On Tue, 22 Jun 2004 11:57:49 -0700, Tim Wescott wrote:

Eskay wrote:

On Tue, 22 Jun 2004 10:09:12 -0700, Tim Wescott wrote:


I have a Kenwood TS-520 sitting on my shelf with a severe VFO problem.
The oscillator frequency intermittently goes unstable, when the
oscillator doesn't cut out completely. The problem will go away if the
tuning knob is bumped a bit, and it seems to be worse at the higher
frequency portion of a band. The radio is unreliable for receiving, and
is not good enough to even think about transmitting.

Without having ripped into the oscillator yet, I am theorizing that
there is a bad connection on the main tuning capacitor. Before I _do_
tear things apart, I wanted to ask:

1. Has anyone out there seen a similar problem? What did it end up being?

2. The oscillator in this rig is well buried, and will take some
careful disassembly to expose. Do any of you have a manual that details
this operation, or have you done it yourself? I'm well capable of doing
it as-is, but if there's a known best way to do it I'd like to start there.

Thanks in advance.


Hi,,I am assuming that the VFO in the 520 is very similar to the one in the
TS 820 that I used to own.
The frequency counter did not always work in certain spots on the dial, and
of course the radio went dead at the same time.
I finally broke down and removed the VFO from the radio and opened the VFO
up. The main bearing of the tuning capacitor was not always making contact
because of dried up lubricant.
Don't remember for sure what I did to clean it, I used vaseline to
lubricate and reassembled the whole thing..It worked OK after that..
73 de Sieb VE3JUA.

That sounds very plausible. I got the radio at a hamfest, and I think I
know why...

Did you have any trouble getting the oscillator out, or was it just a
matter of taking the usual care with such things? On my 520 it looks
like I have to go through a few layers to get to the VFO case.

Not a great deal of trouble but be carefull to remember the sequence of
removal..73 de Eskay.

Did you have any trouble getting the oscillator out, or was it just a
matter of taking the usual care with such things?

Tim-

I was considering purchase of a TS-520S, but it had a very similar problem when
I tried it. Unfortunately it was gone by the time I figured out how to get
into the VFO.

I found a service manual on the web, it may have been at http://www.mods.dk.
It appears that you only need to remove a few screws and front panel knobs, and
the front panel comes off with the VFO attached. I believe there is a co-ax
cable and a power cable at the rear of the VFO that can be unplugged, with a
single screw holding the shield to the VFO.

The way it acted was almost identical, working smoothly at the low end of the
band, but acting erratic above about 100 KHz or so. By the "feel" of it, I was
convinced that there was something like a wire that was touching capacitor
plates when they opened up to the critical frequency. However, the suggestion
that it might be a bad rotor contact, is also plausible.

Good Luck!

73, Fred, K4DII

Did you have any trouble getting the oscillator out, or was it just a
matter of taking the usual care with such things?

Tim-

I was considering purchase of a TS-520S, but it had a very similar problem when
I tried it. Unfortunately it was gone by the time I figured out how to get
into the VFO.

I found a service manual on the web, it may have been at http://www.mods.dk.
It appears that you only need to remove a few screws and front panel knobs, and
the front panel comes off with the VFO attached. I believe there is a co-ax
cable and a power cable at the rear of the VFO that can be unplugged, with a
single screw holding the shield to the VFO.

The way it acted was almost identical, working smoothly at the low end of the
band, but acting erratic above about 100 KHz or so. By the "feel" of it, I was
convinced that there was something like a wire that was touching capacitor
plates when they opened up to the critical frequency. However, the suggestion
that it might be a bad rotor contact, is also plausible.

Good Luck!

73, Fred, K4DII

Eskay wrote:

On Tue, 22 Jun 2004 11:57:49 -0700, Tim Wescott wrote:


Eskay wrote:


On Tue, 22 Jun 2004 10:09:12 -0700, Tim Wescott wrote:



I have a Kenwood TS-520 sitting on my shelf with a severe VFO problem.
The oscillator frequency intermittently goes unstable, when the
oscillator doesn't cut out completely. The problem will go away if the
tuning knob is bumped a bit, and it seems to be worse at the higher
frequency portion of a band. The radio is unreliable for receiving, and
is not good enough to even think about transmitting.

