SB-310 Question

[Fred Wittman]

Well, I'm playing with my "new" SB-310, a great rig after cleanup.  However, one minor problem - there's a small amount of hum, not volume-specific, not noticable when listening to a strong station, but louder than I get on my SB-301.  I suspect the power supply, which is a two-diode/centertap-XFMR type feeding into a 100uf cap and a string of dropping resistors.  All the voltages measure per spec, except that I measure 2.5V of AC at the junction of the two diodes and the 100uf cap.  If my math skills are not stuck in stupid, that should be a regulation of about 98%.  That shouldn't be enough to hear, but I'm not sure, so I'm asking.  Also, after the radio warms up, it plays for about a minute without the hum, then it sets in.  Waddiya think?

While I'm here, I'm also interested in finding an SB-type dial without any cracks or crazing.  Anyone got one?  Thanks in advance.

Fred Wittman  -  KG6NYK

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