I've just taken delivery of a pretty hummer in quite good cosmetic condition which was listed as fully working but it isn't so it's going back for a refund.
I'm curious though: it hums nicely, winding forwards on the crown all three hands turn, the sweep second hand sweeping throught each "minute" but with the crown pushed back in nothing happens with the hands. It hums but stands still: cosmetically it would be a keeper but what do we know about this no movement phenomenon please?

 

Could be a problem with the index jewel or the pawl jewel. Or perhaps lack of one or the other. Sometimes, check proper positioning of the jewels on the index wheel and re-phasing will solve a problem such as this. But since you’re returning it, does what the problem might be really matter?

 

It needs a service, same happened to mine.

 

Sounds like an index wheel issue. They had hundreds of fine teeth that were easily ruined.

 

Those index wheels are why my watchmaker refuses to work on any hummer movement anymore

 

.... and just one of the reasons I'll never buy another Accutron / hummer again. (besides that battery thing)

 

If the sweep second hand is moving it is not a big issue. Only a bad friction wheel. It can be easily be adjusted or swapped. This is the part that is causing the trouble:

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I have at least 10 of them laying in a drawer. The sweep seconds hand is directly connected to the index wheel. All other hands and he date wheel are connected to the friction wheel. If the friction is to low, the hands are not moving. If the friction is to high, the index wheel will be damaged when setting the hands by crown.

 

As the OP says, with the crown in the “run” position, nothing happens with the hands. I infer from that comment, that the seconds hand doesn’t turn either. When the crown is pulled to the set position, all 3 hands turn. The way he phrased his post, exactly what happens isn’t entirely clear. At least to me.

 

Then I had misunderstood it. Sorry for that, I'm not a native speaker. If the seconds hand is only turning when setting the hands there can be lots of different problems, friction wheel, index wheel, pawl finger and index finger.

 

Since the OP seems to have lost interest in the thread concerning his errant f300, and since he has (seemingly) decided he will be returning it to the seller, not much purpose in pursuing this any further.

 

Oh bother - I knew what I meant and I'm sorry. I've highlighted in your response what happens.

 

No, I haven't lost interest but what I had lost was any real time for dawdling on the internet and this lovely forum in particular over the past 24 + hours, but here I am now. And whilst this particular watch has been returned to the seller it was such a pretty thing that I'd be happy with repair or refund.
Apart from the fate of this particular watch it is good to know what happens between crystal and case back and I thank you all for your knowledge.