more than 15
seconds on SSB phone in that case. I dont have a mic wired up to try
it yet but it would probably peg faster than CW because of the duty
cycle. I don't know what could possibly be wrong with the rig. The
finals were replaced, with a match set, it checks out ok for
neutralization, and I replaced the driver tube with a new one just
last week. What could it be? I don't know much about tube rigs, but
I do know something is definitly wrong. Thanks and any info is highly
appreciated, going to post this on packet as well..

73 DE KB1JEC

Short version:

The whole problem stemmed from the fact that the "B" series of tubes is not
the same as the "plain" and "A" series. The parasitic oscillations were
caused by the different bias requirements and by the "fixed" neutralization
of the driver and/or amplifier tube in the Motrac. There was no practical
way to change the circuitry to handle the "B" series tubes. Also, making
such a change would void the "type acceptance" of the units.

In a "practical" sense, it is "OK" to mix 6146 and 6146A tubes since the
primary difference is in the design of the heaters. But, NEVER mix 6146 /
6146A tubes with a 6146B! This is really "asking for trouble".

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Only reply through ARRL forwarding service to W9GB

"Douglas Harrington" wrote in message
om...
Hello...

Last night (Friday)
I went through the manual and tuned up the radio for 14.075 CW
operation. I then tuned the antenna with the tuner, but could only
get 30 watts out, or the SWR would be over 2 : 1. That was fine since
I was on HF and running CW, so I proceeded to switch to SEND and
started calling CQ. I got as far as: CQ CQ CQ DE KB1JEC/AG KB1JE and
then the meter (set to IP position) pegged and the lights on the radio
dimmed and seemed to go on and off very fast. The overhead lights in
the room went dim. I could hear something, like an arcing noise,
apparently from the finals section (i think?)

Not all 6146 tubes are identical, first find out what tubes were placed in
this
Kenwood.

Then read Glen Zook's K9STH web page article on the 6146 Family of tubes.
http://home.comcast.net/~zcomco/The_...of_Tubes_1.htm

That's a start.

G. Beat
w9gb
--
DO NOT use Reply.
Only reply through ARRL forwarding service to W9GB

I have used a TS520 for as many years as they have been out and never
had a minute's problem. Never any problem with various tubes. You need
to try it into a dummy load.

Makes sense, but the original tubes had the same problems in the past
few years, thats the reason why the owner replaced them before letting
me use it, and like I said, the tubes in there now are neutralized..
73

KB1JEC

Howdy Douglas...In your post, the one thing that jumped out at me was
your statement "But then, whether I was keying or not, the needle slowly
started to rise, slow at first, then faster and faster until it pegged
and then the lights on the radio flickered quickly and the room lights
dimmed, the rig making the arcing noise again". This more sounds like
a bias problem, and would be a typical sort of problem I've seen in rigs
of the era whereby the bias voltage to cutoff the tube during receive
starts to fail causing the tube to conduct.....more conduction=more heat
and it degenerates into the sort of symptoms you've described. Typical
things could be shorted screen or cathode bypass capacitors or even a
bad zener diode used to regulate screen voltage (the rig escapes me at
the moment). Check in your manual (hopefully) to see what the idling
current should be.....if set high, for example this could aggravate the
problem. It's been at least 10 years since I stuck my head inside a 520
so circuit details don't come to mind to help further. Best of luck.

73 - Gord VE1AJF

"Douglas Harrington" wrote in message
om...

Makes sense, but the original tubes had the same problems in the past
few years, thats the reason why the owner replaced them before letting
me use it, and like I said, the tubes in there now are neutralized..
73, KB1JEC

OK, I have seen a similar problem with a 6146 and 6146W mixed -
which resulted in a resistor failure.

gb

I have tuned it up into a dummy load and the problem still occurs in
dummy load mode. Its not the antenna or tuner. Although the dummy
load IS inside the tuner. Im 100% new to electronics, well, maybe 75%
at least , so I don't know much about the internal workings or how
to change things inside other than the potentiometers and tubes. I
will tell all of this info to the rig owner tommorow and see what he
says/can do about it. 73 all and keep the posts coming if you folks
have any more info that could help me

73 De KB1JEC
Seekonk, MA, USA
On HF Soon (hopefully)


"G. Skiffington" wrote in message ...
Howdy Douglas...In your post, the one thing that jumped out at me was
your statement "But then, whether I was keying or not, the needle slowly
started to rise, slow at first, then faster and faster until it pegged
and then the lights on the radio flickered quickly and the room lights
dimmed, the rig making the arcing noise again". This more sounds like
a bias problem, and would be a typical sort of problem I've seen in rigs
of the era whereby the bias voltage to cutoff the tube during receive
starts to fail causing the tube to conduct.....more conduction=more heat
and it degenerates into the sort of symptoms you've described. Typical
things could be shorted screen or cathode bypass capacitors or even a
bad zener diode used to regulate screen voltage (the rig escapes me at
the moment). Check in your manual (hopefully) to see what the idling
current should be.....if set high, for example this could aggravate the
problem. It's been at least 10 years since I stuck my head inside a 520
so circuit details don't come to mind to help further. Best of luck.

