The fact that it has a V+ connection suggest that it is a quadrature optical
encoder. When you turn the encoder clockwise, channel A leads channel B;
counterclockwise rotation, channel B leads channel A. That is how you get
the directional cueing.
You need to check if there is 5V at the V+ terminal. Your wild meter
readings tell me that the unit is outputting the 5V pulses when rotating.
Get ahold of the schematic from mods.dk and go through the circuit. You
could have a bad uP, in which case the radio is now trash. Hopefully, that
isn't the case.

Pete

"Dale Parfitt" wrote in message
news:eTSNg.51753$Qb2.3597@trnddc08...

"Clayton" wrote in message
ups.com...
Hi,
I have an Icom IC-290A that I am working on...The problem being that
when I turn the tuning knob it doesn't change frequencies,it acts as if
the knob is slipping.
After determining that it wasn't the knob slipping I proceeded to
disassemble the front to get at the tuning potentiometer.
If your familiar with this unit you know that the potentiometer is
continuous and has teeth that catch when you turn the knob to make
tuning easier.
Now when I hook up my ohm meter to the wiper and to either end of the
potentiometer all I get is an OL reading and when I turn the shaft the
reading jumps around wildly. If I connect the meter to the wiper and to
the case of the(I am assuming this is correct?) potentiometer I should
get a reading of Zero ohms but again the only reading I get is OL.

Am I safe in saying that the potentiometer is bad?

If so how do I go about figuring out what type of potentiometer I need
to replace the bad one?
The schematic doesn't tell me what value it is and there isn't a parts
list or part number either.

I hope I have made myself clear enough to be understood,if not please
let me know so I can try and make things clearer.

Any help on this would be greatly appreciated.
Thank you

You really should not be working on this rig if you think tuning is
accomplished by a pot. This era rig has to use a mechanical or optical
encoder. Send it in to a repair location.

Dale W4OP