J720's Enemy~NEC MC/HC 300HC

And may I add that the arrow (cursor) keys are in the stnadard inverted T layout, instead of the one across layout for MP780/790s ...

Adding in the fact that it has a ARM cpu, it might just be a good inbetween HPC ... not too big, nor too exp.

If only it is available to US. I'm sure then parts can be gotten for spares and repairs.

i see.. still, if you can find out how that happened i'd be interested..
also, i'm not sure if i understand right how you meant the user lost the rom? was the whole rom erased or just damaged, or..?
how was the user able to copy another rom out of another 300HC? again, thanks for the info

wow, thanks for the additional info.. it could have been a very nice HPC then! (but for the poor quality control and that it isn't available outside china etc.. )

ahh i won't wait for the images from shumazu.com ... can't someone post them here? (don't link to http://www.shumazu.com, please, but post the real pics)

Almost everything is repairable. But the key issue is the cost and the returns. If u have the know-how and the required tools, repairing a defective unit might still be cost-effective and has a lot of fun. However, if someone is not an expert in this regard (like me, hehe), he has to have the machine repaired, something could make the cost too high. So, it depends…

ROM loss means the rom seems to be completely erased. It is zero. The machine can not power on, even after removing the main and backup battery for a long time and reinstalling them. Btw, Chinese users could not find an official hard reset method except removing both batteries.

In China, the power voltage is 220 volts. In jp, its 110v. so, using 300hc requires a 220v-110v converter since its supplied power adapter works in 110v. The HPC trader suspected that plugging in and unplugging the converter for a few times generates too much static. Excessive static damages the rom and seems to have erased it. Hoho, believe it or not. Maybe it’s the trader’s excuse. He made it up to soothe those unfortunate buyers. I don’t believe in this explanation.

As a hard-core HPC user, I think u must be familiar with the EPROM programmer (machine). The unfortunate buyer finally copied a rom image from a working 300 with such a programmer and then restored it to the dead unit. After that, his 300hc worked fine and did not have any similar problem.

I think linking to image is better coz the forum has limited and precious attachment space? Anyway, I will try 2 post some pics later coz my connection to HPC factor is slow, even with some fast proxies. Still slow.

thanks for the info again

i was able to download the images in the end (with much difficulty..), so it's not necessary to post them here. though it would still be nice to have pics of the hc300 here.

a little correction. What i owned is the Japanese version of Mobile Pro 880, not 780. All comparison is against MP880, a big big machine with only DSTN LCD.

Isn't it 100V in Japan???

does it matter if it's 100 or 110??
i'd like to know..
i couldn't find a 100V converter for my sigmarion III, only a 110 one...

Line voltages are averages, in NA they go from -163 to +164, and the root mean square average is about 110v. I may be off a little in the numbers, but you get the idea. We've been suffering brownouts here, meaning they drop the average line output about 5v.

What matters is what comes out of the dc plug. If you're within 5% or so of the rated output you're good. If you measure cheap transformers unloaded they may be 30% higher than their rating.

ok, thanks for the advice
it's not a cheap transformer, it's the original ac adapter/charger for the sig3. but i'll check it in any case.

It is not really the question whether the transformer is cheap or not. The problem is rather different. If a mains transformer is used then you need a converter. You can consider transformer as a linear element (without a load). So, half a voltage on input side results in half of the output; higher input voltage in higher output voltage...

There's a completely different story with modern AC/DC adapters. AC input is first rectified and then chopped with much higher frequency than 50 (60) Hz. There are different methods used, with fixed frequency (20 - 40 kHz) and variable pulse lenghth or fixed pulse length and variable period. The circuit in such power supply is measuring the output voltage and adjusting the parameters of a switching circuit. They are also called switching power supplies. Because of higher frequency the transformers are much smaller and their weight is signifficantly lower. Their output is not very sensitive to the input voltage and they usually cover the whole range from 100 - 240 V. Their efficiency depends on the input voltage - but who cares. The dissipation is higher at 100 V but the output is stable.

So, for the first approximation: if it weights half a kilo or something, it probably needs a converter. If it has about 100 g - it probably doesn't.

But, don't blame me if you burn your baby...

thanks for the information.. it was really an interesting read.
the sig3 adapter is very light and small.. and i know someone else has actually used it on 220V. until i successfully scared her out of her mind still, i wouldn't try it... especially as i'm not sure this statement about sizes is always true. is it?? and why is 100V written on it if it's good for even 240??
the converter itself is a brick... and is designed for only 230V input (we had 220V earlier, 230 now). so that corrensponds with your observations.