Without having ripped into the oscillator yet, I am theorizing that
there is a bad connection on the main tuning capacitor. Before I _do_
tear things apart, I wanted to ask:

1. Has anyone out there seen a similar problem? What did it end up being?

2. The oscillator in this rig is well buried, and will take some
careful disassembly to expose. Do any of you have a manual that details
this operation, or have you done it yourself? I'm well capable of doing
it as-is, but if there's a known best way to do it I'd like to start there.

Thanks in advance.


Hi,,I am assuming that the VFO in the 520 is very similar to the one in the
TS 820 that I used to own.
The frequency counter did not always work in certain spots on the dial, and
of course the radio went dead at the same time.
I finally broke down and removed the VFO from the radio and opened the VFO
up. The main bearing of the tuning capacitor was not always making contact
because of dried up lubricant.
Don't remember for sure what I did to clean it, I used vaseline to
lubricate and reassembled the whole thing..It worked OK after that..
73 de Sieb VE3JUA.

That sounds very plausible. I got the radio at a hamfest, and I think I
know why...

Did you have any trouble getting the oscillator out, or was it just a
matter of taking the usual care with such things? On my 520 it looks
like I have to go through a few layers to get to the VFO case.


Not a great deal of trouble but be carefull to remember the sequence of
removal..73 de Eskay.

With Ed's link to a manual I think I know how to do it -- it _should_
have occurred to me to take the front panel off!

Now I just need to find the time, and if the bearings _are_ dried out
I'll need to decide what to put back in.

--

Tim Wescott
Wescott Design Services
http://www.wescottdesign.com

Eskay wrote:

On Tue, 22 Jun 2004 11:57:49 -0700, Tim Wescott wrote:


Eskay wrote:


On Tue, 22 Jun 2004 10:09:12 -0700, Tim Wescott wrote:



I have a Kenwood TS-520 sitting on my shelf with a severe VFO problem.
The oscillator frequency intermittently goes unstable, when the
oscillator doesn't cut out completely. The problem will go away if the
tuning knob is bumped a bit, and it seems to be worse at the higher
frequency portion of a band. The radio is unreliable for receiving, and
is not good enough to even think about transmitting.

Without having ripped into the oscillator yet, I am theorizing that
there is a bad connection on the main tuning capacitor. Before I _do_
tear things apart, I wanted to ask:

1. Has anyone out there seen a similar problem? What did it end up being?

2. The oscillator in this rig is well buried, and will take some
careful disassembly to expose. Do any of you have a manual that details
this operation, or have you done it yourself? I'm well capable of doing
it as-is, but if there's a known best way to do it I'd like to start there.

Thanks in advance.


Hi,,I am assuming that the VFO in the 520 is very similar to the one in the
TS 820 that I used to own.
The frequency counter did not always work in certain spots on the dial, and
of course the radio went dead at the same time.
I finally broke down and removed the VFO from the radio and opened the VFO
up. The main bearing of the tuning capacitor was not always making contact
because of dried up lubricant.
Don't remember for sure what I did to clean it, I used vaseline to
lubricate and reassembled the whole thing..It worked OK after that..
73 de Sieb VE3JUA.

That sounds very plausible. I got the radio at a hamfest, and I think I
know why...

Did you have any trouble getting the oscillator out, or was it just a
matter of taking the usual care with such things? On my 520 it looks
like I have to go through a few layers to get to the VFO case.


Not a great deal of trouble but be carefull to remember the sequence of
removal..73 de Eskay.

With Ed's link to a manual I think I know how to do it -- it _should_
have occurred to me to take the front panel off!

Now I just need to find the time, and if the bearings _are_ dried out
I'll need to decide what to put back in.

--

Tim Wescott
Wescott Design Services
http://www.wescottdesign.com