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Author Topic: Neutralizing finals...looking for an easy way out  (Read 12869 times)

carson

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Neutralizing finals...looking for an easy way out
« on: September 04, 2008, 02:42:37 PM »
My ancient Kenwood TS520 is starting to show signs of age.

    The plate current drops off slowly when the carrier is switched on. Also cannot achieve full load anymore.

Methinks that the finals (a pair of 6146's driven by a 12BY7) are getting tired for the first time.

  I do not have an oscilloscope for neutralizing a new set of tubes. Does anyone have a method of doing that with a non-scope situation?

73 carson FL

 
Carson, 
 West Central Florida
Ex RV'er. (1995 Winnebago Adventurer)
2007 Buick Rendezvous, SUV / CROSSOVER

...Logic works like a charm...

Tom

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Re: Neutralizing finals...looking for an easy way out
« Reply #1 on: September 04, 2008, 04:49:49 PM »
It's been many moons since I used vacuum tubes, and couldn't recall anything from my grey matter about neutralization. Had to go look it up. Found lots of references, including this and this.
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carson

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Re: Neutralizing finals...looking for an easy way out
« Reply #2 on: September 04, 2008, 06:21:21 PM »
Thanks, Tom.

Was surprised to see you jump in here. I too was raised among mountain of vacuum tubes. I know the theory behind neutralization but haven't done that for many a year.

   The link from W8JI is helpful, thank you. The Wiki link does not apply. I have read a few others as well but thought maybe one of our members had a sneaky way of doing that.

   I think I have an old handbook here somewhere with instructions, but can't easily find it. In one of my boxes... somewhere. lol

   First I have to order the tubes, and they ain't cheap anymore.

My transmitter manual probably has a chapter in it.. I always read the manuals as a last resort. :o

  carson FL


Carson, 
 West Central Florida
Ex RV'er. (1995 Winnebago Adventurer)
2007 Buick Rendezvous, SUV / CROSSOVER

...Logic works like a charm...

Tom

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Re: Neutralizing finals...looking for an easy way out
« Reply #3 on: September 04, 2008, 07:53:13 PM »
Carson,

I saw the tubes on eBay, some without a reserve.
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Ned

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Re: Neutralizing finals...looking for an easy way out
« Reply #4 on: September 05, 2008, 06:42:11 AM »
I had 6146s as my output stage of my modulator but never used them in any RF circuits.  But that was 50 years ago.  Never had to neutralize my RF finals.
-- Ned -- Fulltimer 1997-2013
1997 Holiday Rambler Endeavor LE
2007 GMC Canyon

carson

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Re: Neutralizing finals...looking for an easy way out
« Reply #5 on: September 05, 2008, 02:09:01 PM »
Here is a little follow up...

   1. After checking the manual, the instructions were there and easy to do. I don't even need a sensitive RF voltmeter. I can use my second receiver tuned to 28.5 mhz and tune for smallest S-meter reading. The tube heaters will have to be "OFF". Luckily my xmtr has a switch on the rear (SG) which will do that.

   Further, I found a supplier on the web, located very near where I live. Prices were best of any other on the web. I would never buy used tubes for half the price. (6146A-$22.00) (12BY7-$12.00), new.

   Thanks for all the comments,

carson FL


   
Carson, 
 West Central Florida
Ex RV'er. (1995 Winnebago Adventurer)
2007 Buick Rendezvous, SUV / CROSSOVER

...Logic works like a charm...

Jim Godward

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Re: Neutralizing finals...looking for an easy way out
« Reply #6 on: September 05, 2008, 04:03:22 PM »
Carson,

I am rejuvenating my old HW101 and need the 6146s so I would like the name of your source as they are pricey little devils.
Jim
Jim & Pat Godward
AC7PO & KD7ZDM
Hillsboro, Oregon

carson

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Re: Neutralizing finals...looking for an easy way out
« Reply #7 on: September 05, 2008, 04:22:04 PM »
Hi Jim, glad to help out.

    The company is at vacuumtubes.net ...   here

An old company located in La Crosse, FL, near Gainesville, Fl.

   On the website click on prices on the left side to see there inventory.

Make sure you get the right 6146; my xmtr requires the 6146A. If you pick the wrong suffix you may get into trouble.

