Classic rs232 port 9volt power

[dgd]

I have an UNO with rs232 shield and LC1602/keypad shield connected to a Classic using the middle rs232 jack. The cable connects the rx,tx and Ground to the shield's RS232 port and the +9v and Ground to a power plug that fits the UNO power input socket.
No issues and it all works as expected.
However, when I recently included an ethernet shield it appears that the 9v supply droops and the UNO becomes intermittent. I have tested all the shields on the UNO using an external 9V wallwart supply and they work well.
So question is What current can that 9v supply provide? and is it commoned with the 9v supply on the top (MNGP remote) rs232?
I was also wondering if it was the very light cable providing the 9v, I cut the end of a faulty BTS sensor's cable to use the mini telco plug that fits the Classic's ports.
dgd

[boB]

I don't know what a UNO or a LC1602 keypad is (I could Google it of course except the UNO)

The two RS232 jacks come from the same 9V supply but they both have their own
PTC in series with them and you can drive two MNGPs at the same time.
So, if your equipment doesn't draw too much, it should work.  How much current ?
If it is too much, the PTC will open and usually, the Classic will reset when its 3.3V
drops momentarily.  Then, the Classic will come up again but you won't have
9V at the jack if it is still over-currenting the PTC.

Not sure how much current it can actually put out ?  But 150 mA or maybe more should be fine
I would think.

[zoneblue]

Ethernet raises the power consumption of an arduino by an order of magnitude.