A plug for the lowly Sherwood S-3300

Posted by stellavox (A) on December 8, 2009 at 05:39:17

Now I haven't researched this but it would appear that this model was one of, if not Sherwood's first solid state tuners. I ended up with it after doing an incomplete repair job for a customer who then didn't want it.

Seems that this model underwent quite a few changes during its lifetime; later revisions adding early FET's to the front end and RCA CA3028 IC's as an amp and limiter in the IF section - instead of "just" transistors. O yeah, it uses all tuned circuits - predated ceramic filters. The unit I have is an early one (no IC's); with a pretty skimpy power supply - marginal B+ and no effective regulation. Changing the rectification from half to full wave increased the voltage enough so I could add zener regulation and solve the drifting problem. Big problem was lack of sensitivity which I traced to improperly working AGC. AGC was derived from the last IF stage and fed to a transistor amplifier, which controlled the gain of the FET RF amp in the front end. Turned out that the transistor wasn't properly biasing the FET - keeping it effectively turned off and not providing any gain. Changing a resistor value seems to have fixed things.

Why the bother - well apart from the challenge to fix the damn thing, the tuner SOUNDS great. Of course this was after spending QUITE a bit of time to get the alignment as good as its design and parts implementation would allow. Audio was enhanced by changing out the ceramic coupling caps in the multiplex decoder stage.

Considering that FM reception and station choice sucks where I live, this little puppy may join my bench "system" for a while, till I get tired of it.

HAPPY HOLIDAYS

Charles

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Topic - A plug for the lowly Sherwood S-3300 - stellavox 05:39:17 12/8/09 (2)

RE: A plug for the lowly Sherwood S-3300 - Brian Levy 17:26:54 12/8/09 (0)

"Brian" here and at AK loves the things, Charles (nt) - mhardy6647 08:51:24 12/8/09 (0)

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