"Arfa Daily" wrote in message
...

"Jack" wrote in message
...
The FL display is very dim on this unit.
I replaced all three electrolytics on the display board, but it did not
help.

Any experience on these??

-Jan



I take it that it is 'evenly' dim ? Have you checked the negative supply
volts ? Should be around -29v. You can check it between chassis, and the
filament pins at one or other end of the display panel (the AC filament
supply is normally 'floated' on the DC supply, so it's a convenient place
to check it). I'm not sure how the voltage is derived on that model, but
often, it comes from a voltage multiplier or an AC coupled transformer
winding. In either case, it is usually the coupling electrolytics that
cause the voltage to be low. I have also seen Sony use AC coupling on the
filament supply. One particular tape deck of theirs, used to suffer
regularly from the caps failing and making the display dim.
Unfortunately, if the problem wasn't caught early enough, it used to do
damage to the panel itself. If it is a switch mode power supply, it will
be derived direct from a winding on the switching transformer.

Just as a slightly separate thought - the machine hasn't got a
fluorescent display "dim" or "off" function in the user software, has it
? I've been caught by that more than once ... :-)

Arfa




"Jack" wrote in message
...
Thanks for the advice.

I checked this voltage earlier and if my memory serves me correctly, it
was around -17v.
I will have to check that voltage again.
There was a small transformer on the PCB that looks like it is used to
generate this voltage and it had a 22 micro 50v cap on the output, which I
changed.

-Jan

I have never seen the supply to a VFD panel on any piece of kit, to be as
low as -17v. -29v is much more the 'norm', so I would say that is
definitely the reason that the display is dim. 22uF seems a bit low for the
smoothing cap if that is what it is. Either way, if that is an independant
supply just for the VFD, it shouldn't be too complicated and hard to
troubleshoot for why it is low. Any safety resistors on the board that may
have gone high ? Leaky diode maybe ? Regulator transistor, zener ? Tried a
'scope on it to look for ripple ? (bearing in mind of course that if you
check at the filament pins, it will have 1 - 3v of AC 'ripple' on it from
the filament supply)

Arfa