This would be so much easier to understand if you had the Camcorder in your hand but I will try my best to explain the problem.

Is the problem with the AC adapter or with the Camcorder.

I bought the HDR-HC1 camcorder(used) without an AC adapter- just a battery charger without a cord to the Camcorder.
I been using the battery for the few days I had the Camcorder.
but I need a AC power supply.

So I went to Ebay and Purchased a stated "ORIGINAL" Sony AC-L100 8.4V 1.5A adapter ( $30 )

here is the problem:

1. when I try to Power up the camcorder using the AC adapter - it turns on for a couple of seconds then it shuts off again - then it turns on again ... repeating that on/off rhythmic cycle all by itself.
The camera does not want to stay on! it just keeps cycling on/off endlessly.

2. In that short time frame that it pwrs on -( when the green CAMERA mode light is lit) - I quickly toggle it to MEMORY mode or TAPE mode. the light stays on in those two modes! it works fine in those two modes.
But when I attempt to toggle it to CAMERA mode from there it starts the crazy on/off cycle.

3. the power supply has no problem charging the battery while on the camera. (the yellow light is on indicating it's charging)

more baffling:

4. If I take out the DV tape and power it up - it comes on fine.( in mind that CAMERA MODE is the default setting when the Camcorder is first powered on). but if I try to load the tape it goes haywire again - it starts cycling on/off. It does not even manage to stay on long enough for the tape to fully load.

even more baffling:

5. If I power it up using the battery alone it Powers up fine. (The camera has no problem working with battery power)
while the battery is on the camera I hook up the AC adapter and it stays on fine ( I can see the battery minutes display disappear as soon as i hook up the AC adapter indicating it is using the adapter power and not the battery.
so now I managed to get the camera on in CAMERA mode powered by the AC adapter! what a hassle that was. But at that point I would not dare to toggle it to TAPE or MEMORY because I know I wont be able to get it back to CAMERA mode without going through that hassle again.

in short summary:
it seems like the camera initially does not want to be powered on using the AC adapter.
I can powered it on using the battery then switch to AC adapter.

5. does this sound like a defective camera or is it the power supply.

I know it is easy to suspect the AC adapter.
But I can not say that 100% because the power supply does manage to 'work' (if you can say that). but I have to go through the hoops to get it working in CAMERA mode.

Does all that make any sense?

I have to find out fast if it's the camera or the AC adapter because I only have seven days before I can ship back the power supply minus the shipping and 15% restocking fees and all the hassle i will have to go through to get any money back from Paypal.

Help.

Found the problem.
Sony Imitation AC adapter.
Took the Camcorder to a Sony Style store to check it with their adapter - worked like a charm!
I could now see the two adapters are not the same.
conclusion:
I been suckered into buying a supposedly "ORIGINAL" , "MADE IN JAPAN" relatively high priced Sony adapter.
taking about Buyer Beware. I THOUGHT I WAS AWARE.
After doing some, which i thought was enough, researching to get the real thing.
and now this guy has the gal to charge me 15% restocking fee for returning it.
some of the adapters out there on Ebay are clearly not the real thing and the sellers are not dishonestly trying to get you to believe otherwise (by the price and the product description and picture.)
but this guy has no problem lying straight out in large colored Bold print.
I was red mad.
I paid for shipping
paid for shipping it back.
and now I have to pay 15 % so he can take the junk thing back.

I just hope I can get something back from this guy/Ebay/Paypal or whatever and from what i hear - it is not a pretty process.
I dont want to buy electronics from Ebay - especially from the Ebay Stores.