What was interesting about this rig, was there was only one electrolytic
cap I could identify and it was a low voltage one. All the large power
supply caps appear to be oil filled caps. After the USUAL procedure of
gradually raising the line voltage and letting it cook for awhile (just
a metaphor - don't be alarmed :) I did notice the AC line filter was
getting warm and smelly. I will end up changing it. I don't usually
change resistors and capacitors unless they actually are out of range or
noisy. I prefer to troubleshoot to the actual problem rather than
shotgun change parts.
I really would like to get some information and help with this rig
instead of just a discussion about how to power up an old radio. I
appreciate any help you can provide.
Dave
Joseph Gray wrote:
I'll have to agree with Bill's good advice. I often have people ask me
about some old tube radio that "Grandma" used to have. I always tell
them to not plug it in to see if it still works.
With any piece of equipment from the tube era, you can bet that as a
minimum, the electrolytic caps need replacing. Only after that is done
do I even try to power it on, and even then, I use a variac. To do
things right, all the paper caps should also be replaced. Then it is a
matter of checking other components. Old resistors like to change in
value over time.
As Bill said, don't burn up a vintage piece of equipment. Once the
magic smoke gets out, you'll never get it back in again.
Joe Gray
KA5ZEC
On Sun, Dec 20, 2009 at 9:53 PM, Bill Hawkins <[email protected]> wrote:
Dave,
Please, folks, don't just turn on a piece of vacuum tube equipment.
That could burn out an irreplaceable power transformer. If you do
not have equipment to test for shorts or bad electrolytics, then
make a jig with a light bulb socket to put the bulb in series with
the line. Start with a 40 watt bulb (CFLs won't work) and work up.
If the bulb is always bright, don't apply line power to the set.
I sold my LA-800 last spring. Don't remember what paper went with it,
but I had the schematic at one time. Sadly, my "filing" system does
not make it possible to retrieve anything without going through all
of the paper collected over 25 years. Try Manuals Plus.
The standard input on the left of the panel feeds selected multipliers
that produce 10 MHz. This is fed to a phase shift network such that
the scope produces a circular sweep at 10 Mc (circles per second).
Sounds like the horizontal scope amp is dead, if you supplied a local
standard signal and the multipliers worked. The 90 deg phase shift only
produces a circle at 10 MHz.
The WWV section on the right side only receives 5 or 15 MHz. Some magic
is used to get 10 MHz out of either carrier. This is used to intensity
(Z input) modulate the circle. Dunno why they don't receive 10 MHz.
Several years ago, here in MN, I had an HP-103 as the standard and was
listening on 5 MHz. Propagation was such that WWV would alternate with
the female voice at WWVH. The bright half of the circle would change
sides, illustrating the phase shift with distance. Neat stuff.
I'm willing to help you get this fine receiver back in action.
Nice workbench.
Bill Hawkins [email protected]
-----Original Message-----
From: Dave
Sent: Sunday, December 20, 2009 4:03 PM
Hi Timenuts,
My first email to the list. I've had this LAVOIE LA-800D (see picture)
receiver for about 10 years now. Before that, it was sitting in an
ariplane hanger for some unknown number of years and was headed for the
trash when I aquired it. Well, I finally put it on the work bench and
was quite surprised that I was able to power it up without anything
exploding. I've determined that it will receive WWV on 5mc quite well
and produce a vertical deflection on the scope. I can hear a very weak
400hz on the speaker. I can also feed 400 kc into the local standard
input and see it getting filtered and amplified internally. This is a
far as I can get. I am not sure how this device is suppose to work but
am fairly certain that most of it is functional. I really need to find
schematics and some operating instructions to make it work all the way.
I've already done the quick google and other customary searches for info
without avail. If anyone out there could email me pdf's of the
schematics, and other manuals it would help me a lot in getting this
classic piece of equipment back in operation. Pointers to info would
also be appreciated.
Thanks,
Dave
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