Hi,

I'm restoring a Heathkit SB-400 transmitter, and need some info on how
to realign the LMO (Linear Master Oscillator). Currently, it is
running about 75 KHz high at the lower end of it's range (i.e., on the
40M band, it will not tune below 7.075 MHz), and is out of linearity
by 16 KHz at the top of its range.

There is an adjustment on the LMO sealed with red paint - adjusting
this brings the frequency range down to where it should be (not sure
if this causes any other problems, though - it was sealed for a
reason??), but the linearity problem remains.

Does anyone have any suggestions or literature on this unit? (the LMO
is Heath Part No. 110-32)

Thanks,

Pat

"Pat Richardson" wrote in message
...
Hi,

I'm restoring a Heathkit SB-400 transmitter, and need some info on how
to realign the LMO (Linear Master Oscillator). Currently, it is
running about 75 KHz high at the lower end of it's range (i.e., on the
40M band, it will not tune below 7.075 MHz), and is out of linearity
by 16 KHz at the top of its range.

There is an adjustment on the LMO sealed with red paint - adjusting
this brings the frequency range down to where it should be (not sure
if this causes any other problems, though - it was sealed for a
reason??), but the linearity problem remains.

Does anyone have any suggestions or literature on this unit? (the LMO
is Heath Part No. 110-32)


Pat -

First go to K4XL BAMA web site and download the tutorial for Heathkit LMO
Repair by Ed Kotkiewicz
ftp://bama.sbc.edu/downloads/heath/lmo/

You will need the DjVu reader -- if you do not already have it
http://bama.sbc.edu/viewers.htm

I may want to try the HeathKit reflector of owners and former engineers.

Subscription control - http://www.tempe.gov/lists/control.asp?list=HEATH
To post -
Archives - http://interactive.tempe.gov/archives/HEATH.html

Greg
w9gb

On Mon, 21 Jul 2003 13:26:12 UTC, Pat Richardson
wrote:

Hi,

I'm restoring a Heathkit SB-400 transmitter, and need some info on how
to realign the LMO (Linear Master Oscillator). Currently, it is
running about 75 KHz high at the lower end of it's range (i.e., on the
40M band, it will not tune below 7.075 MHz), and is out of linearity
by 16 KHz at the top of its range.

There is an adjustment on the LMO sealed with red paint - adjusting
this brings the frequency range down to where it should be (not sure
if this causes any other problems, though - it was sealed for a
reason??), but the linearity problem remains.

Does anyone have any suggestions or literature on this unit? (the LMO
is Heath Part No. 110-32)

Thanks,

Pat

I've been in the LMO.

SB-400? You have a tube model.

1. Tube is known good?

2. What do you mean by 75 kHz high? Do you mean the output signal
or the LMO as measured by a frequency counter is off?

3. I found a cold solder joint on one of the temp compensating caps
in a tube LMO. This was not on the wire to circuit joint. This was
the little coil of wire soldered to the end of the cap's ceramic
tube.

4. There is a known problem with dirty contacts between the LMO cap
rotor and the spring clip. Cleaning instructions are on my page
at http://www.kiyoinc.com/heathstuff.html

5. How "pure" is the LMO's signal? What does a scope show you or
how does it sound on a general coverage receiver?

6. Check the voltages too.

I'm guessing that you're close to getting it going.

de ah6gi/4

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