John,
Does the power out jump up after you raise the input power so far? Do you hear
any high pitched squeal when this happens or just before it? I have seen the
coax connectors go bad and cause this. Most of the time though they'll arc and
you'll hear the squeal from the arc. The only problem is you cant see it where
its inside the connector.
I'm not sure what the one circuit is mounted on the strap above the load C. It
may be a RF sniffer for the wattmeter? The red choke at the front is a safety
choke to ground off load C.
In the bottom, it looks like they shielded the bases of the socket which is a
very bad thing. There's no way to cool them this way. I'll bet the solder ran
out of the heater pins quick on that amp. I see they added a bunch of heavy
feedthru caps through the shield for the heater I imagine and the choke is
inside the shield.
The input looks like it comes into a project box/relay and so the output? If it
were me, I'd mount the antenna relay as close to the coax connectors as
possible. you'll still have to run coax to the input tuning, and the load C.
I dont have any idea why they moved the zener. A power zener is better mounted
to the chassis to cool it. I highly doubt that little heatsink will do very
much at all. Those were made to cool the small metal can transistors.
Best,
Will
*********** REPLY SEPARATOR ***********
On 8/30/05 at 2:56 PM John wrote:
>I have this highly modified sb-220 that I bought several years ago.
>Please take a look and make any suggestions.
>http://www.geocities.com/w4kv/sb220
>
>Thanks
>John
>w4kv
>
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