Tom says he's bypassed the tuner's meter and the creep upward is still apparent.
From his description, it appears he's narrowed it down to six components: the
two variable caps, the roller inductor* and the SO-239 connectors.
*- while he says he's replaced the roller inductor with a fixed coil as a test,
it's possible if he simply re-used the inductor's chassis connection, a fault
here could be an issue.
Given that it appears the only variable here is the state of connections,
between components and between chassis, resoldering and improving chassis
connections are the obvious choices.
A thought did occur to me: Tom, when you said you bypassed the tuner SWR
circuit, did you take it out of line entirely or simply parallel a wire past
it? If you simply paralleled a wire from the input to the first gang of the
switch, you may have left a capacitor to ground in the mix. Maybe it's the
fault?
73, Kelly
ve4xt
Sent from my iPad
> On Jan 3, 2015, at 9:10 AM, "Jim Hargrave" <w5ifp@gvtc.com> wrote:
>
>
>
> -----Original Message-----
> From: Jim Hargrave [mailto:w5ifp@gvtc.com]
> Sent: Saturday, January 3, 2015 9:08 AM
> To: 'Tom Osborne'
> Subject: RE: [TowerTalk] Tuner SWR won't stay down
>
> Tom,
> Have you replaced the 1N34 diodes?
> Does the forward power meter change or just the reflected meter.
>
> 73, Jim – w5ifp@gvtc.com
>
>>> -----Original Message-----
>>> From: TowerTalk [mailto:towertalk-bounces@contesting.com] On Behalf
>>> Of Tom Osborne
>>> Sent: Friday, January 2, 2015 11:11 AM
>>> To: towertalk@contesting.com
>>> Subject: Re: [TowerTalk] Tuner SWR won't stay down
>>>
>>> I have 7 antennas here. It will drift on every antenna.
>>>
>>> There seems to be some confusion on my first posting. This is what I
>>> asked:
>>>
>>> "Hi
>>>
>>> I picked up an MFJ-989C tuner that has a problem (don't want to hear
>>> about 'mitey fine junk).
>>>
>>> The problem is that the SWR goes down and then slowly creeps back up.
>>>
>>> I got a new roller inductor and installed it and the SWR still
>>> doesn't stay low, even at low power.
>>>
>>> I took the roller inductor out and put in a switch/coil combo to
>>> eliminate the coil problem. SWR still climbs up.
>>>
>>> Bypassed the SWR circuitry and ran the input from the antenna
>>> directly to the capacitor. Still won't stay low.
>>>
>>> I thought it might be the SWR circuitry but I put another tuner in
>>> front of this one and when I tune the SWR down with the other tuner,
>>> it stays down, so don't think it should be the SWR circuit.
>>>
>>> This really has me puzzled. Can't see anything left to check. Any
>>> ideas? Thanks and 73 Tom W7WHY "
>>>
>>> I would think the fact that I can tune the SWR down and it stays down
>>> with the other tuner would mean the jumpers and coax are all OK as
>>> the 2 tuners are in series with each other. There is definitely a
>>> problem with the bad tuner, but just can't figure it out.
>>>
>>> But - I did put the output of the tuner into the dummy load and it
>>> still drifts at low power. Maybe it's time to strip out the parts
>>> and build it into something else :-)
>>>
>>> One last thing I'm gonna try is borrow one of those heat sensors from
>>> a friend of mine and shoot it at all the components and see what is
>>> heating up. It has to be that what is causing the problem. 73 and
>>> appreciate all the suggestions.
>>> Tom W7WHY
>>>
>>>
>>>> On 1/1/2015 10:10 PM, Jim Thomson wrote:
>>>> Date: Thu, 1 Jan 2015 18:56:58 -0600
>>>> From: "Bill Aycock" <billaycock@mediacombb.net>
>>>> To: "Charles Farr" <cefarr@hughes.net>,
>>> <towertalk@contesting.com>
>>>> Subject: Re: [TowerTalk] Tuner SWR won't stay down
>>>>
>>>> I'm puzzled that no one has mentioned the FIRST and most
>>> helpful
>>>> trouble shooting test-- substituting a dummy load for the
>>> antenna.
>>>> Bill—W4BSG
>>>>
>>>> ## agreed ! We don’t even know what ant he is using. Is it a
>>> yagi, or
>>>> an OCF dipole, or is it a dipole fed with open wire line, OR coax.
>>>> What band or bandS does it drift on. Do you have some kind of
>>>> defective balun at the feedpoint of the ant ??
>>>>
>>>> ## Since it drifts, even with low power, you gotta real problem.
>>>>
>>>> ## Run ONE good coax, directly from the output of the tuner....
>>> to a dummy load.
>>>> Don’t even mess with a wattmeter, or anything else between
>>> output of
>>>> tuner and input of dummy load.
>>>>
>>>> ## Then try and.... match the dummy load..and do it on every
>>> band, IF
>>>> it doesn’t drift, your tuner is not the issue.
>>>>
>>>> ##If it does still drift, the tuner is the problem.
>>>>
>>>> Jim VE7RF
>>>>
>>>>
>>>> _______________________________________________
>>>>
>>>>
>>>>
>>>> _______________________________________________
>>>> TowerTalk mailing list
>>>> TowerTalk@contesting.com
>>>> http://lists.contesting.com/mailman/listinfo/towertalk
>>>
>>> _______________________________________________
>>>
>>>
>>>
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>
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>
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