Casio CZ/ VZ/ FZ - Pro Series

I am using a power bank 450ma supply which powers all other casios ok.
I did try batteries, but I think the ones I tried were not fresh.
There is no problem with the analogue supply to actuators or seemingly the digital one to the processor and ancillary Mos chips.
It's just the led display and midi out.

I have tracked the midi signal from the processor to a hex inverter, the signal is ok passing the inverter and then leaves the board to meet the output board via a brown wire. The same signal is present at the other end of the cable where it then passes a tranny on the output board, the only other active component before it meets the socket.
When connected to a midi usb connector the led on the lead seems 'underwhelmed' by the signal as if it is not strong enough. One can see the data being generated, but nothing happens at the receive end.
A forum posting I read attested to the same problem on another az,so perhaps what has happened here is some achilles heel.

Sent from my iPhone

On 27 Oct 2015, at 04:53, "dlonrattam@... [CZsynth]" <CZsynth@yahoogroups.com> wrote:

> Casio hardware is notorious for being sensitive to "under-spec" power supplies.
> 
> 
> The CZ-1, for example, when plugged into a power supply that doesn't fully deliver the required current, can "seem" to be powered on, with LEDs lit up and everything, but may not respond properly or make strange or no sounds.
> 
> What are the power requirements of the AZ-1 and what are the specifications of the power supply you are using?
> 
> Even if these two things match, are you sure the power supply (if old) is still operating to spec?  Can you try another power supply?
> 
> Also, does the AZ-1 power up and operate properly when powered by fresh batteries?
>