   They have 2 phone numbers for ordering: 800- 326- 4140  or 386- 462- 4646

Good luck with your HW101

73  carson FL
Carson, 
 West Central Florida
Ex RV'er. (1995 Winnebago Adventurer)
2007 Buick Rendezvous, SUV / CROSSOVER

...Logic works like a charm...

Jim Godward

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Re: Neutralizing finals...looking for an easy way out
« Reply #8 on: September 05, 2008, 11:00:44 PM »
Carson,

Thanks, I'll get at it on Monday or Tuesday.  I'm up to me ears developing a Comm plad for an Airport drill.  I need 2 separate ones, the first if we get a tower and antennas installed before then and the second for the case where they are not done.  All this with little definition from the airport as to their requirements or expectations.  Always something!!  VBG

73,

Jim
AC7P0
MT
Jim
Jim & Pat Godward
AC7PO & KD7ZDM
Hillsboro, Oregon

John From Detroit

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Re: Neutralizing finals...looking for an easy way out
« Reply #9 on: September 06, 2008, 08:05:51 AM »
I recall that there is a non-scope method mentioned in the ARRL handbook... I actually have a copy, i'ts 0.65 miles from where I'm sitting

I would suggest an older version of the handbook though, say a 1960's or 1970's edition
Nothing adds excitement like something that is none of your business
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PancakeBill

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Re: Neutralizing finals...looking for an easy way out
« Reply #10 on: September 06, 2008, 08:21:31 AM »
Carson
Sounds like you are on the right track.  I did mine for my Swan.  Had a TS 520 for a very short time.  Didn't like it as much as my friend did, so bartering happens. 

When you order the tubes ask for them to be matched.  By running them on a good analyzer the op can gettwo that are closely matched.  Buddy of mine back home was always a good source.  He would write the numbers on the tubes when testing and store them together.

If set on a good analyzer I wouldn't have an issue with used.  Off a flea market table however... 
Bill & Jolene W & Koda

Old Faithful, Yellowstone Association Bookstore
1997 Southwind 35P
Toads: 1997 Honda Accord & 1986 Westfalia
FMCA F-401354
1995 OMI Dobro F-60
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carson

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Re: Neutralizing finals...looking for an easy way out
« Reply #11 on: September 06, 2008, 09:17:54 AM »
To John and Bill,

   I am sure you are right, John. I have an old copy ca 1980, but haven't found it yet.  ;D

Bill, My Kenwood manual specifically states that these tubes don't need to be a matched pair; wouldn't hurt if they were.

   As stated in a previous post, a scope is not necessary. Kenwood recommends 2 methods.

1. Use a good RF meter at the 50 ohm dummy load and tune for minimum voltage. This is done with transmitter turned on, i.e. transmit on 28.5 mhz and the finals not energized, no heater voltage. Any parasitics will appear at the dummy load.

2. Without an RF meter, simply use a second receiver tuned to 28.5 mhz and tune the neutralizing capacitor for minimum S-meter reading, if any. Works for me.  :)

Thanks for the help, carson FL


 
Carson, 
 West Central Florida
Ex RV'er. (1995 Winnebago Adventurer)
2007 Buick Rendezvous, SUV / CROSSOVER

...Logic works like a charm...

carson

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Re: Neutralizing finals...looking for an easy way out
« Reply #12 on: September 11, 2008, 11:36:35 AM »
A little "correction" in my old posts.

I mentioned that the heater voltage must be OFF and my SG switch would do that. My error....

It is the screen voltage that must be OFF and that is what the SG switch is for.
  Received my new tubes in great shape and am in the middle of installing them.

   carson FL

Carson, 
 West Central Florida
Ex RV'er. (1995 Winnebago Adventurer)
2007 Buick Rendezvous, SUV / CROSSOVER

...Logic works like a charm...

carson

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Re: Neutralizing finals...looking for an easy way out
« Reply #13 on: September 11, 2008, 04:53:41 PM »
Another little update on my current activity.

    I attacked the transceiver today to change the finals and the driver (see above)..

