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Pioneer SX780 am fm tuning meter repair or replace

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Captn Conch

New Member
The 780 works great, fm stereo good and sound balanced the little red led comes on fine but the tuning meter stays right in the center even while tuning in stations, no wiggle, zero needle fluctuations, zip. The watt meters are fully functional.
So is time for a used replacement tuning meter or is there some testing to be done? I've googled the audiokarma forum but no info to be found on my situation, Thanks for any help.
 
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If you want to check it yourself, you just need a basic volt/ohm meter.

Set it on DC volts and just put the probes across the two meter lugs noting which ones are positive and negative. Tune your tuning dial and see if your volt/ohm meter changes. If it does, the meter in the receiver itself is bad. If your volt/ohm meter doesn't change, then there is a problem elswhere in the receiver.
 
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Good advice from Cademan ^^^^.

I use an SX-780 tuning meter on my KLH table radio. It works great but there is a narrow range. This is one of the (very common) meters that is centered when voltage is closest to 0.

As you approach the lowest voltage for that station the needle moves toward center and as you keep going, farther away from the lowest voltage the needle moves away from center.

Not all tuners work this way, but yours does.
 
Sometimes when the selector switch is in need of a cleaning, the tuning meter won't work properly. In rarer cases, I've seen them get stuck, usually from rough handling. Even rarer still, is an open circuit failure of the meter. In nearly 20 years of working on Pioneer, I've never seen a meter on one fail open.
 
OK so I connected my volt meter to dc and measured a battery voltage to make sure it was working, yep ok, hooked it up to the meter ,yellow wire hot- black wire ground I hope? turned on amp, selector to fm and spun the dial .... zero fluctuation. So Cadman, looks like meter is bad.
Dumb question here but do i need the antenna hooked up for this test? Also are my above mentioned wires polarity correct, I think it's right as the watt meters and tune meter all have black wires same position connected on left side.
 
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Captn Conch said:
OK so I connected my volt meter to dc and measured a battery voltage to make sure it was working, yep ok, hooked it up to the meter ,yellow wire hot- black wire ground I hope? turned on amp, selector to fm and spun the dial .... zero fluctuation. So Cadman, looks like meter is bad.
Dumb question here but do i need the antenna hooked up for this test? Also are my above mentioned wires polarity correct, I think it's right as the watt meters and tune meter all have black wires same position connected on left side.
Click to expand...

If you have an analog meter, it will deliver enough current to swing the tuning meter needle, a quick and dirty test to see of the tuning meter itself is functional.
The next test is to see if there is a voltage change showing at the meter when you change stations. Did you DeOxit the selector switch yet?
 
It's possible the jewels the needle pivot in are dirty or the unit was dropped, and the crush is too tight.. you night need to nudge the needle as see if it sweeps freely.
Be careful throwing voltages over 1v at the meter...
 
I ordered a used meter now on the way, I haven't pulled the meter yet. I tapped it a few times w/ no deflection.I did spray cleaner in the selector switch while rotating, however all the switches and pots etc do work and have no static. I'll go ahead and pull meter.
 
I pulled the meter then tilted it back and forth (not violently ha) this did move needle but not much and I did recheck with the volt meter as I turned tuning knob there were voltage variations but meter still no move. so it still appears to be the fm/am meter....I hope.
 
You need to check the meter with your DVOM on ohms, not volts. The DVOM will supply voltage to the meter and you should see it deflect - either forwards or backwards depending upon how you have your test leads oriented.
 
If when you had the voltmeter connected across the meter, tuned across the dial, and saw no indication of any voltage, that would indicate there is no drive to the meter, not that the meter itself is bad. As someone above mentioned, using you meter set to an ohms range, connect it to the meter. The meter should deflect. Reverse the meter leads and it should deflect in the other direction.

But let's back up a bit. That is a sensitive meter, and takes very little voltage across it to deflect it full scale. Did you have your voltmeter set to a 'mV' range? If not, the voltage changes across the meter may have been too small to see. Instead, connect your voltmeter across R30. The 2 Volt range of the meter, (or leave it on autoranging) should be OK there as the voltage changes will be much larger than what is seen across the meter itself. Do connect an antenna, and tune across the band. As you approach a station, you should see a voltage of 1 volt or so, (may be positive or negative, doesn't matter), as you tune to the station center, the voltage should drop to zero, and as you tune away from the station the voltage should increase in the opposite direction as you saw when approaching the station.
 
Well, I got my new used signal meter an hour ago and went through the hassle of installing it, I now have a fully functional SX780 with working am/fm signal meter! Ya Baby Ya! Thanks to all who responded! Cadman, big Thanks.
 
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