You must have done something to lock out the EPROM firmware. You will have
to have Sony service, change the EPROM if it is truly locked out, and then
do a complete factory setup on the set.

This is why the service people don't want the clients messing around inside
of the service setup. These adjustments are factory set. If there are any
changes, this is from a failed component. Component failures should be
serviced, and cannot be adjusted out.

Many of the adjustments in the service setup require specialized
instrumentation to get them back to factory specs.

The time involved to change the EPROM, and put the set back to factory specs
can be about 2.5 hours average if no other repairs are necessary.

--

JANA
_____


"Ynte Broekhuizen" wrote in message
...
While fiddling around in Service Mode I managed to lock-up my Sony
KV21X4D. It's similar to the KV21C4. I'm not very familiar with
servicing TVs, so I'll try to describe the problem as detailed as
possible. Hopefully somebody will be able to provide some advice on how
to fix this.

Here's what happened:

I was trying out a few of the TT service commands, when suddenly the set
stopped responding to inputs. The broadcast kept playing in the
background, but I couldn't change channel, volume or any other setting,
nor could I power off using the standby button on the remote.

The set has been in this state ever since. All I can do is turn it off
and back on with the front power switch. After powering on it will
immediately go back to playing the same channel that was on when it
locked up. The screen also keeps showing the same green text "TT07".
It's the last service command I entered. I believe it stands for 'Ageing
Mode'.

It looks to me as if the contents of some EPROM or other memory chip
have become corrupt.

Here's what I tried so far:

- Keeping the unit unplugged from mains for 24 hours. No change.
- Ordered the official service manual. No luck here either.

Can anybody provide some helpful suggestions? I know my way around with
a screwdriver and a multi-meter and I'm not afraid to open up the unit.
If you are in a possition to help me, I could send you the service
manual in return (a 150MB PDF file).

Ynte