[Heath] SB-102 LMO

[Kenneth G. Gordon]

On 13 Apr 2018 at 8:35, Mike Fitzgerald wrote:

> Anyone been inside the LMO used in the SB-102?  Repairable?  This LMO
> seems to have a very strange (to me) problem...When first trying to
> zero beat against the CAL signal, the zero beat tone is very erratic
> and impossible to tune, however if the main tuning knob is turned back
> and forth quickly several times in the area where the zero beat will
> occur, it's smooth as silk..Go to the next 100KHz CAL point and the
> process has to be repeated to obtain a smooth zero beat.  Any ideas? 
> Tnx de Mike AA7WU 

Hello, Mike:

Sorry I was not able to get back with you on this yesterday. It was a real zoo around here.

That problem is quite common these days with any of the Heathkit LMOs. I have had the 
one in my own SB-102 (and SB-101, SB-301, SB-401) open. You will have to remove the 
LMO from the rig to fix it.

Glenn Zook has an article on his website detailing the repair procedure.

Here is the link to his information:

<http://nebula.wsimg.com/d6a8106142d2492dec285d95be47aaf6?AccessKeyId=D1250C43
3DB440D6B60D&disposition=0&alloworigin=1>

Or use this one:

https://tinyurl.com/yb77ag4c

Anyway, what it amounts to is that the contact between the rotor and the stator of the tuning 
cap has gone intermittent.

To fix it permanently, the LMO must be removed and opened. One can remove ONE side 
(ONLY) of the LMO. As I remember it, that side is the one which contains NO OTHER 
screws except those round the outside edge which hold it in place.

Then a piece of the braid from a length of RG58, or a length of SolderWick, must be 
soldered to the rotor, enough length must be used to allow the cap to be rotated to both 
stops, then the other end of the braid must be soldered to a nearby close ground point.

Then the LMO must be reassembled and reinstalled.

This completely fixs the problem you are describing.

Follow Glenn's instructions and all will be well. Let us now how it goes.

vy 73,

Ken W7EKB

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