Gregory Braun schrieb:

I have a Sony ICF-SW7600 I bought on ebay. "Works Great" turns out to
be a joke and the seller changed his tune to "as-is" after the fact!!!

Not really a nice experience. :-/ Seems like a case for negative
feedback.

Anyone have schematics for this model? Sony provides an operators
manual and that's it. Repair options with Sony are limited to a $120.00
swap-out. I pretty much need to fix it or trash it. Any help would be
greatly appreciated. Unit powers up ok but the FM and MW bands are
completely dead and the sensitivity on LW might as well be.

First, I hope you have soldering gear suitable for SMD and a loupe or
microscope - you're likely to need it. (Along with a scope and suitable
probes; a multimeter may be useful as well.) You can find a service
manual he
http://bama.sbc.edu/sony.htm
Once you've got that, check the +14V voltage first, there's a testpoint
at the back of the main circuit board. If it shows heavy ripple or is
way off spec, the buffering cap inside the DC/DC converter (22µ elect)
is quite likely to be dead - when replacing it, be sure to put, say,
100nF ceramic in parallel (the original cap is prone to early death
partly because this was left out during construction). (This voltage is
also used in the PLL lowpass filter so it's quite likely the receiver
would not be receiving much with it missing.) That is not to say that
all the other caps are still working fine (some like C69 can cause a
weakened DC/DC converter to be overloaded altogether when not in good
shape), be sure to check them all for leakage.
The mechanics:
Getting the back off still is easy, ditto for the front and the clipped
on part over the controls on the right-hand side. I'd then suggest to
unclip the microprocessor board first (careful not to damage the ribbon
cable connecting both boards). The ribbon cable is held by a connector
on the main board, which you need to unlock carefully (push up the upper
part) with a small screwdriver or such. Once the µP board is off, you
can remove the main circuit board from the frame after removing a screw
pretty much in the center (may be covered). Ah yes, the rod antenna will
have to be unsoldered as well, be sure not to mix up any of the wires
when reconnecting it afterwards. Then you can finally take the PCB off
and look at it closely. The DC/DC converter is under the shielding can
near the DC power socket.
Also see http://stephan.win31.de/sony7600.htm#7600_repair.

BTW, what's the cereal, err, serial number of your SW7600? (Mine's a bit
over 300,000, and I'm wondering whether they may have started at 300,001
instead of 1 for whatever reason. This would mean mine is a very early
sample, while otherwise it would be a late one.)

Stephan
--
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