[!! SPAM] RE: [1000mp] Help!... VFO scan-down problem

[Rod Elliott]

Hi Pete...

Many thanks for these excellent instructions... just what I was looking for!

So, I took the tuning knob and jog ring off and 
found that the sensor (a tiny linear 
potentiometer) was centered mechanically, but NOT 
electrically. Whazzat??? Well, the section of the 
pot where the VFO does not scan is from 20 to 40 
percent of its travel from its left-hand end. 
Those numbers should be 40 to 60 percent, cuz the 
jog ring centers it mechanically at the 50 percent position.

Unfortunately, there is no way to physically move 
the pot far enough to re-center it.

I interpret this to mean that something has 
happened electrically to shift the pot's 
electrical centerpoint... probably related to the 
two spontaneous resets just before the scanning problem started.

BTW, there is no evidence of a short to ground on 
those tiny wires that connect to the jog ring pushbuttons.

So, I'm now going to dig into the Technical 
Supplement, find where that little pot connects, and measure some voltages.

Will post an update when I find out where that takes us.

Thanks again Pete!

73
Rod Elliott VE3UW




At 19:56 9/25/2007, you wrote:
>Pull the rubber band ring off the main tuning knob.
>You will then see allen screw holding the main knob on.
>loosten that allen screw.
>pull the main knob off.
>carefully observe the position and arrangement of springs and stuff for the
>jog ring.
>Observe the little slot that the jog control sits in.
>carefully move the jog slot contol with a screwdriver or something.
>All this can be done with the rig on.
>Actually it must be on or you would have no idea what to do.
>You will then see that the rig will stop scanning if you move the little
>control one way or the other.
>Fiddle with it till it stops.
>It may be necessary to remove the springs and stuff.
>and then replace everything.
>To keep this from happening again, don't use shuttle knob.
>At least dont use it to it's limit and then let it go.
>It is not really a pain to do this. About 15 minutes will fix the problem.
>
>Pete K4OM
>
>-----Original Message-----
>From: 1000mp-bounces at mailman.qth.net
>[mailto:1000mp-bounces at mailman.qth.net]On Behalf Of Rod Elliott
>Sent: Tuesday, September 25, 2007 2:46 PM
>To: 1000mp at mailman.qth.net
>Subject: [1000mp] Help!... VFO scan-down problem
>
>
>I have a 3-year-old FT-1000MP MkV Field. It has
>become unusable due to a very peculiar problem.
>In short, the main VFO continuously scans down
>the band at about 1 MHz per minute. If I let it
>keep scanning,  it goes all the way down to
>100KHz. The rig then resets itself to 7.000.00 MHz.
>
>Transmitting stops the scan at whatever frequency
>it was at when switched to TX. As long as it’s in
>TX, it does not scan, but resumes scanning as
>soon as switched back to RX. Makes it devilishly hard to work anybody
 hi!
>
>This behavior first appeared several months ago,
>shortly after the rig did a couple of spontaneous
>memory resets for unknown reasons. At first, the
>scanning behavior was intermittent and
>short-lasting, starting and stopping
>spontaneously. As time went by, these scans
>became more frequent and lasted longer. Now it
>scans all the time, starting as soon as I turn
>the rig on. Nothing I’ve done with the controls
>and memory settings, including a full CPU reset,
>has fixed it. No further spontaneous resets though.
>
>To research the problem, I read this reflector
>going back several years and searched the VA3CR
>FT-1000MP website. To summarize, this is a rare,
>but not unknown problem. The causes fall into two categories:
>
>1: RFI getting into the rig:
>Not my problem
 the scanning happens when I am
>not transmitting, and there are no nearby
>transmitters. To ensure it’s not some unknown QRN
>(like farmer’s electric fences, etc.) I clipped
>ferrite chokes on all the leads in and out of the
>rig and computer. No improvement.
>
>2: Shuttle jog mechanism has a shifted center-point or shorted wire:
>Could be
 discovered that I could pause the scan
>by holding the jog ring about 10 degrees
>clockwise. More clockwise it scans UP, less
>clockwise it scans DOWN. Fine, but also
>devilishly hard to operate holding the jog ring 

>
>I have no idea how to get a look at the jog ring
>mechanism. Even the FT-1000MP Technical
>Supplement is silent on that. In any case, it’s
>not certain my rig has mechanical problems in the
>shuttle jog
 might also be an electrical fault in the scan circuitry.
>
>The only mod in this rig is an INRAD roofing
>filter board which was installed two years before the scan problem showed
>up.
>
>So
 a couple of questions for the MP gurus here...
>1. Has anybody here had this problem and how did you fix it?
>2. Can anybody offer a possible electrical diagnosis?
>3. Anybody know how to take the VFO-A tuning
>assembly apart to inspect the shuttle-jog mechanism?
>
>All inputs welcome!  Many thanks in advance...
>
>73
>Rod Elliott  VE3UW
>
>
>BTW, I have now worked around this problem by
>buying a new FT-2000. Super rig
 a quantum leap
>over the FT-1000 series! Still want to fix the Field and keep it as a
>backup.
>
>
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