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Author Topic: Neutralizing Finals Kenwood 520  (Read 4683 times)
KJ6TSX
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Posts: 116




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« on: July 08, 2012, 10:07:11 PM »

I need to Neutralize my finals on my Kenwood 520, I understand the principles but am a little hazy on what I can use for a RF voltmeter. I currently only have a digital multimeter. What should I be looking for? I tried watching my s meter on my other rig, but with the switch in the sg mode I did not pick up any signal. (Two radios side by side 520 into dummy load) with sg switch off I got some movement but not sure I was going in the right direction.
Any help would be appreciated
Thanks
George
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AD4U
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Posts: 2153




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« Reply #1 on: July 09, 2012, 06:20:39 AM »

Generally you do not have to neutralize the 2001 or 6146 finals in a 520, 820, 830 unless somebody monkeyed with the neutralization or you had to replace the original Japanese finals with American made tubes.

Since you said you lack a RF voltmeter, many of us old timers do it this way.  This usually provides acceptable results.

Tune the rig into a dummy load on 10 or 15 meters.  Observe the plate current "dip" on the meter.  If the needle on the plate current meter moves smoothly and about the same on both sides of the "dip", the rig does not need further neutralization.  If not turn the neutralization cap about 1/8 turn and try again.  Repeat until the needle on the plate current meter moves smoothly on both sides of the "dip".

Dick  AD4U

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WB2WIK
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Posts: 20547




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« Reply #2 on: July 09, 2012, 09:59:41 AM »

I need to Neutralize my finals on my Kenwood 520, I understand the principles but am a little hazy on what I can use for a RF voltmeter. I currently only have a digital multimeter. What should I be looking for? I tried watching my s meter on my other rig, but with the switch in the sg mode I did not pick up any signal.

That borders on unbelievable.  Remember you don't use the "SSB" position on the 520 for this, you use "CW" to create a carrier.  Impossible that a receiver placed close by wouldn't hear that, with the SG switch off.

Normally, the signal is "too" strong and you have to move the second receiver farther away. Wink
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AD4U
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Posts: 2153




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« Reply #3 on: July 09, 2012, 11:07:28 AM »

On second thought, are you trying to null the carrier?

Dick  AD4U
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KJ6TSX
Member

Posts: 116




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« Reply #4 on: July 09, 2012, 08:29:40 PM »

Well her's the whole story, I bought this radio on ebay.. when I got it fired up it was arcing at the band-switch inside the HV cage. The band-switch was destroyed. I bought a band-switch from Bob KE5FTF, Bob suggested I replace the whole HV Cage that it would be easier and it was. I removed both Finals and reinstalled them Plus a different TC1, Tank Coil and choke..... so I am assuming something has changed especially since I cannot get my plate current to dip noticeably and I have only 150ma. Max watts out 75
The other scenario is I might need new finals. and If I do I would have to neutralize them too

So thats my tail of woe and I am having a great time any help is greatly appreciated
George
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KE4DRN
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Posts: 3714




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« Reply #5 on: July 10, 2012, 04:35:57 PM »

hi George,

from the ts-520 group on yahoo

http://groups.yahoo.com/group/TS-520_820_530_830/message/14288

don't want to be a wise guy, be sure to use insulated tool to adjust
the trimmer capacitor, lethal voltage in the final cage, use the
one hand method, the other is in your pocket.

please join other ts-5xx and 8xx hybrid fans

73 james
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WB2WIK
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Posts: 20547




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« Reply #6 on: July 10, 2012, 06:34:22 PM »

Well her's the whole story, I bought this radio on ebay

There ya go.

When will people learn that eBay is for the most part where people sell stuff for more than it's worth because it doesn't really work? Cheesy

I cannot recall the last item I saw on eBay that I couldn't buy locally for a lower price, and have the opportunity to try it out first. 

I hope, pray and dream that this endless scam will eventually dissolve and there will be peace on earth once again.  I'm wagering that will take about 5-10 more years. Wink
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KJ6TSX
Member

Posts: 116




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« Reply #7 on: July 10, 2012, 08:20:05 PM »

James
That link helped a lot, radio tubes seem to be neutralized, However my plate current is very low 150ma, The longer I keep the final hot the better the output. Does that mean the final are on the way out???
Quote
When will people learn that eBay is for the most part where people sell stuff for more than it's worth because it doesn't really work?

I bought the radio as a project for $100 I can't complain Hamfests are few and far between
Thanks
George 73s
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KE4DRN
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Posts: 3714




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« Reply #8 on: July 13, 2012, 06:56:56 PM »

hi George,

since the radio is used, have you done a through cleaning of the
switches and pots, took a peek inside, and lubricated the fan bearings?

Often these radios do not like to sit idle, once cleaned up, they work great.
Then you can start to study the schematics and use the test points to
verify what is going on inside the radio.

Otherwise you can end up looking for a problem that is not there and
replacing good  parts for no reason.

can you tell us what the reading is on the meter for your HV  high voltage
and what the idle current set to?

all the manuals for operation and service are in pdf

http://www.n6wk.com/kenwood/

please join the ts-520 yahoo group if you have not done so already.

73 james
« Last Edit: July 13, 2012, 06:58:29 PM by KE4DRN » Logged
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