Sony DTC-700 dark display

On Sat, 3 Sep 2005 08:05:43 -0400, "BoborAnn" put finger to keyboard and composed:

I'm not familiar with your device, but many displays use a cheap readily available incandescent lamp as a backlight.

-- Franc Zabkar

Please remove one 'i' from my address when replying by email.

Unfortunately its not that simple this is one of those with a blue display that can be partially turned off (air only the level meters remain on) which would rule out a lamp Bob

I think that this unit uses a VFD. You can easily identify one of these. It's flat, glass, has an evacuation pip, a single row of pins along the top edge, all equally spaced, except for the last two at the left and right ends, which have an extra space. Thes 4 pins are the device heater connections - each is a parallel pair so the heater is connected between the left two end pins, and the right two. There should be about 2 to 4 volts AC across these pins, and measuring from ground to either pin pair should give you about -30v DC, as the heater is floated on a negative 30v supply to keep it at about the same potential as the segment drives.

It's very common for the -30v supply to fail, usually due to dried out electrolytic caps. Also, with some models using this type of display, there is a small picofuse, or safety resistor in series with the heater feed. These often fail for no apparent reason.

Arfa