73 - Gord VE1AJF

Douglas Harrington wrote:

Hello...
Someone is lending me a TS-520S to use and I have been listening to HF
on it for a few months now. Thursday evening I got my CW and general
credits. I had only planned on leaving with CW but I got my general.
I have an inverted V, about 130' long, in my backyard. The feedline
is 450 ohm ladderline and it is converted to 50 ohm coax at a balun at
the window, where all my cables enter the shack. Last night (Friday)
I went through the manual and tuned up the radio for 14.075 CW
operation. I then tuned the antenna with the tuner, but could only
get 30 watts out, or the SWR would be over 2 : 1. That was fine since
I was on HF and running CW, so I proceeded to switch to SEND and
started calling CQ. I got as far as: CQ CQ CQ DE KB1JEC/AG KB1JE and
then the meter (set to IP position) pegged and the lights on the radio
dimmed and seemed to go on and off very fast. The overhead lights in
the room went dim. I could hear something, like an arcing noise,
apparently from the finals section (i think?) I immeadiatly shut the
main power on the radio off and turned off the heater and send
switches before turning it back on. I had done everything the manual
said to do, all in the proper order. I then re-tuned up for 14.075
CW, thinking maybe I had made a mistake somewhere and done something
wrong. Same thing happened again while calling CQ. I then turned to
a large group of hams i've known on IRC since before I had my ham
license. They walked me through everything for about 4 hours. They
had me look to see if the tubes were properly neutralized and
everything seemed to check out fine. After 4 hours and no success I
thanked them and then talked to the owner of the rig. He said that
the same thing had happened to him before, but he replaced the 6146
final tubes with a new 'match set' before giving me the rig to use.
He will be coming here to have a look at the radio Sunday, but hes not
sure of what could be wrong and neither am I. I tried a different
band, 80 meters, this morning to see if that would make a difference.
I tuned up for 3.530 CW and then tuned the antenna, still getting only
30W out to keep SWR below 2 : 1. I proceeded to call CQ, carefully
watching the plate current meter. The meter would rise a little from
60mA every time I keyed my straight key. But then, whether I was
keying or not, the needle slowly started to rise, slow at first, then
faster and faster until it pegged and then the lights on the radio
flickered quickly and the room lights dimmed, the rig making the
arcing noise again. I can prevent it from pegging by switching from
SEND to REC before the needle pegs, but how am I supposed to hold a CW
QSO like that? And what about SSB phone? I couldnt talk more than 15
seconds on SSB phone in that case. I dont have a mic wired up to try
it yet but it would probably peg faster than CW because of the duty
cycle. I don't know what could possibly be wrong with the rig. The
finals were replaced, with a match set, it checks out ok for
neutralization, and I replaced the driver tube with a new one just
last week. What could it be? I don't know much about tube rigs, but
I do know something is definitly wrong. Thanks and any info is highly
appreciated, going to post this on packet as well..

73 DE KB1JEC

I hit a similar fault on an TS-820S. Remove the cover from the final
compartment. Tune the rig into the dummy load. Increase power until
you hit the arcing. Dim the lights in the room and watch the plate
tuning capacitor. In the case I cured, the mechanical joint between
the rotor shaft and the capacitor frame had become dirty. I fixed
it with some control cleaner and that fixed the fault. Hopefully
this will help. Note that arcing cannot easily be seen in a normally
lit room. Also, be very careful as you have pretty high voltage in the
final cage just looking for something to hit!

Irv VE6BP
--
--------------------------------------
Diagnosed Type II Diabetes March 5 2001
Beating it with diet and exercise!
297/215/210 (to be revised lower)
58"/43"(!)/44" (already lower too!)
--------------------------------------
Visit my HomePage at http://members.shaw.ca/finkirv/
Visit my very special website at http://members.shaw.ca/finkirv4/
Visit my CFSRS/CFIOG ONLINE OLDTIMERS website at http://members.shaw.ca/finkirv5/
--------------------
Irv Finkleman,
Grampa/Ex-Navy/Old Fart/Ham Radio VE6BP
Calgary, Alberta, Canada

Before you burn up everything put the correct fuse in the radio. It should
be a 6A. If it's dimming the lights in the room then it's too big.

--
Clif Holland, KA5IPF
AVVid
Authorized Kenwood and Icom Amateur Service
www.avvid.com
1-800-214-5779


"Douglas Harrington" wrote in message
om...
I have tuned it up into a dummy load and the problem still occurs in
dummy load mode. Its not the antenna or tuner. Although the dummy
load IS inside the tuner. Im 100% new to electronics, well, maybe 75%
at least , so I don't know much about the internal workings or how
to change things inside other than the potentiometers and tubes. I
will tell all of this info to the rig owner tommorow and see what he
says/can do about it. 73 all and keep the posts coming if you folks
have any more info that could help me

73 De KB1JEC
Seekonk, MA, USA
On HF Soon (hopefully)


"G. Skiffington" wrote in message
...
Howdy Douglas...In your post, the one thing that jumped out at me was
your statement "But then, whether I was keying or not, the needle slowly
started to rise, slow at first, then faster and faster until it pegged
and then the lights on the radio flickered quickly and the room lights
dimmed, the rig making the arcing noise again". This more sounds like
a bias problem, and would be a typical sort of problem I've seen in rigs
of the era whereby the bias voltage to cutoff the tube during receive
starts to fail causing the tube to conduct.....more conduction=more heat
and it degenerates into the sort of symptoms you've described. Typical
things could be shorted screen or cathode bypass capacitors or even a
bad zener diode used to regulate screen voltage (the rig escapes me at
the moment). Check in your manual (hopefully) to see what the idling
current should be.....if set high, for example this could aggravate the
problem. It's been at least 10 years since I stuck my head inside a 520
so circuit details don't come to mind to help further. Best of luck.

73 - Gord VE1AJF