My old Kenwood TS 520 is built like a tank. Just to get the covers off there were 18 screws. In addition to that there were another 6 screws to get at the "final" department. Of course the wiring and number of components, switches and what-have you are staggering. This was nothing new to me, used to be my Biz.

   This radio is vintage 1975 and has not had to be repaired until today. Lotsa crud, dust and grime inside.

  The neutralizing procedure was easy, there seemed to be no major adjustment needed. I replaced both finals as well as the driver.

   After reassembling (no parts left over) the real test would be to tune it up on the air. First I checked on full power (100W) and ...no problem.  (Was down to 40 questionable, wavering watts with the old tubes).
   Got on the air on PSK31 as a first try... one CQ for about 10 seconds and wham.. a contact. The band on 20m was quite busy at this time (20:15 UTC) and a reply came seconds after from YO9BPX, a ham from Ploiesti, Romania, named Mihai. Obviously I was pleases to chat with him for a while.

   To show the power of ham radio I should let it be known the my antenna is a short, loaded vertical sitting at near ground level; the RF power output to the antenna less than 10 watt. And to top it all off, hurricane IKE is sending a lot of clouds over this area as I speak.

    What a boring subject, but not for us true hams.

carson FL



Carson, 
 West Central Florida
Ex RV'er. (1995 Winnebago Adventurer)
2007 Buick Rendezvous, SUV / CROSSOVER

...Logic works like a charm...

PancakeBill

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Re: Neutralizing finals...looking for an easy way out
« Reply #14 on: September 11, 2008, 06:17:05 PM »
Good job!  PSK31 is pretty amazing.  Fun to keep dropping power and see what level is still good copy.  I was setup with all that back when I had a permanent shack. 

The 520 has a nice military look to it.
Bill & Jolene W & Koda

Old Faithful, Yellowstone Association Bookstore
1997 Southwind 35P
Toads: 1997 Honda Accord & 1986 Westfalia
FMCA F-401354
1995 OMI Dobro F-60
WA1RI

carson

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Re: Neutralizing finals...looking for an easy way out
« Reply #15 on: September 11, 2008, 06:25:27 PM »
The 520 is neat for RV operation. It has a built in DC-DC converter, so it can be used on 115VAC as well as 12VDC. It also has a PI-network output which means it can match to a wide variation of antenna loads without an external antenna tuner; within reason. I'll call it a keeper.

carson FL
Carson, 
 West Central Florida
Ex RV'er. (1995 Winnebago Adventurer)
2007 Buick Rendezvous, SUV / CROSSOVER

...Logic works like a charm...

John From Detroit

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Re: Neutralizing finals...looking for an easy way out
« Reply #16 on: September 11, 2008, 06:57:10 PM »
I can tell you this about PSK31.. Built my own inerface between the Kenwood in my forward head and the laptop that sits beside or on top of it... Fired that sucker up and made a contact... I had not felt that way since WN8YXM (my novice days... Back then Novices were WN#@@@ and extra and above WA# (or b in some areas)

I am still amazed that pushing around 30 watts I chat with folks all over the country, and in fact half way around the globe, pushing 30 watts into a random length wire via a KAT-1 tuner mounted outside the rig.

Imagine what i could do with a proper tuned dipole or a tri-bander!!!!

Nothing adds excitement like something that is none of your business
My Home is where I park it.

PancakeBill

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Re: Neutralizing finals...looking for an easy way out
« Reply #17 on: September 12, 2008, 07:29:20 AM »
John
I know what you mean, I was WN1BZY back in 64.  Had an Ameco 25 watt transmitter and a converted parlor SW receiver, to a longwire in the backyard.  What a thrill when you hear your call in morse and it wasn't you sending it!
Bill & Jolene W & Koda

Old Faithful, Yellowstone Association Bookstore
1997 Southwind 35P
Toads: 1997 Honda Accord & 1986 Westfalia
FMCA F-401354
1995 OMI Dobro F-60
WA1RI

N6OIL

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Re: Neutralizing finals...looking for an easy way out
« Reply #18 on: October 27, 2015, 11:43:21 AM »
Just going to jump in on this old thread not sure if the org hams are still here but when you use a second receiver disconnect the coax and kick on the attenuation and make sure you use a non-conductive tweaker. I run a TS-820S

73
N6OIL
Rory 

 

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