SB-303 LMO Problem

[Pat Bunsold]

I finally got this junker SB-303 to play and it seemed to work well, 
until I turned the dial up.  All the voltages are correct, which is 
the 10V, but at dial settings above 100 khz, the LMO takes off and 
starts to oscillate in funny ways.  I disconnected it from the Mixer 
and watched it on a scope.  in the 0 to 100 khz region, it is fine.  
I know it is not 0-100, that is just the dial reference.  Looking at 
the cams, all the cams are fully CCW until you reach the 100 khz 
mark, so it may have something to do with that.  It completely freaks 
out at some frequencies, taking off and providing a white noise type 
of effect. The sine wave has multiple ringing and very fuzzy.   Returning it to below 100 khz and it works fine with a 
clean pure sine wave.  What could be wrong?  I know the LMO must be 
defective, but What in the LMO is defective?  Since these go for a 
MINT on Ebay, I will have to tear this apart and try to fix it.  Is 
it the transistor or FET that is freaking out or something about the 
LMO Coil?  I saw another one listed on Ebay today that had the same 
problem.  Works fine 0-100 Khz and then dies.  Anyone have any 
ideas???
--
Pat Bunsold WA6MHZ
San Diego Section Manager
Curator, Crest Radio Museum

-----------------------------------------------------------
Products bought, sold or traded here is the responsibility of the
parties involved.  This list and the City of Tempe are not responsible
for losses or misrepresentations of any kind.  Buyer beware!

-----------------------------------------------------------
This list is a public service of the City of Tempe, Arizona
-----------------------------------------------------------

Subscription control - http://www.tempe.gov/lists/control.asp?list=HEATH
To post - HEATH at LISTSERV.TEMPE.GOV
Archives - http://listserv.tempe.gov/archives/HEATH.html