[time-nuts] HP105B HP 105B 1 amp fuse blowing

[Roy Thistle]

Hi All:
A 105B (quartz oscillator) is blowing the 1A fuse, after it is on about 1 hour.
The fuse appears to have just melted (not a black mark as the result of a flash, in the case of a high current short.)… just looks like the fuse wire (inside the glass capsule) melted into some little blobs, for about 1/4  the fuse length, near the middle. It wasn't a fast-blo or slow-blo fuse... just the normal kind.
I think the unit is drawing just a little too much current, as the result of the batteries needing charging (I had the fast charge option on when the fuse blew.) And so, the fuse heated up, and finally melted. Not sure why the batteries were not charging normally... but 20.1 volts is what I measured across the pack, initially, and 23.4 V after about 45 min of charging.
I am charging the batters, from a power cube, at 510 ma, and dropping (cube gives 25V, 500mA max)… the batteries are 20 C size NiCads, wired in series... that of course is a retrofit.
I don't want to put another fuse in, and blow that too, without some reasonable explanation of why the first one failed!
Please, any comments, or hints/suggestions... much appreciated.