SB-610 schematic - many thanks

[mark allison]

Many thanks for the help with the schematic for the SB610 gents,  I obtained
this unit middle of last year from a radio rally for a derisory sum (£10)
I've managed go get it going but it needs some "fine tuning".  I notice that
many of the high value resistors need changing, virtually all of the 1 meg.
ones have gone low in value, typically around a 100K or so and the 330K ones
have doubled in value,  I have not had to change any of the others at all.

   I'm also restoring a Heath HW100 obtained from the same source but am
having one or two problems with it.  I managed to get it working ok with the
minimum of fuss, but am experiencing problems with oscillations on 3.5 and
7Mhz.  I tried the usual methods of trying to supress parasitics but have a
hunch the problem lies with the driver valve.  I've also had problems with
vfo warble, a topic which regularly gets mentioned on this group.  I cured
this by removing the VFO assembly and replacing the fet with a 2n3819, I
also used a fet source follower and a transistor amplifier in
place of the 6au6 buffer, although I left the valve in place with its
filament connected, works fine now and no warble!

I'm also have a mint DX100 which I regularly use with a Racal RA17 rx ( or
sometimes the Hammarlund SP600), puts out 150w no problem.

Again, many thanks for your help, it's much appreciated.


mark allison
G0BTP

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