Michael,

While there could be any number of things going on,if it is a silver 
plated inductor and it is that old, it probably needs a good cleaning 
anyway.   Of course you should check the manual.

The problem  may or may not  occur across all bands.  There are going to 
be places more cruddy than others on the inductor.   When it happened 
to me, I noticed it on 160 and 75/80 meters.    Your XYL  should be able 
to see  the black oxidation that silver gets when exposed to air.

When on the frequency in question, and with the tuner  tuned to the 
right settings, slowly turn the inductor 2 or so turns in each 
direction.   If you hear any scratchy  sound in the RX, or slight drop 
in signal,  that would tell me  it is dirty.    Even if you hear no 
scratchy stuff, it probably should still be cleaned (of course depending 
on what the manual says).

73,  good luck, Steve KW3A

On 11/10/2013 8:54 PM, Michael Ryan wrote:
> Hi Steve:=20
>
> Well 1ST up, my tuner is very old. I bought it last winter from a Guy =
> who was the 3RD owner of it. So, its probably in access of 15 to 20 =
> years old.=20
> It probably needs a good cleaning no doubt. There was no fluctuations in =
> the SWR or full power out when the antenna was directly connected to the =
> 570. I got my XYL to look at the display for that one.=20
> The flux only occured around 3.79MHZ with the MFJ-989  and I had to =
> rotate the roller inductor knob about 10DG clock or counter clock wise =
> to keep the SWR flat.=20
> So, this is how it goes. I tune for the low SWR, unkey, key up to check =
> and the SWR would be up to about 10/1. I'd key again and rotate the =
> roller inductor again to lower the pitch and SWR, take a reading and it =
> would be flat. I would receive for about a couple of 2nds and want to =
> take a reading so would key up and boom, the SWR would pop back up =
> again.=20
> All other bands perfect. Almost something might be arcing in there but =
> don't see any sparks or hear any crackling or smell any smoke. LOL=20
> The thing is, if it was the roller inductor, wouldn't that occur on all =
> bands or it depends on if you happen to hit that spot that might be very =
> dirty? The tuner is rated at 2KW SSB/1500W CW, my rig is rated at 175W =
> CW, so don't think 75/80W is too bad.=20
>
> 73:=20
> Michael DE VO1AX=20
>
>
>