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

Hi,
Well,from what I can see this is a potentiometer.
There isn't any infrared LED or photosensitive transistor or diode.
Now you have me wondering what's going on...?

Thank you

Just an observation, but does that model radio have a lock feature?

"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

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

Hi Brenda Ann,
Ok,I got a closer look at the switch and it isn't a pot(not that I was
doubting you)that's for sure.
Thank you for the offer on the schematic,I just got one downloaded.
Is there a way to test this switch(out of circuit) to see if its the
culprit?
Do you think that this is even what could be causing my problem?
I did notice that if I turned the knob real fast I could get a 5-10 KHz
change on the display but that's it.

Hi rEn,
I'm not seeing a lock feature on the rig or in the manual.
That would be great if that was the problem though,but I can get a a
few 5-10 KHz change on the display when I turn the knob but that's
it...its like its slipping in a way only everything feels tight.

Dale,
Your right,I probably shouldn't be working on it but there's no better
way to learn. Plus when you don't have the money to get it
professionally worked there's not much else to do.

Hi Pete,
Ok,I will put the encoder back in and check for 5 volts on the V+
terminal.
If I do get 5 volts then I might have a bad uP(what's that?)is there a
way to test that as well?
I sure hope the radio isn't trash,I would really love to run it as it
has a bunch of features non of my other radios have and I sure wouldn't
be able to afford one with these features.


Thanks for the help everyone its most appreciated

"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

My apologies Clayton- my comment was inappropriate regarding you working
on the 290.
A scope on the encoder will tell you immediately whether it is working. The
mecahnical ones were much more prone to failure than optical encoders.
As Pete said, if it has +5 on it, it is likely optical.

73,
Dale W4OP

On 12 Sep 2006 22:46:06 -0700, "Clayton" wrote:

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.

I had the same problem with an Icom 735. The tuning knob turns an
encoder, which had stopped working. Icom no longer sold the encoder. I
found a repairman who figured out which diodes were burned out, and he
replaced them and got the encoder working again. You might look for a
good repair guy.

Bob
k5qwg


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

It's funny that when Clayton turns the encoder quickly there is a frequency
change. I repaired a Kenwood R5000 a few months back that had the same
problem. The cheap plastic disc inside of the encoder was slipping from the
tuning shaft. I was able to super-glue the assembly back together and get it
working again. If it was my own receiver, I would have probably replaced the
encoder with either a Grayhill or Bourns optical encoder.

Pete

"Bob Miller" wrote in message
...
On 12 Sep 2006 22:46:06 -0700, "Clayton" wrote:

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.

I had the same problem with an Icom 735. The tuning knob turns an
encoder, which had stopped working. Icom no longer sold the encoder. I
found a repairman who figured out which diodes were burned out, and he
replaced them and got the encoder working again. You might look for a
good repair guy.

Bob
k5qwg


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

Hi Dale,
Well,unfortunately I don't have a scope(Yet...I know a scope is a must
have when working with this stuff,that's why its at the top of my"Must
Have List")so I am going to take a chance that the encoder is okay once
I reinstall it and test for the 5 volts on the V+ terminal.

Hi Bob,
I wish that were an option,but right not it just isn't going to happen.
This stuff has always been a big interest to me so what better way to
learn.

Hi Pete,
Hey,I better take the encoder back apart(I had it apart once and
cleaned it...there's not much to an encoder is there)I never thought to
check and see if the disk with all the teeth was slipping on the shaft.
I will check that before I put the encoder back in circuit.

You mention replacing yours with a Grayhill or Bourns optical
encoder...If I find that my encoder is the culprit can you just put in
any old encoder? as long as it fits the space and voltage requirements?

Here I go putting the cart in front of the horse again,I better check
the things you all have mentioned first before I do anything else.
I'll let you all know what I come up with.

Thank you everyone.