[AMRadio] SB-10 Modification (was DX-100B on Phone - bad audio distortion / oscillation)

Gary Schafer garyschafer at comcast.net
Fri Dec 9 12:58:29 EST 2011

Hi Rick,

If it had the SSB modification I would first remove the coax cables that go
to the coax connectors on the back. They cut the wire between the grid of
the 6146's and the driver tank and rout them separately to the in and out
connectors on the back. I don't remember now if it was first routed thru an
added front panel toggle switch. Either way, just reconnect the driver tank
output directly to the grids per the original schematic. That may solve your

Also check that the clamp tube is operating properly. With the SSB mod there
were two OB2 regulator tubes added for screen regulation. someone may have
done something funny in that circuit and may have messed with the screen
bypass caps. The screen bypass caps should be directly connected from each
tube socket to ground with short leads.

Gary K4FMX

> -----Original Message-----
> From: amradio-bounces at mailman.qth.net [mailto:amradio-
> bounces at mailman.qth.net] On Behalf Of Rick Poole
> Sent: Thursday, December 08, 2011 11:34 PM
> To: amradio at mailman.qth.net
> Subject: [AMRadio] SB-10 Modification (was DX-100B on Phone - bad audio
> distortion / oscillation)
> Do any of you have a DX-100B that you're running with the SB-10
> sideband adapter?
> This one has the SSB modification, and I have the SB-10 to go with
> it.  There is an additional mod whereby the AM/SSB switch was
> replaced with a 3-position switch, with the third position for spotting.
> I'm wondering if the modification is part of my self-oscillation
> problem.  The mod involves running long lengths of wire the entire
> width and depth of the transmitter, terminating at some points that
> could be sensitive, and picking up who-knows-what along the way...
> certainly I can see these long wires picking up RF and feeding it to
> places it doesn't belong.
> If any of you has a DX-100B with this modification I'd be interested
> in knowing how well it has worked out for you.
> Meanwhile I'm considering backing out of the modification altogether
> and seeing where we go from there.  With five rice boxes of various
> vintage, a KWM-2A, and a Marauder, it's not like I don't have enough
> SSB equipment to get me by... don't really need another SSB
> transmitter.  And the old way of spotting with the DX-100... pressing
> the key with the Plate switch off... always seemed to work fine with
> my first DX-100 back in the early '60's (doesn't look like this one
> has the grid block keying mod so using the key for spotting should work
> fine).
> More than one of you has advised backing out of all modifications and
> returning the rig to its original configuration, so that's what I
> think I'll likely do.  Still, would like to know if any of you have
> the DX-100B / SB-10 configuration and how you like it.
> Rick WA1RKT
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