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Author Topic: TS-520S VFO problem  (Read 1268 times)
AH6FY
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Posts: 5




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« on: October 31, 2000, 12:44:55 AM »

The problem with my TS-520S is at various points in each band when I tune the VFO the frequency jitters around by the sound of the signals being received.  As I tune across some stations rather than hear the audio go from low to high frequency the signal is garbled.  If I leave the VFO knob alone the signal being received settles down.  By using the RIT I can fine tune.  The problem started at the high end of each band and over several years has expanded to cover most of each band.  If anyone has insights I am all ears!  Thanks!
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NA9Q
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Posts: 13




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« Reply #1 on: November 05, 2000, 10:19:43 AM »

At one time I had this same problem on the main VFO of my TS820S.  The problem is that the variable capacitor rotating plates connect to the VFO circuit through a set of bearings at each end of the shaft.  Over the years the bearings get dirt into them and the contact becomes somewhat intermittent.  Like you I observed that the 'bad spots' reepeated at the same points in the band you were on.  

If you look into the radio, the VFO tuning cap is sealed inside an aluminum can making it extremely difficult to get into.  The solution I found was to use a liquid contact enhancer called STABILANT 22A distributed by D. W. Electrochemicals of Ontario.  I put a drop or two of this on the front bearing which you can get to by removing the fron knob and vernier tining dial.

MAKE SURE YOU STUDY HOW THIS VERNIER WORKS AND IS ASSEMBLED SO THAT YOU CAN REASSEMBLE IT CORRECTLY.

Removing the knob and vernier exposes the front of the tuning capacitor and most importantly, the front bearing. A drop or two of the contact enhancer into the bearing cleared the problem up for me and when I sold the radio a couple of years later it was still quite OK.

Good luck as this was a very annoying problem.  On the 820, not only did the problem show up in the audio but you could see the frequency jumping around on the digital display which the 520 does not have.  The jumping numbers was what led me to finding out just what was happening.

73, Mike, NA9Q
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AH6FY
Member

Posts: 5




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« Reply #2 on: November 05, 2000, 11:34:33 PM »

Mike,

Thanks so much for the info!  You know I took off the side cover of the VFO and after using the shopvac (I thought it was maybe junk between the cap plates) the bad spots on each band changed in that now it acts up in only a few places.  But it still didn't go away completely.  I would have never guessed it would be in the bearings.  I'll heed your warnings.  I haven't used the rig much for a number of years as it has been a real annoyance.  So thanks again!

Scott
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AH6FY
Member

Posts: 5




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« Reply #3 on: November 05, 2000, 11:43:52 PM »

Mike,

Just checked the VFO and there's access to the front bearing from the VFO enclosure side access so it looks like I won't have to mess with the vernier.

S
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AH6FY
Member

Posts: 5




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« Reply #4 on: November 07, 2000, 01:43:05 AM »

Mike,

Final update.  Didn't find the product you mentioned but did find a conductivity enhancing grease.  Put it in from the side access and the VFO is now stable across the band except for one or two small stuborn areas and I think they'll work out soon too.  (Now you've made me think about getting a better antenna for it!)

Scott
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NA9Q
Member

Posts: 13




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« Reply #5 on: November 07, 2000, 01:59:37 AM »

Scott,  I glad that the suggestion worked for you.  I know how frustrated I got with the frequency jumping before I got in and found the cause.  I too had a couple of stobborn areas but they eventually went away with use.  I think that there may have even been a bit of corrosion involved as well as dirt.  Who knows.  My old 820 is in use in Qatar by a local there and he says it is still going strong, no sign of the difficulty.

73, Mike
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AH6FY
Member

Posts: 5




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« Reply #6 on: November 25, 2000, 03:23:55 AM »

Mike,

In case you come back, the VFO problem is cleared up completely.  Put up my 12 year old Butternut vert and in the first hour or two talked with Florida, Japan, Korea and Chile (from Hawaii on 10M).  Just got a 59 from Japan.  Anyway thanks again for the info!

Scott
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KB9EZL
Member

Posts: 1




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« Reply #7 on: July 31, 2006, 10:21:42 AM »

Scott,

I read some of your messages concerning the 520 VFO jump. Several years ago, I bought a used TS-520S at the Peoria, Illinois HamFest. Several CBers had been into the radio trying to get it converted over to the 11-meter band. They botched up the Hetrodyne oscillator board by burning the foil off of the board trying to solder the crystals in the unit. I fixed the board and had the thing on the air a week later. I only used the radio a few months after I fixed it. I moved to another area of the county and never fired the unit up till a year later after the move. I immediately noticed when I fired the radio up at the new location the the VFO would jump while tuning across the bands. I suspected the VFO bearings were worn or the special conductive grease was dried out on the bearings. Kenwood's service bulletins said the problem could be many things. I've had the VFOs out of many of the old TS-520s and the laterTS-520S. I need to take the unit down again and find some of the conductive grease to lubricate the bearings on the VFO. I was wondering where you obtained the grease? I would appreciate your help.

Dennis
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