N8LP wattmeter kits

[N8LP]

Just in time for Christmas... sort of.  For all of you who expressed
interest in the LP-200 project, I have added "Buy Now" PayPal buttons on
the LP-200 webpage. Deliveries will start in early January, due to
manufacturing lead time on the PCB and bottom plate.

I made some small changes, which include adding the HP dual Schottky
diode detector, which eliminates diode matching and some of the
calibration procedure... and I also changed some of the cal screens,
adding a second gain screen for high power, and an offset screen for
zero'ing out the opamp offset error.

I have also started a new wattmeter project, the LP-300, which is a
handheld, battery operated directional wattmeter with digital readout.
The project is in the prototype/testing phase, and should be ready in
2-3 weeks. It borrows heavily from the LP-100 and LP-200, has digital
readout and a number of features important for portable use. I mention
this only because I thought you should all know about it in case you
feel it is better suited to your needs than the LP-200. I believe the
three wattmeters provide different needs, but there is obviously some
overlap of features since they are all wattmeters ;-)

I have also added a webpage with a comparison matrix of the three
projects. If you go to my home page, www.telepostinc.com, you will find
links in the LATEST NEWS section to the LP-200, comparison matrix and a
preliminary look at the LP-300.

73,
Larry N8LP
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[John Clifford]

I know, this is about as far from a K2 as one can get, but you guys are the
only people I know who understand electronics.

I'm trying to diagnose and fix a Sony laserdisc player (the old analog 12"
babies) that I've owned since new. The player worked fine until I didn't use
it for a couple of years after I got Dish TV and a DVD player. The player
will not provide a good picture but instead there is 'jitter' as if the
vertical sync needs to be adjusted on the TV set.

>From what I know of LD players, the laser pickup retrieves an analog signal
that represents a complete picture scan/frame. The CAV LD format has one
frame per track so getting a still image means just keeping the head on the
same track and letting it read the same frame over and over. There is a
servo circuit that controls the head position, and it looks like the head
position is controlled by voltage instead of discrete 'steps' using a
stepper motor.

This brand of LD player had a reputation for developing such problems due to
electrolytic capacitor failure, and that seems like what the problem is
here. I'm wondering if a bad cap is letting a voltage vary sufficiently to
allow the head to wander because I can't even get a good still picture and I
can hear the head moving ever-so-slightly when the signal is bad (it is
quiet during the few moments the picture is good). Or, if there is a cap to
damp voltage swings that has gone bad.

I've got the service manual and I've done a preliminary voltage check on the
power supply and things look to be where they're supposed to be... so the
problem has to be downstream. My next step is to try and look at the voltage
coming from the head positioning motor on back to whatever controls it and
see if something is bouncing around when it shouldn't be. I'm hoping that I
can just tack-solder a discrete component across any surface-mount caps that
might be bad and make the problem go away. It doesn't have to look pretty,
it just has to work.

I'm open to any troubleshooting ideas, and have the service manual in PDF
format if anyone would like to look at it. I don't have the special service
circuit boards or the service disc... but, hey, NASA went to the moon with
less, didn't they? I do have a 100 Mhz scope and a good digital meter, and
of course my trusty soldering iron, and thank goodness this thing has a lot
of discrete components.

Why am I posting here? Because building a K2 and fixing other radios has
given me just enough electronics knowledge to be dangerous. It's all Eric
and Wayne's fault!!

 - jgc

John Clifford KD7KGX

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